Impeller looks a bit tired...

[vas]

so since I've removed, cleaned, changed o-rings, reassembled and refitted all heat exchangers in both engines, I thought I should check/replace impellers as well. Especially as I found a small bit of a vane on the port engine CAC.

Started with the easy one (port) as impeller is in the v.easy to access space between the two engines.
Had already replaced the flat headed screws with nice ss alen ones, two minute job to remove the cover plate.
A bit puzzled as what I saw was rather unexpected:

So got a screwdriver and tried to see what's behind , rather worn impeller behind all the salt deposits:

impeller removed, loads of salt deposits working like sandpaper on the impeller rubber:

that's how the housing looks like after a bit of cleaning, will come back with some salt remover spray and water to clean it properly:

and the impeller:

Now, I obviously going to replace it, have a Jabsco Profile Y kit with silicone/grease, gasket and even a rubber plug for the centre/shaft, but that's not the point.
This impeller was fitted new on Aug 2015 at the end of the refit. Engines have clocked around 120h since in three seasons. Is that condition acceptable?

I'm asking as my friend with CAT engines has the boat for around 8yrs (bought s/h) and each year opens up the cover plate, has a peak, looks brand new, retightens the cover plate, that's it.
Also the next door neighbour with a single IVECO 300 engine replaced the impeller on the 6th year and the one removed looked fine to me.

Am I missing something, or is there's something wrong with mine?
FWIW, engine was running fine, was actually cooler than the stbrd one by 3-4 degrees (port engine had heat exchangers cleaned back in 2015, stbrd cleaned last week)

Haven't bothered to remove the stbrd engine yet as I need to get a couple of more impellers will do over the w/e

cheers

V.

 

[Portofino]

They are not OEM install those engines iirc ?
Where I,am going with this is that they look free draining caused by the relative pump height of the none originally installed Ivecos and basically the WL

By way of example my pumps are mounted low relative to the main engine mass are level with the WL so I suspect don’t free drain and stay primed .

Question is , if the clock was turned back to the new build project would the Iveco guys sign that off or return with a different pump mount position and recommend that to the builder ??

Similar considerations should be given to the strainer location with regards the WL and the lid top height .

My 0.02 p worth .

Impeller certainly ready for replacement.I believe there’s different quality with theses as well .

Do you regularly run them in the winter ? I realise some times it’s on the hard.
That’s another reason I run mine every month in the off season to exercise the rubber impellers helps prevent a “set “

But your problem is a draining down pump body .

 

[rafiki_]

I change my Cat impellers every 3 years. They come out looking like new. Quite a hassle as I have to take the pumps off to access the impeller. Port engine a real struggle for access, dangling through the saloon floor. Had to change the shaft/bearings on the stbd pump last year as the seal was leaking. Sterling pumps, a rubbish design.

 

[jfm]

Looks odd vas. My small genset impellers fail at 250hours quite consistently and never have salt deposits. My main engine impellers on all boats I've ever had have zero salt and last 2 years +250 hours and look perfect - I change them for the hell of it. Youve got something wrong but I don't know what.
I totally don't buy that impellers can set in a month or whatever as Porto worries. Quality OEM impellers that are properly cured in manufacture won't post cure into a new shape (that being the main cause of set) at normal resting temperature of a berthed boat ie 20 deg C. Of course a badly made rubber component will set into a new shape if kept stretched/compressed for a month at much higher temps.

 

[[2068]]

The impeller isn’t the problem, it’s getting shredded by the deposits.
I’d be looking upstream for something that is dissolving to cause those deposits.

 

[Portofino]

I wonder if there’s been any wear of the pump housing or cover plate?
The new rubber vanes I suspect will stretch out and seal against the pump house inner barrel , but even with a new rubber if there’s been wear on the cover plate that might not re seal up satisfactory.

So it might struggle to prime as the salt has basically and unwittingly contributed to the air seal at initial start up .

There’s an awfully thick ( relative to pump seals ) thickness of salt behind that cover plate .

More on “ set “ for folks deliberations
http://www.galmukoffmarine.com/sx-html/

 

[burgundyben]

What material were the original cover plate screws?

 

[jfm]

No way that impeller pictured was like that after "months" unless they meant 36, 48 or 60 months. You can find anything you want on the internet Porto, as you do often. https://wiki.tfes.org/A_hundred_proofs_the_Earth_is_not_a_globe

 

[longjohnsilver]

The impeller isn’t the problem, it’s getting shredded by the deposits.
I’d be looking upstream for something that is dissolving to cause those deposits.

The deposits are surely a mixture of salt and calcium in the seawater, but you may be on to something FP.

Have you had any overheating issues on that engine Vas? It looks as though you have seawater sitting in the pump and not draining away, which seems most odd. As everyone else has said, when I change my impellers they look virtually new.

