Water Pumps - Why Different?

[Formaleins]

OK, I have 2 Water Pumps, one is brand new and the other is a few years old but just overhauled with new bearings seals and windings ( virtually a new machine). Both pumps are centrifugal (not the old impeller type).

 

The question I have is why is the brand new one so damn noisy and rattly?

 

Both pumps are 2" input and 2" output, both pumps are using 2HP motors with similar sorts of pump drive.

 

The new one is a "Superpump" by Mitsubishi whereas the other is some fake Italian type job.

 

When the Italian pump runs, it is virtually silent other than the whir of the motor, it does not matter what pressure is on the output, or even if it is totally free flowing, it makes very little noise.

 

On the other hand, the Mistsubishi pump sounds like it is running with a box of marbles inside it whenever it is allowed free or unrestricted output flow. - If I close the outlet valve to this pump it starts to quieten down but is always loud and rattly.

 

The more you open the outlet on the Mitsubishi the louder and more rattled it seems to get (It is a huge difference compared to the other pump).

 

Both are pulling water from about the same depth, 8-10m bore with water at about 5 metres below ground, both fed from 2"pipe with strainers inside a 3"sleeve. (No there is no sand or stones) The Mitsubishi has been moved to two different bore holes and is the same on both.

 

Could there be air in it even though it is pumping water at a good pressure?

 

Could I damage it running it when it is rattling away?

 

Mitsu is a WCM1505S see link here

 

https://www.meath-co.com/web/es-mit/UploadFile/WCM.pdf

 

http://www.vpowertools.com/product/88/mitsubishi-ปั๊มน้ำหอยโข่ง-มิตซูบิชิ-super-pump

 

Thanks.

Edited March 23, 2017 by Formaleins

[dbrenn]

The noise is caused by the rear gearbox layshaft making contact with the flutter valve heatsink mounting bracket. It's normal and nothing to worry about.

[SussexExpat]

The new one might have the wrong size flim-flom flange.

[geronimo]

Personally, I think it can only be the rear flange on the dongle, which as we all know, would then push the blingle onto the belt,and once the bingle touches the belt, this will activate the anti-theft device, which is what is making the noise!

 

Solution?

Get the old Italian one cloned.

 

Hope that helps.

[Crossy]

All of the above

 

Seriously, we have pumps of assorted sizes and manufacture. All (apart from the Grundfos that supplies the house) make varying degrees of "bag of nails" noises. Oddly, the biggest (a 3HP LuckyPro) is by far the quietest of the lower-cost units.

 

A quick bleed of the pump housing should remove any air that's trapped.

It's possibly cavitation caused by poor (ok different) impeller design but if it's working well worry not.

 

[grollies]

7 hours ago, Formaleins said:

OK, I have 2 Water Pumps, one is brand new and the other is a few years old but just overhauled with new bearings seals and windings ( virtually a new machine). Both pumps are centrifugal (not the old impeller type).

All centrifugal pumps work with an impellor.

 

 

 

[Formaleins]

6 minutes ago, grollies said:

All centrifugal pumps work with an impellor.

 

 

 

Yes, my bad. I should have said that the old style I have uses an open type impeller, with the fins visible when you remove the pump housing. The newer versions use a type of self contained impeller that is enclosed by bronze casting when the case is removed (The fins are not visible).

[grollies]

Sounds like you've got small stones in the pump head. Strip off the suction side, pull off the impellor and look see if any stone jammed in the impellor ports.

 

Other than that, cavitation due to air in pump head/pump struggling to lift 5m/shaft bearings goosed.

[dbrenn]

22 hours ago, geronimo said:

Personally, I think it can only be the rear flange on the dongle, which as we all know, would then push the blingle onto the belt,and once the bingle touches the belt, this will activate the anti-theft device, which is what is making the noise!

 

Solution?

Get the old Italian one cloned.

 

Hope that helps.

Dongles have not been used since reverse polar helical brushless armatures were introduced. 

 

Layshaft flutter valve contact can be prevented by inserting fibrous spacers between the autothrust knuckle joint and the bipolar magneto exciter retaining pin.

Edited March 24, 2017 by dbrenn

[CGW]

9 hours ago, dbrenn said:

Layshaft flutter valve contact can be prevented by inserting fibrous spacers between the autothrust knuckle joint and the bipolar magneto exciter retaining pin.

Would that not create latent inversion thrust?

[dbrenn]

6 minutes ago, CGW said:

Would that not create latent inversion thrust?

Not if the counter rotating balancer shafts are correctly aligned with the overpressure stepping spigot assembly. 

Edited March 25, 2017 by dbrenn

[CGW]

Ah! old school, based on Wozengruds theory, off course hemicylindrical will never be run on the same wavelength as ellipitical due to the frequency change! should have realised!!

