Selección de Compresores
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Compressor Selection Compressor Selection Nov.13 2006
description
Seminario de Selección de Compresores de Dresser Rand
Transcript of Selección de Compresores
Compressor SelectionCompressor Selection
Nov.13 2006
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Engineering Co. utilize in house data from accumulated vendor information
Customer need vendor’s basic data to performBasic thermodynamic formula with unit conversion
Table-1. Parameter for Each Frame
Excel spread sheet (Hand over separately)
Sample compressor selection
Thermodynamic calculationThermodynamic calculation
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Basic thermodynamic formula to be usedBasic thermodynamic formula to be used
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Fundamental Formulas generally usedk -1 / k
ηp = (1)
Polytropic efficiencyn - 1 / n
n - 1 k - 1Td = (Pd /Ps ) n x Ts = (Pd /Ps ) k ηp x Ts ( 2 )
n - 1 k - 1Zav R Ts n Zav R Ts k ηp
H = [ (Pd /Ps) - 1 ] = [ (Pd /Ps) - 1 ]n -1 k -1
n k ηp
= Zav R Ts (r m - 1) / m ( 3 )
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k-1
where, r = Pd / Ps, m = ( 4 )k η p
From equation ( 2 ), ηp and Td can be back calculated from operation data
k - 1 Log( Pd / Ps )ηp = ( 5 )
k Log( Td / Ts)
Td = Ts x r m ( 6
Qd = Qs x r m/ r ( 7 )
Head coefficient µ can be expressedH
µ= ( 8 )U2 / g
πD Nwhere U = Ft/ Sec Impeller peripheral velocity ( 9 )
60 x 12D : Impeller diameter in Inch,N : Operating speed , rpm
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Gas power GHPWF x H
GHP = (10 )33000 x ηp
where WF is weight flow ( lb / min), From equation ( 1 ),
v = Z R T / 12 x 12 P ft3 /lb ( 11)where R= 1545.32 /MW, T = °R = °F + 460 , P = psia = ( lb/ in2 )
Volume Q (CFM = ft3 / min) can be expressed:
Q = WF x v ( 12 )
For multistage centrifugal compressor, operating speed N(rpm) can beapproximately expressed:
1300 Total HN = ( 13 )
Av. D √ s x µ
where s : Number of impellers , Av. D : Average impeller diameter in inch
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Table 1: DATUM DataTable 1: DATUM DataTable-1: Parameter for each Frame( Value for MU & NH are by writer's experience) Rev. 1 Nov 2 2
Frame 2 4 6 8 10 12 14 16 18 20 22 24 26Nom.Imp dia, inch 9.516 11.045 12.819 14.879 17.269 20.043 23.263 27 31.337 36.372 42.215 48.996 56.867Max. MCS, rpm 26470 22800 19650 16930 14580 12570 10830 9337 8040 6925 5965 5140 4430Max.100% spd 25209 21714 18714 16123 13885 11971 10314 8892 7657 6595 5680 4895 4219Nominal NH, % 82 82 82 83 83 83 83.5 83.5 84 84 84.5 84.5 85Nominal MU 0.47 0.48 0.5 0.51 0.53 0.53 0.53 0.54 0.55 0.55 0.55 0.55 0.55Nom. Flow, ACFM 5400 7200 9800 13000 18000 24000 32000 43000 59000 79000 106000 143000 193000 ,AM3/H 9175 12233 16650 22087 30582 40776 54368 73057 100241 134221 180094 242957 327907Case ID, inch 20.617 20.617 23.93 27.774 32.235 37.414 43.424 50.4 58.5 67.894 78.8 91.459 106.152 , cm 51.8 51.8 60.2 69.8 81.0 94.1 109.2 126.7 147.1 170.7 198.1 229.9 266.9
350 ( 24.6)400 (28.1) X600 (42.1) X X X X
psig (kg/cm2G) 800 ( 56.2) X1200 (84.3) X X X X X X X X X X X X
1795 (126.2) X X X X X X X X X X2995 (210.5) X X X X X X X X X4995 (351.1) X X X X X X X X7200 (506.2) X X X X X X8500 (597.6) X
10500 (738.2) X X X X X170 (11.9) X X X X300 (21.1) X X X350 (24.6) X X
psig (kg/cm2G) 400 (28.1) X X X X X X600 (42.1) X X X X X800 (56.2) X X X X900 (63.2) X X X
Note: 1.Nominal value of MU is purely by writer's experience. 2. Nominal flow for double flow casing is double of each frame.
