Design of Piping Systems

Design Of Piping Design Of Piping SystemSystem

Prepared by Tengku SyahdilanPrepared by Tengku Syahdilan

Aim of SeminarAim of Seminar

To know piping design basics by going To know piping design basics by going through the following points:through the following points:

Design of pressure components.Design of pressure components. Pipe Span calculations.Pipe Span calculations. Design of pipe supports & hangers.Design of pipe supports & hangers. Stiffness & flexibility.Stiffness & flexibility. Expansion & stresses.Expansion & stresses. Line expansion & flexibility.Line expansion & flexibility. Supports & anchorage of piping.Supports & anchorage of piping.

Design of pressure pipingDesign of pressure piping

Many decisions need be made in the design phase to Many decisions need be made in the design phase to achieve this successful operation, including:achieve this successful operation, including:

- Required process fluid quantity.- Required process fluid quantity.- Optimum pressure-temperature.- Optimum pressure-temperature.- Piping material selection.- Piping material selection.- Insulation selection (tracing).- Insulation selection (tracing).- Stress & nozzle load determination.- Stress & nozzle load determination.- Pipe support standard.- Pipe support standard.

The codes provide minimal assistance with any of these The codes provide minimal assistance with any of these decisions as the codes are not design manuals.decisions as the codes are not design manuals.

Design of pressure componentsDesign of pressure components Pipe Structure “static” design, not Layout design.Pipe Structure “static” design, not Layout design.

Limitations: Code, Pressure, Temperature, How long is the Limitations: Code, Pressure, Temperature, How long is the plant lifetime, What is the plant reliability, etc..plant lifetime, What is the plant reliability, etc..

Piping designed according to B31.3 has less lifetime than Piping designed according to B31.3 has less lifetime than B31.1 due to lower F.S.B31.1 due to lower F.S.

Reliability of piping under B31.1 should be higher than Reliability of piping under B31.1 should be higher than B31.3B31.3

Given that the code is a product of pressure technology, Given that the code is a product of pressure technology, one of the concerns is the pressure-temperature ratings of one of the concerns is the pressure-temperature ratings of the components.the components.

Design of pressure componentsDesign of pressure components Each system be it vessel or piping has some base pressure-Each system be it vessel or piping has some base pressure-

temperature rating. This is essentially the pressure temperature rating. This is essentially the pressure temperature rating of the weakest member of the system. temperature rating of the weakest member of the system. This can be translated that no minor component (valve, This can be translated that no minor component (valve, flange, etc) shall be the weakest link.flange, etc) shall be the weakest link.

The key components of the design conditions are the The key components of the design conditions are the design pressure and the design temperature.design pressure and the design temperature.

Design pressure is defined as the most severe sustained Design pressure is defined as the most severe sustained pressure which results in the greatest component thickness pressure which results in the greatest component thickness and the highest component pressure rating.and the highest component pressure rating.

Design temperature is defined as the sustained pipe metal Design temperature is defined as the sustained pipe metal temperature representing the most severe conditions of temperature representing the most severe conditions of coincident pressure and temperature.coincident pressure and temperature.

Design of pressure componentsDesign of pressure components

Thus we can try to simplify our stresses into two main Thus we can try to simplify our stresses into two main categories;categories;

Pressure stress is the circumferential stress (primary stress) Pressure stress is the circumferential stress (primary stress) or hoop stress, which is known to be not self limiting.or hoop stress, which is known to be not self limiting.

Temperature stress is the shear or bending stress Temperature stress is the shear or bending stress (Secondary stress), known to be self limiting.(Secondary stress), known to be self limiting.

In addition In addition VIBRATION, has to be addressed as low cycle VIBRATION, has to be addressed as low cycle high stress named as “thermal expansion cycles”, high stress named as “thermal expansion cycles”, represented by f=1 for 7000 cycles, otherwise detailed represented by f=1 for 7000 cycles, otherwise detailed design has to be performed to prove that the pipe will design has to be performed to prove that the pipe will withstand high cycle, low stress loads.withstand high cycle, low stress loads.

Design of pressure componentsDesign of pressure componentsWall Thickness CalculationWall Thickness Calculation

The code assists the designer in determining adequate pipe The code assists the designer in determining adequate pipe wall thickness for a given material and design conditions as wall thickness for a given material and design conditions as follows:follows:

- Calculate the pressure design thickness “t”- Calculate the pressure design thickness “t”

- Add the mechanical corrosion and erosion allowances “c” - Add the mechanical corrosion and erosion allowances “c” to obtain the thicknessto obtain the thickness

tm=t+ctm=t+c

- Add mill tolerance (MT) to tm, then select the next - Add mill tolerance (MT) to tm, then select the next commercially available wall thickness.commercially available wall thickness.

- Provided t<D/6, if not high pressure piping equations - Provided t<D/6, if not high pressure piping equations apply.apply.

Design of pressure componentsDesign of pressure components Code Equation:Code Equation:

ttmm = PD= PDoo/2(SE/2(SEqq + PY) + A = t + A+ PY) + A = t + A

wherewhere::P = Internal design pressureP = Internal design pressureDDoo = pipe outside diameter = pipe outside diameterS = the pipe material allowable stress, S is for the S = the pipe material allowable stress, S is for the

listed pipe material at hot temperaturelisted pipe material at hot temperatureE = quality factorE = quality factorY = stress-temperature compensating factor.Y = stress-temperature compensating factor.


The The E FACTORE FACTOR is a “allowable stress penalty” based on is a “allowable stress penalty” based on the method of manufacture of the pipe. It is based on the the method of manufacture of the pipe. It is based on the quality of the weld in seam-welded pipe and will have a quality of the weld in seam-welded pipe and will have a value ranging from E = 0.6 for FURNACE BUTT value ranging from E = 0.6 for FURNACE BUTT WELDED (FBW) to E = 1.0 for SEAMLESS PIPE, WELDED (FBW) to E = 1.0 for SEAMLESS PIPE, (SMLS). This FACTOR is a carry-over from the old days (SMLS). This FACTOR is a carry-over from the old days where pipe was manufactured using rivets.where pipe was manufactured using rivets.

The The E FACTORE FACTOR for seam-welded pipe can be improved: for seam-welded pipe can be improved: increasing this factor from 0.8 to 1.0.increasing this factor from 0.8 to 1.0.

The The Y FACTORY FACTOR is included to account for effects of creep is included to account for effects of creep considering the non-linear reduction in ALLOWABLE considering the non-linear reduction in ALLOWABLE STRESS at design temperatures above 482º C (900º F).STRESS at design temperatures above 482º C (900º F).


Wall thickness problemWall thickness problem::P = 4135 KPa (41.35Bar)P = 4135 KPa (41.35Bar)D = 219.1 mm (8.625 in)D = 219.1 mm (8.625 in)S = 130 MPa at 260ºC (18,900 psi at 500º F), from TABLE A-iS = 130 MPa at 260ºC (18,900 psi at 500º F), from TABLE A-iE = 0.85 (TABLE A-lB for A53 pipe)E = 0.85 (TABLE A-lB for A53 pipe)Y = 0.4 (TABLE 304.1.1)Y = 0.4 (TABLE 304.1.1)Convert MPa allowable stress to kPa for consistency of units, thenConvert MPa allowable stress to kPa for consistency of units, then::

t = 4135*219.1/2(13000*0.85+0.4*4135)t = 4135*219.1/2(13000*0.85+0.4*4135)Metric units:Metric units:

t = 4.0 mmt = 4.0 mmthen tthen tmm plus mill under run tolerance is plus mill under run tolerance is::

ttmm = 4.0 + 1.6 + 1.0 = 4.0 + 1.6 + 1.0(The 1.0 mm value is 12.5% mill under run tolerance of 8.2 mm nominal (The 1.0 mm value is 12.5% mill under run tolerance of 8.2 mm nominal

wall pipe expected to be purchase).wall pipe expected to be purchase).ttmm = 6.6 mm = 6.6 mm


U.S. customary unitsU.S. customary units::t =8.625*600/2(18900*0.85+0.4*600)t =8.625*600/2(18900*0.85+0.4*600)

t =0.159 incht =0.159 inch t tmm = 0.159 + 0.063 + 0.040 = 0.159 + 0.063 + 0.040

ttmm = 0.262 in = 0.262 in..

(The 0.04 inch value is 12.5% mill under run tolerance of (The 0.04 inch value is 12.5% mill under run tolerance of 0.322 inch nominal wall expected to be purchase).0.322 inch nominal wall expected to be purchase).

The next commercially available pipe wall is SCHEDULE The next commercially available pipe wall is SCHEDULE 40, with a nominal wall of 8.2 mm (0.322 in.).40, with a nominal wall of 8.2 mm (0.322 in.).

This is the wall to use for these stated conditions.This is the wall to use for these stated conditions.

Design of pressure componentsDesign of pressure componentsTest PressureTest Pressure

The hydrostatic test pressure at any point in the system The hydrostatic test pressure at any point in the system should be not less than 1.5 times the design pressure.should be not less than 1.5 times the design pressure.

For Temp. above 650F (343C), the min. test pressure PFor Temp. above 650F (343C), the min. test pressure PT T is is given by;given by;

PPT T = 1.5(S= 1.5(STT/S)(Design Pressure)/S)(Design Pressure)

SST T = allowable stress at 650F, = allowable stress at 650F,

S = allowable stress at design temperatureS = allowable stress at design temperature

QuestionsQuestions

..

Design of pressure componentsDesign of pressure componentsMiter BendsMiter Bends

..

Design of pressure componentsDesign of pressure componentsMiter BendsMiter Bends

Miter Bends have a pressure limitation, as calculated by equations Miter Bends have a pressure limitation, as calculated by equations (4a), (4b), or (4c) of paragraph 304.2.3 of B31 .3 which could derate (4a), (4b), or (4c) of paragraph 304.2.3 of B31 .3 which could derate a piping system. A miter is defined when the angle a piping system. A miter is defined when the angle αα is greater than is greater than 3 degrees at a weld as shown in Fig. 12.03 degrees at a weld as shown in Fig. 12.0....

Multiple miters are, whose angle of miter cut is less than 22.5 degrees, Multiple miters are, whose angle of miter cut is less than 22.5 degrees, limited to a pressure that will generate HOOP STRESSES not to limited to a pressure that will generate HOOP STRESSES not to exceed 50% of the yield strength of the material at temperature. exceed 50% of the yield strength of the material at temperature. This is done by restricting the maximum pressure to the lesser value This is done by restricting the maximum pressure to the lesser value as calculated by equations (4a) or (4b) in the codeas calculated by equations (4a) or (4b) in the code..

Single miters, or miters whose bend angle is greater than 22.5 degrees Single miters, or miters whose bend angle is greater than 22.5 degrees is limited to HOOP STRESSES of 20 % of the yield of the material is limited to HOOP STRESSES of 20 % of the yield of the material at temperature by equation (4c).at temperature by equation (4c).