Off to get a life now :)

[grollies]

CGW & dbrenn

 

If I showed my missus your posts she'd think you were super-brainy

 

 

[sappersrest]

On 3/24/2017 at 0:52 AM, Formaleins said:

OK, I have 2 Water Pumps, one is brand new and the other is a few years old but just overhauled with new bearings seals and windings ( virtually a new machine). Both pumps are centrifugal (not the old impeller type).

 

The question I have is why is the brand new one so damn noisy and rattly?

 

Both pumps are 2" input and 2" output, both pumps are using 2HP motors with similar sorts of pump drive.

 

The new one is a "Superpump" by Mitsubishi whereas the other is some fake Italian type job.

 

When the Italian pump runs, it is virtually silent other than the whir of the motor, it does not matter what pressure is on the output, or even if it is totally free flowing, it makes very little noise.

 

On the other hand, the Mistsubishi pump sounds like it is running with a box of marbles inside it whenever it is allowed free or unrestricted output flow. - If I close the outlet valve to this pump it starts to quieten down but is always loud and rattly.

 

The more you open the outlet on the Mitsubishi the louder and more rattled it seems to get (It is a huge difference compared to the other pump).

 

Both are pulling water from about the same depth, 8-10m bore with water at about 5 metres below ground, both fed from 2"pipe with strainers inside a 3"sleeve. (No there is no sand or stones) The Mitsubishi has been moved to two different bore holes and is the same on both.

 

Could there be air in it even though it is pumping water at a good pressure?

 

Could I damage it running it when it is rattling away?

 

Mitsu is a WCM1505S see link here

 

https://www.meath-co.com/web/es-mit/UploadFile/WCM.pdf

 

http://www.vpowertools.com/product/88/mitsubishi-ปั๊มน้ำหอยโข่ง-มิตซูบิชิ-super-pump

 

Thanks.

OK lets get back on track a little.

Even though appear to be the same model albeit  with different ends, i.e. one is  flanged and the other is not.

Firstly they are 2hp  you say that they are sucking from about 8m deep depending on water table, what is the delivery height, are they filling a tank or for irrigation?

I have several thoughts on this and the same  has happened to me in the past.

[dbrenn]

59 minutes ago, CGW said:

Ah! old school, based on Wozengruds theory, off course hemicylindrical will never be run on the same wavelength as ellipitical due to the frequency change! should have realised!!

Off to get a life now :)

With all due respect, Wozengruds theory referred to triple harmonic resonance that was observed in the residual baseline stator current. Since capacitative inductance motor diaphragms cause a blanking effect, this theory is no longer relevant. 

[dbrenn]

1 hour ago, grollies said:

CGW & dbrenn

 

If I showed my missus your posts she'd think you were super-brainy

 

 

You are fortunate to have a wife who has expert knowledge of mechanical and electrical engineering. Please ask her to share with us her critique of the discussion this far.

[CGW]

^^Silly me! yes learned Sir you are indeed correct!

 

Edited March 25, 2017 by CGW

[grollies]

39 minutes ago, dbrenn said:

You are fortunate to have a wife who has expert knowledge of mechanical and electrical engineering. Please ask her to share with us her critique of the discussion this far.

OK, showed the wife this thread and she makes the following observations:

 

Pump noise is either:

 

1) Mechanical, or;

2) Fluid

 

Since the Mitsubishi 'Superpump' is new it is unlikely to be a mechanical problem. These usually present themselves through poor design or parts. The impellor may be too close to the pump casing (unlikely as design has improved in recent years).

 

Of course it could be debris trapped in the impellor vanes causing the noise.

 

Failing that a misaligned shaft or failed bearing is the likely (mechanical) culprit.

 

However, classic cavitation caused by net positive suction head (NPSH) could be the cause. Throttling in against the pump and consequent noise reduction evidents this.

 

Poor suction pipe design is another cause, the suction pipe should be straight for at least 5 x suction pipe diameter.

 

Introducing a small amount of air into the suction pipe can alleviate cavitation/pump noise.

 

To summarize, her opinion is that if it's not a fluid problem and not debris in the pump impeller, it's probably f*#cked.

 

PS: It's that or the capacitative inductance motor diaphragm has split.

 

Love, Mrs grollies.

[Formaleins]

On ‎24‎/‎03‎/‎2017 at 4:39 PM, grollies said:

Sounds like you've got small stones in the pump head. Strip off the suction side, pull off the impellor and look see if any stone jammed in the impellor ports.

 

Other than that, cavitation due to air in pump head/pump struggling to lift 5m/shaft bearings goosed.

Actually, I think you might be right! The well has not been used for almost 3 years so it is very likely that the sand / stones around the bore have collapsed. I have been switching it off and back on and a lot of the rattles have gone, which as you correctly stated may be stones and sand.

