SAFETY PRECAUTIONS
-On FWE get immobilization permission and propeller clearance from bridge.
-under piston spaces and scavenge space ventilate by blower.
-Stopped engine
-Shut off starting air supply At starting air receiver
-Block the main starting valve
-Shut off starting air distributor/distributing system power supply
-Shut off safety air supply
-Shut off control air supply
-Shut off air supply to exhaust valve – Only with stopped lubricating oil pumps
-Engage turning gear
-Shut off cooling water
-Shut off fuel oil
-Stop lubricating oil supply
-Lock the turbocharger rotors
-isolate expansion tank than only drain jacket drain jacket cooling water and open purging valve so that air pressure helps in draining.
Preparations in the crankcase
1. Access: Open the crankcase door to the cylinder concerned.
Turn the crosshead down far enough to
give access to the piston rod stuffing box
and the piston rod/crosshead connection.
2. Stuffing box:Release the stuffing box by removing the innermost screws from the stuffing box flange.
On engine models where the drain pipe is
connected directly to the stuffing box:
Disconnect the stuffing box drain pipe.
3. Loosen the piston rod crosshead
connection:
Remove the screws from the piston rod.
4. Stuffing box distance pieces:
Mount the two distance pieces on the pis-
ton rod foot to protect the lower scraper
ring and to guide the stuffing box.
Preparations on the cylinder top
5. Cylinder cover:
Remove the cylinder cover. See Procedure
901 1.2.
Make a scratch mark in liner and pis-
ton cleaning ring to ensure correct re mounting. Remove the piston cleaning
ring.Carefully remove any wear ridges at the topof the cylinder liner. See Procedure
6. Piston lifting tool:
Turn the piston to TDC. The top of the piston is now free of the cylinder liner.
Clean the lifting groove of the piston crown
and mount the lifting tool.
7. Piston lift:
Lift the piston out of the cylinder liner and guide the piston rod foot through the stuffing box flange.If the engine is equipped with long distance pieces for the stuffing box, the piston rod foot can pass between two cylinder cover studs.Place the two halves of the support around one of the openings in the platform. Lower the piston rod foot and stuffing box through the opening in the platform. Secure the two support halves with screws and
lower the piston on the support. Check the piston is resting on the piston rod flange.
8. Protect the crosshead bearing:
Place a cover over the opening for the piston rod stuffing box in the bottom of the cylinder unit. Turn the crosshead down far enough to
permit mounting of the protective rubber cover on the crosshead bearing cap. The protective rubber cover is found on tool
panel. The covers must remain in place to protect the crosshead bearing journal from impurities until the piston is remounted.
Clean, measure and recondition the cylinder liner. See Procedure.
1. Piston support:
Place the piston in the support and remove
the piston lifting tool. Clean the piston top and the piston rings.
Piston top template:
-Check that the piston top template is permanently marked with the piston top centre diameter D02 48.
-Check that the centre area C has been marked off, and write the maximum permissible burn away rate on the template.
-Mark the outer part of the template R for ring area, and write the maximum permissible burn away rate for the ring shaped
area. See data D02 49.
Piston crown top:
Clean the piston crown and check the burn away by means of the template. For maximum permissible burn away on the piston top centre area, see Data D02 47.
For the ring shaped area, see Data D02 49.Check the burn away on the whole circumference of the piston crown top.If the burn away exceeds the values given in Data, contact MAN Diesel for advice.
Note down the results for later reference.
-Remove the stuffing box. See Procedure 902 2.3.
2. Piston ring dismantling:
Take off the piston rings by means of the ring expanders. If the engine is equipped with two ring expanders, the short ring ex-
pander is for the uppermost ring. First remove the uppermost ring, then ring No. two, three and four.
Clean and inspect the rings and the ring grooves.
-Ring inspection:-fig 2 below
Inspect the rings, one at a time, and note down the results.
-Ring tension:-fig 3
Check the tension of the piston rings, by pressing against them with a wooden stick.
-Ring grooves- axial clearance -fig 4 below
Measure the total clearance between the piston ring and the ring groove. The total clearance must not exceed the value stated
in Data. Measure the clearance at the top (E) and
bottom (F) of the piston ring groove. Total clearance = E + F.
