liquid ring pump noise

[amazing azza]

Hello friends,

I would like to ask for a second opinion about a sanitary liquid ring pump. This is an Alfa Laval MR185S and it is used for CIP return applications.

Compared to a centrifugal pump, it is very loud when it is pumping water. When the water is depleted, the volume is reduced dramatically. The pump is brand new.

Is this normal? I am attaching a short video of the noise in question. In the video, water at about 60 C is being transferred between tanks.

PS. If the color in the video appears corrupted, try to skip forward/backward to see if the picture is restored. I had to compress it quite a bit to make a reasonably sized attachment.

video of pump in action (3 MB)

 

[Artisi]

Do you have or can you tell what the inlet pressure is, the pump could be cavitating if the suction pressure is low, especially at 60c.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[amazing azza]

Do you have or can you tell what the inlet pressure is

The inlet pressure is just the level of liquid in the tank (maybe about a meter or two up from the pump inlet), so that would make about 0.1-0.2 barg.

 

[LittleInch]

By the sound of t you're pumping pure water? I.e. no air entrained?

When I look at these sorts of pumps they don't seem to be built to handle 100% liquid, but instead are much better with an air / water mix.

What does the vendor say about pumping 100% water?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

https://www.alfalaval.co.uk/products/fluid-handling/pumps/centrifugal-pumps/mr/

"The MR range of pumps is specifically designed for pumping liquids that contain air or gas."

I think you are breaking your pump if its not got air in it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[amazing azza]

When I look at these sorts of pumps they don't seem to be built to handle 100% liquid, but instead are much better with an air / water mix.

That is an interesting thought... So far my MO has been to avoid pumping air, but it being OK if it happens. I haven't considered purposefully running it with a degree of air suction. I will try an experiment tomorrow. Still waiting to hear from the vendor.

 

[MikeHalloran]

LR pumps are intended to move large volumes of gas, using a very modest flow of water. The water is internally recirculated within the liquid ring; additional water is needed only to make up for carryover and evaporation.

It sounds like you are using them completely wrong, and need to read the operator's manual again.


Mike Halloran
Pembroke Pines, FL, USA

 

[amazing azza]

you are using them completely wrong, and need to read the operator's manual again

zing!

 

[amazing azza]

LittleInch, you nailed it! I turned down the speed of the CIP supply pump to be a little bit below that of the return pump (the liquid ring in question). This gave a continuously empty tank and a return pump that was continuously sucking air. Sort of the opposite of what one would normally do with a centrifugal pump, haha. The result was that the running volume (noise) was significantly reduced.

Thank you very much!

PS. Here is a new video of the pump running under the new conditions. The sound does not appear that much quieter in the video, but that is due to the phone auto adjusting the mic gain.

New pump video (5 MB)

 

[LittleInch]

Well that's a good result - thanks for getting back to us, sadly too few close the loop.

I think as Mike also says to run with entrained air isn't just a good idea, but is actually essential in order not to break your pump. Hopefully you haven't done it any damage, but it now needs to be somehow written into the operating procedures to positively not happen any other way.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[amazing azza]

I don't think any damage's been done yet, I am still in the testing phase. No major pumping. The CIP machine is full auto, I will add a check for supply flow < return flow which should ensure air suckage. This pump is pretty tricky - cannot run fully empty, cannot run fully full, heh.