What is wrong with this waterpump?

[winterbeater]

I agree with Blakeword that electrolysis damage would be more evenly distributed and re-iterate: Take it back to Hesco. I'm sure they'll take care of it. That casting had issues (as aluminum castings often do).

 

[Goat]

Not chemical corrosion, not galvanic corrosion either. It's discharge cavitation.

 

[squirrel80]

For the love of GOD! Someone call Hesco and find out what they have to say.hasta

 

[XJJack]

For now I am going to put a new NAPA pump in and see if theat will keep it cool.

 

[ratman572]

For whatever it's worth, I repair pumps for a living. The damage on that impeller appears to be from cavitation.

When the cavitation bubbles implode, the imploding bubble vortexes to a fine pinpoint, -and can collapse with a force of up to 50,000 psi. This is exactly how an ultrasonic cleaner works (for whatever that's worth). The destructive force of the collapsing bubbles can be extremely destructive.

The point at which the cavitation bubbles collapse is the point at which the delta-p normalizes, -usually at a point on the impeller or volute (where an increase in pressure is found).

The causes of cavitation are not having enough net positive suction head available (called out as NPSHA).

Every impeller made has an NPSHR (net positive suction head required) curve, -and is always based on water with a SG (specific gravity) of 1.0

The causes are too numerous to mention, -as a small piece of casting flash inside the closed-vane impeller could induce cavitation. I would try changing the pump and seeing what happens.

Also, -do not discount what old man said about galvanic corrosion, -it is a very real phenomenon, and does happen.

My .02

 

[winterbeater]

The causes of cavitation are not having enough net positive suction head available (called out as NPSHA).

Every impeller made has an NPSHR (net positive suction head required) curve, -and is always based on water with a SG (specific gravity) of 1.0

The causes are too numerous to mention, -as a small piece of casting flash inside the closed-vane impeller could induce cavitation. I would try changing the pump and seeing what happens.

Also, -do not discount what old man said about galvanic corrosion, -it is a very real phenomenon, and does happen.

My .02

Does this mean that the pump was too powerful for the amount of water flow that was available to it?

 

[ratman572]

Does this mean that the pump was too powerful for the amount of water flow that was available to it?

Well, in essence, yes.

It could also be due to other "restricted inlet" factors such as a collapsing hose, etc.

 

[neanderpaul67]

Dumb Question.......do you have the anti-collapse spring in the lower rad hose?

 

[Blaine B.]

The spring isn't always needed. The new molded hoses do not need it. Which means they are preformed for bends and such and have thicker walls.

The older hoses with thinner walls needed the spring, as do "universal hoses" which are not premolded for bends...

So the "spring" theory is not always correct...just an FYI!

 

[Mudderoy]

If you look cloce in the block it looks like a circular pattern on the left..

I have used tap water with a aluminum pump and heads never had anything look like that..

Dont reuse it.......................

Yes I noticed those marks as well.

 

[Blaine B.]

I was talking about those marks as well but he said they were normal. I mentioned the one above the little pool of coolant.

 

[XJJack]

It sounds like cavitation from what I am gathering here and other places. I think what started it was the leak so it would not hold presure so that would alow air in the water.

 

[Gojeep]

I have the same HESCO pump and pulled it a few times over the last 4.5 years and have never seen any corrosion what so ever. Still looks like new but I do always run demineralized water with coolant and make sure my engine to ground contacts are sound to avoid any stray current going through my system.

 

[ratman572]

It sounds like cavitation from what I am gathering here and other places. I think what started it was the leak so it would not hold presure so that would alow air in the water.

Actually, the introduction of air into the water will kill cavitation. Whenever we are testing a big pump where I'm right up on the edge of the NPSHR curve, -the pump will rattle slightly, -indicating it is just starting to cavitate. I have a small 1/4" ball valve on the inlet pipe that I crack open to allow some air into the liquid going through the pump. If the noise abates when allowing air into the system, then it is surely cavitation. Cavitation causes reduced pump performance, -and in extreme cases major damage to components. NHI (national hydraulic institute) states that a pump shall not operate at a point where there is either a 5% reduction in capacity (flow) or a 5% reduction in power (capacity and power are obviously tied together). As a matter of fact, -it is at that VERY 5% point that plots the point on the NPSHR curve for a given impeller trim.

My solution when this happens? Well, typically, I will chill the water in the test tank, -just low enough to change the vapor pressure to get me through a test with no cavitation, -that way I can pull some real world numbers during the test (not running off the NPSHR curve).

Sorry for all the pump-techno-garbage, it's just what I do for a living and wanted to pass on some of the knowledge.

Entrained air will not cause cavitation.

Rich.