However, I did have an issue with my cooler for my stabilisers. My port engine was gradually producing more and more steam from the exhaust, but not overheating. I cleaned everything, or so I thought, until the downstream tail of the stab heat exchanger, (that was first in line from the inlet seacock and strainer) broke off!! It was then that I saw that it was almost completely clogged with the sort of deposit shown in your pic, with just a small pencil sized hole in the middle allowing just barely enough cooling water through.

What I hadn’t realised is that there were 2 pencil anodes in the cooler, so these hadn’t been changed in about 7 years, but strangely only the downstream bronze tail exiting the cooler was blocked, the upstream one was as clean as a whistle.

So maybe as FP says, there is some corrosion issue going on upstream of the pump that gradually seeps back once the engine has stopped and over time, causes your clogging issue. Do you have any anodes upstream of the pump? If so, have they been checked regularly. After my issue I read that pencil anodes should be checked every 4 months. But I’d bet that most are looked at just once a year, mine certainly were, apart from this cooler where I didn’t even know there were anodes!

Please keep us updated as to what you find.

 

[vas]

thanks guys for an interesting set of ideas/Qs.
on with the replies then!

PF:
MiToS was reengined before my ownership from DD. Will check carefully the seawater level argument and draining as I think it is semi-draining, feel that the W/L is halfway the pump housing.
Housing is not worn (from what I can see at least), it's a bit awkward to bend down there so taking lots of 16Mpix pics and checking them with specs on
Plate is worn on the central boss thing, ie a grove where the central rubber tube is just outside the metal spline. Plan is to turn it over for now.
Vanes are not really deformed, they hold to their shape quite well (and better than the yanmar gen engine!), they're just shreaded by the salt deposits.

P:
at least mine are an easy reach comparatively, and no play in the shaft and no leaking at the back

JFM:
IIRC I'd bought them as nitrile ones having read that they're better than stock ones. Mind, the Jabsco one I have in it's box also says nitrile.

FP:
upstream there's 1.5inch plastic all the way! Trudesign injection/seacock, rubber hose with wire to plastic strainer and then hose again to pump body. All look fine so nothing to dissolve, but LJS may have a point (re downstream anodes!)

BB:
don't remember! either galv steel or ss, probably galv. Bearing in mind that I didn't have a paper gasket and used some instant seal, a film of it I had to remove yesterday when I opened it up, I assume that there was some isolation between and anyway haven't seen any suspicious pitting or anything, faces completely clean and smooth

PF:
I'm with JFM on that, this impeller was probably "set" for a 4-5yrs in that position, not just through a winter, unless run dry on the hard for 5-10mins to heat up nicely and then left to cool in form

JFM: managed up to #10 in the list and gave up...

LJS:
Engine running v.cool, never ever overheated!
However, first pencil anode is 20cm after the pump body on the way up to the CAC. Second pencil anode is on the CAC endcap.
I've picked up the second anode (facing down and held in the bronze 24mm nut by just hammering it in...) on the gbox oil cooler (the natural place to loose it as it drops straight into it after a downfacing elbow).

First anode is facing upwards so not really easy to disslodge/wear it self and drop back down to the pump body. Could have happened as I don't recall the condition of all anodes over these three years. I do replace them annually and they really don't come out good, so I should do it more often.

So out of all ideas:

A. I may have a drying pump assembly which I gather is a bad thing (or not???), but getting a slightly longer hose from the strainer and siphoning it up before going down to the pump should solve that, right?

B. I may have bits of dissolving pencil anodes dropping down to the housing and helping the destruction of the impeller as well as helping the built-up. Plan is to switch to screw on pencil anodes, need to machine new bronze plugs with internal M6 (or M8) threads to bolt them on and need to start checking anodes more often.

will come back with some measurements and photos of sbrd impeller housing

cheers

V.

 

[simonfraser]

corrosion dropping back to the impeller, that's a lot of stuff, why is it not being pumped right out of the system when the engine runs ?

 

[omega2]

120 hours in three years?

 

[longjohnsilver]

corrosion dropping back to the impeller, that's a lot of stuff, why is it not being pumped right out of the system when the engine runs ?

Maybe a combination of corrosion, bits of old anode, salt and calcium build up? We’re all guessing, if the engine has been running at normal temperatures none of this makes sense.

Vas, was the white stuff in your pics solid or sludge?

 

[BartW]

this is indeed very strange,
we all know that salt normally dissolves in water, so there must be something wrong,

it would be interesting to know if the other pump has the same issue ?

 

[MapisM]

Maybe a combination of corrosion, bits of old anode, salt and calcium build up? We’re all guessing, if the engine has been running at normal temperatures none of this makes sense.

Vas, was the white stuff in your pics solid or sludge?

+1.
There's obviously much more than a normal usage, behind those awful conditions.
As BartW said, makes me also very curious to hear about the pump on the other engine.

