MAN Diesel

MAN Diesel A/S • Denmark

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MAN Diesel A/S
Teglholmsgade 41
2450 Copenhagen SV
Denmark
Phone: [phone]
Fax: [phone]
[e-mail]
www.manbw.com

PrimeServ
Teglholmsgade 41
2450 Copenhagen SV
Denmark
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[e-mail]

PRODUCTION
Teglholmsgade 35
2450 Copenhagen SV
Denmark
Phone: [phone]
Fax: [phone]
manufacturing/[e-mail]

FORWARDING & RECEIVING MAN Diesel A/S
Teglholmsgade 35 Denmark
2450 Copenhagen SV Reg. No.: 39661314
Denmark
Phone: [phone]
Fax: [phone]

MAN Diesel – a member of the MAN Group

Service Letter

SL06-469/JOF

December 2006

Accumulator Charge Pressure
Overhaul and Maintenance, ME Engines
Action Code: WHEN CONVENIENT

The ME engines are provided with membrane accumulators to ensure the necessary flow
of hydraulic oil to the fuel pressure booster and exhaust actuator. To prevent undesired
pressure peaks in the hydraulic oil system, it is important to maintain the accumulators
properly. A cross section of an accumulator is shown below.

Fig. 1: Cross section of the accumulator

The accumulator is charged with pressurised nitrogen. To obtain the correct function
of the accumulator, the right charge pressure must be present. We have experienced
a number of membrane fractures in accumulators caused by either too low or too high

MAN Diesel

- 2 -

a pressure. In both cases, the disc in the centre of the membrane may hit the steel
housing and fracture (see the picture below).

Fig. 2: Fractured disc

A change in charge pressure results in only a marginal change in injection pressure
(within the measuring uncertainty), and it can therefore be concluded that the charge
pressure of the accumulators have only marginal influence on the combustion process.
Therefore, we recommend lowering the N

B

2

B

charge pressure to 95 +0/-5 bar at 20°C.

We draw attention to the checking procedure for the accumulator pressure. The
accumulator tightness should be checked within the first week of service. Next check
should be made around 4 months later, followed by checking

U

every 6 months

U

(as

described in the maintenance manual).

MAN Diesel recommends that these checks are logged for later use and document-
ation. Should any leakages be found, the accumulators have to be replaced.

A minor leakage from the accumulators is unavoidable, and service experience shows
that a pressure drop in the range of 2-5 bar/month is to be expected. It is important,
that recharging of the accumulators is done according to the procedures described in
our instruction manual chapter 906-23. After refilling, the minimess gas filling valve
can advantageously be checked with a leak detection spray to ensure tight sealing. It
should also be checked that the minimess caps have all been re-attached and
tightened, since these caps actually provide an additional sealing (Fig. 3). The caps
should be tightened by hand only without the use of tools.

The minimess should be secured by Locktite to prevent loosening.

MAN Diesel

- 3 -

Fig. 3: Illustration of the minimess, and the sealing areas

It has been discovered that when opening valve 420 (= open for hydraulic pressure to
the HCU (hydraulic cylinder unit)) while the system is pressurised, there is a risk of
damaging the membrane in the accumulator. As a consequence, the following
warning has been introduced in the instruction books.

Warning!

To protect the accumulators from unnecessary stress (fast acceleration of the
membrane) and oil jets, the valve Pos. 420 must not be opened while the system is
pressurised. After check/overhaul or any other situation where valve 420 has been
closed, the opening procedure is:

1. Stop the engine (stop the start-up pumps and release

the oil pressure with valve 421)

2. Close valve 421 and open valve 420
3. Pressurise the system by starting the start-up pumps

Summary:

- Revised charge pressure 95 +0/-5 bar (at 20°C)
- Check for leakages at minimess
- Always re-attach the minimess cap after checking and charging
- Never open valve 420 while the system is pressurised

Page 1 (2)

MAN B&W Diesel

SAFETY PRECAUTIONS

Data

Special Running

Data

106-23

When referring to this page, please quote Data D10623 Edition 0006

For detailed sketch, see 900-2

Ref.

Description

Value

Unit

X

X

Stopped engine

Shut off starting air supply –

At starting air receiver

Block the main starting valve

Shut off starting air distributor/distributing system supply

Shut off safety air supply –

Not ME engines

Shut off control air supply

Shut off air supply to exhaust valve –

Only with stopped lubriating oil pumps

Engage turning gear

Shut off cooling water

Shut off fuel oil

Stop lubricating oil supply

Lock the turbocharger rotors

Shut down hydraulic power supply

D06-201

Accumulator

24/55

kg

D06-202

N2 Charging pressure

95

bar at
20°

Pressure Adjustment Table

Accumulator temperature t °C

0

89

bar

10

92

bar

20

95

bar

30

98

bar

40

101

bar

50

105

bar

60

108

bar

70

111

bar

80

114

bar

90

118

bar

100

121

bar

D06-216

assembly off-set 4-liter accumulator

9

mm

D06-217

assembly off-set 10-liter accumulator

10

mm

D06-226

Screw, flange to Accumulator

100

Nm

D06-227

Screw, flange to Hydraulic Cylinder Unit

150

Nm

Page 2 (2)

MAN B&W Diesel

The task-specific tools used in this procedure are shown on the plates at the end of this chapter or in the
chapters indicated by the first three digits in the plate number, e.g. P90951 refers to chapter 909.