-Uppermost piston ring:fig 5
If possible, measure the depth of the pressure relief grooves with a calliper. The piston rings must be replaced if the radial depth of the grooves has worn down to less than stated in Data D02 46.
Free ring gap-butt clearance- fig 7 below
Before dismantling the piston rings, measure the free ring gap of all the piston rings.
Radial ring width - for back clearance -fig 8
Measure the radial width of the rings. Note down the results
Clean the ring grooves and check them for burn marks or other deformation. Measure the ring grooves with a calliper
gauge, see Data Clearance in piston ring grooves:
The maximum vertical height in a worn ring groove must not exceed the value statedin Data. The groove is also worn out if
there is no chromium layer. If the ring grooves are worn out, the piston crown must be reconditioned, contact MAN
Diesel for advice.
3. Piston crown dismantling:
Remove the locking wire and the innermost screws between the rod and the piston crown.
Lift the piston crown and skirt clear of the piston rod.
4. Piston rod and cooling pipe:
Remove the screws from the cooling oil pipe flange. Mount the eye bolts and lift out the cooling oil pipe. Clean and inspect the cooling oil pipe and the piston rod, then remount the cooling oil pipe, see Data.Check that the surfaces of the O ring groove is clean and smooth.Mount a new O ring on the piston rod flange.
5. Piston crown turning:
Unhook crane from the piston lifting tool, and connect the lifting tool and the crane hook by means of a wire rope. Lift up the piston crown. Fit two eye bolts in the piston skirt and a wire rope between the bolts as shown in the sketch. Install a tackle in a suitable place with sufficient space below for the piston crown. Attach the tackle to the wire rope on the piston crown and carefully turn the piston
crown upside down. Use both cranes if the engine room is equipped with two cranes. Land the piston lifting tool and the piston crown on a sufficient support of wood pieces. Loosen the piston lifting tool and lift the piston crown clear of the tool.
6. Piston crown dismantling and cleaning:
Place the piston crown with skirt on a wooden support as shown.
Remove the locking wire and the screws in the skirt. If necessary use two dismantling screws to pull the skirt out of the piston crown. Mount two eye bolts in the skirt. Lift the skirt and land it on a couple of planks. Discard the sealing ring on the piston skirt.Thoroughly clean and inspect all parts of the crown and skirt. If coke deposits are found in the cooling spaces of the piston
crown, they should be washed clean with Carbon Remover or a similar cleaning fluid.When all coke deposits have been dissolved, clean and inspect the piston crown again.
7. Piston crown assembly:
Mount a new O ring on the piston skirt. Check that the surfaces of the O ring groove are clean and smooth. Coat the ring with lubricating oil before mounting. Mount the piston skirt on the piston crown. Tighten the screws to specifi ed torque, see data D02 05. Lock the screws with locking wire, see Procedure 9
8. Piston crown and skirt mounting:
Mount the guide screw to ensure the correct positioning of the piston rod in relation to the piston crown. Lubricate the O ring on the piston rod flange with lubricating oil. Land the overhauled piston crown and skirt on the piston rod. Remove the guide screw.Mount and tighten the screws between the piston rod and the piston crown,
Sealing ring and pressure test
According to current class rules, the piston must be pressure tested hydraulically. It is possible to carry out a test of the sealing rings with compressed air before filling the piston with oil. The sealing ring test can also be carried out when the piston is resting in the support tool.
9. Sealing ring test:
Mount the pressure testing tool on the piston rod foot. Connect compressed air to the testing tool and fill the piston to 4 5 bar. Close the valve on the testing tool and remove the air connection. The piston must now hold the pressure for minimum 30 minutes.Spray a little soap water on to the surface joints between piston rod/crown/skirt and around the bolt heads to detect leaks.Dry off all soap water.
10. Pressure test:
For this test, the piston must be turned upside down (see next step to turn a complete piston). Fill the piston and piston rod with lubricating oil. Mount the pressure testing tool on the piston rod foot. Pressure test the piston at the pressure stated on the Data
Sheet. Check the contact surfaces of the piston and the sealing rings for tightness. Check that there are no cracks in the piston crown.