Designers wishing to use miters in a system but do not wish to pay this Designers wishing to use miters in a system but do not wish to pay this pressure penalty can simply increase the wall thickness of the miter, pressure penalty can simply increase the wall thickness of the miter, thus reducing the HOOP STRESS to values less than the Code thus reducing the HOOP STRESS to values less than the Code limit. This technique seems straight forward, but one question limit. This technique seems straight forward, but one question remains, where does the miter start? The code provides a method remains, where does the miter start? The code provides a method to determine the distance the miter extends into the straight pipe. to determine the distance the miter extends into the straight pipe.

This distance is defined as M [ 304.2.3(c)], whereThis distance is defined as M [ 304.2.3(c)], where::

M = the larger of 2.5 x (r x T)M = the larger of 2.5 x (r x T)0.50.5 or tan ( or tan (θθ) x (R) x (R11- r- r22) ) as shown in Figure 12.0. as shown in Figure 12.0.

The T used in this equation is T less mill toleranceThe T used in this equation is T less mill tolerance..



An example of Miter Bend maximum allowable internal An example of Miter Bend maximum allowable internal pressure calculations per paragraph 304.2.3 for pressure calculations per paragraph 304.2.3 for өө =22.5° =22.5° and and өө = 30° is as follows: = 30° is as follows:

Calculate the maximum allowable internal pressure in a Calculate the maximum allowable internal pressure in a DN900, 9.5mm nominal wall (NPS 36, 0.375in. nominal DN900, 9.5mm nominal wall (NPS 36, 0.375in. nominal wall) miter bend constructed of A515 Gr 60 plate mat, wall) miter bend constructed of A515 Gr 60 plate mat, Temperature=260°C (500°F), c=2.5mm (0.10in.), E=1.0 Temperature=260°C (500°F), c=2.5mm (0.10in.), E=1.0 (fully radiographed), R1=1 .5D, r(fully radiographed), R1=1 .5D, r22=0.5(D=0.5(Doo-T). Mill -T). Mill tolerance=1.2 mm (0.047 in., 12tolerance=1.2 mm (0.047 in., 12½½ %). %).

A. For A. For θθ = 22.5º equation 4(a): = 22.5º equation 4(a):

PPmm= SE(T-c)/r= SE(T-c)/r22 * T-c/[(T-c)+0.643 tan * T-c/[(T-c)+0.643 tanθ√θ√(r(r22(T-c)](T-c)]

Design of pressure componentsDesign of pressure componentsMetric unitsMetric units::S = 119266 kPa, E = 1.0, T = 9.5 -1.2 = 8.3 mm, S = 119266 kPa, E = 1.0, T = 9.5 -1.2 = 8.3 mm, rr22 = 0.5(914.4-9.5) = 452.5 mm, then = 0.5(914.4-9.5) = 452.5 mm, then::

PPm m =(119266*5.8/452.5) * 5.8/[5.8+0.643tan(22.5)*√(452.5*5.8)=(119266*5.8/452.5) * 5.8/[5.8+0.643tan(22.5)*√(452.5*5.8)PPmm = 455 kPa = 455 kPa

Equation 4(a) using U.S. customary unitsEquation 4(a) using U.S. customary units::S = 17300 psi, E 1.0, T = .375 - .047 = .328, S = 17300 psi, E 1.0, T = .375 - .047 = .328, rr22 = 0.5(36 - .375) = 17.813, then = 0.5(36 - .375) = 17.813, then::

PPm m =(17300*0.228/17.813) * 0.228/[0.228+0.643tan(22.5)*√(17.813*0.228)=(17300*0.228/17.813) * 0.228/[0.228+0.643tan(22.5)*√(17.813*0.228)PPmm = 66 psig = 66 psig


Next test equation 4(b) with Next test equation 4(b) with θθ = 22.5° = 22.5°PPmm=SE(T-c)/r=SE(T-c)/r22* R* R11-r-r22/(R/(R11-0.5r-0.5r22))Metric unitsMetric units:: PPmm=119266x5.8/452.5 * (1373 - 452.5)/(1373 - 0.5 x 452.5)=119266x5.8/452.5 * (1373 - 452.5)/(1373 - 0.5 x 452.5) PPmm=1225 kPa=1225 kPa

U.S. customary unitsU.S. customary units:: PPmm=17300 x 0.228/17.813 * 54-17.813/ (54-0.5*17.813)=17300 x 0.228/17.813 * 54-17.813/ (54-0.5*17.813)

PPmm= 178 psig= 178 psig

As we usually consider the lesser value of the above calculations, the As we usually consider the lesser value of the above calculations, the multiple miter elbow with multiple miter elbow with θθ=22.5=22.5°, results in°, results in maximum allowable maximum allowable pressure to be 455 kPa (66 psig).pressure to be 455 kPa (66 psig).


B. For a miter fabricated using B. For a miter fabricated using θθ= 30= 30°° test using equation (4c): test using equation (4c):PPmm= SE(T-c)/r= SE(T-c)/r22 * T-c/[(T-c)+1.25 tan * T-c/[(T-c)+1.25 tanθθ √(r √(r22(t-c))](t-c))]

MetricMetric::PPmm= 119266*5.8/452.5 *5.8/[5.8+1.25*0.577*√(452.5x5.8)]= 119266*5.8/452.5 *5.8/[5.8+1.25*0.577*√(452.5x5.8)]

P = 205 kPaP = 205 kPaU.S. customary unitsU.S. customary units::

PPmm= 17300*0.228/17.813*0.= 17300*0.228/17.813*0.PPmm = 30 psig = 30 psig

The maximum pressure for this piping system containing a miter with The maximum pressure for this piping system containing a miter with θθ= 30= 30°° is 205 kPa (30 psig). is 205 kPa (30 psig).

If the maximum pressure of this system were greater than 205 kPa, (30 If the maximum pressure of this system were greater than 205 kPa, (30 psig), then the designer would have to either change psig), then the designer would have to either change θθ to a lesser to a lesser angle or increase the wall thickness of the miter and recalculate Pangle or increase the wall thickness of the miter and recalculate Pmm..

Design of pressure componentsDesign of pressure componentsBranch ConnectionBranch Connection


Branch ConnectionsBranch ConnectionsBranch connections are made in piping systems by any one of several Branch connections are made in piping systems by any one of several

methods. These could be tees, pad reinforced or unreinforced methods. These could be tees, pad reinforced or unreinforced intersections, crosses, integrally reinforced weld-on or weld-in intersections, crosses, integrally reinforced weld-on or weld-in contoured insert fittings, or extrusions. [ 304.3.1].contoured insert fittings, or extrusions. [ 304.3.1].

The philosophy of the code for intersections is centered around the The philosophy of the code for intersections is centered around the available pressure reinforcement offered by the geometry of the available pressure reinforcement offered by the geometry of the intersection. The process of making an intersection weakens the run intersection. The process of making an intersection weakens the run pipe by the opening that must be made in the run pipe. Unless the pipe by the opening that must be made in the run pipe. Unless the wall thickness of the run pipe is sufficiently in excess of that required wall thickness of the run pipe is sufficiently in excess of that required to sustain pressure at an intersection that is NOT manufactured in to sustain pressure at an intersection that is NOT manufactured in accordance with a LISTED STANDARD, it is necessary to provide accordance with a LISTED STANDARD, it is necessary to provide added reinforcement. This reinforcement is added metal, local to the added reinforcement. This reinforcement is added metal, local to the intersection, that is integral with the run and branch pipesintersection, that is integral with the run and branch pipes


The amount of required pressure reinforcement is determined by The amount of required pressure reinforcement is determined by performing AREA REPLACEMENT CALCULATIONS using the performing AREA REPLACEMENT CALCULATIONS using the design conditions established for the intersection. Area replacement design conditions established for the intersection. Area replacement calculations are not required for intersections using LISTED-RATED calculations are not required for intersections using LISTED-RATED or LISTED-UNRATED TEE INTERSECTIONS provided the or LISTED-UNRATED TEE INTERSECTIONS provided the intersection is used within the pressure-temperature bounds stated intersection is used within the pressure-temperature bounds stated in the LISTING STANDARD. Area Replacement calculations are not in the LISTING STANDARD. Area Replacement calculations are not required for UNLISTED TEE INTERSECTIONS provided the tee required for UNLISTED TEE INTERSECTIONS provided the tee component has successfully completed the requirements of component has successfully completed the requirements of paragraph 304.7.2, which areparagraph 304.7.2, which are::

1) duplicating a successful operating system1) duplicating a successful operating system,,2)2) experimental stress analysisexperimental stress analysis,,3)3) proof testproof test..



The branch & run angle between 45 and 90 deg. And the The branch & run angle between 45 and 90 deg. And the axes intersect.axes intersect.

The principle is that the area removed by the opening is The principle is that the area removed by the opening is added or accounted for as added reinforcement or excess added or accounted for as added reinforcement or excess area due to thickness above the pressure requirements.area due to thickness above the pressure requirements.

d1 = effective length removed from the run at the branch, d1 = effective length removed from the run at the branch, d1 = Db or d1 = [Db - (Tb-c) ] / sin d1 = Db or d1 = [Db - (Tb-c) ] / sin ββ

d2 = 1/2 the width of reinforcement zoned2 = 1/2 the width of reinforcement zoned2 = greater of d1 or [ (Tb – c) +(Th – c) +d1/2 ], but less d2 = greater of d1 or [ (Tb – c) +(Th – c) +d1/2 ], but less than Dhthan Dh


L4= height of reinforcement zone = smaller of L4= height of reinforcement zone = smaller of 2.5(Tb – c)+Tr and 2.5 (Th – c)2.5(Tb – c)+Tr and 2.5 (Th – c)

Dh: Outside diameter of headerDh: Outside diameter of header Db: Outside diameter of branchDb: Outside diameter of branch

th: header pressure design thicknessth: header pressure design thickness tb: branch pressure design thicknesstb: branch pressure design thickness

Th: header thickness minimum per purchase or minus mill Th: header thickness minimum per purchase or minus mill tolerancetoleranceTh: nominal wall thickness of headerTh: nominal wall thickness of header

Tb: branch thickness minimum per purchase or minus mill Tb: branch thickness minimum per purchase or minus mill tolerancetoleranceTb: nominal wall thickness of branchTb: nominal wall thickness of branch


Tr: thickness of reinforcement padTr: thickness of reinforcement pad

c: sum of mechanical (thread & groove), corrosion and erosion c: sum of mechanical (thread & groove), corrosion and erosion allowancesallowances

β: angle between the header and the branch axesβ: angle between the header and the branch axes

Required area A1 = th.d1.(2 - sin Required area A1 = th.d1.(2 - sin ββ))

A2: excess area in run =(2 d2 - d1) (Th – th - c)A2: excess area in run =(2 d2 - d1) (Th – th - c)

A3: excess area in branch = 2.L4 (Tb –tb – c) / sinA3: excess area in branch = 2.L4 (Tb –tb – c) / sinββ

A4: area provided by weld & area of reinforcement padA4: area provided by weld & area of reinforcement pad

A2+ A3 + A4 A2+ A3 + A4 ≥≥ A1 A1


Area replacement rules of B3 1.3 are valid for branch connections meeting Area replacement rules of B3 1.3 are valid for branch connections meeting the following conditionsthe following conditions::

1) the run pipe diameter to thickness ratio (D1) the run pipe diameter to thickness ratio (Dhh/T/Thh) is less than 100 and the ) is less than 100 and the branch to run diameter ratio (Dbranch to run diameter ratio (Dbb/D/Dhh) is not greater than 1.0.) is not greater than 1.0.

