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NAPIER Turbochargers

Siemens Industrial Turbomachinery Ltd 2006

CONFIDENTIALThis bulletin is the exclusive property of Siemens Industrial Turbomachinery Ltd and is disclosed in confidence to Siemens Industrial Turbomachinery Ltd customers solely for their use inconnection with the operation and maintenance of their Siemens Industrial Turbomachinery Ltd turbines. Its contents shall not be used for other purposes or copied or disclosed without writtenauthorisation of Siemens Industrial Turbomachinery Ltd. The information set out in this bulletin is offered by Siemens Industrial Turbomachinery Ltd as part of its ongoing product supportservices for you as one of its customers. However, the final decision for operating your plant in a safe and responsible manner rests entirely with you. This involves many factors outside ourknowledge and control, and therefore Siemens Industrial Turbomachinery Ltd is unable to accept (and hereby disclaims) any liability (whether based on breach of contract, warranty or statutoryduty, negligence or otherwise) for damage or loss of any kind which may be incurred as a result of applying this information.

SB-295-A-011-01 Page1 of 5All correspondence to:SiemensTurbochargers Division Siemens Industrial Turbomachinery LtdP.O. Box 1 Registered Office:Waterside South Ruston HouseLincoln LN5 7FD England Waterside SouthTel: +44 (0) 1522 584000 Lincoln LN5 7FD EnglandFax: +44 (0) 1522 584910 Registered in England No. 4729734

SB-295-A-011-01

SUBJECT: NA295 TURBINE SIDE WATER WASHING

A. TURBOCHARGERS AFFECTED

All NA295 turbocharger with single entry turbine inlet.

B. REASONS FOR BULLETIN

Experience has shown that turbocharger system performance in Heavy Fuel Oil (HFO)applications is adversely affected by ineffective cleaning of the turbocharger nozzle andturbine. These components are prone to heavy fouling and consequential loss ofefficiency in an HFO environment. Through experimentation and trials using aninstrumented turbocharger, a method has been developed which if adhered to, offerseffective distribution of injected water and consequently longer intervals between manual

stripping and cleaning.

C. CHANGES / MODIFICATIONS

No turbocharger parts need to be modified. Potential changes relate to water washinghardware, water supply and method. A new design of water injector has the followingpart number and is available from Napier Turbochargers Ltd.: SP14216.

Napier documents affected Installation Design Manual (IDM) and NA295Instruction Manual to be updated accordingly.

In the short term, this service bulletin may be added to the current IDM as an update tosection 7.3, Hardware and Water Supply.

ADVISORY

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D. DESCRIPTION

Scope:This bulletin outlines a combination of hardware and procedural requirements that, ifimplemented, can result in a significant improvement in the maintenance of the

cleanliness of turbine side components. The method is highly recommended for HFOinstallations that currently have fouling problems leading to performance deterioration, orwhich manually dis-assemble and clean on a frequent basis in order to avoidperformance deterioration. The method applies only to installations that have a waterdrain installed at the turbine outlet casing.

The advice contained in this service bulletin does not guarantee successful cleaning. Thefrequency of cleaning and the cleanliness of the water injectors will be influenced by fuelquality and application, a combination outside the scope of this document which isentirely the responsibility of the operator. The advice contained herein therefore cannotdetract from the responsibility of operators to determine, through a superior knowledge of

their plant, the most effective cleaning regime. This advisory service bulletin reflects animproved knowledge regarding what measures will result in an improved waterdistribution around the turbocharger nozzle, provided injectors are kept clean and theprescribed settings are adhered to.

NOTE: Experience is being gained constantly about methods of turbochargercleaning in HFO applications. This bulletin does not represent the scopeof understanding of Napiers on the subject, but is a fair reflection ofconclusively supported findings. As observations are verified,recommended hardware and procedures may be subject to refinement.

