Kinder Morgan Compressor Equations and WinFlow Detailed Station Calculations (DSC) 11/13/2013 – 2013 PKR 1
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Kinder Morgan Compressor Equations
and
WinFlow Detailed Station Calculations(DSC)
11/13/2013 – 2013 PKR 1
Show of Hands…
Who Uses Detailed Station Calculations?
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Tennessee Gas Pipeline (El Paso) has been usingDSC since the 80’s.
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1. This was in an era when Companies had dedicated CompressorServices departments that could test machines, develop accurateequations and generate and update coefficients.
2. Planning could easily incorporate these unit parameters in WinFlowmodels.
3. Today all TGP stations are modeled with DSC.
11/13/2013 – 2013 PKR4
KMI’s acquisition of El Paso resulted in a re-evaluation of the approach for compressor stationmodeling
1. Evaluation team included members of KMI pipelines NGPL, KMTP,MEP, TGP, SNG, EPNG, CIG
2. Existing capacity models demanded that TGP be able to continuewith DSC modeling to ensure firm deliveries can be met (e.g.,changing to block horsepower would impact capacity)
3. Modifications were made to equations to accommodate NGPL’sstation modeling in a stand-alone application
4. Other KMI assets will begin using DSC on an as-needed basis andwill adopt the new compressor equations
5. Long term plan is to migrate turbine/centrifugal stations to GreggEngineering’s C5 equation in NextGen
Good News!
The equations that you see today are inthe public domain and can be used by
your company
11/13/2013 – 2013 PKR 5
1. Reciprocating Compressor Throughput
2. Reciprocating Compressor Required Horsepower
3. Reciprocating Engine Allowed Horsepower
4. Reciprocating Engine Fuel
5. Gregg Engineering’s Turbine/Centrifugal C5 Tables
6. Turbine Allowed Horsepower
7. Turbine Part Load Fuel
8. Centrifugal Compressor Throughput
9. Generic Driver and Compressor
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Equations Evaluated by the Team
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TfRmREREENSVQ ncccb
s
1
000,000,1*728,1
440,1*
12
210
b
S
N
SV
Q
Throughput (mmscfd)
Swept Volume (in3)
Compressor Speed (rpm)
Suction Density (lbm/ft3)
Base Density (lbm/ft3)
@60F, 14.73 psia
n
T
m
R
EEE
f
c
210 ,, Volumetric Efficiency Coefficients
Compression Ratio
Clearance Ratio (CV/SV)
Throughput Factor
Polytropic Coefficient
Reciprocating Compressor Throughput
11/13/2013 – 2013 PKR 8
Reciprocating Compressor Throughput (cont’d)
EVNSVQb
s
000,000,1*728,1
440,1*
Fundamental form of throughput equation:
Many different forms of EV (volumetric efficiency) used by compressormanufacturers, pipeline companies, academics
Volumetric Efficiency = The ratio of the volume of fluid actually displaced by thepiston to its swept volume.
11/13/2013 – 2013 PKR 9
Ariel Compressors Volumetric EfficiencyTypical Industrial Form
Reciprocating Compressor Throughput (cont’d)
%CL = m in KMIequations and “k”is “n” in KMIequations
KMI Volumetric Efficiency
11/13/2013 – 2013 PKR 10
TfRmREREEEV nccc
1
12
210
Allows user to curve fit to non-linear historical data.Setting E0 to 100, E1 to -1 and E2 to 0 allows equation to match Ariel equation.
Tf is not so much part of the volumetric efficiency but is another tuning factor thatthe modeler can adjust with an online model or historical data. TGP uses 1.0 andI’m not aware of cases where a different value is used.
Reciprocating Compressor Throughput (cont’d)
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Reciprocating Compressor Required Horsepower
pxcreq HPHPHPHP
p
x
c
req
HP
HP
HP
HP Horsepower Required from Driver
Compressor Horsepower (includes pulsation loading and valve losses)
Auxiliary Load (e.g., oil pumps, engine driven fan loads)
Parasitic Horsepower (deactivated ends)
11/13/2013 – 2013 PKR 12
Reciprocating Compressor Required Horsepower(cont’d)
EMLFWFRRRmR
n
nPNSVHP n
n
cnccn
n
cS
c
1111
1000,396
** 111
n
P
N
SV
HP
S
cHorsepower
Swept Volume (in3)
Compressor Speed (rpm)
Suction Pressure (psia)
Polytropic Exponent (~1.3)
(no heat transfer, natural gas)
EM
LF
WF
R
m
c
Compressor Clearance Ratio (CV/SV)
Compression Ratio
Waste K Factor (Valve Losses)
Pulsation Loading
Mechanical Efficiency (~0.95)
11/13/2013 – 2013 PKR 13
Reciprocating Compressor Required Horsepower(cont’d)
2210max cc RuRuuW
2210min cc RvRvvW
1100
cR
KWF
minminmaxminmax
min WWWNN
NNK
44
33
2210 cccc RLRLRLRLLLF
If field test data is not availablefor the unit then all coefficientscan be set to 0 and a singlevalue of “K” used.