2)2) for run pipe with (Dfor run pipe with (Dhh/T/Thh) ≥100 ) ≥100 the branch diameter Db is less that one- the branch diameter Db is less that one- half the run diameter Dhalf the run diameter Dhh..

3) angle is between 45 and 90 degree.3) angle is between 45 and 90 degree.

4) the centerline axis of the branch intersects the centerline axis of the run4) the centerline axis of the branch intersects the centerline axis of the run..

Branch intersections that do not meet these conditions may be qualified by Branch intersections that do not meet these conditions may be qualified by proof testing or other means specified in paragraph 304.7.2 of the codeproof testing or other means specified in paragraph 304.7.2 of the code..


The required percent replaced area within the prescribed reinforcing The required percent replaced area within the prescribed reinforcing boundaries depends on the angle of the intersection. This percent boundaries depends on the angle of the intersection. This percent required area will range from 100% of the area removed, required area will range from 100% of the area removed,

th.d1.(2 - sin th.d1.(2 - sin ββ), ),

for a 90 intersection to about 130% required for 45 intersections. for a 90 intersection to about 130% required for 45 intersections.

The strength of an intersection grows increasingly weaker as the The strength of an intersection grows increasingly weaker as the branch angle branch angle ββ departs from 90. This increasing weakness in departs from 90. This increasing weakness in strength with decreasing 1 is accounted for by the term (2 - sin strength with decreasing 1 is accounted for by the term (2 - sin ββ) in ) in the required area equation. The change in required area for the required area equation. The change in required area for decreasing decreasing ββ, expressed in percent is illustrated in Figure 13, expressed in percent is illustrated in Figure 13..



An example of the area replacement rules, consider the following two An example of the area replacement rules, consider the following two 900 intersections, the first is an 900 intersections, the first is an UNREINFORCED FABRICATED UNREINFORCED FABRICATED TEETEE, the second is a , the second is a PAD REINFORCED FABRICATED TEEPAD REINFORCED FABRICATED TEE, (see , (see Figure 14.0). Both intersections are the same pipe sizes and have Figure 14.0). Both intersections are the same pipe sizes and have the same design conditions.the same design conditions.

Find the replaced area in the UNREINFORCED FABRICATED TEE for Find the replaced area in the UNREINFORCED FABRICATED TEE for the conditionsthe conditions::

Run pipe: DN 200 Nom. Wall 8.2 mm (NPS 8 Sch 40) ASTM A53 GrB. Run pipe: DN 200 Nom. Wall 8.2 mm (NPS 8 Sch 40) ASTM A53 GrB. Branch pipe: DN 100 Nom. Wall 6.0 mm (NPS 4 Sch 40 ASTM A53 Gr Branch pipe: DN 100 Nom. Wall 6.0 mm (NPS 4 Sch 40 ASTM A53 Gr

B SMLS B SMLS P = 4135 kPa (600 psig), T = 204º C (400º F), c = 2.5mm (0.10 in).P = 4135 kPa (600 psig), T = 204º C (400º F), c = 2.5mm (0.10 in).



Example Example A, metric area replacement calculation for an intersectionA, metric area replacement calculation for an intersection::DN 200, P = 8.2 mm x DN 100, T = 6.0 mm, UNREINFORCED FABRICATED DN 200, P = 8.2 mm x DN 100, T = 6.0 mm, UNREINFORCED FABRICATED

TEETEE..

I. NomenclatureI. Nomenclature. (Reference FIG. 304.3.3). (Reference FIG. 304.3.3)T=204ºC, P=4135kPa, c=2.5mmT=204ºC, P=4135kPa, c=2.5mmDDhh = 219.1 mm T = 219.1 mm Thh = 8.2 mm Header Material: A53 Gr B ERW E=0.85 = 8.2 mm Header Material: A53 Gr B ERW E=0.85DDbb = 114.3 mm T = 114.3 mm Tbb = 6.0 mm Branch Material: A53 Gr B SMLS E=1.0 = 6.0 mm Branch Material: A53 Gr B SMLS E=1.0

Material SE, Header: 117 MPa, Branch: 138 MPaMaterial SE, Header: 117 MPa, Branch: 138 MPaTThh = 7.2 = 7.2 TTbb = 5.2 = 5.2 (T - 12½ % mill tolerance)(T - 12½ % mill tolerance)d = Dd = Dbb – 2(T – 2(Tbb - c) = 114.3 - 2(5.2 - 2.5) = 108.9 mm - c) = 114.3 - 2(5.2 - 2.5) = 108.9 mmdd22 = the greater of d or (T = the greater of d or (Tbb - c) + (T - c) + (Thh - c) + d = 108.9 mm - c) + d = 108.9 mmLL4 4 == the lesser of 2.5(Tthe lesser of 2.5(Thh - c) or 2(T - c) or 2(Tbb - c) + T - c) + Trr LL44 = 2.5(5.2 - 2.5) + 0 = 6.7 mm = 2.5(5.2 - 2.5) + 0 = 6.7 mm


The pressure design thickness for the header and branch pipes, using The pressure design thickness for the header and branch pipes, using equation (3a):equation (3a):

t =(PxD)/2(SE+PxY); tt =(PxD)/2(SE+PxY); thh=3.8 mm t=3.8 mm tbb=7 mm=7 mm..II. Required AreaII. Required Area

AA11 = (t = (thhxdxdll)x(2-Sin()x(2-Sin(ββ)) =413.8mm)) =413.8mm22

III. Area Contributing to ReinforcementIII. Area Contributing to ReinforcementAA22 = (2xd = (2xd22-d-d11)*(T)*(Thh-t-thh- c) = 98 mm- c) = 98 mm

AA33 = 2*L = 2*L44(T(Tbb-t-tbb- c) = 13.4mm- c) = 13.4mmA = (area of additional metal, including weld metal, within the reinforcing A = (area of additional metal, including weld metal, within the reinforcing

zone, tzone, tcc = 4 mm) = 32 mm = 4 mm) = 32 mm22

AA55 = A = A22 + A + A33 + A + A44 =143.4 mm =143.4 mm

IV. PERCENT AREA REPLACEDIV. PERCENT AREA REPLACED = (A ) x 100 = 34% = (A ) x 100 = 34%


Example Example A intersection is not suitable for pressure design. Considering A intersection is not suitable for pressure design. Considering the percent replaced area is only about 33%, a reinforcing pad must the percent replaced area is only about 33%, a reinforcing pad must be added to the intersection and area replacement calculations are be added to the intersection and area replacement calculations are tested again as follows in example B. Had the above example tested again as follows in example B. Had the above example percent replaced area been very near the 100% minimum, possibly percent replaced area been very near the 100% minimum, possibly more weld metal could be added to obtain the 100% mark. The weld more weld metal could be added to obtain the 100% mark. The weld metal tested was the minimum as required by Para. 328.5.4 of the metal tested was the minimum as required by Para. 328.5.4 of the codecode..

The retest with the pad in example B yields about 200% replaced area, The retest with the pad in example B yields about 200% replaced area, the code requirements for pressure design of the intersection are the code requirements for pressure design of the intersection are satisfied. The pad was made from excess run pipe. The pad OD satisfied. The pad was made from excess run pipe. The pad OD selected for this intersection is 203.2 mm (8 inches).selected for this intersection is 203.2 mm (8 inches).


Example Example B, metric, intersection: DN 200, th=8.2 Nom. wall x DN 100, B, metric, intersection: DN 200, th=8.2 Nom. wall x DN 100, tb=6.0 mm Nom. wall, 900 PAD REINFORCED INTERSECTION, Pad tb=6.0 mm Nom. wall, 900 PAD REINFORCED INTERSECTION, Pad dimensions: Tdimensions: Trr = 8.2mm, dia = 203.2 mm. (Mill tol. 12.5%) = 8.2mm, dia = 203.2 mm. (Mill tol. 12.5%)

I. Nomenclature. (Reference FIG. 304.3.3)I. Nomenclature. (Reference FIG. 304.3.3)T = 204º C P = 4135 kPa c = 2.5 mm TT = 204º C P = 4135 kPa c = 2.5 mm T rr = (8.2 - 1.0) = 7.2 mm = (8.2 - 1.0) = 7.2 mmDDhh=219.1mm, T=219.1mm, Thh =8.2mm, Header Material: A53 Gr B ERW E=0.85 =8.2mm, Header Material: A53 Gr B ERW E=0.85DDbb =114.3mm, T =114.3mm, Tbb =6.0mm, Branch Material: A53 Gr B SMLS E=1.0 =6.0mm, Branch Material: A53 Gr B SMLS E=1.0

Material SE, Header:Material SE, Header: 117 MPa, Branch: 138 MPa 117 MPa, Branch: 138 MPaTThh = 7.2 mm = 7.2 mm TTb b = 5.2 mm= 5.2 mm (T-12.5%(T-12.5% mill tolerance)mill tolerance)dd11 = D = Dbb – 2(T – 2(Tbb - c) = 114.3 - 2(5.2 - 2.5) = 108.9 mm - c) = 114.3 - 2(5.2 - 2.5) = 108.9 mmdd22 = the greater of d or (T = the greater of d or (Tbb - c) + (T - c) + (Thh - c) + d = 108.9 mm - c) + d = 108.9 mmLL44 = the lesser of 2.5( T = the lesser of 2.5( Tbb - c ) or 2.5( T - c ) or 2.5( Tbb - c) + T - c) + Trr

LL44 = 2.5(7.2-2.5)= 11.7 mm = 2.5(7.2-2.5)= 11.7 mm


The pressure design thickness for header and branch pipes, calculated by The pressure design thickness for header and branch pipes, calculated by equation (3a):equation (3a):

t = (P x D)/2(SE + P x Y); tt = (P x D)/2(SE + P x Y); thh = 3.8 mm, t = 3.8 mm, tbb = 7 mm = 7 mmII. Required AreaII. Required AreaAA11 = (t = (thh x d x (2 - Sin ( x d x (2 - Sin (ββ)) = 413.8 mm)) = 413.8 mm22