Water Wash Hardware RequirementsTwo injectors may be used, mounted opposite each other. The nearest exhaust flange tothe turbine inlet is suitable as indicated in Figure 1. The injectors and associated fittingsshould be made of a suitable material such as stainless steel type 410S21 (BS970). Therecommended water injector detail is shown in Figure 2. For the single entry NA295,these are available from Napier. The water injector part number is SP14216.This produces a flat fan shaped jet of large surface area and low water droplet inertia,capable of mixing efficiently with the exhaust flow. The hemispherical end of the injectorshould protrude beyond the inner wall of the ducting and into the exhaust flow. Theinjectors should be oriented so that the fan shaped spray is normal to the exhaust flow,

thereby mixing through the largest possible area. Figure 2 also shows the orientation ofthe injector. A flange is provided which should be used for mounting in a fail safeorientation. Two M8 durehete capscrews are recommended with an appropriate hightemperature anti-seize compound (Rocol) and flange sealant. A flow meter capable ofdisplaying 25 litres per minute and a pressure gauge with full scale deflection of 6 barshould be incorporated into the water supply lines. It is advised that a three way valveconnected to water and air is used to ensure that when water is not being injected, an airpurge is present to keep injector orifices clean.

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Figure 1 Water Injection Position

Figure 2 Water Injection Geometry

Water Wash Procedure

Take a record of performance parameters. Turbocharger speed, exhaust temperaturesand boost pressure are critical. Allow temperatures to stabilise after setting the engineload to 25%. The turbine inlet temperature should not be allowed to exceed 450C beforewashing. For all single entry NA295 applications, this load will result in approximately thesame exhaust mass flow, which means that the procedure is relevant for all engineswhich use the single entry NA295. Open the turbine outlet casing water drain. This willprevent a pool of water accumulating in the turbine outlet casing. It is not essential toobserve the cleanliness of any water emerging from the drain, since it is possible that thewater running from the drain is black after running back down the exhaust stack. Injectwater for a period of one minute, or longer if there is sufficient margin from exhausttemperature alarms (exhaust temperatures may rise during washing, due to choking of

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the nozzle). Provided the correct injector geometry is used (see below), water pressuredrop across the injector will not be a critical determinant of water distribution, although a

differential pressure of at least 2 barshould be ensured. Flow rate is an indicator ofinjector cleanliness and for clean injectors should be about 19 litres per minute for apressure drop of 2 bar. Turn the water supply off. Allow temperatures to re-stabilise

before injecting again. This may take up to 5 minutes. Repeat up to five times, dependingon the site specific requirements as determined by the operator in acknowledgement ofthe fuel quality and operating regime. Check that water flow from the drain has ceasedbefore closing the water drain valve. Return the engine load back to the requiredoperational setting and allow it to run for at least 15 minutes to allow all components todry completely. Take a record of performance parameters, for comparison with therecord before washing. The frequency of cleaning is determined through a combinationof the loading, the quality of the fuel and the effectiveness of cleaning. This should bedetermined by the operator, with once a week being a reasonable starting point.

E. IMPLIMENTATION

This bulletin is graded advisory. The method is known to frequently result inimprovements to operational efficiency, through reduced fouling to the turbochargernozzle and an increase in the intervals between manual stripping and cleaning.

Engine load, injector design, water pressure drop across the injector and injector orificecleanliness are the four most critical elements to the successful implementation of thisadvisory service bulletin.

For components other than the water injectors, it is considered the responsibility of theengine manufacturer to include appropriate changes for new and existing installations. It

is advised that those operating engines which burn heavy fuel oil be encouraged to adoptthe detail outlined in this bulletin.

The water injectors may be provided by Napier Turbochargers Ltd.

F. SUPPLEMENTARY INFORMATION

Summary of Changes to Superseded Water Washing MethodsThe traditional method of water washing was been detailed in two documents, with thehardware and water delivery requirements included in the IDM, and the methoddescribed in the Instruction Manual. This service bulletin outlines a procedure whichsupersedes previous understanding and related documents. The main changes are

outlined below. The next issue of the IDM and Instruction Manual IDM Section 7.3(Hardware and Water Supply): Water injector geometry has changed from a round exithole facing either downstream or normal to the flow and there is now some flexibility onthe number of injectors used, with two or three both resulting in good water distribution.The water flow and pressure drop across the injector have also been more accuratelydetermined for a given engine load.

Instruction Manual, Section 9 (Method): Engine load is now the determinant for goodwater distribution, not exhaust temperatures, although the first time the new procedure is

used, the level of safety with respect to exhaust system temperature alarms, should be

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accurately determined. Injectors mounted on the turbine inlet flange are known to becapable of providing a good water distribution. Importantly, drains are no longer used asa gauge for determining the effectiveness of washing and the water is not injected for aperiod of between 15 and 20 minutes. It should be injected more frequently and for areduced time period, reflecting the necessity for safety margin with respect to exhaust

valve temperatures at a load of 25%.

Date of Issue: 22nd

June 2001