Most TGP units use all of theseparameters. However, goingforward it’s unknown if theseparameters will be developedon new installations.
For the existing fleet it wouldnot add value to simplify theserelationships to a single Kvalue.
11/13/2013 – 2013 PKR 14
Reciprocating Compressor Required Horsepower(cont’d)
minminmaxminmax
min HPHPHPNN
NNAHP totalp
2210min ss PpPppHP
2210max ss PqPqqHP
Parasitic horsepower represents losses resulting from deactivated ends. Fieldtest data is necessary to develop these coefficients.
Atotal is the number of deactivated endsPs is the suction pressure
11/13/2013 – 2013 PKR 15
Reciprocating Compressor Allowed Horsepowerand Fuel (cont’d)Allowed horsepower is obtained from linear interpolation of horsepowerbetween known ambient temperatures. Most recips are rated at single maxhorsepower across a range of temperatures. Some older recips are “ambientup-ratable”.
000,1*
24
100
*
100100
22
210 LHVN
HPNHPFHPFFF
Rated
RatedRated Rated
100x
N
HP
N
HP
Rated
Rated
Dev
LHV = Fuel Lower Dry Heating Value (btu/cf) (default =1000)
Gregg Engineering C5 in NextGenCentrifugal Data from Vendor
11/13/2013 – 2013 PKR 16
Portion of a table representing data for a Solar C65 compressor with a D-2 impeller. Complete tablehas values from speeds of 9000, 8000, 7000, 6000, 5000 and 3990.
The rest of the table is truncated. Just showing the parameters involved in the centrifugal compressor.
Not going to go into the details of what these parameters represent, just showing the concept.
11/13/2013 – 2013 PKR 17
Typical Centrifugal Compressor – Fan Law
“Under certain simplifying conditions, operating points of a compressor atdifferent speeds can be compared”. (Kurz - PSIG 0408, 2004)
Q/N Max
Q/N Min
Surge
Centrifugal Compressor Throughput
11/13/2013 – 2013 PKR 18
sQ
AA
g
D
N
H
30
Head
Compressor Speed (rpm)
Impeller Diameter (in)
Gravitational Constant (32.2 lbm-ft/lbf/s2)
Pressure Coefficient
Flow at Suction Conditions (ACFM)
3
3
2
210
2
2 600,3144 N
QA
N
QA
N
QAA
g
D
N
H sss
30 EE
N
z
T
n
R
R
s
s
c
Gas Constant (1545 ft-ftlb/lbmR)
Compression Ratio
Adiabatic Exponent
Temperature at Suction Conditions
Compressibility at Suction Conditions
Compressor Speed
Compressor Efficiency Coefficients
11
*1
n
n
css Rn
nzTRH
Gregg Engineering C5 in NextGenTabular data from Solar for a Mars100-16000S showing ambienttemperature, nominal horsepower,optimum power turbine speed andheat rate at sea level.
NextGen will interpolate betweendata points instead of solving anequation
11/13/2013 – 2013 PKR 19
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Turbine Max Allowed HorsepowerTurbine allowed horsepower is derived from on-site test data as a function ofambient temperature and speed. The elevation affect is accounted for in thedata regression to obtain the coefficients.
We have not found a need to model the turbine in any more detail, such as atoff-optimum power turbine speeds. We only need to know what the maximumavailable power is based on ambient temp.
turb
a
avail
N
T
HH
HP
70
Maximum horsepower available from turbine
Coefficients developed from test data.
Ambient Temperature (F)
Axial Flow Compressor Speed (rpm) (not power turbine speed)
Planning tuning factor to allow for turbine degradation over time.
TurbAAAAavail NTHNHNHNHTHTHTHHHP 73
62
543
32
210
Turbine Fuel
11/13/2013 – 2013 PKR 21
LHVHPNTFNFNFNFTFTFTFFFFuel DevAAAAPL /2473
62
543
32
210
70
70
CC
FF
F
HP
HP
LHV
N
T
PL
Allowed
Dev
AAmbient Temperature
Compressor Speed
Fuel Lower Dry Heating Value (btu/cf) (default =1000)
Horsepower at Turbine Shaft
Max Allowed HP at Ambient Temp
Part Load Fuel Factor
Fuel Coefficients
Part Load Fuel Coefficients
Allowed
DevA
Allowed
Dev
Allowed
Dev
Allowed
DevAAAPL Hp
HPTC
Hp
HPC
Hp
HPC
Hp
HPCTCTCTCCF
1001001001007
3
6
2
543
32
210
As with the available horsepowerequation the fuel coefficients are basedon site test data and so there is noelevation correction factor.
