CONTENTS 1.0 GENERAL A - TERMINOLOGY A.1. Structure A.2. Foundations B – DEFINITION CRITERIA B.1. Rack Width B.2. Number of tiers 2.0 MATERIAL SELECTION A – MATERIAL USED B – SELECTION CRITERIA 3.0 BASIS OF ANALYSIS A – PERMANENT LOAD A.1. Weight Of Framework A.2. Fireproofing – Heat Insulation A.3. Weight of Piping B – LIVE LOAD B.1. Liquid Load In Pipe <12” B.2. Platform and access load C – EXAMPLES ON THE DETERMINATION FOR THE DISTRIBUTION OF VERTICAL LOAD ON PIPERACK C.1. Determination of the Average Of Pipes Diameter C.2. Load Distribution Between Main Cross Beam And Intermediate Cross Beam. D – CLIMATIC LOAD D.1. Snow D.2. Wind E – SEISMIC LOAD /home/website/convert/temp/convert_html/546acb8db4af9fea158b4b0b/document.doc 1
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CONTENTS
1.0 GENERAL
A - TERMINOLOGY
A.1. StructureA.2. Foundations
B – DEFINITION CRITERIA
B.1. Rack WidthB.2. Number of tiers
2.0 MATERIAL SELECTION
A – MATERIAL USED
B – SELECTION CRITERIA
3.0 BASIS OF ANALYSIS
A – PERMANENT LOAD
A.1. Weight Of FrameworkA.2. Fireproofing – Heat InsulationA.3. Weight of Piping
B – LIVE LOAD
B.1. Liquid Load In Pipe <12”B.2. Platform and access load
C – EXAMPLES ON THE DETERMINATION FOR THE DISTRIBUTION OF VERTICAL LOAD ON PIPERACK
C.1. Determination of the Average Of Pipes DiameterC.2. Load Distribution Between Main Cross Beam And Intermediate Cross Beam.
This document is a guide on the procedures or working methods in the field of civil.
In case of contradiction of this document with the General Protocols, this document superceded the General Protocols.
2. OBJECTIVE
This document covers the regulation by service 347 and 357 of TECHNIP for the piperacks in the petroleum, petrochemicals and similar industries.
Any deviation from this regulation shall be approved by the Head of Service, however the customer particular rules or requirements have priority over this requirement.
3. REFERENCES
This document shall be used with the following documents :-
- GE 357.10.1. Objectives and use of the guide of studies.
- GE 357.10.2. General Rule applicable to the studies.
- GE .357.14.1. Concrete Foundation And Works – General Information.
- GE 357.15.1 Frame and handling – general Information.
A. TERMINOLOGY
Piperacks is a structure made of steel, concrete or mixed supporting :-
- One or more layers of piping.
- Electrical or instrument cable tray.
- Air cooler in certain case.
Piperack comprises of two parts :-
- Steel or concrete structure.
- Concrete foundation.
A piperack composes of various element with the following terminology :-
A.1. Structure
A.1.1. Main Cross Beam
The main cross beam is a horizontal beam connected to two posts to form the portal frame and to support the pipes.
The element of piperack forms by two posts and one or more main cross beams.
A.1.3. Longitudinal Beam
The longitudinal beam is a horizontal beam connecting two portal frame in longitudinal direction.
Generally, the members are used to support the lateral forces, intermediate cross beams and post of coolers.
Especially to transmit the horizontal force to the bracing bay.
A.1.4 Width of Piperack
The width of piperack is the distance between the axis of the posts.
A.1.5 Piperack Spacing
Piperack spacing is the distance between the portal frames.
A.1.6 Intermediate cross beam
The intermediate cross beam is a horizontal cross members supported by longitudinal beams. They are used to reduce the deflection of small pipes. Their requirement is decided by piping department.
The intermediate cross beam shall be steel.
A.1.7 Longitudinal stability
Longitudinal stability forms by two consecutive portal frame connected by members which restraint the longitudinal forces.
