HITACHI MAN-B&W No. ：HZSD-B0603 DIESEL ENGINE SERVICE DATA DATE ：25-8-2006

Accumulator Charge Pressure for ME Engines ENGINE TYPE: ME engines

The ME-engines are provided with membrane accumulators to ensure

the necessary flow of hydraulic oil to the fuel pressure booster

and exhaust actuator and to prevent undesired pressure peaks in

the hydraulic oil system, it is therefore important that the

accumulators are maintained properly.

Please refer to the Fig.1: ME Hydraulic Oil System.

To obtain the correct function of the accumulator, the right charge

pressure should be present. We have experienced membrane

fractures in accumulators charged with 104.3 bar/20℃ N2. It seems that this pressure brings the membrane too close to the steel

surface of the accumulator, and due to the dynamics, it may hit the

steel and fracture. Please refer to the Fig.2 & 3.

We have thus investigated the influence of the N2 charge pressure

on the injection by lowering the N2 charge pressure to 95~90 bar.

Different charge pressures result in a very marginal change in

fuel oil injection pressure, and it can be concluded that the charge

pressure of the accumulators have only marginal influence on the

combustion process. Therefore we recommend lowering the N2 charge

pressure to 95 bar/20℃. Table 1 shows accumulator charge pressure at each accumulator (or ambient) temperature. Please adjust

accumulator charge pressure by referring Table 1.

As for the influence of the N2 charge pressure on the injection

performance, it is ensured that pressure drop up to 30 bar is

acceptable. Therefore, allowable minimum pressure is 65 bar/20℃.

We draw your 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, and finally a check should now be done every 6 months.

REMARKS：

B0603-2/4

It is recommended, that these checks are logged for later use and

documentation. Should any leakages be found, the accumulators

have to be removed.

Please beware that a minor leakage from the accumulators is

unavoidable.

Service experience shows that a pressure drop in the range of

2-5 bar/month is to be expected. It is important, that

refilling of the accumulators is done according to the

procedures described in the instruction manual for main engine,

Volume II Maintenance chapter 906-23.

After refilling, the minimes can advantageously be checked

with an inspection spray in order to ensure a tight sealing.

Please also notice, that the caps on the minimes are all

re-mounted and tightened, since these caps actually provide an

additional sealing (Fig.4). The cap should be tightened only by

hand without use of tools.

Table 1 Accumulator charge pressure at each

accumulator temperature

Accumulator temperature (℃)

Accumulator pressure (±5 bar)

0 89

10 92

20 95

30 98

40 101

50 105

60 108

70 111

80 114

90 118

100 121

B0603-3/4

燃料ブースタポンプ 排気弁アクチュエータ

油圧シリンダユニット

制御油 サンプタンクへ

主潤滑油ポンプ

フィルタ

制御油

機付ポンプ 電動ポンプ

ピストン冷却器＋軸受潤滑

アキュムレータブロック

燃料油

α注油器

サンプタンクより

図１ ＭＥ油圧システム Fig.1 ME Hydraulic Oil System

排気弁アクチュエータ 燃料ブースタポンプ

FIVA 弁 α注油器(ME 用)

油圧シリンダユニット(Ａ部詳細) Hydraulic Cylinder Units (Details “A”)

アキュムレータブロック， アキュムレータ(Ｂ部詳細) Safety and accumulator block,Accumulator (Details “B”)

アキュムレータ

アキュムレータ ブロック

油圧ポンプ

“A”

“B”

ギアボックス

アキュムレータ Accumulator

B0603-4/4

図２ アキュムレータ断面図

Fig.2 Cross section in the accumulator

図３ 破損した金具部分

Fig.3 Fractured steel parts

図４ 注入口とシール部の構造図

Fig.4 Illustration of the minimess, and the sealing areas

SealingsInternal primary and secondary sealing and sealing for screw-in thread made of Buna N.

Screw-in threadDifferent kinds of thread are available

Option: Safety devices against vibrationSafety device against torsion and loosening of metal cap made of Buna N.