COMPRESSED AIR SYSTEM.doc

8/12/2019 COMPRESSED AIR SYSTEM.doc

1/12

9. Air Compressor House

Contents: Introduction

LP Compressor

Specification

LP Compressor control

Compressor surge

LP Compressor start up procedure

Pre start check.

Start up.

Typical LP Compressor face plate readings.

Shutdown procedure of LP Compressor.

Lube oil used in Compressor House.

D!S and D"!TS.

Trouble shooting #LP Compressor$.

HP Compressor.

HP Compressor start%up procedure.

HP Compressor shut down.

"ormal check%up.

HP compressor alarm.

Trouble Shooting #HP Compressor$.

Instrument air dryer.

Details of air dryer thermoprobe.

Tips.

&uide book for 'tility operation( Section )* +ir Compressor Page , of ,-


2/12

Air Compressor House

Introduction:

Instrument and plant air reuirement of whole refinery is met by two "os of LP #low pressure$

compressors with emergency back up of HP compressor which can be run with /0D& power.LP compressors feed air to one number of LP recei1er #2.- 0 3capacity$ at 4.5 kg6cm-. Plant air

and air for nitrogen generation is directly supplied from the LP recei1er through shut off 1al1es

#which got shut at low pr. 5.7 kg6cm-$. Instrument air is supplied from LP recei1er through two

numbers of air dryers. HP compressor feed air to HP recei1er #87.35 03capacity$ at 3- kg6cm-.

In case LP recei1er air pressure drops( HP recei1er feeds air to instrument air header at outlet of

LP recei1er( through pressure reducer #controller$ and non return 1al1es and protected by safety

1al1e with set pressure of ).5 kg6cm-. Incase of power failure air recei1ers are capable to supply

instrument air for about ,5 minutes.

1. LP Compressor:

Specification:

Type* Centrifugal three stage modulated controls and unloading facilities.

0ake* 06S Ingersoll%rand( 0odel* C38 0 9 3. Capacity* 54)7 : - "m3 6hr( discharge press

4.5 kg 6cm-a( rpm -);5( LP recei1er normal pressure 4.7


3/12

Status 0odulated

control

Two step control 0odulated ATwo step

control

CompressorS6D I6L 161 full closed6P 161 full open I6L 161 full closed( 6P 161full open I6L 161 full closed( 6P161 full open

Compressor

started

I6L 161 open to

unload position

#-;$(

I6L 161 open to unload

position #-;$(

I6L 161 open to unload

position #-;$(

Discharge

pressure less

than set pr.

+ir demand is

more

ypass 161 will

be modulated to

closed then( inlet

161 will modulate

open.

+t cut in pressure #min

allowed pressure$( bypass

161 will fully closed and

inlet 161 will fully open.

+t cut in pressure # min

allowed pressure$(

bypass 161 will fully

closed and inlet 161 will

fully open

Discharge

pressure

increasesabo1e set

pressure. +ir

demand is less

Inlet 161 will be

throttled upto

throttle range#57$( then

bypass 161 will

modulate open.

+t cut out pressure #ma:

allowed Pressure$( bypass

161 will fully open andinlet 161 will throttle to a

position permitted by the

unload limit regulator

#-;$.

Inlet 161 will be throttled

upto throttle range( if

still pressure is highcompressor will unload

#bypass 161 will fully

open and inlet 161 will

throttle to a position

permitted by the unload

limit regulator #-;$.

Description:

,. >hen compressor started in unload( I6L 161 will remain open at -;. >hen selector

changed o1er from unload to modulated control( I6L 161 will open 57 #CLL 1alue$ keepingbypass 161 open at ,77.

-. >hen compressor is started on modulated control I6L 161 will open -; till Epre lube timeF

elapsed #,4sec$( after that I6L 161 will open to 57.

3. Throttling @ange of inlet 1al1e* This is the minimum #flow$ opening of inlet 1al1e. If further

inlet 1al1e is throttled( compressor will run in surge range hence unstable and may getsurged on further flow reduction. So compressor air flow should always be more than surge

1alue( in other words inlet 161 should not be throttled more than throttle range #57$.

Compressor surge:

when compressor could not de1elop pressure more than the system press( re1ersal of flow

takes place which may damage the compressor impeller. It is called surge.

The surge sensor is a differential pressure switch that senses the difference between normal

operation pressure and rapidly decreasing discharge pressure( which occur during surge

condition. n sensing surge( it unloads the compressor #I6L 161 open -;( and bypass 161

fully open.

&uide book for 'tility operation( Section )* +ir Compressor Page 3 of ,-


4/12

LP Compressor start up procedure

Pre start check:

,. Check that( lube oil le1el and temp is normal.

-. pen the block 1al1e in discharge line.

3. Charge cooling water system.2. Line up lube oil system.

5. 0aintain seal air pressure more than ,7 psig.

8. Drain condensate from air coolers( accumulators and piping etc by opening trap bypass 161.

;. If starting after long shut down( 1ent cooler!s waterside.

