CAT Problem

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alanocean
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CAT Problem

Postby alanocean » Sun Sep 20, 2009 12:48 pm

Here is a small problem that is starting to get under my skin a bit....... Diesel Gen , Cat 3306... I notice that the overboard sea water discharge pipe is very warm conpared to the other one identical set up> I have cleaned the sea strainer, replaced the damaged Jabsco impeller and end cover.. installed new running Cam for the impeller.. removed both end covers from the J/W cooler and punched the tubes through and it did help but not perfect like the other one. It holds it's normal running temp but is at it's peak..meaning and loss of flow or restriction in the sea water system would cause the temp to rise and it to overheat?! Any idea's of something I may have overlooked?? The only thing I can think of is maybe it is getting some air from the sea strainer cover or possibly the block heater is not cutting out when running?? Just thought I would put out some feelers before I continued my Jouney.

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D Winsor
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Re: CAT Problem

Postby D Winsor » Sun Sep 20, 2009 3:00 pm

Sounds like there may be a leaking Pre-combustion Chamber. This will put combustion gas into the cooling system which would lead to overheating.
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alanocean
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Re: CAT Problem

Postby alanocean » Sun Sep 20, 2009 4:02 pm

Well noted.. Thanks

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Big Pete
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Re: CAT Problem

Postby Big Pete » Sun Sep 20, 2009 11:22 pm

I note that you say the sea water overboard temp is high, as well as the Fresh water.

The amount of heat transferred in a system is always proportional to the change in temperature and the mass flow of fluid.
With identical engines running at the same power the quantity of heat produced should be the same. The pumps have the same designed mass flow so the difference between the Fresh water inlet & outlet to the engine should be the same and so should the difference between the sea water inlet and outlet to the cooler.

(You can not directly compare the FW in & out to the cooler because the thermostat will bypass some of the FW, so the flow is variable)

If for one engine the difference in Fresh water temperatures is higher, than either that engine is putting more heat into the water (e.g. exhaust gas leak in the cylinder head) or the water flow is less.

If the difference in temperature is the same, but both the inlet & outlet are hotter, then there is a problem with the thermostat.

If the difference in between the sea water inlet and outlet is greater, either the cooler is putting more heat into the sea water or the pump flow is restricted.

By comparing "Delta T" (difference between inlet and outlet temps) for the coolers and both engines you should be able to see if the the problem is in the Sea water system or Fresh water.

Obvious question but have you watched the overboard discharges for the engines to see if one is discharging more water than the other?
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Big Pete
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Re: CAT Problem

Postby Big Pete » Sun Sep 20, 2009 11:36 pm

Post Script:-

I just re read your post and I note that you said you "punched through the tubes" this sets off allarm bells!!!

Many Engineers hammer metal rods through cooler tubes, but all Engineering text books and manuals warn that this can damage the heat exchanger tubes and should NEVER be done, also while it may clear any major blockages and allow the water to flow through the cooler it will not remove scale from the surface of the tubes and so does not improve heat transfer.
Coolers should always be cleaned with a tube brush until the inside of the tubes are bright and shiny or circulated with inhibited acid until all the deposits have been removed.

I hope all of the above helps you solve the problem.
BP
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alanocean
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Re: CAT Problem

Postby alanocean » Mon Sep 21, 2009 10:31 am

I did a few more checks and narrowed it down to low pressure from sea water pump. I checked the drawings for the pump and found a wear plate in the back of the casing that I had overlooked. I belive this is the reason the Jabsco impeller is not pushing as much water as expected. I check it out and hopefully this will sort it out. Thanks for the replies.. Much appreciated!!