III. Area Contributing to ReinforcementIII. Area Contributing to ReinforcementAA22 =(2*d =(2*d22-d-d11)*(T)*(Thh-t-thh-c) = 98mm-c) = 98mm22

AA33 =2*L =2*L44(T(Tbb - t - th h – c)=23.4 mm– c)=23.4 mm22

A = (area of PAD: 7.2(203.2 - 114.3) = 640 mmA = (area of PAD: 7.2(203.2 - 114.3) = 640 mm22 (pad OD = 203.2 mm), plus (pad OD = 203.2 mm), plus weld metal, (2tweld metal, (2tcc

22 + 0.51Tr + 0.51Tr22 = 68.9 mm = 68.9 mm22 within the reinforcing zone, within the reinforcing zone, t tcc = 4.2 mm) = 708.9 mm = 4.2 mm) = 708.9 mm22

AA55 = A = A22 + A + A33 + A + A44 = 830 mm = 830 mm

IV. PERCENT AREA REPLACEDIV. PERCENT AREA REPLACED = (A x 100 = 200% = (A x 100 = 200%

Questions Questions

BREAK BREAK

ŏ ŏŏ ŏΔΔºº

Pipe SupportingPipe Supporting

Pipe SupportingPipe Supporting The objective during the pipe supports design The objective during the pipe supports design

phase is to prevent the following:phase is to prevent the following:

• overstress of pipingoverstress of piping• leakage at jointsleakage at joints• overstress of supportsoverstress of supports• excessive forces on equipmentexcessive forces on equipment• excessive interference with thermal expansionexcessive interference with thermal expansion• excessive pipe sag (especially for piping requiring drain)excessive pipe sag (especially for piping requiring drain)• excessive heat flow, exposing support to temperature excessive heat flow, exposing support to temperature

outside their limitsoutside their limits• Etc..Etc..

Pipe SupportingPipe Supporting The purpose of pipe supports is to control the weight effects of the The purpose of pipe supports is to control the weight effects of the

piping system, as well as loads caused by pressure thrust, vibration, piping system, as well as loads caused by pressure thrust, vibration, wind, earthquake, shock, and thermal displacement. The weight wind, earthquake, shock, and thermal displacement. The weight effects to be considered shall be the greater of operating or hydro-effects to be considered shall be the greater of operating or hydro-test loadstest loads..

The B3 1.3 guidance for pipe support types and materials of The B3 1.3 guidance for pipe support types and materials of construction is presented in the B31 .3 TABLE 326.1 LISTED construction is presented in the B31 .3 TABLE 326.1 LISTED STANDARD, MSS SP-58. STANDARD, MSS SP-58.

The material selection for clamps and bolts, for example, is of The material selection for clamps and bolts, for example, is of particular importance in elevated temperature service. SP-58 particular importance in elevated temperature service. SP-58 assistance would be in the selection of a clamp material for example assistance would be in the selection of a clamp material for example in 750F (400C) service. in 750F (400C) service.

A review of the tables in SP-58 reveal that Carbon Steel clamp A review of the tables in SP-58 reveal that Carbon Steel clamp material would not be suitable, nor would the common type bolting, material would not be suitable, nor would the common type bolting, ASTM A307 used in clamps. ASTM A307 used in clamps.

The designer would be guided to use an alloy steel for the clamp The designer would be guided to use an alloy steel for the clamp such as ASTM A240 and ASTM A193-Grade B7 boltssuch as ASTM A240 and ASTM A193-Grade B7 bolts..

Pipe Supporting - SpanPipe Supporting - SpanPipe Support Span, based on deflectionPipe Support Span, based on deflection

Pipe support span is a decision that faces the designer in most pipe supporting Pipe support span is a decision that faces the designer in most pipe supporting jobs. As a guide to the selection of support spacing, the following equation jobs. As a guide to the selection of support spacing, the following equation based on permissible mid span deflection is offeredbased on permissible mid span deflection is offered..

The permissible mid-span deflection, y, concept is one technique commonly The permissible mid-span deflection, y, concept is one technique commonly selected for support spacing. This technique is based on a specified mid-selected for support spacing. This technique is based on a specified mid-span, y deflection of the supported pipe considering the pipe, contents, and span, y deflection of the supported pipe considering the pipe, contents, and insulation weights. The equation isinsulation weights. The equation is::

L= [y.E.I / 22.5.W]L= [y.E.I / 22.5.W]¼¼

wherewhere::L = pipe support spacing, feet, L = pipe support spacing, feet, y = permissible mid-span deflection, inchesy = permissible mid-span deflection, inchesE = modulus of elasticity at design temperature, lb/in (TABLE C-6E = modulus of elasticity at design temperature, lb/in (TABLE C-6((I = moment of inertia of pipeI = moment of inertia of pipe..W = weight of supported pipe, including pipe, contents, insulation, lb/ftW = weight of supported pipe, including pipe, contents, insulation, lb/ft..

Pipe Supporting - SpanPipe Supporting - Span

Pipe Support Span, based on stressPipe Support Span, based on stress

As a guide to the selection of support spacing, the following equation As a guide to the selection of support spacing, the following equation based on permissible stress is offeredbased on permissible stress is offered..

The permissible mid-span deflection, y, concept is one technique The permissible mid-span deflection, y, concept is one technique commonly selected for support spacing. This technique is based on commonly selected for support spacing. This technique is based on stress of supported pipe material considering the pipe, contents, stress of supported pipe material considering the pipe, contents, and insulation weights. The equation isand insulation weights. The equation is::

L= [0.33.Z.Sh / W]1/2L= [0.33.Z.Sh / W]1/2wherewhere::L = pipe support spacing, feet, L = pipe support spacing, feet, Z = section modulus, in3Z = section modulus, in3Sh = Allowable tensile stress for pipe materialat design temp., psiSh = Allowable tensile stress for pipe materialat design temp., psiW = weight of supported pipe, including pipe, contents, insulation, lb/ftW = weight of supported pipe, including pipe, contents, insulation, lb/ft..

Pipe Supporting - SpanPipe Supporting - Span

Pipe Supporting - SpanPipe Supporting - SpanAn example of the deflection pipe span approach isAn example of the deflection pipe span approach is::What is the span of a seamless ASTM A106 Grade B, 6.625 inch OD, 0.28 inch wall What is the span of a seamless ASTM A106 Grade B, 6.625 inch OD, 0.28 inch wall

thick, water filled pipe with 3 inch of insulation with a design temperature of 400 F? thick, water filled pipe with 3 inch of insulation with a design temperature of 400 F? The specifications limit the mid-span deflection to 0.25 inchThe specifications limit the mid-span deflection to 0.25 inch..

SolutionSolution::Determine the uniform load, pounds per footDetermine the uniform load, pounds per foot..Pipe = 19.0 lbs per ftPipe = 19.0 lbs per ftWater = 12.5 lbs per ftWater = 12.5 lbs per ftInsulation = 7.6 lbs per ft ( 85 % Magnesia Calcium Silicate) Insulation = 7.6 lbs per ft ( 85 % Magnesia Calcium Silicate) then ,W = 39.1 lb per ftthen ,W = 39.1 lb per ftI = ( I = ( ππ /64)(D /64)(Doo

44 – D – Dii44), D), Doo = 6.625, D = 6.625, Dii = 6.065 = 6.065

I = 28.14 inI = 28.14 in44

E = 27.7 x 106 psi, Table C-6, C ≤ 0.3 at 400°FE = 27.7 x 106 psi, Table C-6, C ≤ 0.3 at 400°F..finally, L = [ 0.25x27.7x10finally, L = [ 0.25x27.7x1066 x28.14/(17. 1x39. 1)] x28.14/(17. 1x39. 1)]1/41/4

L = 23 feet spanL = 23 feet spanThe pipe support spacing would be 23 feet with a mid span deflection of 1/4 inchThe pipe support spacing would be 23 feet with a mid span deflection of 1/4 inch..

Pipe Supporting - DrainagePipe Supporting - Drainage

DrainageDrainage

Piping systems should be installed to drain by gravity, in direction of Piping systems should be installed to drain by gravity, in direction of normal flow.normal flow.

Each span must be pitched so that the outlet will be lower than the Each span must be pitched so that the outlet will be lower than the maximum sag of the pipe.maximum sag of the pipe.

The pitch of pipe spans is the ratio between the drop in elevation and The pitch of pipe spans is the ratio between the drop in elevation and the length of span. It is called the average gradient and is expressed the length of span. It is called the average gradient and is expressed in inches per foot or mm per meter run.in inches per foot or mm per meter run.

Gradient check for drainage;Gradient check for drainage;G = drop in elevation / span (in/ft.)G = drop in elevation / span (in/ft.)

While, condition for good drainage;While, condition for good drainage;G ≤ 4(maximum deflection) / spanG ≤ 4(maximum deflection) / span

QuestionsQuestions

Pipe Supports & HangersPipe Supports & Hangers Support Selection & DesignSupport Selection & Design

• Selection and design of pipe hangers is an important part of the Selection and design of pipe hangers is an important part of the engineering study. High temperature, high pressure pipes are critical engineering study. High temperature, high pressure pipes are critical to a point that early in the basic design phase supports locations and to a point that early in the basic design phase supports locations and loads have to be decided upon. Concentrated hanger loads on loads have to be decided upon. Concentrated hanger loads on structures, buildings and their effect on equipment have to be well structures, buildings and their effect on equipment have to be well known from the very beginning of the project.known from the very beginning of the project.

• Basic information has to collected before proceeding with calculations Basic information has to collected before proceeding with calculations and detailing of pipe supports, as follows;and detailing of pipe supports, as follows;- A complete set of piping drawings- A complete set of piping drawings- A complete set of steel and structural drawings/ data.- A complete set of steel and structural drawings/ data.- A complete set of drawings showing locations of ventilating ducts, - A complete set of drawings showing locations of ventilating ducts, electrical cable trays, equipment locations (pumps, tanks, etc)electrical cable trays, equipment locations (pumps, tanks, etc)- A complete set of piping specifications and data.- A complete set of piping specifications and data.- Insulation specification.- Insulation specification.- Movement of all critical equipment connections such as boiler - Movement of all critical equipment connections such as boiler headers, steam drums, turbine connections, etc..headers, steam drums, turbine connections, etc..- The results of stress, flexibility, and movement calculations - The results of stress, flexibility, and movement calculations performed for critical systems.performed for critical systems.

Pipe Supports & HangersPipe Supports & HangersApplying the previously mentioned basic info shall be in the following Applying the previously mentioned basic info shall be in the following

steps;steps;- The determination of hanger locations.- The determination of hanger locations.- Determination of the thermal movement of the piping at each - Determination of the thermal movement of the piping at each hanger location.hanger location.- The calculation of hanger loads.- The calculation of hanger loads.- The selection of hanger types, spring assembly, either constant - The selection of hanger types, spring assembly, either constant support type, variable support or rigid support type.support type, variable support or rigid support type.- Checking of clearances between the hanger components and - Checking of clearances between the hanger components and nearby piping, electrical cable trays, conduits, ventilating ducts, nearby piping, electrical cable trays, conduits, ventilating ducts, equipment, etc.equipment, etc.

