Impeller fragments

[zoidberg]

There's a discussion elsewhere about trapping fragments of broken-up raw water impeller - something that has vexed a few. Here's some of the text. Any good ideas....?

KH - You need to find all the pieces. They are probably in the heat exchanger. Why? This blockage can contribute to engine overheating under high load, or high rpm. When the engine is running hard it is using the whole heat exchanger. Blocked passages prevent this.

EB - I will admit freely that I don't know much about these engines but.. It seems that if these impellers are prone to fail as this one has, shouldn't there be some sort of strainer prior to the heat exchanger to catch chunks big enough to clog up the passages? Or maybe the exchanger is easy enough to service that "it" serves that purpose.

WB - I've queried/suggested that to a very experienced 'Boat Rescue Service' engineer, who poo-poo'd it. He reckoned such would restrict the flow to the engine. I'm not so sure, as a coarse mesh filter could do that job without much restriction - certainly not as much as barnacles/mussels in the inlet - and we hear of many examples of impeller break-up part-blocking the heat exchanger.

EB - Just seems like it would be a low cost, and potentially easy to service device, certainly easier that taking the heat exchanger apart and poking out all the tubes. A course mesh strainer (which is all you would need if you are only interested in catching bits that would clog the exchanger) would not cause any restriction unless it was clogged with debris, which is precisely what you want it to do!

WB - There has to be 'something' that could be cannibalised, with a clear enclosure, which would do the job.

 

[simonfraser]

do i just have an odd engine ? my impeller is fitted before the water filter, no way the bits could get to the heat exchanger.

 

[RichardS]

do i just have an odd engine ? my impeller is fitted before the water filter, no way the bits could get to the heat exchanger.

That seems very unusual but rather clever provided that something hard does not get sucked in and wreck the impeller. Is the filter bolted to the engine near the pump or do the hoses go from the pump, over to a bulkhead-mounted filter and then back to the engine again?

Richard

 

[RichardS]

There's a discussion elsewhere about trapping fragments of broken-up raw water impeller - something that has vexed a few. Here's some of the text. Any good ideas....?

If I were that bothered, I would fit an inline coarse filter of the sort that fits into the toilet sea-water inlet.

Richard

 

[simonfraser]

That seems very unusual but rather clever provided that something hard does not get sucked in and wreck the impeller. Is the filter bolted to the engine near the pump or do the hoses go from the pump, over to a bulkhead-mounted filter and then back to the engine again?

Richard

The filter is bolted onto the engine, just above the bolted on pump.
Intake is through eight or so narrow slots.

 

[zoidberg]

Here's a candidate, from Force4....




Clickit. About £9.

 

[RichardS]

Here's a candidate, from Force4....




Clickit. About £9.

That's the model I have fitted near the toilet seacocks. If I was going to fit one in the cooling water hose I would connect it to a hosepipe first to check the throughput and possibly enlarge the small holes in the backplate inside the filter to increase the throughput if necessary. I don't think there would be a problem with the current holes but they are only 3mm or so.

Richard

 

[zoidberg]

That's the model I have fitted near the toilet seacocks. If I was going to fit one in the cooling water hose I would connect it to a hosepipe first to check the throughput and possibly enlarge the small holes in the backplate inside the filter to increase the throughput if necessary. I don't think there would be a problem with the current holes but they are only 3mm or so.

Richard

Makes sense...

 

[john_q]

About 6 years ago I fitted a Vetus Water strainer between the pump and the heat exchanger on a Perkins 4236M and ir works really well. it is the same type of strainer that I have fitted between the sea cock and the pump