Turbine Fuel (cont’d)
11/13/2013 – 2013 PKR 22
MechHydr
SSDev
HQHP
000,33
Mech
Hydr
Dev
s
s
H
HP
Q
Compressor Throughput
Suction Density
Horsepower at Turbine Shaft
Head
Compressor Efficiency from Fan Curve
~99% based on type of bearing in centrifugal(overhung, 2 bearing or mag bearings)
30 EE
N
z
T
n
R
R
s
s
c
Gas Constant
Compression Ratio
Adiabatic Exponent
Temperature at Suction Conditions
Compressibility at Suction Conditions
Compressor Speed
Compressor Efficiency Coefficients
11
1
n
n
css Rn
nzRTH
3
3
2
210
N
QE
N
QE
N
QEE sss
Hydr
Generic Unit - Can Represent Turbine, Recip or ElectricMotor and Recip or Centrifugal Compressor
11/13/2013 – 2013 PKR 23
ElevAAAAavail NTHNHNHNHTHTHTHHHP 73
62
543
32
210
Elev
Elev
a
avail
Ft
N
T
HH
HP
70
Maximum horsepower available from turbine
Coefficients developed from test data.
Ambient Temperature (F)
Compressor Speed (rpm) (not turbine speed)
Elevation correction factor
Feet above sea level (ft)
1*215.3*73.14 5000,27
Elev
elev
Elev Ftee
Coefficients can be generated from the Solar 2 program for the Solar fleet of units.To simulate an electric or recip H0 is rated horsepower and elevation term is 1.
Gregg Engineering will use the second formof elevation correction for computationalsimplicity
Solar 2 Program to Model Turbines
11/13/2013 – 2013 PKR 24Generate table of values from theseinputs and calculated power output
Sample Output from Solar 2
11/13/2013 – 2013 PKR 25
6,000
7,000
8,000
9,000
10,000
11,000
12,000
10 20 30 40 50 60 70 80 90 100
Allo
wab
le H
orse
pow
er
Ambient Temperature (F)
Solar Taurus 70
Sea Level - Solar 2
Sea Level - Calculated
2,000' - Solar2
2,000' - Calculated
5,000' - Solar2
5,000' - Calculated
Coefficients generated from Solar 2 data (solid lines)Equation results match well (dash lines)
Generic Unit - Can Represent Turbine, Recip or ElectricMotor and Recip or Centrifugal Compressor (cont’d)
11/13/2013 – 2013 PKR 26
B
s
Mech
c
f
s
Dev
n
K
R
T
P
HP
Horsepower available from driver (turbine, motor or recip engine)
Suction pressure
Throughput Factor
Compression Ratio
Mechanical Efficiency (~0.95)
Recip waste K factor
Polytropic exponent
Suction density
Base density
Tf and K can be adjusted to provide adesired overall unit/station efficiency.
Adjust these terms to get ~ 80% to 83%depending on expected efficiency ofproposed unit.
The generic horsepower and throughputequations on this slide and the previousslide are used for quick analysis in theabsence of specific unit paramters and arenot recommended for capacitydeterminations.
11
10303.3 1
1
c
n
n
cS
B
SMechDev
R
KR
n
nP
TfHP
Q
11/13/2013 – 2013 PKR 27
Examples Illustrating the Benefit ofUsing Detailed Station Calculations
Why Use Detailed Station Calculations?
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1. Ensure Capacity Isn’t Oversold
2. Ensure Max Capacity Is Identified
3. Identify Possible Compressor/Station Operating Gapsa. Expansion scenarios or change in station
operations may require compressors to operateoutside of design range
b. Block horsepower won’t capture this
Example 1: Capacity with Installed HP
11/13/2013 – 2017 PKR 29
Assume that throughput represents sold capacity
22,700 Installed HP
Example 1: Stations with DSC at 50F
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Example 1: Stations with DSC at 100F
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11/13/2013 – 2013 PKR 32
Block Versus DSC: Example 1
ModeAmbient
Temp VolumeDifferencefrom Block
Block Station Horsepower NA 1,608Detailed Station Calcs 50 1,596 -12 OversoldDetailed Station Calcs 100 1,570 -38 Oversold
Turbine/centrifugal stations 2 and 4 have low efficiency and the ambient temperaturereduces capacity.
Example 2: Repurpose Existing Station
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Can’t get back to thehigh MAOPdischarge
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Example 2: Repurpose Existing Station(cont’d)
Different station conditions in thebackhaul mode prevent LS1 unitsfrom fully loading and 18, 19 can’tcome on.
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Example 2: Repurpose Existing Station (cont’d)
Example 2 take-aways:
1. Using block horsepower in the forward haul direction would grosslyoverestimate the station capability ( 45,613 max usable versus48,100 installed)
2. Units 18 and 19 cannot run in the backhaul condition. This is mostlikely because there are units which need additional unloading stepsto allow all units to unload enough to let 18 and 19 come on.Different spreads prevent units in Line Service 1 from fully loading.
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