pump trouble

[monkeybrewer]

So i have a pump that is not pumping with any force. It's rotating properly, in the correct direction. There aren't any obstructions in the lines. City water pressure easily tops the force through the pump and hoses compared to when it is pumping. Also, while not being very scientific, the sound it is making is very quiet compared to what I'm used to. Also deadheading the pump doesn't change the sound. It almost sounds like it does when the pump hasn't been purged of air and it is run....except that it is pumping liquid, just slowly. My electrician has looked at it and he can't seem to find an issue. Though he says the pump is only drawing 2.5amps out of 4. Any one had a problem like this?
Cheers

[dick murton]

You don't really give enough info about the pump type - so these are a few stabs in the dark..

I assume from the comments about 2.5 amps vs spec of 4 that this is a single phase pump. Otherwise if it is a 3 phase, then check all the windings. They will often run quite happily but developing little power on two phases, and I guess possibly even on one, though I have not experienced that.

Otherwise it sounds as though a couple of the windings have gone, giving a similar problem to a 3 phase running on 2.

If this is a centrifugal pump and you have opened up the pump housing recently - have you put the impeller back in the right way round ? If it is possible to change the impeller round, and the blades are not radial, but curved from the centre, then this will make a difference. If curved, the vane normally rotates so it leads from the centre.

If the pump is like a car water pump with little rubber vanes, have any of these broken off ?

[CaptainEBC]

Did you check if the actual impeller is spinning? The shaft could be rotating, but the connection to the impeller could be sheared or missing.

[dick murton]

Ah

Good point. Better to go back to basics eh ?

[monkeybrewer]

some info

so the impeller is spinning for sure...in the proper direction. Also it has not been opened or changed since it was running properly. It did sit for two years outside after being exposed to smoke from a fire we had at the hotel complex but was not exposed to enough heat to melt any plastic on the pump or cart. It was also jostled around a bit bringing it down from the upstairs cold room but that's nothing new to it. It is a centrifugal pump, that is 3 phase. Right now my electrician is checking to see if the windings have come undone. He did check all three phases and got identical readings across all three lines...so he was thinking it's not likely the the windings but worth checking.
Thoughts?
BTW thanks everyone for such quick responses...it is much appreciated!
Cheers

[monkeybrewer]

windings

windings are supposedly OK...
why else would the pump draw only 2.5 amps instead of 4 while being at full load?

[dick murton]

Is it wired up the right way round. Three phase can be wired up Star formation or Delta formation. In big pumps, you atart in one pahse then once up and running, switch to the other - from memory start up in star winding configuration, and then switch to delta once more or less up to speed. If you have it in star winding, it will make very little power, and need to change it to delta. For a small pump such as this, then you probably wont need star at start up.

Also, what is th emotor set up for - are you running at 50 hz, when it is designed for 60 hz ?

[PanConsulting]

Sounds like you may be pumping up from one floor to the next and your pump may not be properly sized. This is a good guide.

http://www.pumpfundamentals.com/download/calculate_press_anywhe.pdf

[ParishBrewingCo]

Is it sucking air? Sitting outside for two years made me think about dry seals... The pump head may be sucking air either through a bad seal or crack or something else, losing ability to move liquid. Just a thought.

[monkeybrewer]

more info

So this change in operation has occurred without any changes to the pump. It's wired the same way it was when it worked great. It's definitely properly sized for what we've done here for 15 years. The seals are good, had them checked and they don't leak. Also have a sight glass in line and can see that no bubbles are being pumped along. And according to an electrician and an electric motor guy they both say the motor is running perfect, electrically speaking. I don't know about star or delta formations but the pump hasn't been rewired since a time it worked great. Again not sure about 50 or 60 hz but again the pump hasn't been altered electrically from a time it worked. This definitely has a few people scratching their heads. My pump guy is going to take the pump face off of the not working pump and put in on a working pump motor of ours to see where the problem is. Though he's not very confident we'll find an issue...
Thanks again everyone...anymore thoughts?
Cheers

[dereknobleluke]

most three phase places are delta here in RI--but if it was wired delta and you have Y, it probably wouldn't work after a while! Same with 60 hz.

What does the nameplate say on the motor housing?
do you have a tri-clover fitting with a pressure guage that will go to 30 psi on a t?
If so, use a brewer hose and hook it up to your municipal water into the front of the pump. Turn on the water. Then turn the pump on--any change in the pressure?

[liammckenna]

Pull the rotor out of the stator and inspect the windings and the rotor surfaces. A few years of dormancy may have caused some damage if there was any previous issues with seal face or moisture ingress.

Also to echo Dick, ensure your vanes are going the right way. I've attached a diagram if the vanes are curved. Hope it loads.

Pax.

Liam

[monkeybrewer]

inspected

impeller has been inspected and is on correctly. And when run with out any load or the pump face on, it spins just like a properly working one (at least as far as the eye can see). definitely no doubt that I have a consistent flow, it's just about half as fast as normal. Also when I hooked it up to my whirlpool valve I was able to open it all the way without having it cavitate...something that never happens. I usually get it about half way open before it starts to cavitate when I'm setting my whirlpool. That is using two ten foot hoses to make the loop. It seems to me that my rpms are down from where they should be. Good idea about hooking up a pressure gauge, dereknobleluke. I'll take an arm off my filter and block it and see what I get for a pressure. I'm sure it will be low or not rise above city pressure at least. I get the pump back today on a different motor...hopefully this will at least get me moving beer before I can figure what's up with this pump.
Cheers and Thanks

[monkeybrewer]

one key fact

I can't believe I never thought to mention this but...
I have an identical pump that is my primary pump (it's in the shop thanks to leaky seals). It is setup exactly the same way as the pump that isn't pumping much but it works like a champ, like the old one used to. The pump with the problem is kept in my cold room/serving tank room and is only used to CIP the serving tanks.
Just thought I'd give some more info on the situation....
Cheers

[Guestimate]

Without being able to see the pump. I would bet the farm the motor is shot. Yeah, I know what your electrician said. The basics of a pump is transfer of energy. We are taking electrical energy and transferring to mechanical energy which then transfers the energy into fluid flow. If you can verify that the pump is structurally sound. I.E. holds pressure, does not have a broken shaft or impeller, pump housing is not mangled. Then the issue has to be that there is no liquid or the motor is not efficiently transferring energy. Try swapping motors with the identical one in the shop. If that does not work, check the switches, wires, and the plug.

Kevin