Start up:

,. Turn on the cooling water to the air coolers and ensure the water circulation. Cooling water

inlet pressure should be 3.5


5/12

!pical LP compressor face plate readings:

"unction Actual Alert Shut do#n

il temp. high 7C 23 2) 5-

il temp. low 23 35 3-

Kibration stage , #mills$ 7.,; 7.42 ,.72

Kibration stage - #mills$ 7.-, 7.47 ,.77

Kibration stage 3 #mills$ 7.-, 7.47 ,.77

+ir temp. stage - -4 2) 5-

il pressure


6/12

Do%s and don%ts:

,. +uto Condensate trapes should always be in ser1ice. Periodically check its working byopening bypass 161.

-. Periodically drain recei1er 1essels and drier moisture separator.

3. 0onitor dp across pre filter( adsorber( after filter if it is high than normal take correcti1e

action and inform shift incharge.

2. Don!t take heater in ser1ice without sufficient air flow.5. Periodically monitor operating parameter( lube oil filter dp and suction filter dp.

8. 0aintain lube oil temp ,,7 7B to ,,5 7B.

rou$le shooting &LP Compressor':

,. Power failure.

-. Compressor discharge temp high.

3. Low system air pressure.

2. High 1ibration*5. Low lube oil pressure.

8. High lube oil temperature.

;. Compressor is not taking start.4. Compressor surge*

1. Po#er failure:

(ffects:

LP air compressor and hp air compressor will trip.

LP air compressor au:iliary lube oil pump cuts in auto after getting emdg power supply.

+ir drier heater will cut out.

Plant air and instrument air pressure will drop.

Plant air to nitrogen plant( shut off 1al1e will close.

Hp recei1er to instrument air control 1al1e will open to maintain instrument air pressure.

Cooling water supply may fail.

Seal air pressure may drop.

Actions:

Hp air compressor may be started after starting emdg.

pen hp recei1er outlet control 1al1e bypass 1al1e( if reuire.

n resuming power( charge cooling water system.

pen lp cooler condensate drain and moisture separator drain 1al1es.

@estart compressors after resumption of power.

Check that seal air pressure is ok.

&uide book for 'tility operation( Section )* +ir Compressor Page 8 of ,-


7/12

). Compressor discharge temp high:

+ir flow may be 1ery less causing after cooler inlet temperature high.

Cooling water to compressor acket cooling is not effecti1e.

Check acket cooling line for choking.

Oacket may be dirty #hp compressor$.

Check inter stage coolers inlet 6 outlet temperature.

Cooling water flow 6 pr. Low or temp. High.

+fter cooler is not working.

Check cooling water pressure( flow and temperature.

Cooler tubes may be choked or dirty.

/:cessi1e number of tubes may be plugged to arrest tubes leakage.

Dirty or plugged air cooler on water side or air lock.

*. Lo# discharge +s!stem air pressure:

'nloading 1al1e is open or passing.

Inlet 1al1e is not open up to reuirement.

Suction filter is choked.

+tmospheric temperature is 1ery high.

Inter stage cooler outlet temperature is high.

+ir consumption is 1ery high.

Compressor not loaded or low surge.

>orn out impeller.

,. High -i$ration:

earings damaged.

0oisture le1el high in air.

Low oil temperature.

0isalignment with dri1er.

@otor damaged due to damaged aero parts.

@otor unbalance due to buildup.

Induced 1ibration from dri1er due to worn coupling6spacer.

. Lu$e oil pressure lo#:

Lube oil le1el low( lube oil pump fail or pressure gauge faulty

@elief 161 setting improper.

Suction 6discharge line or cooler leak.

Suction strainer 6 discharge filter dirty.

Standby pump nr1 passing.

Lube oil temperature may be high.

/. High lu$e oil temperature:

&uide book for 'tility operation( Section )* +ir Compressor Page ; of ,-


8/12

Cooling water flow 6 pr. Low or temp. High.

Cooler tube dirty or air lock.

0. "ail to start:

"o primary power to starter.

"o control panel power.

Defecti1e motor starter.

Seal air pressure low( lube oil temperature high( lube oil pressure low and cw flow low.

Bailure to clear shut down or interlocks de1ice.

. Compressor surge:

Discharge block 1al1e closed.

Dirty inlet filter

Improper calibration of surge sensor.

High inter stage air temperature

>orn aerodynamics part.

Improper adustment on llr or low current limit.

). HP Compressor*

Three stage reciprocating air compressor( third stage split into two part installed at both end of

compressor. Loading6 unloading pressure -4


9/12

8. Start lube oil pump for ,7 to ,5 minutes in auto mode and note that lube oil pressure is

abo1e ,.4 kg6cm- and ELube oil pressure low E alarm got reset.

;. "ow start compressor and slowly close bypass 1al1e fully and also condensate drain 1al1es.4. Check that au:. Lube oil pump stopped in auto.

HP Compressor Shut Do#n:

,. pen bypass 1al1e fully and close discharge 1al1e .-. Stop the compressor.