The material used for the piperack structure are as follows :-
- Metal frame- Concrete- Mixed (metal frame – concrete)
B. SELECTION CRITERIA (If the material is not specified by Client)
The selection criteria are :-
- The cost of finishes work.- The completion date.- Nature of contract
The choice of materials used must be made by specialist engineers after detail economic survey in agreement with the project engineer and various factor especially the contract requirement :
- Fireproofing.- Planning schedule (duration)- Reduce time for studies (in the case of standard contract of fixed price for studies).
For overseas contract :
- Cost of transport (distance)- Possibility of material supply locally.- Potential of local labour.
3.0 BASIS OF ANALYSIS
This chapter will explains the determination methods for loads on piperacks.
The guides are as follows :
A - PERMANENT LOAD
A.1. Weight of framework.A.2. Fireproofing – heat insulation.A.3. Weight of piping.
B - LIVE LOAD
B.1. Liquid load in piping with diameter 12”.B.2. Platforms and access load.
1) The loads for pipes of > 12” shall be calculated separately.
2) Normally the uniform load per m2 for insulated pipes is smaller than the uninsulated pipes due to the space provided between pipes for the insulated pipes.
A.3.2 Reference Diameter of Piping
The calculation can be simplified by taking the average diameter of pipes for load calculation.
Pipes with diameter more than twice the average diameter of pipes layer shall be considered as follows:-
- Uniform load shall be recalculate without these pipes.
In these particular case, the operating load will be the load provided by the service piping, however the other possible loads due to operation shall be considered.
Liquid phase of the material Present of ice on cold line, etc.
B.1.2 Case for Pipes Ø > 12”
The value of the operation load will be the actual values provided by the service piping.
D.2.3. Example of calculation for transverse wind load.
Note :
To simplify the calculation of wind load, the load will be applied :
- At the piping layer elevation,- At the base of column.
However wind load shall be applied at the right location when justified by beam size/or location, mainly for tie beam.
Wind load at Elev = 5.5 : H1
Column : 100 x 1.8 x 0.24 x 2.75 x 2 = 238Longitudinal Beam : 100 x 1.8 x 0.24 x 7.5 x 2 = 648Intermediate Column : 100 x 1.8 x 0.12 x 1.0 x 2 = 43Piping : 100 x (0.4 + 0.1 x 6) x 7.5 = 750
H1 = Load applied at the tie beam level on the first portal.H2 = Load applied at the tie beam level on the last portal.
Wind on transverse support.+Wind on horizontal and vertical surface of pipe layer in zone length L1. +Wind on tee off pipe layer in zone L1. + effect of wind on post and bracings in zone L1 (at concerned height).
Wind on transverse support. +Wind on horizontal and vertical surface of pipes layer in zone L2. +Wind on the tee off pipes layer in zone L2.+ effect of wind on post and bracing in zone L2 (at concerned height).
Seismic load shall not be combined with climatic load.
If the particular rule require to check for seismic, it will be checked for para paraseismic regulation.
F THERMAL LOAD
F.1 STRUCTURE EXPANSION/SHRINKAGE
F.1.1 Entirely Steel
Load developed due to steel expansion shall be taken into consideration when it will give abnormal effect on the frame (expansion coefficient 11 x 10-6 per °C)Metal steel frames expose to air, in France it is acceptable for a variation of temperature ± 27°C which is correspondent to the variation in length of ± 0.3 mm per meter length.
Under this conditions, load due to the expansion of the frame is negligible when the distance between two expansion joints does not exceed 60m.
F.1.2 Entirely Concrete
The concrete pipe rack with tie beam cast in situ to the column, the problem will be severe as the beam cannot expand freely. In this
The force Ff shall be applied on the top flange of the intermediate cross beam with the following assumptions :-
- Only the inertia of the top flange will be taken for determination of the horizontal bending stress.
- The bending stress in the vertical plane is negligible because of the lateral support provide by the friction lines.
b) On the main cross beam
- Friction (Ff = friction force)
Horizontal force due to pipe movement on the sliding support shall be determined as follows :
Ff = x p x
Ff = horizontal force acting on main support and which development deflection on the horizontal member.
= coefficient of friction between pipes shoes and cross beam.
= 0.4 (steel on steel)
= 0.05 to 0.1 (for teflon or similar)
= Coefficient depend on the percentage of pipes on the cross beam with temperature more than 150°C.