Recognizing that each new piping design presents an abundance of Recognizing that each new piping design presents an abundance of new problems to the engineer, no attempt is made to state fixed new problems to the engineer, no attempt is made to state fixed rules and limits which would be applicable to every hanger design, rules and limits which would be applicable to every hanger design, only guidance to ideas to solve simple practical support problems.only guidance to ideas to solve simple practical support problems.

Pipe Supports & HangersPipe Supports & Hangers Support DesignSupport Design

• Restraints (anchors and guides) are provided to direct Restraints (anchors and guides) are provided to direct thermal expansion to areas designed to absorb it and to thermal expansion to areas designed to absorb it and to ensure that expansion joint movements occur in the ensure that expansion joint movements occur in the directions for which the joint is designed. Expansion joint directions for which the joint is designed. Expansion joint design shall conform to the requirements of Appendix X, design shall conform to the requirements of Appendix X, which provides guidelines for the design, fabrication and which provides guidelines for the design, fabrication and installation of bellow type expansion joints.installation of bellow type expansion joints.

• Supports’ elements shall be designed for all loads Supports’ elements shall be designed for all loads applied including weight, pressure, wind, earthquakes, applied including weight, pressure, wind, earthquakes, friction …etcfriction …etc

Pipe Supports & HangersPipe Supports & Hangers

• Spring supports are designed to carry the Spring supports are designed to carry the weight loads and prevent misalignment, weight loads and prevent misalignment, buckling, eccentric loading and unintentional buckling, eccentric loading and unintentional disengagement of the load. Spring supports disengagement of the load. Spring supports should be provided with position indicators.should be provided with position indicators.

• Constant supports of the counterweight and Constant supports of the counterweight and hydraulic types should be provided with safety hydraulic types should be provided with safety devices and stops.devices and stops.

Pipe Supports & HangersPipe Supports & Hangers

• Integral attachments such as plugs, ears, shoes, plates,Integral attachments such as plugs, ears, shoes, plates,…etc, are designed to minimize localized stresses, stress …etc, are designed to minimize localized stresses, stress concentration in cyclic service and any harmful concentration in cyclic service and any harmful temperature gradient. The material should be of good temperature gradient. The material should be of good quality and all requirements of the Code for welding, quality and all requirements of the Code for welding, preheating and post-weld heat treatment should apply. preheating and post-weld heat treatment should apply. Reinforcement by pad and complete encirclement Reinforcement by pad and complete encirclement reinforcement shall be used to distribute stresses and reinforcement shall be used to distribute stresses and reduce heat effect in alloy piping.reduce heat effect in alloy piping.

• Non-integral attachments include clamps, U-bolts, Non-integral attachments include clamps, U-bolts, cradles, saddles, straps, clevises. For vertical pipe cradles, saddles, straps, clevises. For vertical pipe weight support, the clamp should be located below a weight support, the clamp should be located below a flange or fitting or a welded lug.flange or fitting or a welded lug.

Hangers ExampleHangers Example

Example Problem:Example Problem:

1-Problem Description.1-Problem Description.

2-Thermal movement calculations.2-Thermal movement calculations.

3-Hanger Load Calculations.3-Hanger Load Calculations.

4-Selection of proper hangers.4-Selection of proper hangers.


Hangers Example, MovementHangers Example, Movement


Hangers Example, MovementHangers Example, Movement

Hanger SupportsHanger Supports

Rod Hanger AssemblyRod Hanger Assembly

Rod Hanger AssemblyRod Hanger Assembly

The pipe attachment and the structural beam The pipe attachment and the structural beam attachment of a rod hanger assembly should attachment of a rod hanger assembly should allow the hanger to swing to allow for lateral allow the hanger to swing to allow for lateral movement of the pipe where there is horizontal movement of the pipe where there is horizontal pipe expansion. It should be noted that horizontal pipe expansion. It should be noted that horizontal movement of the hanger will result in a vertical movement of the hanger will result in a vertical movement as shown previous slide. The movement as shown previous slide. The subsequent horizontal forces should be checked.subsequent horizontal forces should be checked.

Variable Hanger AssemblyVariable Hanger Assembly

Variable Hanger SupportsVariable Hanger Supports

Variable spring hangers are recommended for general use in non Variable spring hangers are recommended for general use in non critical piping and where vertical movement is small on critical critical piping and where vertical movement is small on critical piping.piping.

Acceptable practice is limit amount of supporting force variation Acceptable practice is limit amount of supporting force variation (difference between hot load and as installed-cold load) to 25% for (difference between hot load and as installed-cold load) to 25% for critical piping systems on horizontal piping.critical piping systems on horizontal piping.

The amount of variation can be calculated by multiplying the The amount of variation can be calculated by multiplying the spring scale in lb/inch (Kg/mm) by the amount of vertical spring scale in lb/inch (Kg/mm) by the amount of vertical expansion in inches (mm).expansion in inches (mm).

The main problem with variable spring hangers is that this The main problem with variable spring hangers is that this variation in load must go somewhere, it is transferred to the variation in load must go somewhere, it is transferred to the nearest restraint or equipment which may cause damage both to nearest restraint or equipment which may cause damage both to the equipment and/ or piping system.the equipment and/ or piping system.

Variable Hanger SupportsVariable Hanger Supports Calculating the variability in accordance with MSS SP-58:Calculating the variability in accordance with MSS SP-58:

Var. = (Hot load – Cold load)/Hot load x 100Var. = (Hot load – Cold load)/Hot load x 100

The load margin between the maximum load, either hot or The load margin between the maximum load, either hot or cold, and the load at the maximum limit of the operating cold, and the load at the maximum limit of the operating range must also be considered. This load margin should be range must also be considered. This load margin should be greater than the weight of the hanger hardware that is greater than the weight of the hanger hardware that is supported by the spring, ex. Clamps and hanger rods used supported by the spring, ex. Clamps and hanger rods used to connect the piping to the spring. If the total piping loads to connect the piping to the spring. If the total piping loads plus the load of the supported hanger hardware cannot be plus the load of the supported hanger hardware cannot be accommodated within the spring hangers operating range accommodated within the spring hangers operating range an alternate spring hanger design should be considered.an alternate spring hanger design should be considered.

Constant Load SupportConstant Load Support Constant support hangers provide constant supporting force for piping Constant support hangers provide constant supporting force for piping throughout its full range of vertical expansion and contraction.throughout its full range of vertical expansion and contraction.

Constant Load SupportConstant Load Support This is accomplished by the use of a helical coil spring This is accomplished by the use of a helical coil spring

working in conjunction with a bell crank lever in such a way working in conjunction with a bell crank lever in such a way that the spring force times its distance to the lever pivot is that the spring force times its distance to the lever pivot is always equal to the pipe load times its distance to the lever always equal to the pipe load times its distance to the lever pivot.pivot.

For use when the variation in a variable spring hanger is For use when the variation in a variable spring hanger is above 25%.above 25%.

The variation is transferred to the closest restraint or The variation is transferred to the closest restraint or equipment and, in the case of equipment,. This increase in equipment and, in the case of equipment,. This increase in the load and/ or moment on the nozzle may cause the load and/ or moment on the nozzle may cause structural damage. In such cases a constant load hanger structural damage. In such cases a constant load hanger would be selected.would be selected.

Because of it’s constant load effect the constant support Because of it’s constant load effect the constant support hanger is used where it is desirable to prevent pipe weight hanger is used where it is desirable to prevent pipe weight load or expansion loads being transferred to connected load or expansion loads being transferred to connected equipment or adjacent supports or hangers. Therefore they equipment or adjacent supports or hangers. Therefore they are used for the support of critical piping systems.are used for the support of critical piping systems.

Constant Load HangerConstant Load Hanger

Spring HangersSpring Hangers

Spring Hangers ExampleSpring Hangers Example Returning back to our Example:Returning back to our Example:

Difference in effect in using a variable spring as compared to a Difference in effect in using a variable spring as compared to a constant spring support hanger, as per Fig. H-1, page 157.constant spring support hanger, as per Fig. H-1, page 157.

Load for Hanger H-1 was calculated as 5363lb.Load for Hanger H-1 was calculated as 5363lb. Vertical movement at H-1 was 2.41 inches up, from the cold to the hot Vertical movement at H-1 was 2.41 inches up, from the cold to the hot

position of the pipe.position of the pipe. Amount of variation is 1500lb/in x 2.41in.=3615lb, while the hot load Amount of variation is 1500lb/in x 2.41in.=3615lb, while the hot load

was 5363lb, so as the direction of movement from cold to hot is was 5363lb, so as the direction of movement from cold to hot is upward, the cold load is 5363lb + 3615lb, or 8978lb.upward, the cold load is 5363lb + 3615lb, or 8978lb.

Pipe weight does not change throughout it’s cold to hot cycle, while Pipe weight does not change throughout it’s cold to hot cycle, while the supporting force varies.the supporting force varies.

Thus the hanger would exert an unbalanced force on the pipe equal to Thus the hanger would exert an unbalanced force on the pipe equal to the amount of variation, or 3615lb. the amount of variation, or 3615lb.

Most of this force would be imposed directly on connection A., where Most of this force would be imposed directly on connection A., where limits are established for the force which maybe applied.limits are established for the force which maybe applied.

Changing the spring scale to lower the variability still imposes a high Changing the spring scale to lower the variability still imposes a high force on A.force on A.

Appropriate hanger support type for H-1 is a constant support. The Appropriate hanger support type for H-1 is a constant support. The hanger will be calibrated to the calculated pipe weight, so it’s hanger will be calibrated to the calculated pipe weight, so it’s supporting force would be 5363 lb at cold position, and 5363lb also at supporting force would be 5363 lb at cold position, and 5363lb also at hot position.hot position.

Selection of Pipe supporting Selection of Pipe supporting DevicesDevices

Piping Systems: Temperature classification. Piping Systems: Temperature classification. Piping systems, are divided into the three main temperature Piping systems, are divided into the three main temperature

categories in order to provide a basis for the selection of hangers, categories in order to provide a basis for the selection of hangers, anchors, or supports.anchors, or supports.