3. pen all condensate drain 1al1es.

2. Check that pre Lube oil pump is started on auto.

5. Stop pre lube oil pump after half an hour.

3ormal Check2up:

,. Drain condensate from recei1er( moist. Separator and lines etc.-. Check that all moisture traps are working.

3. Check lube oil filter differential pressure.

2. Check motor bearings temp and amps. It should not run with 1ibration or abnormal sound.

5. Check for any lube oil leakage.

8. Check that all parameters are normal.

HP compressor alarm:

S.". T+& " I"ST@'0/"T +L+@0 T@IP

, BSL%,33- Blow low after cooler

- B+L%,33, Blow low of c.w.r. header

3 P+L%,33, Lub oil pressure lo ,.4 kg6cm-

2 PSLL%,333 Lub oil pressure lo lo ,.8 kg6cm-

5 T+H%,33, Temp. Hi of ,ststg. Inter cooler ,85 7C

8 T+HH%,33- Temp. Hi hi of ,ststg. Inter cooler ,;7 7C

; T+H%,333 Temp. Hi of -nd stg. Inter cooler ,85 7C

4 T++H%,332 Temp. Hi hi of -nd stg. Inter cooler ,;7 7C

) T+H%,335 Temp. Hi at discharge ,85 7C

,7 T++H%,338 Temp. Hi hi at discharge ,;7 7C

rou$le Shooting &HP Compressor':

,$ Discharge pressure low

-$ Suction pressure high

3$ +ir flow low

2$ +ir temperature high

5$ Kal1e body hot.

8$


10/12

1. Discharge pressure lo#

Suction 161( discharge 161 #mounted on cylinder$ passing.

Consumption high #recei1er pressure 1ery low$.

Inlet 6 outlet 1al1es passing. Check each stage inlet and outlet pressure and temperature.

Inlet pressure and suction 1al1e body temperature unusually high indicates inlet 1al1e of that

stage is passing. utlet pressure unusually low and discharge 1al1e body temperature high

indicates discharge 1al1e of that stage is passing.

Suction filter is choked.

+ir suction piping is plugged with moisture6condensate.

+ir coolers are leaking.

Compressor discharge relief 1al1e or moisture drain 1al1e may be passing.

). Suction pressure high: Suction 1al1e may be passing.

*. Air flo# lo#

Suction 6 discharge 1al1e passing.

Suction strainer dirty or piston ring worn out.

Compressor running unloaded.

,. Air temperature high

Cooling water flow or pressure low or cooler tube dirty.

5. 4al-e $od! hot: Kal1e may be passing.

/. 5nocking sound:

If knocking sound is coming from crankcase( bearing of the big end of connecting rod may

ha1e e:cessi1e play.

If sound is from cylinder( piston ring may be broken or piston rod on cross head may not be

tightened properly.

Symptom Possible cause6 correcti1e action

Lube oil

pressure low

Lube oil le1el low( lube oil pump fail or pressure gauge faulty

@elief 161 setting improper( suction 6discharge line or cooler leak.Suction strainer 6 discharge filter dirty or standby pump nr1 passing.

High lube oiltemperature

Cooling water flow 6 pr low or temp high.Cooler tube dirty or air lock.

High air

temperature

Dirty or plugged air cooler on water side or air lock.

Cooling water flow 6 pr low or temp high.

Low system

air pressure

Compressor not loaded or low surge.

Dirty inlet filter or greater demand than realiQed( worn out impeller.

High

1ibration

Low oil temperature. 0isalignment with dri1er.

>orn coupling6spacer. @otor damaged due to damaged aero parts.

@otor unbalance due to buildup. Induced 1ibration from dri1er.

&uide book for 'tility operation( Section )* +ir Compressor Page ,7 of

,-


11/12

Bail to start "o primary power to starter. "o control panel power. Defecti1e motor

starter. Trip 1al1e not reset.

Seal air pressure low. Bailure to clear shut down or interlock de1ice.

Continual

surge

Discharge block 1al1e closed. Dirty inlet filter

Improper calibration of surge sensor. High inter stage air temperature

>orn aerodynamics part improper adustment on llr or low current limit.

Instrument Air dr!er:

Two "os of air drying unit Supplied by 06S Lloyds Steel Industries Limited # Prabhade1i(

0umbai.$ thru order "o% "@L63-226-,%L"%P%27),6744. ear built% ,));. 0odel* "LP%+%

33-7.Design condition* Inlet air at 4.5


12/12

+dsorber ed temp during reacti1ation at bottom ,85 7C. and at top ,57 7C.

Temperature of bed which is in ser1ice* at bottom -7 7C. and at top 37 7C.

@eacti1ation air flow in bed from bottom to top.

"ormal air for drying ( flow in bed from top to bottom.

oth heater bank will trip( in case skin temperature goes to --7 7C. or regeneration flow is

less than 5;7 "036 hr.

&uide book for 'tility operation( Section )* +ir Compressor Page ,- of

,-

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COMPRESSED AIR SYSTEM.doc