5 COMPRESSOR MAINTENANCE
5.2 Maintenance Instructions
The following procedures are intended for the use of the technician responsible for the maintenance of the compressor. It is essential that any necessary adjustments, servicing or overhaul work should only be carried out by competent persons who are familiar with the compressor installation and who have the appropriate authority (Permit to Work). To avoid possible warranty invalidation the following instructions should be read before attempting to maintain the machine.
WARNING!
When working on compressor rotational parts you MUST fit piston rod clamps to prevent possible uncontrolled movement of the crankshaft and motion work. THIS COULD RESULT IN INJURY OR LOSS OF LIFE.
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JOB No. 001
CRANKCASE OIL CHANGE
LIST OF SPECIAL TOOLS
Description Qty
Thin Spanner (approx. 10 mm thick) 1
LIST OF CONSUMABLES
Crankcase Oil SAE 30 oil (ISO VG 100) (Normal Operating Conditions) As required Industrial cleaning fluid (White Spirit) & lint free cloth As
required
WARNING!
To avoid scalding by hot oil, allow the compressor to cool down before beginning work.
1) Isolate mains power and display appropriate warning signs.
2) Remove the crankcase doors whilst taking care not to damage the oil seals.
3) Wipe any excess oil off the doors using an industrial cleaning fluid and a lint free cloth.
Place the cover in a clean location to avoid oil contamination when refitting.
4) Empty the oil sump using suitable equipment and clean out the crankcase sump (using a lint-free cloth, to avoid fouling of the oil strainer).
5) To avoid oil spillage, never remove the oil suction strainer while oil remains in the crankcase
6) To remove the oil strainer use a thin spanner, on the strainer body hexagon to unscrew the strainer whilst holding the external hexagon fitting to prevent turning. This fitting is not screwed into the crankcase - it passes through a clear hole.
7) Refit the oil strainer and check that all tools and cleaning cloths have been removed from the crankcase sump.
8) Refill the crankcase sump with the required quantity of clean, new oil.
9) Refit the crankcase doors after checking the condition of the door seals.
10) Test run the compressor and check for oil leaks around the strainer seal and crankcase doors. If all is satisfactory, return the machine to service.
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JOB No. 001 - CRANKCASE OIL CHANGE (Cont)
Crankcase Assembly
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JOB No. 002
FIT PISTON ROD CLAMPS
LIST OF SPECIAL TOOLSDescription Qty
Piston Rod Clamps 1 Set
LIST OF CONSUMABLES
Industrial cleaning fluid (White Spirit) & lint free cloth As required 1) Isolate mains power and display appropriate warning signs.
2) Remove the distance piece access covers from the line of motion works NOT being worked on. Wipe any excess oil off the covers using an industrial cleaning fluid and a lint free cloth. Place the cover in a clean location to avoid oil contamination when refitting.
3) Mark the position of the oil shedder on the piston rod and remove shedder.
4) Loosely assemble the piston rod clamps onto the piston rod.
5) Manually 'bar-over' the compressor to the desired position and hold steady.
6) Whilst one person holds the crankshaft bar in position, the other must tighten the one piston rod clamp firmly against the packing gland box and the other firmly against the scraper gland box.
7) Only when both clamps are tight in place can the crankshaft bar be carefully released and safe work or inspection takes place.
When working on the third stage of this compressor the following additional checks MUST be made to ensure that the compressor is safe to work on.
8) Isolate the non-return valve to prevent possible blow-back pressure.
9) Isolate the compressor from the receiver at the stop valve.
10) Vent down the third stage at the anti-surge vessel immediately after the cylinder.
11) Carefully open the vent valves on the third stage cylinder to check de-pressurising has been completed successfully.
12) When removing the valve cover very carefully slacken the fasteners initially in case there is any residual pressure present.
WARNING!
When maintenance work has been completed the piston rod clamp MUST be removed.
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JOB No. 003
CYLINDER TOP COVERS - REMOVE & REFIT
LIST OF SPECIAL TOOLSDescription Qty
Lifting Eye-Bolts 1 Set
Slings, Lifting Equipment As
required LIST OF CONSUMABLES
Industrial cleaning fluid (White Spirit) & lint free cloth As required To Remove
1) Ensure that the compressor is fully de-pressurised, electrically isolated and isolated from the air supply.