Special Running

Data

106-23

When referring to this page, please quote Data D10623 Edition 0006

Plate

Item No.

Description

P90653

P90653

Tools for Accumulator

P90674

P90674

Test Equipment for Accumulators

P91356

P91356

Lifting Tools, Etc.

P91359

P91359

Torque Spanners

P91366

P91366

Instruments

Page 1 (9)

906-23.1

When referring to this page, please quote Procedure M90623 Edition 0210

MAN B&W Diesel

Checking

Accumulators

M906230209C02

315

340

ON

OFF

00:00

Bourdon Sedeme

CC

M901010253D02

455

ON

OFF

00:00

Bourdon Sedeme

CC

420

421

2.

1.

Check of Accumulators on Hydraulic
Cylinder Unit

1.

Check of the hydraulic accumulator can be
done with running engine at reduced
speed. See Volume I, Operation.

Connect a pressure gauge at “minimess”
point 455. Check the pressure.

Close the high pressure inlet valve 420 and
open the high pressure outlet valve 421 to
drain all oil out of the accumulator.

Check that the system is pressure free.

Check the nitrogen pressure.

For correct pressure, see Data D06-204.

For use of pressure setting tool, see step 3.

Check of Accumulators on Hydraulic Power
Supply Unit

2.

Check of accumulators on the accumulator
block can only be performed on a stopped
engine and with stopped start-up and
booster pumps.

Connect a pressure gauge at “minimess”
point 340. Check the pressure.

Open valve 315 to de-pressurise the hy-
draulic system and drain all oil out of the
accumulators.

Check that the system is pressure free.

Check the nitrogen pressure.

For correct pressure, see Data D06-204.

For use of pressure setting tool, see step 3.

Accumulators

Page 2 (9)

906-23.1

When referring to this page, please quote Procedure M90623 Edition 0210

MAN B&W Diesel

Checking

M906230206C03

ON

OFF

00:00

Bourdon Sedeme

CC

A

B

C

D

E

D06202
D06204

Use of Reducing Valve as Pressure Setting
Tool

3.

Assemble the reducing valve as shown in
the figure, and mount the reducing valve on
the nitrogen cylinder. If necessary, use a
threaded adaptor.

Before mounting the filling hose on the ac-
cumulator, check that the accumulator top
is clean.

Check that valves A and D are closed.

Mount the filling hose on the relevant accu-
mulator with the union nut E.

It is now possible to read the actual nitro-
gen pressure in the accumulator on the
digital gauge C on the filling valve.

If the accumulator needs to be refilled with
nitrogen, open valve A and adjust the outlet
pressure on spindle B to 1-2 bar above the
pressure stated in the Pressure Adjustment
Table. See Data D06-204.

Keep valve A open until the accumulator is
filled.

Close valve A.

Wait five minutes for the temperature to
stabilise.

Check the pressure in the accumulator on
gauge C according to the Pressure Adjust-
ment Table. See Data D06-204.

Adjust the pressure in the accumulator at
bleed screw D.

Unscrew the union nut E to remove the fil-
ling valve from the accumulator.

3.

906-23.2

MAN B&W Diesel

Dismantling

Accumulators

Page 3 (9)

When referring to this page, please quote Procedure M90623 Edition 0210

M901010253D02

455

ON

OFF

00:00

Bourdon Sedeme

CC

420

421

Dismantling of Accumulators from Hydraulic
Cylinder Unit

1.

This can be performed on a running engine
at reduced speed. See Volume I, Opera-
tion.

Connect a pressure gauge at “minimess”
point 455. Check the pressure.

Close the high pressure inlet valve 420 and
open the high pressure outlet valve 421 to
drain all oil out of the accumulator.

Check that the system is pressure free.

Note!

Great care must be taken to ensure that
the area around the workplace is clean
before and during any dismantling of the
hydraulic system

.

1.

Accumulators

906-23.2

MAN B&W Diesel

Dismantling

Page 4 (9)

When referring to this page, please quote Procedure M90623 Edition 0210

M906230210D02

2.

Turn the square to closed, lift off the lock-
ing disc.

Turn the locking disc 180

°

and place it on

the square again to lock the valve.

2.

906-23.2

MAN B&W Diesel

Dismantling

Accumulators

Page 5 (9)

When referring to this page, please quote Procedure M90623 Edition 0210

M906230209D03

D06-201

3.

