Connecting Rod

08028-0D/H5250/94.08.12

L23/30H

Description:

Cleaning, inspection and test measurement of connecting rod.

L23/30H

Cleaning of Connecting Rod

1.Clean all machined surfaces on the connecting

rod.

2.Degrease the serrated joint faces, tapped holes and connecting rod screws with a volatile solvent and blow dry with working air.

Visual Inspection of Serrated Faces

3.Inspect the serrated joint faces.

Damages, in the form of visible wear marks and pittings or even cracks, may be in the serration due to relative movements between the surfaces.

Wear marks and cracks are visible, but not perceptible with a fingernail. Pittings and impact marks are both visible and perceptible.

Note!! Handle the connecting rod with care. In case of damaged serration caused by improper handling, the bearingcapcannolongerbetightenedtotheconnecting rod without ovalness of the big-end bore.

4.Register observed damages in the scheme

"Connecting Rod Inspection" for historic use only. See page 4.

5.Carefully smooth single raised spots in the serration caused by pitting and impact marks with a filesmall.

Inspection of Connecting Rod Screws

6.Inspect the connecting rod screws for seizures in the threads and pittings on the contact surfaces of the screwheads.

7.Turn the connecting rod screws into bottom position in the threaded screw holes by hand.

Measurement of Big-end Bore

For check of ovalness the bearing cap has to be mounted onto the big-end bore without bearing shells.

Note !! The ident. No on the connecting rod and the bearing cap must always be the same, see fig 3.

8.Mount the bearing cap onto the connecting rod

Fig. 1. Point of measurement

by means of the connecting rod screws.

9.Tighten the screws with the prescribed torque, see working card 506-01.25.

10.Measure five different diameters in the middle of the boring, see fig 1.

11.Register the measurements in the scheme "Connecting Rod Inspection". See page 4.

12.Calculate the maximum ovalness as the difference between biggest and smallest diameter measured.

13.Check if maximum ovalness is exceeded, see page 500.35.

08028-0D/H5250/94.08.12

08028-0D/H5250/94.08.12

Connecting rod

Ident no.

Note ! The ident no. on the connecting rod and on the bearing cap, must always be the same.

Fig 2. "Connecting Rod Inspection".

The example, see fig 2, shows measurements and damage observations for two connecting rods on the scheme "Connecting Rod Inspection" (in case the specified maximum ovalness is exceeded, contact MAN B&W Diesel A/S, Holeby for overhaul).

For connecting rod No 1 the maximum ovalness is 0.07 mm and thus reuse is acceptable.

L23/30H

0.125mmandthereforetheconnectingrodisrejected.

Inspection of Connecting Rod Bush

1.Inspect the surface of the piston pin and the connecting rod bush.

2.Measure the clearance between the piston pin and bush.

3.Check if max clearance is exceeded, see page 500.35.

If the specified clearance is exceeded, contact MAN B&W Diesel A/S, Holeby for replacement.

Inspection of Bearing Shells for Big-end

Criteria for replacement of connecting rod big-end bearing, see working card 506-01.16.

Connecting rod

Ident No

Fig 3.

08028-0D/H5250/94.08.12

L23/30H

Mounting of Tools

1)Mount the lifting device comprising eye screw, shackle and wire rope on the piston.

2)Lift up the piston and connecting rod and mount the piston and scraper rings, see point 14, and working card 506-01.10.

3)Remove the backstop for cylinder liner and place the piston guide ring on top of the cylinder liner, see fig 1.

Note: A crank throw position of approx 50 degrees before TDC will ensure this and also be suitable for the further mounting procedure.

Mounting of Big-end Bearing

6) Lower the piston further down, lubricate the ends of the bearing shells (as in fig. 2) with copaslip, molycote pasta or similar and mount the upper shell of the big-end bearing.

Fig 1.

Lowering of Piston and Connecting Rod

4)When the piston approaches the guide ring, stop the lowering, coat guide ring, piston, piston rings and scraper ring, with clean lubricating oil in order to minimize friction during the subsequent lowering of the assembly.

5)Make sure that the crank throw is in a position allowing the connecting rod to go clear of both crank journal and cylinder liner skirt during further lowering.

Fig 2.

7)Coat the crank journal with clean lubricating oil.

8)Lower the piston and connecting rod slowly into correct landing on the journal.

During this the connecting rod must be guided by hand to ensure correct approach and landing on the journal, see fig 3.

08028-0D/H5250/94.08.12

08028-0D/H5250/94.08.12

Fig 3.

Mounting of Bearing Cap

9) Mount the bearing cap with inserted lower shell of the big-end bearing, using the guide pin, see fig 4.

Con. Rod - Ident No.

Fig 4.

Fig 5.

Tightening of Connecting Rod Screws

13) Tighten the screws according to "Tightening Procedure for Connecting Rod Screws", see working card 506-01.25.

Fitting of Piston and Scraper Rings

14) Piston rings should only be removed from and fitted to the piston by the use of a special tool, the socalled piston ring opener.

If the rings are opened further than necessary there is a risk of overstressing, which means that rings will become permanently distorted and will not confirm to the inner running surface of the cylinder.

The piston rings should be installed with the identification mark, which is stamped into the ring close to the ring joints, facing upwords, see working card 50601.10 "Piston".

Ring joint

Fig 6.

Before fitting the coil spring loaded scraper ring, the coil spring is dismantled from the ring by removal of the joint pin. The coil spring is placed and assembled in the ring groove. Then the scraper ring is fitted in the groove in such a way that the ring joint is approximately 180° offset to the spring joint.

Ascertain correct assembling by checking the back clearance.The back clearance is sufficient when the face of the ring is below the groove edge when the ring is pressed against the bottom of the groove.

When installed on the piston the rings should be pushed back and forth in the grooves to make sure that they can move freely. It is also advisable to insert a feeler gauge of adequate thickness between ring and groove.

Adequate clearance is present so the feeler gauge can be moved all the way round.

To prevent gas leakage through coinciding ring joints the piston rings should be turned into positions offsetting the ring joint 180° to each other.