Compressor Head Calculations Design Guide

8/13/2019 Compressor Head Calculations Design Guide

1/24

PROCEDURE NO.

PTD-DGS-125

PAGE OF

1 9

PROCESS TECHNOLOGY PROCEDURES

PREPARED BY

Edited from exiti!"do# $% &.R. B'r!('rt

DATE

A)ri* +, 2,,,

DEPARTENT/ PROCESS ENG0NEER0NG

APPROED BY

&RB

SUB&ECT/ COPRESSOR EAD CA3CU3AT0ONS DES0GN GU0DE RE0S0ON DATE

114,14,2

RE.

1

1.0 SCOPE

This design guide1describes the method used to calculate compressor circuit hydraulics.Refer to the Rotating Equipment Engineering Manual for a detailed description ofcompressor design and operation.

2.0 RESPONSIBILITIES

The process engineer determines the hydraulic requirements for compressor circuits.

3.0 CODES AND STANDARDS

American Petroleum Institute (API

!T" #1$ %entrifugal %ompressors for &eneral Refinery !er'ice

!T" #1 Reciprocating %ompressors for &eneral Refinery !er'ice

4.0 DEFINITIONS

)isted belo* are the definitions of terms associated *ith calculations for centrifugal and

reciprocating compressors using traditional +.!. units.

4.1 Centrif!"# C$%&re''$r'

The API !T" #1$ definitions are sho*n belo* and in ,igure 1.

1. -ormal operating point is the point at *hich usual operation is epected andoptimum efficiency is desired. This point is usually the point at *hich the !uppliercertifies that performance.

/. -ormal speed is the speed corresponding to the requirements of the normaloperating point.

0. ne2hundred2percent speed is the highest speed required for any specifiedoperating point abo'e the normal speed cur'e. If there are no specified operatingpoints that require greater than normal speed3 the 1442percent speed shall be thenormal speed.

5. %ompressor rated point is the point on the 1442percent2speed cur'e at the highestcapacity of any specified operating point.

6. Maimum continuous speed (in re'olutions per minute for compressors dri'en by'ariable2speed prime mo'ers is the speed at least equal to 146 percent of the

1Re. , of t(e Dei"! G6ide 7' 'd')ted 7it( mi!im'* #('!"e from ' P''de!' do#6me!t DSG-P8 9492


2/24

highest speed required by any of the specified operating conditions. Maimumcontinuous speed for constant2speed dri'ers shall be equal to the 1442percentspeed.

#. Minimum allo*able speed (in re'olutions per minute is the lo*est speed at *hichthe manufacturer7s design *ill permit continuous operation.

$. Trip speed (in re'olutions per minute is the speed at *hich the independentemergency o'erspeed de'ice operates to shut do*n a prime mo'er (see Table 1.

. !tability is the difference in capacity (in percentage of rated capacity bet*een therated capacity and the surge point (and rated gas properties.

8. Turndo*n is the percentage of change in capacity bet*een the rated capacity andthe surge2point capacity at the rated head *hen the unit is operating at ratedsuction temperature and gas composition.


3/24

!ource9 API !T" #1$

,igure 1 : %entrifugal %ompressors 2 "efinitions


4/24

Table 1 2 "ri'er Trip !peeds

"ri'er Type

Trip !peed(percent of maimum

continuous speed

!team turbine-EMA %lass A 116-EMA %lasses ;3 %3 " 114

&as turbine 146


5/24

COPRESSOR EAD CA3CU3AT0ONS DES0GN GU0DE

PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

2 25

1. Rated discharge pressure is the highest pressure required to meet the specifiedconditions.


6/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

+ 25

/. Rated discharge temperature is the highest predicted operating temperatureresulting from a specified operating condition.

0. !%,M is an abbre'iation for capacity in standard cubic feet per minute at 15.$pounds per square inch absolute (psia and #4 degrees ,ahrenheit.


7/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

8 25

5. I%,M is an abbre'iation for inlet cubic feet per minute determined at suction(compressor inlet flange conditions of pressure3 temperature3 compressibility3 andmoisture. I%,M and A%,M (actual cubic feet per minute are identical in meaning(at the inlet conditions. To determine I%,M3 allo*ance shall be made forpressure drop across pulsation suppression de'ices and for interstage =noc=out.