Dismount the accumulator flange from the
hydraulic cylinder unit. Use a clothstrap to
lift the accumulator.

Dismount the accumulator flange from the
accumulator.

Dismantling of Accumulators from Hydraulic
Power Supply Unit

4.

Dismantling of accumulators from the accu-
mulator block can only be performed on a
stopped engine and with stopped start-up
and booster pumps.

Open valve 315 to de-pressurise the hy-
draulic system and drain all oil out of the
accumulators.

The accumulators on the hydraulic power
supply unit are dismounted in the same
way as on the hydraulic cylinder unit.

3.

Accumulators

906-23.3

MAN B&W Diesel

Overhaul

Page 6 (9)

When referring to this page, please quote Procedure M90623 Edition 0210

M906230209O05

M906230209O04

M906230209O03

1.

Remove the accumulator with the accumu-
lator flange. See Procedure 906-23.2.

2.

Use the pressure adjustment tool to drain
the accumulator of nitrogen gas.
See Procedure 906-23.1.

3.

Unscrew the “minimess” valve on the accu-
mulator.

Screw the dowel pin from the upper half of
the accumulator tool into the upper part of
the accumulator. Fit an eyebolt into the
dowel pin.

Make sure that the lower half of the accu-
mulator tool is securely fastened to the en-
gine room deck. This can be done by
screwing or welding the flanges of the ac-
cumulator tool onto the engine room deck
in a convenient place.

Use the eyebolt to lift the accumulator into
the bottom half of the accumulator tool.
Make sure that the guides on the tool fit
into the slots on the accumulator.

4.

Mount the upper half of the accumulator
tool with two of the claws fitted, on the ac-
cumulator. The claws must reach below the
ridge on the lower accumulator tool. Make
sure that the guides on the tool fit into the
slots on the accumulator.

5.

Fit the last claw onto the accomulator tool.

Unscrew the upper half of the accumulator.

Use a piece of pipe in the holes at the end
of the wings of the accumulator tool to pro-
vide leverage.

If the upper half binds, it may be loosened
by tapping a few times with a hammer on
the wings of the accumulator tool.

4.

3.

5.

906-23.3

MAN B&W Diesel

Overhaul

Accumulators

Page 7 (9)

When referring to this page, please quote Procedure M90623 Edition 0210

M906230210O06

A

M906230206O08

M906230209O08

6.

Remove the defective diaphragm “A”

7.

Clean both accumulator halves throroughly,
especially the threads, and make sure that
the parts are dry afterwards.

8.

Assemble the two accumulator halves with-
out fitting the diaphragm. Tighten until the
halves are in contact.

Mark the relative position of the accumula-
tor halves.

9.

Disassemble the accumulator and install
the new diaphragm and anti-extrusion ring.

6.

8.

9.

Note!

Check that the new diaphragm is made
of the same material as the old one.

Do not lubricate the diaphragm lip lodg-
ing.

Accumulators

906-23.3

MAN B&W Diesel

Overhaul

Page 8 (9)

When referring to this page, please quote Procedure M90623 Edition 0210

M906230210O12

Loctite

M906230209O11

D06-216
D06-217

10. Lubricate the upper part of the diaphragm

lip and the accumulator threads with
molyb-denum disulphide grease.

11. Assemble the accumulator. Tighten until the

marks made in section 7 are off-set ac-
cording to D06-216.

12. Mount the “minimess” valve, by using a

new O-ring.

Use Loctite ® 243 to secure the minimess
valve. Fill the accumulator with nitrogen gas
as described in Procedure 906-23.1

Use soapy water to check the accumulator
for any leakages.

Mount the accumulator.

11.

12.

906-23.4

MAN B&W Diesel

Mounting

Accumulators

Page 9 (9)

When referring to this page, please quote Procedure M90623 Edition 0210

M906230210M01

D06201
D06226
D06227

M906230209M02

315

Mounting of Accumulators on Hydraulic
Cylinder Unit

1.

This can be performed on a running engine
at reduced speed. See Volume I, Opera-
tion.

Mount the flange and a new sealing ring on
the accumulator.

Mount the accumulator assembly and a
new second sealing ring on the hydraulic
cylinder unit.

2.

Close the high pressure outlet valve 421
and open the high pressure inlet valve 420.

3.

Check accumulator nitrogen pressure. D06-
204.

Mounting of Accumulators on Hydraulic
Power Supply Unit

4.

This can only be performed on a stopped
engine and with stopped start-up and
booster pumps.

The accumulators on the hydraulic power
supply unit are mounted in the same way
as on the hydraulic cylinder unit.

Close valve 315.

1.

2.

Note!

Great care must be taken to ensure that
the area around the workplace is clean
before and during assembly of the hy-
draulic system.

Note!

Use Loctite ® 243 to secure the screws
when mounting the flange and the accu-
mulator.