 

My wife was up at one of the furthest sections of the piping, about 200 Metres from the pump and she found deposits of sand at the outlet (our topsoil if you can call it soil is just clay - so there is no way it came from up top)

 

Thanks for your suggestions, I will take it apart tomorrow and see what lies inside.

 

The pump has ran all day today almost silently, apart from what indeed sounds like a stone or pebble like rattle inside the impeller.

 

As for all the helpful fucktards with their waffle sprockets and foo foo valves - go <deleted> yourselves you dumbasses!

 

It was a genuine question, and responded to in most cases by idiots that probably have only ever pumped a fart!

[Formaleins]

46 minutes ago, grollies said:

OK, showed the wife this thread and she makes the following observations:

 

Pump noise is either:

 

1) Mechanical, or;

2) Fluid

 

Since the Mitsubishi 'Superpump' is new it is unlikely to be a mechanical problem. These usually present themselves through poor design or parts. The impellor may be too close to the pump casing (unlikely as design has improved in recent years).

 

Of course it could be debris trapped in the impellor vanes causing the noise.

 

Failing that a misaligned shaft or failed bearing is the likely (mechanical) culprit.

 

However, classic cavitation caused by net positive suction head (NPSH) could be the cause. Throttling in against the pump and consequent noise reduction evidents this.

 

Poor suction pipe design is another cause, the suction pipe should be straight for at least 5 x suction pipe diameter.

 

Introducing a small amount of air into the suction pipe can alleviate cavitation/pump noise.

 

To summarize, her opinion is that if it's not a fluid problem and not debris in the pump impeller, it's probably f*#cked.

 

PS: It's that or the capacitative inductance motor diaphragm has split.

 

Love, Mrs grollies.

Thanks, see my last response, it is not the pump it is something going into the pump (sand / crap/air / bad foot valve). Pump feed is recommended to be no less than 60cm, but no more if possible, I am at 63cm. If I introduce air into the suction side I lose prime.

 

If I restrict the outflow, I get a quiet pump.

 

We found sand 200 metres from the pump today, so it may well be that the pump is sucking up some marbles from way down deep.

 

Thanks for your suggestions, it is most welcome.

[grollies]

7 minutes ago, Formaleins said:

Actually, I think you might be right! The well has not been used for almost 3 years so it is very likely that the sand / stones around the bore have collapsed. I have been switching it off and back on and a lot of the rattles have gone, which as you correctly stated may be stones and sand.

 

My wife was up at one of the furthest sections of the piping, about 200 Metres from the pump and she found deposits of sand at the outlet (our topsoil if you can call it soil is just clay - so there is no way it came from up top)

 

Thanks for your suggestions, I will take it apart tomorrow and see what lies inside.

 

The pump has ran all day today almost silently, apart from what indeed sounds like a stone or pebble like rattle inside the impeller.

 

As for all the helpful fucktards with their waffle sprockets and foo foo valves - go <deleted> yourselves you dumbasses!

 

It was a genuine question, and responded to in most cases by idiots that probably have only ever pumped a fart!

Don't be too hard on them mate, they're just injecting some humour. Glad you are getting it sorted though.

[Formaleins]

2 hours ago, sappersrest said:

OK lets get back on track a little.

Even though appear to be the same model albeit  with different ends, i.e. one is  flanged and the other is not.

Firstly they are 2hp  you say that they are sucking from about 8m deep depending on water table, what is the delivery height, are they filling a tank or for irrigation?

I have several thoughts on this and the same  has happened to me in the past.

No neither pump is flanged, they are both just screw in 2"plastic joints - The Mitsu Flange model is different.

The pipe depth is between 8-10 metres, into a foot valve then a 3 foot strainer, however, the water level appears to be about 4 metres deep from the pump intake. They are not filling a tank, they are pumping directly overground.

 

The main rattling sounds only happened when the outflow was totally unrestricted, if I closed the outlet valve about 30% the noise decreased dramatically. However, today with the outlet fully open, but with a little back pressure from the length of pipe it has to feed the damn thing has gone almost silent. I will open it up tomorrow and see if it has sucked up some crap.

 

Thanks for your reply, appreciated.

 

 

[Crossy]

11 hours ago, Formaleins said:

The main rattling sounds only happened when the outflow was totally unrestricted, if I closed the outlet valve about 30% the noise decreased dramatically. However, today with the outlet fully open, but with a little back pressure from the length of pipe it has to feed the damn thing has gone almost silent. I will open it up tomorrow and see if it has sucked up some crap.

 

I'll put money on that being cavitation.

 

[whatawonderfulday]

On ‎24‎/‎03‎/‎2017 at 7:46 AM, geronimo said:

Personally, I think it can only be the rear flange on the dongle, which as we all know, would then push the blingle onto the belt,and once the bingle touches the belt, this will activate the anti-theft device, which is what is making the noise!

