Bad motor --> cavitation damage = useless wet end?

[MitchRyan912]

I posted these pics in another thread about my motor, and I'm sorry if I'm starting another thread that's a continuation of another thread...

It appears as if I might have some cavitation damage to my wet end, which could be leaving me with a really nice 2-speed motor but no usable wet end. If my wet end is indeed trashed, should I replace the parts (assuming I can even get a new body/volute!) or should I be looking more at a new pump that would accept the 2-speed motor I have (i.e. find a single speed pump with a motor that has a similar SFHP rating and flange type)

I don't want to go through another smoking motor if the damage that's been done to my current wet end is rendering it useless or less effective enough that it might cause another motor some serious damage.

Damage to the volute:

Diffuser plate:

One fin on the impeller:

 

[mas985]

That looks more like debris damage than cavitation. Cavitation causes pitting on the impeller but usually near the inlet. Both the impeller outlet and volute are at high pressure so cavitation would never occur there.

If you just replace the impeller, it should be fine. Although I would just trim that portion on all the exit points and see if that works.

 

[jblizzle]

That looks like someone tried to use a screwdriver to unscrew the impeller from the motor to me.

 

[MitchRyan912]

I may be a noob, but I'm not that dumb to unscrew an impeller like that!

 

[jblizzle]

Well, ask me how I know

Looking at the bigger picture (not on my phone), it does look rougher than a screwdriver would make it.

 

[MitchRyan912]

All the... "fins" (not sure what they're called) on the impeller have a very rough edge to them like this, but this is the only one that's bend outward slightly.

 

[mas985]

Re: Bad motor --> cavitation damage = useless wet end?

Do you have access to a lathe? That is a great way to trim an impeller?

 

[MitchRyan912]

DO you think I should trim that piece off/back?

 

[zombiejeep]

Doesn't appear to be cavitation. Cavitation is more of a pitting or impingement damage in the suction eye of the impeller, and trailing out the vanes of the pump. looks like a chunk of debris, or the ol' screwdriver trick. (not accusing you, just saying).

I would aim for replacement of impeller as removal of material can lead to unbalancing, which leads to more problems.

I'll throw a caveat in there by saying that my pump experience is 98% dealing with metal parts and pieces though.

 

[ewkearns]

I've seen this before and I vote for "hamfisted mechanic with a screwdriver." However, if the rotor turns freely, you haven't found your "smoking gun." No pun intended....

You could just trim the damage back a bit.... I've fixed these before, with solder, but it looks like you are dealing with some form of composite.... maybe worth replacing the impeller IF you can determine that there is no binding and/or misalignment. Removing an impeller with a screwdriver is a good way to bend the motor shaft.....

 

[mas985]

DO you think I should trim that piece off/back?

Yes, you can trim it off. You don't want it scrapping on the diffuser. But I would trim all the vanes an equal amount to keep the impeller balanced. Or like I said before, you can just purchase a new impeller.

 

[MitchRyan912]

There's plenty of space between the impeller and diffuser. This is from the backside, where the ceramic seal faces the motor mounting plate (I guess Waterway has their seals backwards to most pumps.)

 

[mas985]

I would at least bend it back flush with the impeller outer surface.

 

[OldPoolBoy2]

I'd vote for a replacement impeller.

I know you want to find the reason / source of your problem.
You know the high amp draw with pump attempting normal operation.

So 1. What is the amp draw on motor with no impeller?
2. Amp draw with impeller & no water (warning make this a very short test)
3. Amp draw with pump basket cover off but with first filling the pump basket with water, this will provide lubrication and more resistance to impeller than the #2 "air" test.

 

[MitchRyan912]

It could be the timer sending 12v to the low speed tap while simultaneously sending 237v tap in the high speed setting on my timer???

1. I did a test bench check of the bare motor just sitting on a table, no impeller. I got a 2.5A reading.

I will perform a 1A test with the motor attached to the mounting plate, to see if the seals are problematic/rubbing. I suppose 1C with the impeller would be worthwhile.

Im assuming your #2 test suggestion would be with the motor connected to the wet end, or would that happen on test #3?

 

[mas985]

Make sure the seals are fully seated this time. ;-)

 

[MitchRyan912]

Right. Check that.

Is touching the ceramic face a no-no? According to some videos it is, but something else said to press with your fingers and wipe it off wth a clean rag.

 

[mas985]

If you have to push down on the face, put a clean cloth between the seal and your fingers. But you might want to listen to this video:

http://www.ussealmfg.com/installation-video.cfm

 

[MitchRyan912]

2. Amp draw with impeller & no water (warning make this a very short test)

2a: Started at 6A then quickly back down to 2.5A. This is with the motor attached to the mounting plate but not connected to the wet end.

2b: I installed impeller and got similar results to the above. Still not hooked up to the wet end. I still have a few pipes to finish running before I can get the wet end hooked up to the motor.

So far so good...

 

[MitchRyan912]

SUCCESS!!! Thanks for all the help in multiple threads!!!

Hey all,

I finished up the re-install of a new motor and a re-plumb late last night, and everything seems to still be in working order this morning. Ran it on high for a couple hours last night, then low over night. I was comfortable taking slow steps with the motor, checking amperage each time (consistently getting 5.5A and 1.8A on the two speeds.) I was able to finally use the gauges installed in my pump to check my head, and got some interesting results. More on that later, maybe a separate thread.

The only potential problem is that the diverter valve replumb doesn't seem to like working in the manner it works. I get a ton of air in the pump basket when I'm only sucking from a single 1.5" line. I still suspect a problem with the tubing, but it could just be that I need 2" pipe all around the pool (will do that next time we change the liner, probably.)