Case Rating,Radial
Case Rating,Axial
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Manual CalculationManual CalculationManual Overall Selection( DATUM), Ft/Lbs unit
Project number : Date: Type of Driver:Customer : By:Gas : Barometric pressure: psia Disch. pressure: psiaSour(NACE ) or Sweet gas : Relative Humidity : % Case rating req'd per API(1.25 x Pd-psig)
Operating condition,Sect No 1 2 3 Operating condition,Sect No 1 2 3
Ps-psia Leak Loss, HP ( See table * 2)
Ts- oF( or F+460 oR) Heat loss(LO&SO), HP(See table *3)
MW( Sum of Mol % x Mol Wt of gas) BHP=GHP+Heat Loss+Leak Loss
R = 1545/MW D -inch, Imp. diameter from table(*1)
Zs MU-pressure coeff. from table(*1)
Zav= Zs+Zd / 2 s = Number of Impeller.
Kav N=(1300/D) x (H/ s x MU)1/2 , rpm
WF -Lb/Min or Max. allowable N from table(*1) for the casing
WF=( Nm3/H )x MW/610 Selected compressor model
Svc=Zs RTs/144Ps U = π D N/12x60 , Ft/S: Pai=3.1416
Qs= Svc x WF, ACFM Qs/N
r = Pd/Ps Flow Coeff. = 700 Qs/ ND3
m =(Kav-1/Kav)/NH MU from CIX curve (MUc)
NH assumed from table( * 1) NH from CIX curve(NHc)
H req'd=ZavRTs(rm -1)/m H = MUc x U2 /g where g =32.14
GHP= WF x H /33000 NH Total Head = H x s, Compare with H req'd
Td = Ts x rm : (Td below 380oF) Qd = Qs rm / r
Remark: If no data of table-1,2 & 3 is available, Use NH= 0.8 for below Frame12, 0.83 below Frame 16, and 0.85 for others. Reasonable MU is in the range of 0.48 through 0.54 except for low head impeller.If low head, MU=0.43 is adequate Head per impeller is 8000 through 12000 Ft-Lbs/Lbs depend on MW. Never be more than 18000 Ft Critical speed(NC1 & NC2) has to be checked for adequate separation margin. Min. separation margin per API
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Sequence of CalculationSequence of Calculation
From given Inlet (Ps, Ts, MW & WF) and Discharge condition( Pd), Obtain Head, GHP Speed N and Compressor model using Table 1 attached
No inclusion of mechanical loss by bearing for Brake HP
No inclusion of leak loss effect nor rotor dynamic
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Ps, Ts, MW, Pd, WF Head, GHP Ps, Ts, MW, Pd, WF Head, GHP Calculate Weight Flow (WF) if not given
Calculate Inlet volume Qs = Svc x WF
where Svc= ZsRTs / 1444 Ps ……ACFM, WF……LB/Min
Calculate H= Zav RTs(r m-1)/m …..FtWhere R= 1545.4/MW, r= Pd / Ps, Zav = Zs +Zd / 2
m= (Kav -1 /Kav) / NH,
GHP = WF H/ 33000 NH ….HP
where 33000= 550 x 60 as 1 HP= 550Ft-lb/Sec
Assumed Value: Zs, Zav, Kav, and NH
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ContinuedContinuedAssume number of impeller s: Divide total Head by
8000 to 12000 as standard H ≈ 8000 Ft/ Impeller
Calculate N (rpm)
• Where μ≈ 0.48 to 0.53 corresponding to 8000-12000Ft/imp. Use 0.5 as standard. D av :Imp Dia by inch
Calculate Td = Ts x r m … ° R (460+ ° F)
1300 HN = D avx
µs√
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Excel Spread SheetExcel Spread Sheet
Simple program is separately hand over to audience. Let’s use this with sample selection
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Ps, Ts, MW, Pd, WF -----------> Head & GHP
1st 2ndPs M Pa G 0.511 1.301Ps psia 88.8 203.4
Ts degC 45 40Ts deg F 113 104Ts deg R Ts+460 573 564
Pd M Pa G 1.377 2.845Pd psia 214.4 427.3
MW 7.61 6.25WF kg/h 46663 38013WF lb/min 1715 1397
Q ACFM 15600 6650
Zs 1 1
k 1.35 1.35
efficiency: E 0.82 0.8
(k-1)/k 0.259 0.259
m (k-1) / k / E 0.3162 0.3241
r Pd /Ps 2.414 2.101
r^m Td / Ts 1.321 1.272
Td deg F Ts * (r^m)-460 297.1 257.4
Qd ACFM assuming Zd = 1 8535 4025Total
