Cat 3500 water pump failures. 1

[TugboatEng]

I know there are some people here with experience on this. I operate a fleet of Cat 3512 engines (12 of them) and outside of one other jacket water pump failure I have had one engine have seal failures 4 times since it's top end overhaul (15,000 hours). I'm about to eat the core cost and disect one of these pumps. Is there anything anybody else recommends looking at? The pump has only a thrust bearing, the radial bearings are in the drive gear and I really don't want to tear into that especially when the engine will be replaced in 6 months.

 

[MikeHalloran]

Recurring seal failures suggest that the top end overhaul left something (solvent or particulate) in that one engine's jacket water circuit. ... or that you need to buy better seals or install them better.

I have not seen the inside of a jacket water pump.
I have seen the inside of a few seawater pumps.

Why are you condemning the subject pump?





Mike Halloran
Pembroke Pines, FL, USA

 

[catserveng]

In general the 3500 engine jacket water pumps have been pretty good. Early on there was a seal issue with variable speed engines.

When you take the core back to the dealer have you asked for a failure analysis to be done? If the parts guy or service manager doesn't seem interested ask to talk to the Technical Communicator, its a position CAT requires the dealer to have, and he can generate a service inquiry and see if there is a history of problems on similar units. But insist they open the pump and look at the seal.

You need to see if the seal face is damaged from debris, if the seal carrier (the rubber part around the seal) is damaged, sticky or pitted (could be a sign of corrosive attack, like from some cooling system cleaners).

Is the leak showing up as coolant coming out of the weep hole? What are the engine hours each pump got before leaking again?

When you had the pump off, did you take a look at the gears? Is the wear even? At 15k hours front bearing wear is unlikely but a possibility.

You may also want to check pump suction and discharge pressure, have found a couple after repair repetitive seal failures due to blockage (usually a rag) in the pump suction pipe.

A lot of possibilities but your first step would be inspecting the pump, and you should be able to get it done without losing the core charge.

MikeL.

 

[TugboatEng]

It's from the weephole.

The first failure was within 1000 hours of the top end. I replaced the pump and it ran for close to 12k hours before the next failure. Now it has around 1000 hours and has failed again.

 

[TugboatEng]

We had time to open it up today. Looks like 0.020" of radial play on the impeller. I can see the drive gear moving up and down with it.

 

[enginesrus]

So then its a bearing issue. I'm not familiar with the 3500 but have worked on lots of the smaller Cat engines.
Is it a bushing or a frictionless bearing? I wonder where the units are remaned at?

 

[catserveng]

There is no bearing in this pump other than the thrust ring. 0.020" of radial play actually doesn't seem that bad, I don't see an actual spec for it in the manual I have. I have attached a copy in case you don't have the manual.

I'd really be interested in what the seal face looks like. My son still works for a dealer on the machine side, said there have been some issues lately with some of the REMAN stuff. 12,000 hours on a reman pump seems pretty good, but 1000 hrs is a sure problem.

When the vessel was commissioned was a cooling system audit performed? Unfortunately they don't always get done and later in the vessel's life we sometimes find issues with piping, coolers and other installation types issues. Do you do coolant sampling to check SCA levels, condition of the glycol and TDS levels?

When you pull the pump out (if you do) take a good look at the drive splines, wear should be even. Uneven wear usually indicates bearing wear in the front gear train, which can cause early seal failures in both the jacket and aux water pumps.

Where are you located and who is your dealer? I may be able to point you to someone who could be more help.

MikeL.

 

[enginesrus]

There has to be something supporting the shaft that the impeller is mounted on. If not then there is a design flaw, can't expect any seal to last in that environment.