1. Hot systems1. Hot systemsa.a. The temperature range is from 120F (50C) to 450F (230C). Typical The temperature range is from 120F (50C) to 450F (230C). Typical

examples are low-pressure steam, hot water and certain process examples are low-pressure steam, hot water and certain process piping.piping.

b.b. The temperature range is from 450F (230C) to 650F (340C). The temperature range is from 450F (230C) to 650F (340C). Typical examples are boiler plant and industrial steam and hot-Typical examples are boiler plant and industrial steam and hot-water piping systems.water piping systems.

c.c. The temperature ranges from 750F (400C) and higher. A typical The temperature ranges from 750F (400C) and higher. A typical example is a high-pressure steam power-plant piping systemexample is a high-pressure steam power-plant piping system

d.d. In the temperature range 650F and higher, there is the possibility In the temperature range 650F and higher, there is the possibility of metallurgical change if unalloyed carbon steel is used. It is of metallurgical change if unalloyed carbon steel is used. It is suggested that hangers, anchors, and supports for piping which suggested that hangers, anchors, and supports for piping which operates at above 650 F be of materials at least equal to those of operates at above 650 F be of materials at least equal to those of the piping system itself.the piping system itself.


2. Ambient systems in which the contents of the pipe are not 2. Ambient systems in which the contents of the pipe are not heated or cooled by mechanical means. Temperatures heated or cooled by mechanical means. Temperatures would range up to 120 F. Plant air and service water would would range up to 120 F. Plant air and service water would be typical systemsbe typical systems

3. Cold systems3. Cold systemsa.a. The temperatures range upward from 32 F. A typical The temperatures range upward from 32 F. A typical

example would be chilled water pipingexample would be chilled water pipingb.b. The temperature ranges downward from 32 to minus 20F, The temperature ranges downward from 32 to minus 20F,

as in brine systemsas in brine systemsc.c. Below minus 20 F, as in cryogenic systemsBelow minus 20 F, as in cryogenic systems


..


Pipe Attachments. Hangers for the various systems described above Pipe Attachments. Hangers for the various systems described above may be selected from fig.11 in accordance with the following may be selected from fig.11 in accordance with the following recommendations:recommendations:

For Type 1a systems, hangers Types 1 and 3 through 12 are used. For Type 1a systems, hangers Types 1 and 3 through 12 are used. Rollers should be types 41 through 47 with appropriate saddles of Rollers should be types 41 through 47 with appropriate saddles of Type 39, items 1 and 2. Supports would be Types 35 through 38.Type 39, items 1 and 2. Supports would be Types 35 through 38.

For Type 1b systems, hangers Types 1, 3, 4 and 8 are used. Rollers For Type 1b systems, hangers Types 1, 3, 4 and 8 are used. Rollers should be types 41 through 47 with appropriate saddles of Type should be types 41 through 47 with appropriate saddles of Type 39, items 1 and 2. 39, items 1 and 2.

For Type 1c systems, alloy hangers are used as required by the line For Type 1c systems, alloy hangers are used as required by the line temperature. Hangers should be of Types 2, 3, or 8 with saddles of temperature. Hangers should be of Types 2, 3, or 8 with saddles of Type 39, items 1 or 2, and the rollers of Types 41 through 47Type 39, items 1 or 2, and the rollers of Types 41 through 47


For Type 2 systems, hangers can be of Types 1 and 3 through 12 with For Type 2 systems, hangers can be of Types 1 and 3 through 12 with supports of Types 24, 26, and 35 through 38supports of Types 24, 26, and 35 through 38

For Type 3 systems, the hanger of support must be outside the For Type 3 systems, the hanger of support must be outside the insulation and the vapor barrier must be left undisturbed.insulation and the vapor barrier must be left undisturbed.

A Type 40 insulation protection shield must be used to distribute the A Type 40 insulation protection shield must be used to distribute the loading on the insulation. Hangers sized for the outside diameter loading on the insulation. Hangers sized for the outside diameter of the insulation can be of Type 1, 4, 6, 7, 9, 10, or 11. For the of the insulation can be of Type 1, 4, 6, 7, 9, 10, or 11. For the Type 3c systems, special consideration must be given to the type Type 3c systems, special consideration must be given to the type and nature of the piping and its layout.and nature of the piping and its layout.

Consideration may be given to the use of the welded lug Consideration may be given to the use of the welded lug attachments. Where used on Types 1c and 3c, the welded attachments. Where used on Types 1c and 3c, the welded attachment must be of an alloy material which is compatible with attachment must be of an alloy material which is compatible with the material of the piping system itself.the material of the piping system itself.


Spring supports;Spring supports; For systems which operate at temperatures below 750F, a For systems which operate at temperatures below 750F, a

good rule is that the variation in supporting force be limited good rule is that the variation in supporting force be limited to 25% of the load. When the suggestions are followed for to 25% of the load. When the suggestions are followed for stress limits set forth in MSS SP-58, para 11, and ASTM stress limits set forth in MSS SP-58, para 11, and ASTM specification A125, springs to suit specific conditions may specification A125, springs to suit specific conditions may be designed. be designed.

However, the price of a specially designed spring includes However, the price of a specially designed spring includes engineering and setup charges, and unless a large quantity engineering and setup charges, and unless a large quantity of a particular size is to used, it is not economical to design of a particular size is to used, it is not economical to design special individual springs, and a more prudent approach is special individual springs, and a more prudent approach is to select spring devices which are available commercially.to select spring devices which are available commercially.


Vibration arising from pump pulse, compressor and similar Vibration arising from pump pulse, compressor and similar conditions is a problem in piping systems. Such conditions can be conditions is a problem in piping systems. Such conditions can be avoided by use of commercially available spring supports. avoided by use of commercially available spring supports. Systems that respond to exciting vibrations can be controlled Systems that respond to exciting vibrations can be controlled satisfactorily by the use of dampening device. There are two satisfactorily by the use of dampening device. There are two general types to consider; the coiled spring and the hydraulic general types to consider; the coiled spring and the hydraulic vibration dampener.vibration dampener.

There are two types of coiled-spring vibration dampeners; the There are two types of coiled-spring vibration dampeners; the opposed-spring type and the double acting spring type (type50). opposed-spring type and the double acting spring type (type50). These types should be arranged so that the springs are in the These types should be arranged so that the springs are in the neutral position during normal operating conditions of the system.neutral position during normal operating conditions of the system.

The hydraulic vibration control is a unit which operates by means The hydraulic vibration control is a unit which operates by means of a controlled flow of fluid through an orifice. Resistance to of a controlled flow of fluid through an orifice. Resistance to movement increases with the speed of displacement. One distinct movement increases with the speed of displacement. One distinct advantage of the hydraulic device is that there is a min. of advantage of the hydraulic device is that there is a min. of resistance to thermal movement of the piping.resistance to thermal movement of the piping.

Both spring and hydraulic cylinder devices may be used to control Both spring and hydraulic cylinder devices may be used to control sway and absorb shocks.sway and absorb shocks.


Hanger Rod;Hanger Rod; Rod used for pipe support purposes is usually hot rolled Rod used for pipe support purposes is usually hot rolled

steel with cut threads conforming to National Bureau of steel with cut threads conforming to National Bureau of Standards Handbook H-2 Class 2A, for the coarse thread Standards Handbook H-2 Class 2A, for the coarse thread series. Rolled threads to the same standard may be used. It series. Rolled threads to the same standard may be used. It must be pointed out that the length of a rolled thread must be pointed out that the length of a rolled thread cannot be increased by running a die over it, since the cannot be increased by running a die over it, since the basic diameter of the rod is less than the size of the basic diameter of the rod is less than the size of the threaded portion.threaded portion.

Safe load capacities of rods are based on the area at the Safe load capacities of rods are based on the area at the root of the thread. A generally accepted standard for such root of the thread. A generally accepted standard for such capacities is given in table 5, taken from MSS SP-58.capacities is given in table 5, taken from MSS SP-58.


..


In addition to supporting gravitaton loads, the designer must also In addition to supporting gravitaton loads, the designer must also be concerned with the provision of a suitable system of anchors, be concerned with the provision of a suitable system of anchors, guides, restraints, stops, and braces to control intended guides, restraints, stops, and braces to control intended movement, maintain piping position, and protect equipment from movement, maintain piping position, and protect equipment from possible excessive loading shock forces.possible excessive loading shock forces.

The layout of each system section of piping should be reviewed, The layout of each system section of piping should be reviewed, taking note of such factors as configuration branches, expansion taking note of such factors as configuration branches, expansion joints and loops, pipe sizes, terminal connections, relation stiffness joints and loops, pipe sizes, terminal connections, relation stiffness of each leg in all planes, and system operating conditions. of each leg in all planes, and system operating conditions.

The digestion of all these factors, coupled with visualization of the The digestion of all these factors, coupled with visualization of the normal thermal movement of the system under consideration, normal thermal movement of the system under consideration, enables an evaluation of the specific requirements necessary to enables an evaluation of the specific requirements necessary to assure positive control during all phases of operation.assure positive control during all phases of operation.


Anchors and restraints may be required to establish definite Anchors and restraints may be required to establish definite movement patterns, counteract thrust forces, or, as in the case of movement patterns, counteract thrust forces, or, as in the case of vibration-imposing equipment used to prevent transmittal and vibration-imposing equipment used to prevent transmittal and possible build-up of vibration throughout the entire system. Specific possible build-up of vibration throughout the entire system. Specific examples are the need for properly located anchors in a steam examples are the need for properly located anchors in a steam distribution system to prevent overloading of the smaller branches, distribution system to prevent overloading of the smaller branches, anchors and guides, to actuate and align expansion joints and loops anchors and guides, to actuate and align expansion joints and loops properly, and restraints of fixed points in the vicinity of compressor properly, and restraints of fixed points in the vicinity of compressor equipment or quick-closing control valves. Long straight runs or equipment or quick-closing control valves. Long straight runs or sections of piping that are obviously weak in some plane may require sections of piping that are obviously weak in some plane may require additional guiding or bracing to provide lateral structure stability.additional guiding or bracing to provide lateral structure stability.

As in the case of all applications of anchors and guides, the overall As in the case of all applications of anchors and guides, the overall installation must provide sufficient flexibility to accommodate thermal installation must provide sufficient flexibility to accommodate thermal growth. For sections where the movement does not permit the use of growth. For sections where the movement does not permit the use of rigid struts, guides with sufficient clearance to accommodate the rigid struts, guides with sufficient clearance to accommodate the normal movement may suffice by limiting the displacement. Positive normal movement may suffice by limiting the displacement. Positive strut action can be obtained at points subject to movement through strut action can be obtained at points subject to movement through the use of special devices such as hydraulic snubbers.the use of special devices such as hydraulic snubbers.


Risers are equivalent to concentrated loads; however, in the Risers are equivalent to concentrated loads; however, in the support of the load, several important points must be support of the load, several important points must be considered. These are:considered. These are:

1.1. Is the support to take the entire riser weight, or is this weight Is the support to take the entire riser weight, or is this weight to be distributed among several supports?to be distributed among several supports?