2) Post signs instructing personnel that the machine MUST NOT be used.
3) Isolate and drain the cooling water from the compressor cylinders.
4) Remove cooling water pipes from the top cover and fit blanking plugs to prevent dirt ingress.
5) Check that there are no supply pipes or hoses fastened to the top cover.
6) Release and remove the top cover securing nuts from the cylinder fixing studs.
7) Fit lifting eye-bolts into the relevant lifting holes
8) Attach a suitable sling to the eye-bolts, and using suitable lifting equipment, take up the slack in the sling.
9) Slowly lift and guide the top cover from the cylinder studs.
10) Clean the top cover using an industrial cleaning fluid and a lint free cloth.
11) Lower the top cover onto a suitable, clean work-surface taking care not to damage the machined face.
To Refit
If any maintenance has been carried out on the motion work which may affect the piston to cylinder (bumping) clearances, check the clearances are correct before refitting the top cover. Refer to Job No. 004.
1) Ensure that the cylinder top cover and cylinder top mating faces are clean.
2) Check the condition of the cylinder top cover gasket. Renew if necessary.
3) Fit a new gasket over the cylinder studs and onto the cylinder mating face.
4) Attach a suitable sling to the eye-bolts, and using suitable overhead lifting equipment, raise and position the top cover over the cylinder.
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JOB No. 003 - CYLINDER TOP COVERS - REMOVE & REFIT (Cont)
5) Slowly lower and guide the top cover onto the cylinder, ensuring the correct positioning of the cooling water and gas pockets.
6) When in position, remove the sling and lightly secure the top cover to the cylinder with the fixing nuts.
7) Tighten the cylinder cover nuts (centre nuts first), tighten the nuts down evenly and progressively. Nuts to be torque tightened to the appropriate torque figure. Refer to Chapter 1 Section 1.1.3.
8) Remove the eye-bolts from the top cover and refit the cooling water pipe 9) Secure the supply lines to the cylinder top cover with their fasteners.
10) Re-establish water and electrical supplies to the compressor.
11) Bleed off any trapped air in the cooling system using the plugs in the cylinder water jacket.
12) Test run the compressor on clean, dry air or nitrogen and check for correct operation and freedom from leaks around any of the disturbed gaskets.
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JOB No. 004
PISTON RINGS - REMOVE & REFIT
LIST OF SPECIAL TOOLSPiston rod bullet 1
LIST OF CONSUMABLES
Description Qty Industrial cleaning fluid (White Spirit) & lint free cloth As
required To Remove
There are two ways of removing the piston from the compressor: Method 1 is as a unit without the piston rod (this procedure) and Method 2 as an assembly with the piston rod attached. This method can be used if the maintenance procedure being performed does not call for the piston nut to be removed. If Method 2 is to be used the piston removal procedure is detailed as part of Job No.013 Piston Rod - Remove/Refit.
The '1st stage piston' can only be removed using Method 2.
1) Remove the cylinder top cover as described in Job No.003.
2) Remove the crosshead access cover and gasket from the crankcase.
3) Manually 'bar-over' the compressor to ensure that the piston is at its BDC position.
Measure and record the TDC and BDC "Bumping Clearances". Refer to Chapter 1 Technical Data.
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JOB No. 004 - PISTON RINGS - REMOVE & REFIT (Cont)
4) Bend back the tab on the locking plate retaining the piston rod/crosshead securing pin and remove the pin.
Ensure that the securing pin is removed before slackening the piston nut. Otherwise, if the piston rod turns in the crosshead while the securing pin is in position, the pin will distort making it extremely difficult to remove.
5) Slacken the piston nut.
WARNING!
It is possible that pressure can have accumulated within the interior of the piston. There is a pressure release hole drilled in the piston top half, which is (on assembly) covered by the underside of the piston nut/washer. It is essential, where the hole is covered by a washer, to ensure that the washer is not stuck in place before the nut is unscrewed by more than one turn.
This is to make certain that the pressure relief hole is fully open to atmosphere.
6) Remove the piston nut.
7) Remove the piston and washer by lifting the piston (which is in halves) very carefully off the rod.
