Main Engine Exhaust Valve Parts, Working and Overhaul Procedure

Marine Diesel Engine nowadays employs the hydraulic mechanism of opening and closing the exhaust valve. Just like other machineries, it also requires maintenance from time to time. Let’s have a look at its working and maintenance.

Main Engine Exhaust Valve Parts

·        Hydraulic Pipe
·        Hydraulic Oil Cylinder
·        Air Cylinder
·        Spindle and vanes
·        Exhaust Valve Housing

Working of Main Engine Exhaust Valve

Pressurized hydraulic oil is used to open the exhaust valve, against the air spring pressure of 7 bars. The timing of this hydraulic oil is as per the opening timing of the exhaust valve. So, we have a benefit of changing the timing of opening of exhaust valve, if we are using the hydraulic system.
Below is the diagram of Exhaust Valve
Main Engine Exhaust Valve
Image Courtesy: J COWLEY MEP BOOK
So, at the top, we have the hydraulic operated servo piston and at the bottom we have the air operated piston. When hydraulic pressure is relieved, the air pressure brings the exhaust spindle back to close position.

Overhauling Of the Main Engine Exhaust Valve

1)     First thing first, that the people who will work during the overhaul having been given instructions as per the work profile.
2)    After making sure that proper tools and spares are onboard, unit isolation can be carried out.
3)    Open the hydraulic nuts using the hydraulic jack.
MAN B&W Exhaust Valve
4)    After it place the valve on a wooden platform carefully. First thing to take out is the oil cylinder of the exhaust valve. After that retaining ring for the spindle will be removed with use of special tool.
MAN B&W Exhaust Valve
5)    Also, after this, air piston arrangement is removed.
MAN B&W Exhaust Valve Air Piston, Main Engine Exhaust Valve
6)    Now we have opened everything. We will put main consideration on Spindle Bushing, Spindle and the Exhaust valve seating surface, as these are the places where the actual wear and tear takes place.

Checking the Main Engine Exhaust Valve Spindle Bushing

In the diagram below you can see what you have to check. You can use the dial gauge to measure the clearance.
MAN B&W Exhaust Valve, Main Engine Exhaust Valve


Checking the Bottom Seat Surface

Checking with the help of template, you can check whether clearances are in the right limit or not. Before putting the template, it is wise to remove any type of carbon being deposited on the seat.
Exhaust Valve Seat
·        Small dents, that cannot hamper the sealing of seat, should be avoided for any repair. But yes, if there are tends and erosion, that are damaging the sealing between the exhaust valve spindle and the seat, then some grinding is necessary.
·       Outer seating needs to be lapped smoothly, with the help of special tool shown below. The lapping needs to be one half turn clockwise and half turn anti clockwise.
Exhaust Valve Seat

Checking Exhaust Valve Spindle Seating Surface

·        Manufacturer of the engine provides the standardtemplate for the measuring the clearance of the spindle face. If it is not satisfactory, you can grind it.
·        Secondly, with the help of template, you can also, check the amount of burn off on valve face.
Exhaust Valve Spindle Seat, Main Engine Exhaust Valve


·        Sometime, you need to grind the face, to remove the black carbon depositing on it, so that you can get the actual surface to measure
·        You also need to check the trueness of the spindle shaft. This can be done by putting the one end of the shaft on rolling point and on the other end you can fit the dial gauge. Any difference will tell, whether shaft is true or not.

After doing all the checks and putting necessary spares, it is time to box back the exhaust valve. This exhaust valve overhaul was for the MAN B&W engine. So for other engines, things might vary. So this was all from this article ‘Main Engine Exhaust Valve Overhaul’.

You Might Like to Read These Posts Too:

Ashish S

Hi there! Well I am not a writer, just writes what can help people-that's it. Interested in listening from you. Loves to talk about gadget, music, nerdy stuff and witty substance in the talks. A Good respect in heart- for web.

One thought on “Main Engine Exhaust Valve Parts, Working and Overhaul Procedure

  • August 15, 2017 at 12:49 pm

    I didn’t understand why you have to lap the outer seating


Leave a Reply

Your email address will not be published. Required fields are marked *

Special Topics For You

Read these

Marine Engineering Practice MEP Questions and Answ... In this article get to know about boiler burner maintenance, fuel injector testing, CO2 line testing, cylinder head testing and HP cut out problems ...
What is Overspeed Trip, its types and how it works An overspeed trip is required to ensure that fuel supply will be cut off from engine if its speed exceeds the predetermined value. Over speeding wi...
Marine Engineering Practice Questions And Answer-P... Here are some of the questions for oral preparation for your engineer COC examinations. This article covers the Marine Engineering Practice question...
Marine Engineering Practice Questions and Answers-... This is our second article in the Marine Engineering Practice Series which deals in questions related to the troubleshooting of the ship machinery e...
Properties and Specifications of LSHFO, MDO, and H... Read about fuel Oil Specifications like LSHFO, MDO, and HFO for Main Engine, and Auxiliary Engine Used on Ship. These are particular for a ship and ...
Every Day checks in Engine Room Rounds from Funnel... When a duty engineer is taking rounds, half of the problems or troubleshooting can be done by them, if they check the items below given properly. Th...
Centrifugal Purifiers or Separators Theory, Workin... Learn about centrifugal purifiers working, theory related to their working and about the new ALCAP principal that is used nowadays. Purifiers are on...
Marine Engineering Practice Question and Answer- P... This is the third article in this series. We have covered topics like Steam, Liner, Control air, Sea Water Line, Expansion tank, Sump, Spanners, O- ...
error: Content is protected !!