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DESCALING LOW SPEED MARINE DIESEL ENGINE COOILING WATER SYSTEMS

NOTE: BE CAREFUL – USE PROTECTIVE GLASSES & GLOVES

-          To isolate the system

-          Connect the transparent hose from the low point of the system to the chemical resistance pump.

-          Connect the transparent hose from the high point of the system to the chemical mixing drum. (return line)

-          Prepare a chemical mixing drum (200L)

-          Sufficient “De-scaling Liquid” to mix up a 5-10% solution is successively filled into the mixing drum, well mixed and fed into the inlet manifold.

-          Take a sample of the solution for later color comparison.

-          The solution should be heated to 50C using the engine’s cooling water pre-heater.

-          Circulate the system for 4-6 hours, checking the solution temp. regularly.

-          Fill up the engine with clean fresh water and circulate the system.

-          Open all inspection covers and check that all debris that has formed during de-scaling is flushed out. Close covers.

-          Fill up the engine again and add 0.5% Alkalinity Control.

-          Circulate the solution to remove any remaining acidity and passivate steel surfaces. Circulation must be maintained until an acceptable pH value is obtained (pH7). Drain the engine.

-          Disconnect the cleaning equipments

-          Adding the engine cooling inhibitor Rocor NB Liquid / Dieselguard NB to recommended parameter “N”: 1000-2400ppm; CL: less than 50ppm; pH:8.6-10.0

-          Check the acid content of the system lubricating oil directly after the decaling operation and repeat after 24 hours.

-          When descaling  4 or 2 stroke trunk engines basically the same procedure as above can be followed. However, this kind of engine seldom has shut off valves on the individual cylinders and therefore all cylinders must be circulated simultaneously.

-          Medium-speed engines of this kind often have a drain bore – “Tell Tale Bore” from the space between the upper (water) and the lower (oil) cylinder liner O-ring. This is to monitor for leakages.

-          The bores should be inspected when the engine is running. If leaks are indicated, NO descaling should be performed unless the engine can be dismantled and the cylinder liners pulled out immediately after the descaling operation. Otherwise, one cannot be assured that all acid is flushed out / neutralized and corrosion of the sealing surface may occur.