As an aside, I also wouldn't even consider for a second that "setting" has anything to see with the above situation.
All blades are worn out, not just some of them - and it's rather obvious that the exceptional wear is due to the unbelievable conditions it was working in.
Good thing that it was still able to make some water flow!

 

[Portofino]

Impeller certainly ready for replacement.I believe there’s different quality with theses as well .

Do you regularly run them in the winter ? I realise some times it’s on the hard.
That’s another reason I run mine every month in the off season to exercise the rubber impellers helps prevent a “set “

But your problem is a draining down pump body .

MapisM, for clarity regular winter running or lack of it in this case - if you can for impeller health and longevity is “ another “ reason not THE reason of the this particular aetiology.

Surley regular running would go some way to minimising that build up , like others infer wash / flush it away ?

Opening this thread up , delving a little deeper and we enter into allowing pencil anodic protected coolers to drain down .
First pass feel great no seawater what’s not to like form a corrosion POV ?
Think again - there’s a school of thought if pencil anodes hang in the air all dry then they do not protect effectively.
This is because for zinc anode protection you actually need a sufficiently concentrated electrolytes surrounding the thing you wanna to protect sos to allow the correct quantity of protective subatomic particles to move freely .

Layman's terms a liquid circuit .

Toss in dissimilar metals , the more the greater risk of let’s call it “pencil anode hanging syndrome cooler corrosion “ if they drain down and are left many months air drying inside .
CAT has had huge issues with this leading to American class action law suits , after that cattle prod they totally redesigned there coolers and materials now all titanium, but with the cop out of “lifing “ them .
Now a throw away part every iirc 5 or 7 years .That way when not if they fail ,they will be spared another courtroom drama - again !

 

[vas]

a few more things to clarify,

first engine was running v.cool, producing LOADS of water!

SF:
hard to imagine that anode or whatever droppings were coming back down to the OUTLET of the pump and damaging the vanes... On first run I'd expect they shoot off to the CAC endplate and stay there...

Omega:
yes only 120h but I actually may be wrong and it was 180, have to check the log, don't remember off hand.

LJS:
hard as in V.HARD salt, some would only come off with a bit of hammering on a small screwdriver...

B&P:
dunno, that's why I posted it, looks odd indeed. Sorry real work today, will remove the stbrd impeller tomorrow and will post although most of you lot will be on Easter w/e vacation, ours (orthodox easter) is next w/e so I'm "allowed" to work tomorrow and on Sunday

PF:
checked levels, pump is almost at w/l level, strainer is above it, hose comes just down from the strainer and into the pump so easy to drain the pump dry if it's above...
I could reroute the hose so that I have a siphon and both pump and first anode are always full of seawater if it makes any sense. Well I'll do it anyway and see how they come out next year.
Now, anodic/cathodic protection is too confusing for me right now (had a 20/20 in A-level equiv 38yrs ago but did no chemistry ever since and not even at the uni...), let's see how the stbrd one looks like and we go on from there.

Only thing I don't recall is the condition of the pump body when I replaced the impeller for the last time, could be that it had some salt deposits which I didn't pay attention to and these have been working and damaging the whole thing now...


cheers

V.

 

[longjohnsilver]

Wake up Vas:encouragement:

How was the other impeller?

 

[vas]

zzzzzzzzzzzzzzzzz



slightly stuck LJS, I always try to have at least one engine running whilst in port, you know just in case...

So yesterday I managed to put together all the bits back on port engine and fired it up, all's fine, still produces lots of water, running fine.
I'm rushing the refurb of the generator spot before the yanmar is back onboard hopefully this week, so I've removed old rockwool and perforated panels from bulkhead and ceiling, painted the bilge area and today will be placing the new extra heavy and expensive soundpanels in place.
Once done, I'll be able to move the gen frame from where it's jammed right now to the new ply gen plinth and this will give me access to the stbrd side of the stbrd engine in order to remove the impeller, so I'm afraid you'll have to wait for one more day or two. This 3-4h a day folded in two is killing my back...

cheers

V

 

[longjohnsilver]

zzzzzzzzzzzzzzzzz



slightly stuck LJS, I always try to have at least one engine running whilst in port, you know just in case...

So yesterday I managed to put together all the bits back on port engine and fired it up, all's fine, still produces lots of water, running fine.
I'm rushing the refurb of the generator spot before the yanmar is back onboard hopefully this week, so I've removed old rockwool and perforated panels from bulkhead and ceiling, painted the bilge area and today will be placing the new extra heavy and expensive soundpanels in place.
Once done, I'll be able to move the gen frame from where it's jammed right now to the new ply gen plinth and this will give me access to the stbrd side of the stbrd engine in order to remove the impeller, so I'm afraid you'll have to wait for one more day or two. This 3-4h a day folded in two is killing my back...

cheers

V

Your back might be suffering, but it’s good for the soul