Cooling water filter

[zoidberg]

There are frequent posts, on various forums, about bits of damaged raw water impellers blocking heat exchangers, giving overheated engines.* ( see addendum #5 ) The idea of inserting a coarse mesh filter downstream from the water pump/impeller seems to have polarised opinion. It's quite common practice, I understand, on commercial craft.
Here's one example, from chandler Force 4, costing about £10...

What does the team think?

 

[Freebee]

The issue could be with this that one that bits of rubber could be caught up in the inlet and block flow maybe to the point of stopping flow.

 

[Supertramp]

I have these on a bilge pump feed and grey water tank pump. They have a small area to collect debris and need frequent, simple, if messy, cleaning in my application. I see your point in that water downstream of the pump should be clean and not block the filter. Based on my own engine it might however scale up over time with cooling cycles. I'm also not sure I would want to add more and relatively lightweight joints to a critical engine cooling pipe. I would rather invest in regular impeller replacement and heat exchanger inspection. Interesting to see if any commercial/long hour users do differently.

 

[Neeves]

Impellers, in the grand scheme of things, are cheap. Every time we changed the filters I religiously applied a new impeller (we had 2 engines and did them both the same way at the same time). We never lost an impeller blade, and only very occasionally had a crack at the blade base. Arguably we changed them too frequently (but it was to the Volvo recommended timing - which I now forget).

To us - if you lose a blade you are either buying questionable impellers or changing them with insufficient frequency

We would have had no need for a downstream filter.

Jonathan

 

[zoidberg]

* My concern derives from experience with a friend's boat, which suffered multiple cooling water failures, with broken-up impellers and burnt-out Vetus mixing bottles. These problems caused by e.g. plastic bag blocking of raw water inlet; growth of 'critturs' in the inlet pipe.....

Certainly improved my 'close-quarters handling under sail' skillset! Memory offers Cork/Crosshaven..... Newlyn..... Oban..... Brest/Castle..... and anchorages under sail, too.

It doesn't seem possible to PREVENT such occurences. I do want to MITIGATE the expensive damage they cause.
Of course I carry spare impellers.... and spare faceplate screws.

 

[sarabande]

In conjunction with a temperature sensor and warning shrieker, that would seem to make a lot of sense.

 

[Neeves]

It would be interesting to know member's estimate on the life of an impeller.

Jonathan

 

[Refueler]

There are frequent posts, on various forums, about bits of damaged raw water impellers blocking heat exchangers, giving overheated engines. The idea of inserting a coarse mesh filter downstream from the water pump/impeller seems to have polarised opinion. It's quite common practice, I understand, on commercial craft.
Here's one example, from chandler Force 4, costing about £10...

What does the team think?

Both my indirect cooled Yanmar and the direct cooled Perkins in the other boat - have metal mesh filters in the seacock housing itself. The mesh size appears similar to the picture you post .... so a second filter ? is it really a benefit ?

I have got to be a dab hand at closing seacock - unscrewing top - lift out filter ... shake off debris - put back .. close up ... open valve ---- all with engine still running.

 

[Aja]

Both my indirect cooled Yanmar and the direct cooled Perkins in the other boat - have metal mesh filters in the seacock housing itself. The mesh size appears similar to the picture you post .... so a second filter ? is it really a benefit ?

I have got to be a dab hand at closing seacock - unscrewing top - lift out filter ... shake off debris - put back .. close up ... open valve ---- all with engine still running.

I think the OP is suggesting fitting the new filter after the raw water pump to catch bits of impeller if it disintegrates.

I agree with you that the filter at the seacock and before the raw water pump should be easy to maintain and clean.

 

[zoidberg]

".....the OP is suggesting fitting the new filter after the raw water pump to catch bits of impeller if it disintegrates."

Yes. Preventive maintenance is all very well, but it doesn't prevent a floating polybag, a mass of seaweed, or similar from blocking the raw water inlet. And, once you stop the engine - or it stops itself - the suction at the inlet ceases and the offending debris floats away leaving no 'culprit'.

Ask me how I know!

 

[Refueler]

I think the OP is suggesting fitting the new filter after the raw water pump to catch bits of impeller if it disintegrates.

I agree with you that the filter at the seacock and before the raw water pump should be easy to maintain and clean.

OOP'S .... yes - different part of the system !!

 

[dunedin]

It would be interesting to know member's estimate on the life of an impeller.

I think the point is that if no obstructions then an impeller will last many years, perhaps decades. But if the sea water inlet is blocked by a plastic bag, weed, fish etc the impeller can rapidly overheat and shred. Then little bits can get stuck in the heat exchanger which is a major pain to resolve.

 

[B27]

Has anybody ever had their HE significantly blocked by bits of impeller?
Enough of the tubes blocked to cause a cooling problem?
I would think that an impeller can only lose a couple of vanes before it stops pumping?

 

[Plum]

There are frequent posts, on various forums, about bits of damaged raw water impellers blocking heat exchangers, giving overheated engines.* ( see addendum #5 ) The idea of inserting a coarse mesh filter downstream from the water pump/impeller seems to have polarised opinion. It's quite common practice, I understand, on commercial craft.
Here's one example, from chandler Force 4, costing about £10...

What does the team think?

It it quite common for the larger Volvo Penta engines, those fitted to motorboats, to have filters on the pump outlet such as this (this is noy my engine!)

 

[starfire]

It it quite common for the larger Volvo Penta engines, those fitted to motorboats, to have filters on the pump outlet such as this
View attachment 165081

If you follow the left hand pipe, that's on the inlet.

 

[Plum]

If you follow the left hand pipe, that's on the inlet.

No. I have the same engine type the pump inlet is at the bottom of the pump, outlet at the top. Here is another. The hose out of the filter goes under the crank pulley then up to the heat exchanger

 

[starfire]

No. I have the same engine type the pump inlet is at the bottom of the pump, outlet at the top. Here is another. The hose out of the filter goes under the crank pulley then up to the heat exchanger
View attachment 165085

My Bad. I would assume there is an inlet strainer.

 

[B27]

Perhaps that engine has a heat exchanger more easily blocked than some?

I'm not aware of many yachts suffering from heat exchangers being blocked by stuff that would be picked up by filter after the seawater pump. I've known inlets get blocked by plastic bags, and I've known of heat exchangers getting blocked by mineral deposits.
If modern HX's benefit from fitting a filter upstream then, go for it.
Otherwise it might just be three more things that can leak.
As in the filter seal plus two hose ends which suffer engine movement.
You may already have a syphon breaker mounted off-engine of course.

 

[Tranona]

Perhaps that engine has a heat exchanger more easily blocked than some?

I'm not aware of many yachts suffering from heat exchangers being blocked by stuff that would be picked up by filter after the seawater pump. I've known inlets get blocked by plastic bags, and I've known of heat exchangers getting blocked by mineral deposits.
If modern HX's benefit from fitting a filter upstream then, go for it.
Otherwise it might just be three more things that can leak.
As in the filter seal plus two hose ends which suffer engine movement.
You may already have a syphon breaker mounted off-engine of course.

Not uncommon to find bits of impeller blades in the entrance to the HE tubes. If bits break off the blades for whatever reason, that is where they end up.

 

[B27]

Not uncommon to find bits of impeller blades in the entrance to the HE tubes. If bits break off the blades for whatever reason, that is where they end up.

But do they normally do any harm?