2.2. Are the hydrostatic-test conditions more severe than service Are the hydrostatic-test conditions more severe than service conditions; that is; will the cold-water-filled condition impose conditions; that is; will the cold-water-filled condition impose stresses on the support higher than allowable (in cold stresses on the support higher than allowable (in cold condition) as compared with hot operating condition and the condition) as compared with hot operating condition and the imposed stresses? When this decision is made, the system imposed stresses? When this decision is made, the system erection sequence should be considered and a determination erection sequence should be considered and a determination made whether other supports are effective or ineffective during made whether other supports are effective or ineffective during hydrostatic testing.hydrostatic testing.


3. Is the support to be located at a point of zero vertical 3. Is the support to be located at a point of zero vertical movement and hence to be considered a rigid support? If this movement and hence to be considered a rigid support? If this is the case, then the horizontal and flexural movements must is the case, then the horizontal and flexural movements must be analyzed. Pure horizontal movement can be provided for be analyzed. Pure horizontal movement can be provided for long support rods which are allowed to swing. However, if long support rods which are allowed to swing. However, if flexural movement exists, it may cause tipping, and then must flexural movement exists, it may cause tipping, and then must be assumed that the entire load can transfer to one support be assumed that the entire load can transfer to one support rod. In this case, the riser support must be designed for double rod. In this case, the riser support must be designed for double the calculated load.the calculated load.

Guide SupportsGuide Supports

Guide SupportsGuide Supports

Limit stop SupportsLimit stop Supports

Supports FrictionSupports Friction

Restraint SupportsRestraint Supports

Limit stop SupportsLimit stop Supports

Pipe Rack SupportsPipe Rack Supports

BREAKBREAK

QUESTIONS QUESTIONS

ŏ ŏŏ ŏΔΔºº

Stiffness & FlexibilityStiffness & Flexibility Prismatic member, straight members of uniform cross Prismatic member, straight members of uniform cross

sectional area. They are the building blocks of structural sectional area. They are the building blocks of structural engineering and also piping software packages. Assuming engineering and also piping software packages. Assuming that the displacements are small, so that shortening of the that the displacements are small, so that shortening of the beam due to bending, may be ignored.beam due to bending, may be ignored.

Each member has it’s own “local” axis which do not Each member has it’s own “local” axis which do not coincide with the axis for other members of the structure. It coincide with the axis for other members of the structure. It is thus assumed that a force applied in any one principal is thus assumed that a force applied in any one principal plane causes displacements in that plane only and that the plane causes displacements in that plane only and that the shear centre coincides with the centroid of the member.shear centre coincides with the centroid of the member.

There is a possibility of three linear displacements and There is a possibility of three linear displacements and three rotations at each end of the member. There are thus three rotations at each end of the member. There are thus 12 possible displacement components for each member, or 12 possible displacement components for each member, or 12 degrees of freedom. Associated with each displacement 12 degrees of freedom. Associated with each displacement there is a corresponding force or moment.there is a corresponding force or moment.

Stiffness & FlexibilityStiffness & Flexibility

The result of the derivation section can be summarized in a single The result of the derivation section can be summarized in a single matrix equation for member stiffness as follows;matrix equation for member stiffness as follows;

[F] = [K] [X][F] = [K] [X] This is the member stiffness equation, F & X are 12-term vectors of This is the member stiffness equation, F & X are 12-term vectors of

member force and displacement respectively, and k is a 12x12 member force and displacement respectively, and k is a 12x12 member stiffness matrix. This is the stiffness matrix for the most member stiffness matrix. This is the stiffness matrix for the most general case of a prismatic member in space neglecting shear and general case of a prismatic member in space neglecting shear and with the implicit condition that the deformations are so small as to with the implicit condition that the deformations are so small as to leave the basic geometry unchanged.leave the basic geometry unchanged.

Not all structural members require the full 12 degrees of freedom to Not all structural members require the full 12 degrees of freedom to express their deformations. Since a member in space can have no express their deformations. Since a member in space can have no moments transmitted to it through it’s hinged ends, it’s moments transmitted to it through it’s hinged ends, it’s deformation depends only on the three linear displacements at deformation depends only on the three linear displacements at each end, giving it a total of six degrees of freedom.each end, giving it a total of six degrees of freedom.

It is important to note the symmetry of the member stiffness matrix It is important to note the symmetry of the member stiffness matrix k.k.

Stiffness & FlexibilityStiffness & Flexibility Transformation of axis;Transformation of axis;The system of axis for a prismatic member is a local axis system. The The system of axis for a prismatic member is a local axis system. The

x-axis is defined as coinciding with the centroidal line of the x-axis is defined as coinciding with the centroidal line of the member. In a structure with many members there would thus be member. In a structure with many members there would thus be as many systems of axes. Before the internal actions in the as many systems of axes. Before the internal actions in the members of the structure can be related, all forces and deflections members of the structure can be related, all forces and deflections can be stated in terms of one single system of axes common to all can be stated in terms of one single system of axes common to all the – structure “global” axes.the – structure “global” axes.

The directional cosines matrix can therefore be thought of as the 3x3 The directional cosines matrix can therefore be thought of as the 3x3 rotation matrix Ro. Thus any quantity can be redefined in terms of rotation matrix Ro. Thus any quantity can be redefined in terms of global axes by pre-multiplying by the rotation matrix. When used global axes by pre-multiplying by the rotation matrix. When used to redefine member forces and deflections in structure axes, this to redefine member forces and deflections in structure axes, this process is conventionally referred to as transformation of axes, process is conventionally referred to as transformation of axes, and the symbol T is used for the transformation matrix.and the symbol T is used for the transformation matrix.

T = [Ro 0 ]T = [Ro 0 ] [0 Ro][0 Ro]


Basic requirements:Basic requirements:

Piping systems shall have sufficient flexibility to prevent Piping systems shall have sufficient flexibility to prevent thermal expansion or contraction or movements of piping thermal expansion or contraction or movements of piping supports at terminals from causing;supports at terminals from causing;

- Failure of piping or supports from overstress or fatigueFailure of piping or supports from overstress or fatigue- Leakage at joints.Leakage at joints.- Detrimental stresses or distortion in piping and valves or in Detrimental stresses or distortion in piping and valves or in

connected equipment (pumps and turbines for example), connected equipment (pumps and turbines for example), resulting from excessive thrusts and moments in the piping.resulting from excessive thrusts and moments in the piping.


Specific requirements: Specific requirements:

In brief they are,In brief they are,

- The computed stress range at any point due to The computed stress range at any point due to displacements in the system shall not exceed the allowable displacements in the system shall not exceed the allowable stress range.stress range.

- Reaction forces computed shall not be detrimental to Reaction forces computed shall not be detrimental to supports or connected equipment.supports or connected equipment.

- Computed movement of the piping shall be within any Computed movement of the piping shall be within any prescribed limits, and properly accounted for in the prescribed limits, and properly accounted for in the flexibility calculations.flexibility calculations.

Stiffness & FlexibilityStiffness & Flexibility Concepts:Concepts:Displacement strains;Displacement strains;Thermal displacements, Piping system will undergo dimensional Thermal displacements, Piping system will undergo dimensional

changes with any change in temperature. If constrained from changes with any change in temperature. If constrained from free expansion or contraction by connected equipment and free expansion or contraction by connected equipment and restraints such as guides and anchors, it will be displaced from restraints such as guides and anchors, it will be displaced from its unrestrained position.its unrestrained position.

Restraint flexibility, where restraints are not considered rigid, their Restraint flexibility, where restraints are not considered rigid, their flexibility may be considered in determining displacement stress flexibility may be considered in determining displacement stress range and reactions.range and reactions.

Externally imposed displacements, externally caused movement of Externally imposed displacements, externally caused movement of restraints will impose displacements on the piping in addition to restraints will impose displacements on the piping in addition to those related to thermal effects. Movements may result from those related to thermal effects. Movements may result from tidal changes (dock piping), wind sway (eg. Piping supported tidal changes (dock piping), wind sway (eg. Piping supported from a tall slender tower), or temperature changes in connected from a tall slender tower), or temperature changes in connected equipment.equipment.

Total Displacement strains, Thermal displacements, reaction Total Displacement strains, Thermal displacements, reaction displacements, and externally imposed displacements all have displacements, and externally imposed displacements all have equivalent effects on the piping system, and shall be considered equivalent effects on the piping system, and shall be considered together in determining the total displacement strains.together in determining the total displacement strains.

Stiffness & FlexibilityStiffness & Flexibility Concepts, cont.:Concepts, cont.:Displacement stresses;Displacement stresses;Elastic behavior, stresses may be considered proportional to the Elastic behavior, stresses may be considered proportional to the

total displacement strains in a piping system in which the strains total displacement strains in a piping system in which the strains are well distributed and not excessive at any point (a balanced are well distributed and not excessive at any point (a balanced system). Layout of systems should aim for such a condition.system). Layout of systems should aim for such a condition.

Overstrained behavior, stresses can not be considered proportional Overstrained behavior, stresses can not be considered proportional to displacement strains throughout a piping system in which an to displacement strains throughout a piping system in which an excessive amount of strain may occur in localized portions of the excessive amount of strain may occur in localized portions of the system (an unbalanced system), unbalance may result from one system (an unbalanced system), unbalance may result from one or more of the following;or more of the following;-- highly stressed small size pipe runs in series with large or highly stressed small size pipe runs in series with large or relatively stiff pipe runs.relatively stiff pipe runs.-- a local reduction in size or wall thickness, or local use of a local reduction in size or wall thickness, or local use of material having reduced yield strength.material having reduced yield strength.-- a line configuration in a system of uniform size in which a line configuration in a system of uniform size in which the expansion or contraction must be absorbed largely in a short the expansion or contraction must be absorbed largely in a short offset from the major portion of the run.offset from the major portion of the run.

QuestionsQuestions

Expansion & StressesExpansion & Stresses

Effect of expansion and stresses within a piping system need Effect of expansion and stresses within a piping system need to be determined by knowing the following;to be determined by knowing the following;

Which code that applies to system.Which code that applies to system. Design Temperature and Pressure.Design Temperature and Pressure. Material Specification.Material Specification. Pipe Size & wall thickness of each of the piping Pipe Size & wall thickness of each of the piping

components.components. The layout of the system including dimensions and The layout of the system including dimensions and

thermal movement of terminal points.thermal movement of terminal points. Limitations of end reactions on terminal points as given Limitations of end reactions on terminal points as given

by equipment manufacturers.by equipment manufacturers.


The requirements for formal analysis are identical The requirements for formal analysis are identical to those of B31.1. The Code gives the following to those of B31.1. The Code gives the following equation (same as B31.1) to check if formal equation (same as B31.1) to check if formal (simplified or comprehensive) analysis is (simplified or comprehensive) analysis is required:required:

D y / ( L – U )D y / ( L – U )2 2 ≤ 0.03 ≤ 0.03

• D: outside pipe diameter, mm D: outside pipe diameter, mm • y : resultant of displacement strain, mmy : resultant of displacement strain, mm• L: developed length, mL: developed length, m• U: anchor straight distance, length of straight line joining U: anchor straight distance, length of straight line joining

anchors, manchors, m


Applicable code only will determine the minimum safety Applicable code only will determine the minimum safety requirements for the material at the design conditions of requirements for the material at the design conditions of pressure and temperature.pressure and temperature.