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Big Pete
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Re: CAT Problem

Postby Big Pete » Mon Sep 21, 2009 11:38 pm

Sounds like you have found the problem & the solution, the hard part of our job.
As Sherlock Holmes said "Eliminate the impossible, and whatever is left, however improbable, must be true".
B.P.
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The Dieselduck
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Re: CAT Problem

Postby The Dieselduck » Mon Sep 28, 2009 9:18 am

I have a very similar problem that is similarly getting under my skin, except our engine is a Detroit Diesel. So far we found the overboard line clogged with mud, because we operate in a silty environment, we figure the silt gets deposited from the overboard line. We don't use the engine that often, thank god - its our FiFi monitor pump engine (on a tanker). But we test it on regular basis, although I suspect never fully loaded like we have been doing lately, therefore not noticing the overheating problem from what I can tell from documentation.

When I get back on board, this post has given me some other leads to check, should that cleared line not be sufficient enough of a solution.
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Big Pete
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Re: CAT Problem

Postby Big Pete » Mon Sep 28, 2009 11:34 pm

Another problem that I have had on two different ships has been that there was an overheating problem on an auxiliary engine and previous "engineers" ( I use the term loosely) had decided that the cure was to remove the mechanical thermostatic element!!!

If you think how they work: -

The wax bulb expands as the temperature rises, causing the valve to close the bypass round the cooler and force the water through the cooler. If the thermostatic element is removed, the bypass is full open so is the cooler. The water will take the line of least resistance, usually the bypass.

This will not help an overheating problem.

BP
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JK
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Re: CAT Problem

Postby JK » Tue Sep 29, 2009 4:05 am

The only time I run into overheating in a Cat, it was caused by the turbo cartridge failing. The engine would not carry any load and only ran a few moments before the temperature started going up. I have found Cats to be very reliable as long as the Mfrs manual is followed scrupously.

It should have been picked up as soon as the engine oil consumption started to go up though :oops: .

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alanocean
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Re: CAT Problem

Postby alanocean » Wed Sep 30, 2009 8:51 am

Just as a bit of a follow up. The wear plate was the problem and all is working fine again . Thanks for the few tips... could be used down the road!

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JK
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Re: CAT Problem

Postby JK » Wed Sep 30, 2009 7:53 pm

I just reread my last post and realized that it sounded like the turbo had failed completely, which is not the case. Everything was running fine, only the engine wouldn't take a load without the temperatures climbing. It was only when I took the air filter off and reached in and wiggled the turbo rotor about that we realized it had started to fail.

astat101
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Re: CAT Problem

Postby astat101 » Wed Jun 03, 2015 3:43 am

Hi,
I have just been reading through some of the previous posts on this subject, I note that some of the tube on the charge air cooler were plugged. I would like to add that this is a fairly common thing to do just block leaking tube and allow for the cooler to limp along a little further. How many tubes can be blocked in this manner is a question for a charge air cooler manufacturer, if you need advise on this you can contact a company called Vestas aircoil A/S in Denmark (www.vestas-aircoil.com).

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JollyJack
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Re: CAT Problem

Postby JollyJack » Wed Jun 03, 2015 6:29 pm

All the tubes I hammered plugs into were still plugged when the ship was scrapped!
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Merlyn
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Re: CAT Problem

Postby Merlyn » Thu Jun 04, 2015 12:36 am

Reminds me of plugging tubes in scotch boiler days, " it's only a temp repair " was the norm, Years later and numerous re fits later tube " temp repair " still holding up. I can remember water leaks in the Cat saltwater pumps caused by bearing wear and the shaft running on the lip seal causing the leak. Off with the pump, press out the bearings and note the ball bearing races to be steel and pitted badly both on the balls and the track and carrier. Always tried to fit replacement stainless races where possible. However clever Mr Cat would have different sizes OD and ID by a few thousands of an inch, when you went to a Skefco or RR agent forcing you to pay more money for a genuine part. Always used the inhibitor fluid in the freshwater coolant system to avoid electrolysis problems when refilling as I remember in the 1970's doing loads of piston/liner changes as Mr Electrolysis would drill holes in the liners, first signs were water in the sump, first thought the bottom liner O ring had let go but no, complete piston liner change necessary and many were done. When refilling coolant system part no xyz 123 had to be added to avert further hole drilling as otherwise warranty null and void. In the early 70's herewith was a new thing, an inhibitor fluid.
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