7 семестр (Бормотов А) / 1man_bw_l23_30_chn_23_30_instruktsiya_po_ekspluatatsii / MAN-BW L23-30 (ЧН 225_300)+ / MAN-BW L23-30 H Vol-1 (Instruction)+

L23/30H

Preparations before Dismounting

1) Clean the upper part of the cylinder. If not, the piston may get stuck during removal in the carbon deposited in this area.

a)Turn the piston to the buttom.

b)Place a used piston ring on top of the piston.

c)Mount the tube (for holding down the cylinder liner during the piston withdrawal) on one of the cylinder head studs, screw on the nut and tighten it slightly.

d)Turn the piston in top, in order to push the flame ring out of the cylinder by means of the piston ring.

Info: It is the used piston ring which pushes the flame ring out of the cylinder.

2)Remove the gangway, if any installed, in order to improve the access conditions.

3)Turn the crankshaft to bring the crank throw concerned into a position of approx. 50 degrees before TDC.

This position is identifiable by the connecting rod shaft being very close to the cylinder liner shirt, see fig. 1.

4)Clean the threaded hole in the piston top, and mount the eye screw.

5)Mount the tube (for holding down the cylinder liner during the piston withdrawal) on one of the cylinder head studs, screw on the nut and tighten it slightly.

6)Attach a wire rope to the eye bolt by means of a shackle, hook the wire on to a tackle and pull the wire rope tight.

Note! If minor adjustments of the crank throw position appear necessary for access to the connecting rod screws, the wire rope must be slackened before turning of the crankshaft and tightened up again in the new crank throw position.

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Note! The purpose of the guide pin is to prevent any damage of crank journal, joint faces or bearing surface to occur during dismounting of the bearing cap, and to facilitate easy handling when removing the bearing cap from the crankcase.

9)Remove the screwdriver from the guide pin, and dismount the bearing cap by sliding it along the guide pin, see fig 2.

10)Remove the guide pin from the connecting rod.

Dismounting of Upper Big-end Bearing Shell

11)Pull the piston and connecting rod assembly upwards and remove the upper big-end bearing shell, see fig 3.

12) Lift the piston and connecting rod assembly up through the cylinder liner and out of the engine, see fig 4.

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Safety precautions:

Stopped engine

Shut-off starting air

Shut-off cooling water

Shut-off fuel oil

Shut-off cooling oil

Stopped lub. oil circul.

Description:

Separation of piston and connecting rod for inspection or/and overhaul.

Assembly of piston and connecting rod after inspection or/and overhaul.

Starting position:

Piston and connecting rod are dismounted

Hand tools:

Open-end spanner, 24 mm.

Wooden wedge, 2 pieces.

Wooden support.

Wire.

Replacement and wearing parts:

L23/30H

Landing of Piston and Connecting Rod

1) Land the piston and connecting rod carefully on wooden supports to prevent damage of piston and scraper ring, see fig 1.

6) Take out the securing ring, (seeger circlips), push out the piston pin and lift the connecting rod away.

Assembly of Piston and Connecting Rod

7)For assembly of piston and connecting rod, see point 1-6 in reversed order.

8)Lubricate the piston pin before assembling.

Fig 1. Landing of Piston and Connecting Rod.

2) The bearing cap should be mounted with the screws tightened only by hand, in order to protect the serrated joint faces during handling of the assembly, see fig 1.

3) Remove the shackle and eye screw from the piston crown, see fig 1.

4) Place the piston and connecting rod assembly in upright position resting on the top face of the piston crown, see fig 2.

Note: Wooden wedges should be used to prevent the connecting rod from swinging out and thus impact the piston skirt during the lifting into upright position.

5) Place a wire around the big-end of the connecting rod. Attach a tackle and tighten the wire rope, see

08028-0D/H5250/94.08.12

08028-0d/H5250/94.08.12

Safety precautions:

Stopped engine

Shut-off starting air

Shut-off cooling water

Shut-off fuel oil

Shut-off cooling oil

Stopped lub. oil circul.

Description:

Cleaning and inspection of piston. Control of piston ring, scraper ring and ring grooves.

Hand tools:

Tools for cleaning of piston, steel brush, scraper etc.

Replacement and wearing parts:

L23/30H

Removal of Piston Ring

For removal of piston rings, which are to be used again, and for all mounting of rings, only the special ring opener which prevents local over stressing of the rings should be used.

Straps to expand the ring gap or tools working on the same principle must not be used, as this would result in permanent deformation which might cause blowby or broken rings.

Inspection of Piston

1)Remove the piston and scraper rings.

2)Cleanandexaminethepistonringstodetermine if reuse is acceptable, see page 3.

3)Clean the piston on the outside and on the inside.

4)Inspect the piston ring and scraper ring grooves for wear, see page 3.

The piston has to be scrapped if:

A) The wear limit on the testing mandrel is exceeded, see fig 1A

or

B) The clearance between the new piston/scraper ring and ring groove is exceeded, see fig 1B.

Note! At each piston overhaul:

-The piston and scraper ring must be exchanged.

-The cylinder liner must be honed according to the instructions.

L23/30H

Table 1. Nominal size, new ring groove tolerance and wear limit for ring grooves.

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L23/30H

Position of Piston and Scraper Rings

Piston Ring No 1: marked with ident. No "top 881500-3" or "0946".

Piston Ring No 2: marked with ident. No "top 881502-7" or "0947".

Piston Ring No 3: marked with ident. No "top 881501-5" or "0945".

Scraper ring: marked with ident. No "top 881503-9" or "0120".

Marking of Piston and Scraper Rings

Marking

Identification marks to face upwards against the piston crown when mounted.

Note! The marking may include other figures than mentioned above, for instance trade mark and production codes.

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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.

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