Posted: Sun May 11, 2014 11:44am

When we had our boat built we had hydraulic drive, and to cool the hydraulic fuel there was a skin tank made to cool the oil,but on the day of delivery the boatbuilders told us that the hydraulic skin tank had a leak so the had mad a tank and fitted it under the floor, I have two questions 1 can I have the skin tank tested if so who would I need to get in touch with we are located in Willington Derbyshire 2. What should the oil temperature be.

Posted: Sun May 11, 2014 12:25pm

The Eaton hydraulic equipment site http://www.eaton.com/ecm/groups/public/@pub/@eat on/@hyd/documents/content/ct_233701.pdf gives a maximum temperature of 66C and an optimum running temperature of between 49 and 54C. If you Google tank pressure testing you will find a number of companies that offer thsi service but as they seem to be mainly concerned with industrial tanks they may either not want the work or be very expensive. I am at a loss to know why you accepted the boat with a leaking hydraulic cooling skin tank. I assume this was part of the contract so it is up to the builder to provide it in a working manner. The tank should only have two "holes" in it or three if it is also acting as a reservoir as well so it should not be beyond a reasonable DIYers skill to seal all but one outlet and then cobble something up using a car tyre valve, foot pump and tyre pressure gauge to fit into the other and then do an air tightness test. This has a potential danger in that a weak weld could cause the tank to split and injure you but as you are only using a car foot pump I doubt there is a real danger. Normally this would be tested with oil or water under pressure. You may find a company or individual who will undertake this through your local model engineering club. Try http://derbysmee.co.uk/ . I am a bit concerned about the under floor tank. Is this the hydraulic reservoir or is it an alternative skin tank. If the latter and as long as it only has about half an inch of gap between the top and the boat's base plate it should do the job as long as it has internal baffles. If its the reservoir then the pump will be wasting energy is sucking the oil up and this may cause overheating of the oil. It could also cause cavitation in the pump leading to excess wear. I hope this helps Tony Brooks