 

Solution?

Get the old Italian one cloned.

 

Hope that helps.

Yes but you forgot that the belt is housed in an uninsulated wiggle box which amplifies the sound when the winget revolves

[grollies]

13 hours ago, Formaleins said:

Thanks, see my last response, it is not the pump it is something going into the pump (sand / crap/air / bad foot valve). Pump feed is recommended to be no less than 60cm, but no more if possible, I am at 63cm. If I introduce air into the suction side I lose prime.

Yeah, sorry, that'll only work on a flooded suction.

 

 

13 hours ago, Formaleins said:

 

If I restrict the outflow, I get a quiet pump.

 

We found sand 200 metres from the pump today, so it may well be that the pump is sucking up some marbles from way down deep.

 

Thanks for your suggestions, it is most welcome.

 

[sappersrest]

14 hours ago, Formaleins said:

No neither pump is flanged, they are both just screw in 2"plastic joints - The Mitsu Flange model is different.

The pipe depth is between 8-10 metres, into a foot valve then a 3 foot strainer, however, the water level appears to be about 4 metres deep from the pump intake. They are not filling a tank, they are pumping directly overground.

 

The main rattling sounds only happened when the outflow was totally unrestricted, if I closed the outlet valve about 30% the noise decreased dramatically. However, today with the outlet fully open, but with a little back pressure from the length of pipe it has to feed the damn thing has gone almost silent. I will open it up tomorrow and see if it has sucked up some crap.

 

Thanks for your reply, appreciated.

 

 

Brilliant you seem to have it sorted the noise you heard was defiantly  cavitatation caused by the pump pushing to much water  the fact that you connected 200m of pipe depending on the velocity of water will have given the pump extra head pressure, thus slowing down the flow of water, really the same as throttling a valve.

looking at the pump curve the ideal flow would be around 350 litres per min at 20 m head .

 

 

[CGW]

8 hours ago, Crossy said:

 

I'll put money on that being cavitation.

 

I wouldn't take the bet! Cavitation! the pump is a 2" x 2" in most situations! you always calculate for a larger suction line than discharge, choking a valve in the line would give you this!

[grollies]

1 hour ago, CGW said:

I wouldn't take the bet! Cavitation!

 

I would, because......

 

the pump is a 2" x 2" in most situations! you always calculate for a larger suction line than discharge, choking a valve in the line would give you this!

...You've just described....cavitation

 

Normally, industrial pumps (univacs and the like) up to 6" will have 1x1", 2x2" etc. suction and discharge connection. Impellors are designed to lift and discharge at similar rates and, yes, you're quite right, sometimes it's necessary to gag-in on electric agricultural pumps to avoid cavitation. What I found here is that the foot valves are quite small. For my 1" pond irrigation pump the supplied foot valve was more like 3/4" so I put on the next size up.

 

Jetting pumps are different and over 3" and will have oversized suctions, 4" x 3" and so on but this is because they are supplied on flooded suctions.

[CGW]

^ I didn't explain that well! when you choke the discharge line you effectively have ~1 1/2" x 2" so you now have a pump with a larger suction area than discharge, so you have eliminated cavitation! Which is why I wouldn't take the bet, he is correct IMO.

 

I have no experience with agricultural pumps, I worked 40 years in the offshore oil industry, we use a lot of pumps and never use same sized suction and discharge, there are a number of reasons, one being it prevents cavitation! & gives better efficiency, it is actually slightly cheaper to run a pump with the same sized inlet/outlet. Ideally also you want the fluid velocity to be higher at discharge to optimise NPSA, which depends on outlet piping and frictional losses, long story cut short as really you need to take each pump installation and calculate design criteria, you are a lot better off in 99% of cases having a larger suction than discharge for efficiency.

Doubtless forgotten a lot more that I once knew!

Edited March 26, 2017 by CGW

[grollies]

Ah, I now understand the bet! I can be a bit thick sometimes.

 

No, I do get what you mean. You're right about cross-sectional area on suction and discharge and gagging-in the discharge to get rid of cavitation. We're saying the same thing.

 

Cavitation problems are rare nowadays with improved pump impeller design. It's usually a result of poor installation/suction restrictions and the pump trying to discharge more water than it can pull/is fed.

 

My experience of low pressure/high volume pumps such as univacs is that they have same size suction and discharge pipes.

 

Jetting pumps (high volume/high pressure), like those used for filling pipelines, as you say, have a size larger on the suction side. I assume these are the types of pumps you used offshore?

 

Onshore and landfall oil & gas me, 25 years, ran a pipeline hydrotes company.

Edited March 27, 2017 by grollies
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