If the piston is tight on the rod and cannot be easily lifted, proceed as follows:
8) Manually 'bar-over' the compressor to turn the piston to TDC and insert diametrically opposite (IMPORTANT) two equal length pieces of hard wood via valve pockets to block the piston. Place the wood chocks about 25mm clear of the piston rod sides NOT at the piston periphery.
9) Turn the crankshaft to BDC to withdraw the rod.
10) Carefully turn the compressor back to TDC taking the piston upwards.
11) Insert longer pieces of hard wood if the piston is still tight on the rod and repeat steps 9 and 10.
An observer MUST be stationed to control the piston emerging from the cylinder. The two halves being lifted separately from the rod top with care being taken to remove the piston rings safely during the operation.
12) Remove the wood blocks when the piston has been lifted out.
If the piston halves are stuck together, lift the piston off as an assembly and part the halves carefully on a work-bench taking care not to damage the piston body.
Examination
Piston Pressure Rings - For piston pressure ring dimensions refer to Chapter 1 Technical Data. The pressure rings MUST be replaced with new ones when the radial thickness at any point has worn to 65% or less of the original thickness.
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JOB No. 004 - PISTON RINGS - REMOVE & REFIT (Cont) Piston Rings Renew
13) Remove and discard the old piston rings.
14) Clean piston ring grooves carefully.
15) Insert the new piston ring squarely into the cylinder bore and check that the bearing ring standout and axial clearance is correct. Refer to Chapter 1 Technical Data.
Figure Shows Piston Ring Configuration for 1st Stage Piston
16) Fit the new piston rings by carefully springing them over the piston body (single piece rings only).
17) Ensure that the rings are correctly seated in the piston groove.
If the cylinder bore is cored or very lightly polished with no signs of honing marks it may be necessary to re-hone the bore. (In some cases a flexi-hone can be used!).
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Piston Assembly 1st Stage
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JOB No. 004 - PISTON RINGS - REMOVE & REFIT (Cont)
Piston Assembly 3rd Stage To Refit
1) Place the piston rod to TDC and, after checking that the bottom reinforcing washer is in order and correctly in place, lower the bottom half piston body onto the washer and rod and settle it into place.
2) Fit the top half piston, setting the butt gaps of the pressure rings to opposite sides (i.e.
180o opposed) and carefully lower into place over the rod.
3) After checking that the pressure relieving hole is clear, fit the top half piston to the bottom half piston.
4) Fit the top reinforcing washer onto the piston top half.
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JOB No. 004 - PISTON RINGS - REMOVE & REFIT (Cont)
5) Fit and very lightly tighten the piston nut.6) Check that the crosshead locknut is tight in place and, ensuring that the securing pin is removed from the crosshead, fully tighten the piston nut to the appropriate torque figure. Refer to Chapter 1 Section 1.1.3.
7) Measure and record the end ("bumping") clearances with the piston at the top (Top-Dead-Centre) and bottom (Bottom-(Top-Dead-Centre) of its stroke. Refer to Job No.005.
8) Refit the cylinder top cover as described in Job No.003.
9) Check the piston bumping clearances against the figures earlier recorded to ensure that the piston is properly down.
10) If adjustment is required, adjust as described in Job No.005.
11) Recheck the tightness of the crosshead locknut and fit and tighten the securing pin with its locking plate into the crosshead.
12) Bend over the tab on the locking plate.
13) Refit the crosshead access cover with gasket and tighten the screws.
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JOB No. 005
PISTON/CYLINDER END CLEARANCES - INSPECTION
LIST OF CONSUMABLESDescription Qty
Sealing Gasket (between 0.8mm - 1.0mm thick) As
required Industrial cleaning fluid (White Spirit) & lint free cloth As
required There are two ways of measuring the piston Top-Dead-Centre (TDC) clearance: Method 1 is by removing the cylinder top covers and Method 2 is by removing the valves and checking the clearance through the valve pockets. The Bottom-Dead-Centre (BDC) clearance is checked using Method 2.
Method 1
1) Remove the cylinder top cover refer to Job No.003.
2) Place a sealing gasket of between 0.8mm - 1.0mm on to the cylinder mating face.
3) Place the machined straight-edge across the top of the gasket on the cylinder.
4) Bar over the compressor to place the piston exactly at TDC.