6. Minimum Allo*able !uction Pressure for each stage is the lo*est pressure at theinlet flange belo* *hich the combined rod loading3 or gas loading3 or dischargetemperature3 or cran= shaft torque loading *ill eceed the maimum allo*able

during operation at the setpoint pressure of the discharge relief 'al'e and otherspecified gas conditions for the stage.


8/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

5 25

).0 CALCULATION PROCEDURE * CENTRIFUGAL AND RECIPROCATINGCO+PRESSORS

+sing the %ompressor %ircuit %alculation form3 complete the data section as follo*s9

).1 Ser,i(e C$n-iti$n'

Enter ser'ice conditions and state the tag number and stage number.

).2 F#$ S/et(


9/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

25

+sing the %ircuit Pressure "rop form3 (Ehibit /3 construct a flo* s=etch identifyingpertinent equipment by item>tag number and sho*ing orifices3 control 'al'es3 andalternate flo* routes. Include dimensions for compressor center line from datum3 linesi?es3 static head3 relief 'al'e set pressures3 and bloc= 'al'es. !ho* ele'ations ofequipment.

).3 Line Siin!

%omplete the line si?e calculations using the pro@ect specified method. +se actualrouting3 if =no*n3 or the estimated route3 using coordinates of equipment and allo*ing for


10/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

: 25

change of ele'ation3 pipe fittings3 and 'al'ing. Particular care should be ta=en inestimating the suction line equi'alent length.

).4 C$%&re''$r Differenti"# He"- C"#(#"ti$n'

The compressor differential head calculations shall be performed as follo*s9

1. Enter line "P as calculated abo'e.


11/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

; 25

/. "Ps of flo* measurement de'ices shall be actual 'alues obtained from theinstrumentation and controls super'ising engineer. ;e sure to consider the use oflo*2pressure2drop de'ices for compressor circuits.

0. Identify the echanger or equipment and the "P across the unit. These 'aluesshould be realistic and should be obtained from the heat transfer super'isingengineer. +se only fouled 'alues (allo*able "P.

5. R dynamic "P is the sum of dynamic losses listed abo'e.

6. ,or control 'al'e "P3 consult *ith the instrumentation and controls super'isingengineer to obtain the minimum 'alue that *ill ensure proper control of the


12/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

9 25

compressor circuit. &enerally3 these 'alues *ill be approimately 16 percent of thetotal dynamic losses.

#. %ompressor suction pressure is obtained by subtracting the total dynamic loss andthe control 'al'e "P from the suction 'essel pressure3 allo*ing for static headdifference.

$. Terminal pressure is the pressure at the end point of the compressor system. Thisis generally a 'essel3 the @unction *ith another system3 or the battery limit.


13/24


14/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

11 25

The compressor team is an organi?ation of members from the technical engineeringorgani?ation *hose function is to agree on and to fi information pertinent to the designand procurement of compressor2dri'er units. n a specific pro@ect3 this team may beformal or informal.

The process engineer is responsible for compressor hydraulics and participates inestablishing compressor2dri'er type and number.

.0 EHIBITS

The follo*ing ehibits are referenced in this design guide.


15/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

12 25

Ehibit Title

1 PT"2,RM2111 2 %ompressor %ircuit %alculation ,orm/ PT"2,RM2114 2 %ircuit Pressure "rop ,orm


16/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

1+ 25


17/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

18 25


18/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

15 25

Ehibit 1 2 %ompressor %ircuit %alculation ,orm


19/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

1 25


20/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

1: 25


21/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

1; 25

Ehibit / : %ircuit Pressure "rop ,orm


22/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

19 25


23/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

2, 25


24/24


PROCEDURE NO.

PTD-DGS-125

RE.

1

DATE

114,14,2

PAGE OF

21 25

Ehibit / : %ircuit Pressure "rop ,orm (%ontd

Documents

Compressor Head Calculations Design Guide