Some code specify the modulii of elasticity for commonly Some code specify the modulii of elasticity for commonly used piping materials as well as formulae to determine used piping materials as well as formulae to determine stress intensification factors and flexibility factors.stress intensification factors and flexibility factors.

Codes state that, the piping system shall be treated as Codes state that, the piping system shall be treated as whole, in calculating the flexibility of a piping system whole, in calculating the flexibility of a piping system between anchor points and that the significance of all between anchor points and that the significance of all parts shall be recognized.parts shall be recognized.

In addition, calculations shall take into account stress In addition, calculations shall take into account stress intensification factors which apply to components other intensification factors which apply to components other than sections of straight pipe.than sections of straight pipe.


Expansion & StressesExpansion & StressesThe analysis of piping loaded by pressure, weight and thermal The analysis of piping loaded by pressure, weight and thermal expansion so the analyst needs to understand the application of expansion so the analyst needs to understand the application of the Principal Axis system, to simplify.the Principal Axis system, to simplify.

Consider a cube removed from a stressed section of pipe.Consider a cube removed from a stressed section of pipe.Calculate the stress in the cube and compare it to some Calculate the stress in the cube and compare it to some allowable stress limit.allowable stress limit.

STRESS is ratio of FORCE to AREA or MOMENTS DIVIDED BY PIPE STRESS is ratio of FORCE to AREA or MOMENTS DIVIDED BY PIPE SECTION MODULUS.SECTION MODULUS.

Each force acting on the cube, can be trigonometrically reduced Each force acting on the cube, can be trigonometrically reduced to force components, represented by vectors, acting along each to force components, represented by vectors, acting along each of the principal axis. The resultant of the component of each of the principal axis. The resultant of the component of each force acting on the face of the cube, divided by the area of the force acting on the face of the cube, divided by the area of the cube face is called the PRINCIPAL STRESS. The principal stress cube face is called the PRINCIPAL STRESS. The principal stress that act along the centerline of the pipe is called a that act along the centerline of the pipe is called a LONGITUDINAL PRINCIPAL STRESS. This stress is caused by LONGITUDINAL PRINCIPAL STRESS. This stress is caused by longitudinal bending, axial force loading or by pressurelongitudinal bending, axial force loading or by pressure..


RADIAL PRINCIPAL STRESS, acts on a line from the center of pipe RADIAL PRINCIPAL STRESS, acts on a line from the center of pipe radially through the pipe wall. This stress is a compressive stress radially through the pipe wall. This stress is a compressive stress acting on the pipe ID caused by internal pressure, or a tensile stress acting on the pipe ID caused by internal pressure, or a tensile stress caused by external or vacuum pressurecaused by external or vacuum pressure..

CIRCUMFERENTIAL PRINCIPAL STRESS, sometimes called HOOP or CIRCUMFERENTIAL PRINCIPAL STRESS, sometimes called HOOP or TANGENTIAL STRESS acts on a line perpendicular to the TANGENTIAL STRESS acts on a line perpendicular to the LONGITUDINAL and the RADIAL STRESS. This stress attempts to LONGITUDINAL and the RADIAL STRESS. This stress attempts to separate the pipe wall in the circumferential direction. This stress is separate the pipe wall in the circumferential direction. This stress is caused by internal pressurecaused by internal pressure..

When two or more PRINCIPAL STRESSES act at a point on a pipe, a When two or more PRINCIPAL STRESSES act at a point on a pipe, a SHEAR STRESS will be generated. One example of a SHEAR STRESS SHEAR STRESS will be generated. One example of a SHEAR STRESS would be at a pipe support where a RADIAL STRESS caused by the would be at a pipe support where a RADIAL STRESS caused by the supporting member acts in combination with the LONGITUDINAL supporting member acts in combination with the LONGITUDINAL BENDING caused by the pipe overhangBENDING caused by the pipe overhang..

Expansion & StressesExpansion & StressesAllowable Stress RangeAllowable Stress RangeB3 1.3 establishes a maximum allowable stress range that can B3 1.3 establishes a maximum allowable stress range that can be safely accommodated by a piping system before failure will be safely accommodated by a piping system before failure will commence for two separate stress loading conditions. These commence for two separate stress loading conditions. These limits are for stress levels that canlimits are for stress levels that can,,

1.)1.) cause failure from a single loading, andcause failure from a single loading, and,,2.)2.) cause failure from repeated cyclic loadingscause failure from repeated cyclic loadings..

The ALLOWABLE STRESS RANGE, SA [ 302.3.5(d)] is the stress The ALLOWABLE STRESS RANGE, SA [ 302.3.5(d)] is the stress limit for the 2nd stress level, those stresses that are repeated limit for the 2nd stress level, those stresses that are repeated and cyclic in nature, or simply, it is the allowable for the and cyclic in nature, or simply, it is the allowable for the SECONDARY STRESS, the DISPLACEMENT STRESS RANGE.SECONDARY STRESS, the DISPLACEMENT STRESS RANGE.

B31.3 presents two equations for the calculation of SAB31.3 presents two equations for the calculation of SA..

Expansion & StressesExpansion & StressesEquation 1a is as follows;Equation 1a is as follows;

SA =f(1.25 Sc+0.25Sh)SA =f(1.25 Sc+0.25Sh)

and equation 1b is as followsand equation 1b is as follows,,SA =f[1.25(Sc+Sh)-SL]SA =f[1.25(Sc+Sh)-SL]

Sc and Sh are the basic allowable stresses for the cold and hot Sc and Sh are the basic allowable stresses for the cold and hot conditions as defined in Section 1.3.4. Sc and Sh values are conditions as defined in Section 1.3.4. Sc and Sh values are found in B31.3 Appendix A TABLE A-1found in B31.3 Appendix A TABLE A-1..

f is the STRESS-RANGE REDUCTION FACTOR;f is the STRESS-RANGE REDUCTION FACTOR;

this factor can be selected from the table shown below or can this factor can be selected from the table shown below or can be calculated by equation of B31.3 asbe calculated by equation of B31.3 as::

f=6.0(N-0.2)≤1.0f=6.0(N-0.2)≤1.0


STRESS-RANGE REDUCTION FACTORS fSTRESS-RANGE REDUCTION FACTORS fCycles NCycles N Factor fFactor f

70007000 and lessand less 11.0.0Over 7,000 to 14,000Over 7,000 to 14,000 0.90.9Over 14,000 to 22,000Over 14,000 to 22,000 0.80.8Over 22,000 to 45,000Over 22,000 to 45,000 0.70.7

Over 45,000 to 100,000Over 45,000 to 100,000 0.60.6Over 100,000 to 200,000Over 100,000 to 200,000 0.50.5


•The SL term is the LONGITUDINAL STRESSES to be discussed The SL term is the LONGITUDINAL STRESSES to be discussed laterlater..

•Although equations are both the allowable stress, SA, for the Although equations are both the allowable stress, SA, for the calculated thermal displacement stress range, SE, each calculated thermal displacement stress range, SE, each equation has a specific application. equation has a specific application.

•Equation 1a is a system allowable stress of the entire piping Equation 1a is a system allowable stress of the entire piping system of the same material, thermal cycles, and temperature; system of the same material, thermal cycles, and temperature;

•while equation 1b is a component allowable stress, SA, for while equation 1b is a component allowable stress, SA, for each single component in the piping system where SL has each single component in the piping system where SL has been calculated for that component under analysisbeen calculated for that component under analysis..

Expansion & StressesExpansion & StressesCold SpringingCold Springing

Cold springing is the intentional deformation of Cold springing is the intentional deformation of piping during assembly to lower the initial piping during assembly to lower the initial displacement strains in the operating condition. displacement strains in the operating condition.

It is used to lower the forces transmitted to It is used to lower the forces transmitted to connected equipment and to lower the deviation connected equipment and to lower the deviation from as-installed dimensions, such as inclination from as-installed dimensions, such as inclination of hangers. However, cold springing does not of hangers. However, cold springing does not change the magnitude of stress range.change the magnitude of stress range.

The amount of cold spring ”C.S.” is usually The amount of cold spring ”C.S.” is usually expressed as a percentage or fraction of the total expressed as a percentage or fraction of the total expansion ∆expansion ∆



The B31 .3 Code offers several methods to increase the flexibility The B31 .3 Code offers several methods to increase the flexibility [319.7] of a piping system. Added flexibility may be necessary to [319.7] of a piping system. Added flexibility may be necessary to lower the pipe loads on load sensitive equipment such as pumps, lower the pipe loads on load sensitive equipment such as pumps, turbines, or compressors. The traditional method to increase turbines, or compressors. The traditional method to increase flexibility is to add expansion loops or off-sets in the piping layout. flexibility is to add expansion loops or off-sets in the piping layout. The key objective in adding loops or off-sets is to move the The key objective in adding loops or off-sets is to move the CENTER OF GRAVITY of the system away from the LINE OF CENTER OF GRAVITY of the system away from the LINE OF THRUSTTHRUST..

Consider a simple two anchor piping layout and construct a line drawn Consider a simple two anchor piping layout and construct a line drawn connecting the two anchors. Estimate the center of gravity. connecting the two anchors. Estimate the center of gravity. Flexibility is increased when the added pipe moves the center of Flexibility is increased when the added pipe moves the center of gravity away from this line of thrustgravity away from this line of thrust..


Layout of piping system should provide inherent Layout of piping system should provide inherent flexibility, however, for the cases where the flexibility, however, for the cases where the system lacks flexibility the designer should system lacks flexibility the designer should consider increasing flexibility by means of bends, consider increasing flexibility by means of bends, loops, offsets, swivel joints, bellow or slip type loops, offsets, swivel joints, bellow or slip type expansion joints.expansion joints.


Expansion & StressesExpansion & Stresses This center-of-gravity/line-of-thrust concept is further This center-of-gravity/line-of-thrust concept is further

illustrated by the following two computer analysis of the illustrated by the following two computer analysis of the above pipe layouts. above pipe layouts.

Both piping layouts are the same pipe size, temperature, Both piping layouts are the same pipe size, temperature, and the anchors are the same distance apart. and the anchors are the same distance apart.

The L shape layout has a maximum expansion stress of The L shape layout has a maximum expansion stress of 24,455 psi. 24,455 psi.

The Z shaped has 42,594 psi. The Z shaped has 42,594 psi.

The L shape moved the center of gravity, cg away from the The L shape moved the center of gravity, cg away from the line of thrust which produced a lower stress, greater line of thrust which produced a lower stress, greater flexibility even though the Z shape had one more elbowflexibility even though the Z shape had one more elbow..

Questions, CommentsQuestions, Comments