% 0 to 40 0.4
41 to 60 0.6
61 to 80 0.8
81 to 100 1
p = Vertical load acting on main support (operating condition)
- Anchor (Fa = anchoring force)
- The anchoring forces of pipings on the main cross beam shall be provided by piping discipline.
- In practice, the calculation from piping disciplines is not available during the pipe rack design, therefore the design of pipe rack elements are base on the estimate value.
- When the calculations from piping disciplines is available, a final checks shall be performed especially for cross beam.
- The anchoring force always act on the top flange of the cross beam, the design of main cross beam is identical to the previous intermediate cross beam.
IMPORTANT NOTE
- The forces given by piping disciplines are generally large (temperature used for calculation > operating temperature)
- Therefore, partial safety factor used for load shall be taken as 1.
c) On portal (transversal force)
- Horizontal piping forces shall be applied at the main transversal support levels.
- The following factors shall be applied to determine the transversal forces :
Pipe rack off-site
Ft = 0.1 x p : 1st layerFt = 0.05 x p : 2nd layerFt = 0 : other layers
Ft = Transversal horizontal loadp = Vertical load on the support (operating condition)
Site Pipe rack
Ft = 0.15 x p 1st layer (bottom)Ft = 0.1 x p 2nd layerFt = 0.05 x p 3rd layerFt = 0 others layers
Ø - After reception the actual forces, the previous assumption shall be verified.
Horizontal anchorage and friction forces developed on the main cross beam shall be applied horizontally at the junction to the column for designing the column itself
e) On stability bay (longitudinal action)
The longitudinal force on pipe rack restrain is the sum of various horizontal forces acting between two expansion joint of pipe rack.
- Anchor
Anchoring force to be applied on the pipe rack restrain is the sum of various anchoring forces on the main cross beam.
- Friction
The total friction force applied on the pipe rack restrain is the sum of various forces on the main cross beam.
Horizontal force acting on pipe rack restrain depend on :-
- Location of pipe rack restrain.
- Number of anchor point for the length of the pipe rack concerned.
As shown in the example, it is difficult to generalise a method to determine the total friction force on the piperack.
The value of the anchoring force will reach it maximum when the displacement due to temperature effect has stopped. This mean the combination force of anchoring and friction is only happen during early stage.
Conclusion :
In the operating condition, the anchoring and friction force will not be added for determination of overall forces on the piperack restrain.
The deflection of these beams due to total “Service” load shall not exceed 1/400 of the length.
Intermediate Cross Beams + Longitudinal Beams
The total deflection (intermediate cross beam + tie beam) under total loads in the service case shall not exceed 1/200 of the intermediate cross beam.
Note :
The deflection given above shall be reduced (information given by piping discipline) when allowable pipe deflection is lower.
J.1.2 Concrete Piperack (Where The Intermediate Cross Beam Is Steel)
Intermediate Cross Beam
The deflection o these beams due to total “Service” load shall not exceed 1/300 of the length.
Others elements
Checking of deflection for beam with L/H < 15 normally is not necessary.
J.2 ACCEPTABLE HORIZONTAL DISPLACEMENT ON THE PORTAL FRAME
J.2.1 Steel Portal Frame
Horizontal displacement due to “normal service wind load” shall not exceed :-
- 1/150 e height of piperack if it is not supporting equipment.
- 1/200 e height of the piperack if it is supporting equipment (air cooler)
J.2.2 Concrete Portal Frame
Due to rigidity of the concrete, a verification of horizontal displacement in piperack is not necessary.(Normal density at reinforcement 150 kg / m³ of concrete and density of concrete 350 kg / m³)
It should be noted that the uncertainly of the concrete deformation due to development and formation of cracking only give unprecise value of displacement.
4.0 STEEL PIPERACK
A CONSTRUCTION ARRANGEMENT
A.1 INTERMEDIATE CROSS BEAM
Normally the profile of intermediate cross beam is IPE type.
When the percentage of hot lines is high, it is better to use the profile HEA type which provide better inertia in the horizontal direction (friction).