Turn the piston upside up and drain out the piston oil.
11. Piston turning:
Lift the piston with the normal lifting tool. Lower the piston rod foot until it is close to the platform. Land the foot on a wooden
block. Lower the piston crown to the platform and land it on a wooden block in such a way that it is possible to remove the lifting tool. Mount an eyebolt in the side of the lifting tool, hook on the crane and remove the lifting tool from the piston crown. Attach the lifting bracket to the bottom of the piston rod foot. Hook the crane on to the lifting bracket. Lift the piston rod foot clear of the wooden block. Keep lifting until the piston rod is in a vertical position.
12. Piston completion:
Fit the new piston rings (alternately right hand and left hand cuts, with the ring gaps staggered 180° and with the TOP mark upwards), using the ring expander. When mounting the piston rings, use the ring expanders to prevent unintended deformation of the rings. Do not expand the rings more than necessary. The uppermost ring (CPR ring) must be mounted with the short ring expander. Mount the piston rod stuffing box.
Preparation of piston
1. Preparation of piston:
Check the piston rings and piston crown in accordance with Procedure 902 1.1, if not already done.Mount the lifting tool on the piston crown.See Data D02 25.
2. Stuffing box position:
Ensure that the stuffi ng box is correctly positioned over the distance pieces mounted on the piston rod foot. Both the holes for
the flange and the drain hole for the drain pipe must be positioned correctly. Preparation of cylinder liner.
3. Mount the guide ring:
Mount the guide ring in the top of the cylinder liner. The cut outs for the lifting tool must be turned to fi t the piston lifting tool.
4. Stuffing box cover:
Remove the cover from the piston rod stuffing box opening in the bottom of the cylinder unit. Clean the stuffing box flange.
5. Crosshead position:
Turn the crosshead to a position 45° from TDC (crank web pointing towards exhaust side).
Mounting of piston
6. Mounting of piston:
Coat the O rings of the stuffing box and the piston rod with oil. Coat the piston rings and cylinder liner with cylinder lubricating oil. Lower the piston into the cylinder liner– while guiding the piston rod foot through the cut out in the stuffing box flange – until the piston rings are inside the liner.
7. Protective cover:
Remove the protective rubber cover from the crosshead.
8. Crosshead alignment:
Turn the crosshead almost to TDC, while checking that the guide ring of the crosshead enters the centre hole in the piston
rod. After turning the crosshead fully to TDC, and ensuring that the piston rod has full contact with the crosshead, unscrew the
lifting tool and remove the lifting tool and the guide ring for piston rings.
9. Stuffing box:
Turn down and land the stuffing box on the stuffing box flange. Check that the holes in the stuffing box and stuffing box flange are correctly centered. Tighten the piston rod stuffing box by
means of the screws through the inner holes in the stuffing box flange. For Data, see Procedure 902 2. On engine models where the drain pipe is connected directly to the stuffing box:
• Mount the stuffing box drain pipe. Remove the distance pieces from the piston rod foot.
10. Tightening of the piston rod crosshead
connection:
Mount and tighten the piston rod screws.Tighten the screws to the specified torque and lock with locking wire. See Data. Use either Data D02 02 or Data D02 07.
11. Piston cleaning ring:
Mount the piston cleaning ring in accordance with the scratch mark. If the PC ring is damaged (broken or cracked), it must be
replaced by another ring.See Procedure 903 1.
12. Cylinder cover studs:
If the cylinder cover studs have been re- moved, remount them. Carefully clean the surfaces around the base of the studs and check the O rings on the studs. Mount the cylinder cover studs with the stud setter. Screw the stud down to contact and half a revolution back.
13. Cylinder cover:
Land the cylinder cover on the liner and check the distance that the stud is protruding from the cylinder cover. If necessary,
adjust the distance D01 05 by turning the stud. Tighten the cylinder cover nuts and mount the necessary pipes. See Procedure 901 1.4.
14. Running in:
Smear the piston rod with molybdenum di- sulphide, and turn the crankshaft a couple of revolutions. At the first opportunity, start the engine and keep it running for about 15 minutes at a speed corresponding to “Dead Slow”Ahead.
Then stop the engine and inspect the piston rod and stuffing box.
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