With reference to multi tubular oil cooler describe – (a) Indications of tube leakage (b) Steps to locate leak (c) Temporary correction steps (d) Permanent correction steps

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a) Indications of tube leakage:

* Sump level decreasing (normal oil pressure is higher than circulating SW press.)
* Traces of oil in O/B or expansion tank (for central priming system)
* Pressure decreasing, temperature decreasing.
* p/p discharge pressure gauge fluctuating.
* Trace of oil when cooler end cover purging cock opened.
* When end cover is opened.

(b) Steps to locate leak:

* By pressure test, we can locate the leak. Required components are p/p, pressure gauge, blank flange.
* By starting oil circulating p/p, we can locate the leak normally water passes inside the tubes and oil passes outside the tubes. If oil causes out through the tubes, the leak will be located.
* By “ultra violate lamp test” we can locate the leakage. For that we require ultra violet lamp and fluorescent solution. This is the modern method for finding leakage.

(c)  Temporary corrective steps:

* Plug in or blank to be fitted and pressure test to be carried out.
* Oil temp. to be maintained to prevent crack of tube.
* Cooler to be cleaned (both side) at regular intervals.

(d) Permanent correction steps:

* Tubes stack to be changed and then pressure test to be done.
* Damaged tube can be changed/repaired and pressure test to be done. 
* Oil temp. monitor and alarm CKT to be fitted to prevent the cooler from overheating. 
* Filter to be fitted in SW system to prevent the tube from leakages.
* MGPS (marine growth protection system) to be applied in sea chest/filter casing to prevent the tube from corrosion. 
* Material choice (SW side) – it must be non-ferrous. i.e.                                                                          (Aluminum-brass, cupro-nickel)
* Ferrous sulphate treatment

-          prevent corrosion,

-         Protective oxide film (on NF metal)

-         Requirement (1. Mixing tank, 2. Solution, 3. PVC pipe)