5) Measure the clearance between the straight edge and the piston crown. Ensure that the straight edge is held firmly against the gasket when measuring clearance. record the with a feeler (thickness) gauge. The required clearances are detailed in Chapter 1 Technical Data. If the clearances are out side of the tolerance band the clearance MUST be adjusted (see later in this procedure).
Method 2
1) Remove either a suction or delivery valve from a top cylinder pocket (if measuring TDC clearance) or a bottom cylinder pocket (if measuring BDC clearance).
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JOB No.005 - PISTON/CYLINDER END CLEARANCES - INSPECTION (Cont)
2) With the piston exactly at TDC or BDC, insert a feeler gauge through the valve pocketand measure the clearance. Record the end ("bumping") clearances with the piston at the top (Top-Dead-Centre) and bottom (Bottom-Dead-Centre) of its stroke. The clearances are detailed in Chapter 1 Technical Data. If the clearances are outside of the tolerance band the clearance MUST be adjusted (see later in this procedure).
CAUTION
Feeler gauges MUST NOT be inserted into the valve pocket whilst turning the machine over because if trapped, the machine components could be strained or damaged.
Piston/Cylinder End Clearances - Adjustment
The end ("bumping") clearance is adjusted by screwing the piston rod into, or out of, the crosshead. To adjust the piston to cylinder end clearances proceed as follows:
1) Remove the crosshead access cover and gasket from the crankcase.
2) Bar over the crankshaft to reveal the crosshead locknut and the piston rod securing pin.
3) Bend back the locking plate tab retaining the securing pin and remove the pin.
Ensure that the securing pin is removed before slackening the crosshead nut.
Otherwise, if the piston rod turns in the crosshead while the securing pin is in position, the pin will distort making it extremely difficult to remove
4) Slacken the crosshead locknut.
The piston rod has a slotted end at the crosshead (through which the securing pin fits) it can only be turned in 90o steps, one step represents a linear movement of 0.8mm, (the screwed end of the rod having 8 threads per inch).
5) To adjust the top end clearance, screw the piston rod into or out of the crosshead.
Ensure that the top and bottom clearances are as close to equal as is possible. If equal clearances are not obtainable then always, on final setting, make the TOP clearance the larger of the two (by an amount equal to no more than one quarter turn only of the piston rod in the crosshead i.e., by no more than 0.8mm).
6) Fully tighten the crosshead locknut.
7) Recheck that the piston rod slots are correctly aligned for clearance of the piston rod securing pin.
8) Fit a new locking plate to the securing pin before fitting and fully tighten the pin.
9) Bend over the locking plate tab to prevent the securing pin from rotating.
10) Inspect the crosshead access cover gasket. Renew if necessary.
11) Refit the access cover.
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JOB No. 006
PACKING GLAND ASSEMBLY - REMOVE & REFIT
LIST OF CONSUMABLESDescription Qty Industrial cleaning fluid (White Spirit) & lint free cloth As
required Due to their construction, these packing glands can only be satisfactorily examined and repaired when they are removed from the compressor and disassembled on a suitable workbench.
To Remove First & Second Stage Packing Assemblies Only
1) Fit piston rod clamps to prevent possible uncontrolled movement of the crankshaft and motion works. Refer to Job No.002.
2) Mark the position of the oil shedder on the rod surface and remove shedder with its two clamping screws.
3) Remove the nuts from the small diameter gland assembly tie studs.
4) Remove the securing nuts from the gland cover and lower the cover down the piston rod until it is resting on the oil scraper gland assembly.
5) Slide each container assembly down the piston rod until it is clear of the gland.
6) Slide the container a little way back up the piston rod to expose the packing rings and in turn, unhook the garter springs and remove the packing ring segments.
1st Stage Gland Packing
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JOB No. 006 - PACKING GLAND ASSEMBLY - REMOVE & REFIT (Cont)
2nd Stage Gland Packing
7) Reassemble and carefully store each ring of segments and garter spring, immediately on removal. Repeat Step 7 until all of the packing rings have been removed.
Observe that each ring is marked with matching numbers and letters for use in reassemble. Also the lowermost ring has a peg which locates into a hole in the uppermost ring to form a container pair. The rings can be reused depending upon condition after inspection.
To Refit 1st & 2nd Stage Packing Assemblies Only
CAUTION!
The rings and glands refitted completely without oil (the compressor being an
The rings and glands refitted completely without oil (the compressor being an