A.1.1 Arrangement Detail
Connection :
This type of connection shall not transmit shearing force to the base of post which produce torsion to the cross beam.
Connection :
- The connection shall be able to ensure the stability of the post due to friction load on the intermediate cross beam.
- The connection is considered partially restraint the horizontal forces from intermediate cross beam.
For a continuous piperack, the connection of column to foundation in longitudinal direction to the piperack will be pin-jointed type.
However the connection of column to foundation in the axis of portal can be pin-jointed or fixed type.
A.4.1 Pin Type. (see STC.00.18.10.009)
Advantage :
- no moment transfer
- small size foundation
- two bolts of average diameter
- thin plate without gusset
- simple connection
Disadvantages
- bigger size of the columns and cross beams compared to fixed type connection.
- significant horizontal displacement
A.4.2 Fixed type (see STC.00.18.10.014)
Advantages :
- smaller dimension of the columns and cross beams compared to pin type connection
- reduce horizontal displacement
Disadvantages :
- large foundation
- lot of bolts
- massive connection
- thick base plate and stiffners
Synthesis
The adopted solution will be selected according to technical data (ground characteristic, etc.) and economic (cost of material, nature of contract) by considering the structure (portal + bolt + foundation).
To ensure longitudinal stability of the piperack members due to various horizontal load.
The sections of piperack are separated by methods (oblong holes, corbels) of preventing transmission of horizontal load from one section to another.
The length of the section is limited to 60m for the French climate for negligible effect of thermal expansion.
A.5.2 Choice of Section
The choice of isolation location shall be done according to certain criteria:-
- change in geometric of the piperack (number of levels or width)
- junction of two perpendicular piperack.
- As for as possible, the isolation should not be located, between the principal anchoring of the pipe layer so that the horizontal force apply to the cross member of stability is small.
- An isolation shall be checked for connection of piperack with structures except in the case where the structure ensure the stability of the unit.
- The distance between two bracing stability does not exceed 60m (for French climate).
- The position in the medium of the section is most usually used.
- For piperack with limited bay, the position of stability bracing shall be located at end bay so that the anchoring load do not have to be transmitted from anchoring point at the end of piperack to the stability bracing by tie beam.
- The choice of the position can also depend on obstruction on the ground (road passage, pumps etc.)
A.5.4 Principle
Two general principal are :-
a) Bracing stability bay
Advantages :
Less weight of the structure
Negligible displacement at top which is in agreement with the theory for piping calculation (zero displacement)
- Attention with uplift for the calculation of the anchor bolt for the stability bay.
- In the calculation for this type of stability bay add a horizontal load at the level of cross beam equal to 1/100 of the sum of vertical load acting on this part.
All the piperack members are casted at place. No prefabricated member is used.
B.2 SEMI PREFABRICATION RACK
The footings and posts are cast in placed.
The horizontal beams (longitudinal beams, cross beams, tie beams) are prefabricated.
B.3 PREFABRICATED RACK
The footing is cast in place or prefabricated.
The columns and beam (longitudinal beam, cross beam, tie beams) are prefabricated.
Otherwise, all the members of main frame is prefabricated.
B.4 CHOICE OF METHOD OF EXECUTION
The choice depend on 3 criteria :
- size of piperack
- the size of the work which is the most important consideration
- site and weather condition for economic
In fact, it is impossible to impose a priority to the Subcontractor due to following reasons :
Perhaps the selected Subcontractor does not have necessary material for prefabrication.
The local agent of the subcontractor does not want to construct the rack as method prerecognise by TECHNIP. If the subcontractor is requested to follow the TECHNIP prerecognise method, the subcontractor will always try to find ways for change order.
Generally, the subcontractor under estimate the priority of the execution of concrete racks, they will wait at the last minute to look at the drawings.
However, TECHNIP shall advice the subcontractor during invitation to tender.
It should not be believed that prefabrication reduce the cost of the rack appreciably but it can save a lot of time.
In the actual construction, the prefabrication is very employee because same section always kept, so TECHNIP shall make the prefabricated element similar option through out the piperack.
The preliminary study of concrete piperack is to pre dimension the size of the beams and columns for piping section to detail their drawings.
