4 OPERATING INSTRUCTIONS
4.6. Fault Indications
The following is a list of indications of possible faults which could arise in service;
periodic surveillance of pressures and temperatures, etc, will establish the normally experienced levels applicable to the site and load conditions.
Variation from these due to a fault arising may be slow to impinge - the early effect of a fault (with the robust reciprocating type machine) being, usually very gradual. It is IMPORTANT therefore, to retain a simple daily record sheet of pressures and temperatures. Comparison with previous readings will then warn if there is an untoward trend arising - when reference to the following fault indication's list will indicate the probable cause and remedial action to take. A copy of a typical log sheet is provided in the Appendices located at the end of this manual.
The running performance of the compressor can also indicate when it is necessary to renew a particular part: Generally, wear or malfunction of valves or piston rings will be indicated by variations (other than those due to suction or delivery conditions) in the interstage or final delivery pressure and temperature.
Progressive crankcase bearing wear will slowly give rise to a gradual lowering of the lube oil pressure; if low oil pressure does occur and cannot be traced to any other cause listed, then connecting rod bottom end bearings should be inspected.
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4.6.1 Fault Finding
Minor variations in pressure and temperature readings may occur, due to possible small changes in the suction or delivery conditions. These factors should be considered when checking and assessing instrument readings.
Fault Possible Cause Remedial Action
1) Leaking or broken suction valve
plate in first stage. Replace valve plate -examine seat for damage.
Low first stage delivery pressure (normal or low first stage air
delivery temperature). 2) One or more 1st stage suction valve depressor(s) sticking in
"off-load" position.
Remove, clean and refit
depressor(s) - examine valve for damage
1) Fouling of inlet filter. Renew filter elements.
2) Leaking or broken delivery valve plate in first stage.
Replace valve plate - examine seat for damage.
Low first stage delivery pressure (high first stage air delivery temperature).
3) Worn, broken or malfunctioning
piston rings in first stage. Renew rings - clean grooves.
1) Leaking or broken suction valve plate in second stage.
Replace valve plate - examine seat for damage
2) Second stage suction valve depressor sticking in "off-load"
position.
Examine, clean, and refit valve plate depressor, also examine valve for damage
High first stage delivery pressure (normal or high first stage delivery temperature.
3) Worn, broken or malfunctioning piston rings in third or second stage cylinders.
Renew rings - clean grooves.
High first stage air delivery temperature after cooler.
1) Cooling water flow through first stage intercooler restricted or ceased by blockage.
Examine and clean intercooler tubes (both on air and water sides).
1) Leaking or broken delivery valve plate in second stage.
Replace valve plate -examine seat for damage.
2) Worn, broken or malfunctioning
piston rings in third stage. Renew rings - clean grooves.
3) First stage intercooler tubes blocked on air side.
Examine and clean air side of intercooler tubes.
First stage delivery pressure relief valve blowing.
4) Relief valve defective. Repair or fit new valve.
1) Leaking or broken suction valve plate in second stage.
Replace valve plate – examine seat for damage.
Low second stage delivery pressure (normal or low second stage delivery
temperature). 2) Second stage suction valve depressor sticking in "off-load"
position.
Remove, clean and refit depressor, also examine valve for damage.
1) Leaking or broken delivery
plate in second stage. Replace valve plate – examine seat for damage.
Low second stage delivery pressure (high second valve stage
OPERATION & MAINTENANCE MANUAL
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CHAPTER 4 - OPERATING INSTRUCTIONSIssue: 1
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Fault Possible Cause Remedial Action
High second stage air delivery temperature after intercooler
1) Cooling water flow through second stage intercooler restricted or ceased blockage.
Examine and clean intercooler cooler tubes (both on air and by water sides)
1) Leaking or broken suction valve or delivery valve plate in third stage.
Replace valve plate – examine seat for damage
2) Third stage suction valve depressor sticking in "off-load"
position.
Remove, clean and refit depressor, also examine valve for damage.
3) Second stage intercooler tubes blocked on air side.
Examine and clean air side of intercooler tubes.
Second stage delivery pressure relief valve blowing.
4) Relief valve defective. Repair or replace valve.
1) Demand of end using equipment has overtaken capacity of compressor.
If none of the previous faults are present, i.e. compressor running normally, no remedial action possible.
When demand reduces, the
pressure will rise to normal level (as set by the load controller).
2) Low setting of load controller. Adjust to required pressure.
Low third stage delivery pressure.
3) Malfunction of load controller. Repair/replace pressure controller.
1) Leaking or broken delivery valve plate in third stage.
Replace valve plate – examine seat for damage.
2) Leaking or broken suction valve plate in third stage.
Replace valve plate – examine seat for damage.
3) Third stage suction valve depressor sticking in "off-load"
position
Remove, clean and refit depressor, also examine valve for damage.
High third stage delivery temperature.
4) Worn, broken or malfunctioning
piston rings in third stage. Renew rings and clean piston ring grooves.
1) Isolating valve, between compressor and delivery main closed or partially closed.
Open valve.
2) Incorrect setting or malfunction of load controller.
Adjust to required pressure or repair/replace pressure controller.
High third stage delivery pressure (relief valve blowing).
3) Restriction or blockage of control signal to compressor unloader system.
Remove restriction.
4) Aftercooler tubes blocked or restricted on air side.
Examine and clean air side of aftercooler tubes.
5) Seized closed, or partially closed non-return valve in delivery main (if fitted).
Repair valve.
6) Relief valve defective. Repair or fit new valve.
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Fault Possible Cause Remedial Action
1) Cooling water flow through aftercooler is restricted or ceased by maladjustment of hand valves.
Check and adjust hand valve openings.
High final air temperature from aftercooler.
2) Aftercooler tubes partially blocked on airside, or waterside of tubes is fouled.
Examine and clean air and water sides of tubes.
1) Crankcase oil level is low. Check oil level, add oil as required.
2) Air leakage into suction side of
pumping system. Check oil level. Check connecting unions on suction pipe to pump.
3) Partially blocked oil pump
suction strainer in crankcase. Remove, clean and refit.
4) Oil relief valve set too low or
valve sticking open. Remove, check and reset.
5) Failure or wear of big end or
small end bearings. Renew bearing(s). Check crankshaft for damage.
Low lubricating oil pressure.
6) Partially blocked oil pump
delivery filter element. Replace element.
1) Compressor rotation incorrect (first trial run, or after a rebuild).
Change compressor rotation and recheck
2) Crankcase oil level very low. Check oil level, add oil as required.
3) Serious air leakage into oil pump section pipe or complete disconnection.
Check suction pipe and unions to pump.
Loss of oil pressure.
4) Complete blockage of oil pump suction strainer.
Check and clean oil sump.
Remove, clean and refit strainer.
Change oil as necessary.
5) Oil pump drive failure. Examine drive coupling, ascertain cause of failure and rectify.
6) Oil pump seizure. Replace pump. Check drive coupling.
1) Drain trap blocked. Dismantle, clean and refit.
2) Separator drain pipe to trap
blocked. Dismantle, clean and refit.
No condensate from drain trap of interstage moisture separator or aftercooler moisture
separator. 3) Dry atmospheric conditions. Applies to 1st stage only.
Large quantity of condensate emitted from drain trap.
1) This suggests that there is an internal leakage from the cooling water spaces into the air spaces of the compressor (low pressure stage).
Trace the fault and rectify as necessary.
Note: Water emitted from the traps is usually in the form of a trickle
CHAPTER 5
COMPRESSOR MAINTENANCE
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