H ft Z*(1545.4/MW)*(460+Ts)*(-1+r 118,274 117,052 235,326
GHP hp WF * H / 33000 / E 7,494 6,193 13,687kw 5,588 4,618 10,206
K-value (approx)H2, N2, Air : 1.4 CH4, NH3, CO2 : 1.3 C2H4:1.24, C2H2: 1.23, C2H6 : 1.19, C3H6:1.15, C3H8: 1.13
2 section or 2 casing
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““AA”” Compressor Operating ConditionCompressor Operating Condition
377(54.7)Discharge Pressure, kPa (Psia)
38.8Relative Molecular Weight
34.2 ( 553.5)Inlet Temperature, 0C ( 0R)
118 (17.1)Inlet Pressure, kPa ( Psia)
3.025 (400)Weight Flow, kg/s ( Lb/Min)
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““AA”” Compressor selection resultCompressor selection result
Qs= 3580ACFM, Select D4R Frame, D=11.045”H= 27815Ft , GHP=411 HP , Assume 420BHP with 2% losss = 27815/8000=3.5 Either 3 or 4 ImpellerOperating speed N(rpm)
When s=3, N =1300/11.045 (27815/ 0.5x 3)0.5= 16027 rpmWhen s=4, N =1300/11.045 (27815/ 0.5x 4)0.5= 13880rpm
Conclusion: Either D4R3S at 16000rpm with 420BHP or D4R4S at 13900rpmDR’s program for precise selection is D4R4S with 436BHP at 13581rpm. Our Nazri will present later.
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““BB”” Compressor operating conditionCompressor operating condition
9,513 (1379.8)Discharge Pressure, kPa (Psia)
19.91Relative Molecular Weight
34.6 ( (554.3)Inlet Temperature, 0C (0 R)
2,912(422.3)Inlet Pressure, kPa A (Psia)
6.898 (911.4)Weight Flow, kg/s, (Lb/Min)
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Qs= 645ACFM Smallest compressor D2R is good for Max. flow of 5400ACFM, Min.1000ACFM resulting no suitable quote by centrifugal unit
H= 60441Ft, GHP= 2038HP with centrifugal.
Better go to Recip solution!
““BB”” Compressor selection resultCompressor selection result
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““CC”” CompressorCompressor--2 Section with inter cooler2 Section with inter cooler
Stage 2Stage 1Description
1239(179.7)
24.8
33.5
273(39.6)
21.873(2890)
5294(767.8)Dis. Pressure, kPa ( Psia)
24.8Relative Molecular Weight
60Inlet Temperature, 0C (0R)
1170(169.7)Inlet Pressure, kPa( Psia)
21.873(2890)Weight Flow, kg/s (Lb/Min)
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Sample calculationSample calculationQs=17464ACFM ≥ D12R
H=61631FT
S= 7.7 at 8000Ft/imp or 5 at 12000Ft/imp
GHP=6510
Qs=4427ACFM
H=67083Ft
S= 8.4 at 8000Ft/imp or 6 at 12000Ft/imp
GHP=7261
WF= 2893Lb/Min, Total required impeller is 16 at 8000Ft/imp or 11at 12000Ft/imp. Try to squize to 10 imp/case or 2 casing
Total GHP= 13771HP, Total BHP ≈ 14,050 BHP with 2% loss
D12R10B, D=20.043 , N= (1300/20.043)(127814/10x 0.52)0.5= 10245rpm
D14R10B, D=23.263 , N= (1300/23.263)(127814/10x 0.52)0.5= 8792rpm
D16R10B D=27.0 , N= (1300/27)(127814/10x 0.52)0.5= 7575rpm
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ContinuedContinued
Compressor selection either D12R10B,D14R10B or D16R10B is depend on rotor dynamic.
DR’s precise program resulted to D16R10B at 14628BHP at 8044rpm. Refer Nazri presentation
Note: More than 10 impeller/case is not recommended due to Rotor dynamic problem.
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1219
44.1
4.2
537
12.25
Side stream inlet 1
Side stream inlet 2
Stage 1Description
537
44.1
-36
131
41.13
2197Discharge Pressure, kPa
44.1Relative Molecular Weight
35Inlet Temperature, 0C
1219Inlet Pressure, kPa
31.55Weight Flow, kg/s (wet)
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Selection by DRSelection by DR’’s Programs Program
Ghazali Nazri presentation