This predimension shall be made so as to reduce the maximum the divensite squarrings to facilitate the prefabrication.
C.1.2 Method
- With referring to the general arrangement drawings, list out the data (average Ø of pipes, elevation of cross beam, longitudinal beam etc.
- Using the tables of predimension below, determine the various sections.
- With all these data, establish the preliminary piperack drawing.
- Determination of position of anchoring bay with the position of longitudinal beam.
Note :
If possible, the dimension of the footing is carried out during the calculation for reinforcement. It is necessary to indicate the bottom level of foundation and dimension, for presence of other foundation, pipe & etc.
The table of predimensions are valid for normal case, however the designer need to check it.
The calculation of concrete piperacks is to establish the data of loads acting on the piperack in order for the calculation of reinforcement in order to obtain the quantity of concrete, reinforcement and formwork for costing.
C.2.2 Checking The Reinforcement
The amount of reinforcement in the member shall not exceed 150 kg/m³ of the concrete. The size of the section shall be increase if the amount of reinforcement is high.
D. CONSTRUCTION DETAILING
D.1 REINFORCEMENT
In order to facilitate the execution of piperack at site, the reinforcement of all the elements shall be detail as follows :
D.1.1 Column
See sketch below.
Steel for the columns are similar except for the diameter (range between Ø12 and 25).
The position of reinforcement at the support of the tie beam can be moved to allow for insert plate.
It is necessary to inform the subcontractor that the prefabricated member shall be marked accordingly as per plan of assembly in order to prevent discrepancies during installation.
Base plate or insert plates are used for fixing (particularly the post) the secondary steel frames for supporting pipings, walkways etc.
D.3.2 Flat Plate on Cross Beam and Tie-beam
It is needed for allowing slip of pipings and fixing of anchor on the cross beams or tie-beams. The flat plates are generally 150 mm wide x 10 mm thick.
Flat plate must be provided on the cross beams and fix to the concrete by steel Ø 8.
Flat plates only be provided on tie-beam when required or when there is piping.
Dimension could be as shown below :-
Special “steel-concrete” adhesive can be used if the plats have not be installed during casting of concrete.
These special adhesives are produce by companies such as :-
- “BOSTIK”
or
- “SIKA”
The products are constantly upgraded or revise, therefore the manufacturer shall be contacted for the latest product suitable for the specific condition.
D.3.3 Sleeves
The sleeves are made of plastic.
As a guide the following are some of the brand :-
- ARMOSIG : Elysee 2 - 78170 LA CELLE SAINT CLOUD B.P. n° 2
- SEPEREF - TMP - Z.I. QUINCIEUX - 69650 SAINT GERMAIN AU MONT D’ OR B.P. n° 1
Generally, the diameter sleeves are 22.6 or 25 mm.
D.3.4 Rails
They are embedded in the concrete during casting.
It exist in various types and dimensions produced by many manufacturers as listed below :-
- Rails “HALFEN” distributed by :
Societe SODIMETAL S.A.Immeuble Evolution18, Rue Goubet75940 PARIS Cedex 19 – Tel. 200.67.01
- Rails “JORDHAL” distributed by :
ACIBATZ.I. 68190 UNGERSHEIM – Tel. (89) 48.13.03
- Rails “TRIMBORN” distributed by :
TECNER25, Rue Trebois92300 LEVALLOIS-PERRET
It comes with various coating such as black, galvanised, paint, polymer, stainless steel.
As an indication, a profile 50/30, the basic load is 4.5 ton/meter length with 4 bolts Ø 20.
D.3.5 Conclusion
The accessories increase the cost of the concrete piperack, therefore it shall be reduced to minimum.
It is obvious that the use of anchoring rail will make it easy to fix apparatus or secondary frame. However as it is very costly, it shall not be their installed especially for ‘turnkey contract”. In the service contract, they only be used when requested by client.
The used of plastic “sleeves” shall be maximise as it is rather cheap.
The used of plats on the cross beam are compulsory.
The plats on tie-beam are optional. The need is decided after studing the general drawings.
The plats are anchor to the concrete, if they are install before casting of concrete or adhesive by special product. The adhesive cannot be used for slide (anchoring of lines).