Skip to main content

Procedures and precautions when cleaning both air and water sides of a charge air cooler.

Cleaning air side

On a large 2 stroke crosshead engine the air cooler may be cleaned by injecting an air cleaner chemical into the charge air while the engine is running. The chemical used is hazardous to health and thus protective clothing must be worn, and manufacturers instructions followed. Alternatively, a system using a chemical circulating tank, pump and built in sprays may be used when the engine is stopped. After circulating the chemical for a period of time as instructed, the air cooler must be rinsed using fresh water. Ensure drains from the air cooler to bilge are clear.
On a medium speed engine, the air cooler can be cleaned in situ (with the engine stopped) by blanking the air inlet and outlet and filling with a cleaning solution. However it will be necessary to support the air cooler, as the fastenings used may not be designed to cope with the extra weight. However it may be easier to remove the whole air cooler and place it in a bath of cleaning solution. Again protective clothing must be worn, and suitable ventilation provided. It is normal practise to pressure test the cooler stack when it is in the rinsing bath to check for leaking tubes.

Cleaning water side

This is normally done in situ with the engine stopped. After isolation and draining, the end covers on the cooling water boxes are removed and the cooler is rodded through or blasted using a pressure lance. In the case of the latter suitable protective clothing must be worn. Cleaning the water side is normally only carried out on air coolers using sea water. sacrificial anodes should be inspected and replaced as necessary.

It is necessary to maintain the correct charge air temperature for the following reasons:
    1.    So that the correct mass of air is allowed into the cylinder for combustion of the fuel. (the higher the temperature the greater the specific volume)
    2.    To keep the exhaust gas temperature at acceptable levels. (will rise if air temp is too high)
    3.    To prevent water depositing on the liner surface destroying L.O. film if temp is too low.
    4.    To prevent thermal shocking of liner if temp is too low.


Popular posts from this blog

Differences between MC/MC-C and ME/ME-C engines

The electrohydraulic control mechanisms of the ME engine replace the following components of the conventional MC engine: Chain drive for camshaft Camshaft with fuel cams, exhaust cams and indicator cams Fuel pump actuating gear, including roller guides and reversing mechanism Conventional fuel pressure booster and VIT system Exhaust valve actuating gear and roller guides Engine driven starting air distributor Electronic governor with actuator Regulating shaft Engine side control console Mechanical cylinder lubricators. The Engine Control System of the ME engine comprises: Control units Hydraulic power supply unit Hydraulic cylinder units, including: Electronically controlled fuel injection, and Electronically controlled exhaust valve activation Electronically controlled starting air valves Electronically controlled auxiliary blowers Integrated electronic governor functions Tacho system Electronically controlled Alpha lubricators

Shell Expansion Plan

It is a two dimensional drawing of a three dimensional surface of the ship’s hull form. This plan is very useful for the following information:It is used for marking the location of a hull Damage on this plan by identifying the strake number , letter and frame number so that the exact location of the damage and also suggested repairs are marked in a localised copy. The shell expansion can be used for finding areas of painting surfaces such as topside, boot topping and bottom areas by applying Simpsons rules directly.  In the shell expansion the vertical scale used is different from the horizontal scale and a suitable adjustment has to be made when calculating areas. This becomes useful in solving disputes concerning areas of preparation and painting. It gives information on the thickness of the original strake which is indicated by the number in the circle shown in the strake.  The quality of steel used is also shown by letters A,B,D E and AH, BH,DH, EH.

Why is a man hole door elliptical in shape?

Any opening in a pressure vessel is kept to a minimum and for a man entry an elliptical hole  is lesser in size than the corresponding circular hole. More over it is prime concern to have a  smoothed generous radius at the corners to eliminate stress concentration. Hence other  geometrical shapes like rectangle and square are ruled out.  To compensate for the loss of material in the shell due to opening, a doubler ring has to be  provided around the opening. The thickness of the ring depends on the axis length along the  dirrection in which the stresses are maximum and the thickness of the shell. It is important to  align the minor axis along the length of the vessel, as the stress in this direction is  maximum. Longitudinal stress: Pd/2t where P= pressure inside the vessel, d= diameter of the arc, t=  thickness of the shell plating  Circumferential stress: Pd/4t  More over a considerable material and weight saving is achieved as minor is along the  direction of maximum stress.