Packo self-priming CIP return pump excess vibration and noise 1

[Dezsi1982]

Hi All,
I am looking for some pointers regarding a Packo CRP2/50-160/1102 self priming CIP return pump.
It is working well for most of the time, but every so often we get serious vibration from it, and it also becomes very noisy.
The pump has a 20m long 2" SS suction line, and the delivery head is approx 15m, the maximum flow is around 20m3/h.
If someone has some experience with this kind of issue, some pointers would be greatly appreciated.
Thank you

 

[Artisi]

That is happening to the operation conditions every so often, is the flow / supply constant, any air entrainment?
Without understanding the full operating conditions it is only guess work what the likely problem could be.

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.)

 

[Dezsi1982]

Thanks for the reply.
The supply is somewhat constant, but this is a CIP return pump, so there is certainly air entertained in the flow.
The feed is coming through a sprayball, at 20m3/h, and that's quite steady. However, the pump needs to remove all the liquid from the tank for effective cleaning, therefore there always be air entertained in the flow.
For this reason it has an air separator installed on it:
Link
Thanks

 

[Artisi]

Possible the entrained air builds up to point where the pump goes "off prime" occasionally leading to vibration as the pump struggles and takes time to re-prime.

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.)

 

[Dezsi1982]

Thanks, that makes perfect sense.
Can I do anything about it?

 

[Artisi]

After the spray, where does the return water go, into a tank or into a drain?


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.)

 

[Dezsi1982]

It goes to a tank.
On the pipe from the pump there is a non-return valve, 8 m vertical rise, around 30 m horizontal piping, 5 m vertical drop, and it goes into an atmospheric tank.
Thanks

 

[LittleInch]

Can you post some details of this particular pump - it's not easy to find online.

and also don't assume everyone knows what CIP is - Clean in Place? - I working on it being something like this?

https://texasprocesstechnologies.com/collections/self-priming-cip-return-pumps

My guess is its just gulping a lot of air at that point and not much liquid. These pumps are supposed to be self priming, not necessarily like a hoover

Couldn't you use a PD pump like a progressive cavity one? or a diaphraphm pump? They realy don't care how much air is entrained.

What you linked to is the priming system not a separator per se. Basically it needs a certain volume of water left in it so that when you get a lot of air, the liquid stays in the vessel and goes round and round the pump. Reality is that some liquid will go down the discharge pipe as drops or glugs and if the air gulp is long enough you could run out of liquid or get to a very low level.

the only thing you could do is make that priming tank a bit bigger and monitor liquid level and then add some water to maintain liquid level at say 1/3 full.

The other option is to use a vessel and stick a vacuum pump on top and pump out the liquid flow to keep maybe 50% full??





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

 

[Artisi]

The return water free falling into the tank is a recipe for air-entrainment, you need to review this if a solution is needed.
How big is the tank, can the return be directed to one spot and a series of baffles be installed to assist in de-airing the water.
More detail from you on the installation might help.

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.)

 

[Compositepro]

Your drain pump has higher capacity than the supply to your spray ball, so it keeps losing its prime. Without prime it basically stops pumping liquid and acts as a low capacity air suction. It sucks air by churning it into the water in the impeller casing and then separating the air from the water in the chamber above the pump. When the suction pipe becomes filed with liquid, the pump becomes primed and it quickly pumps the suction pipe dry again. A slug of liquid leaves the pump, pushing air in front of it and causing water hammer in the pipe. There will be large forces on the pipe at elbows and the pipe will rattle.

You can prevent this by filling the tank to a low level and then recirculating the drain flow directly back to the spray ball. This way the spray flow will always be equal to the drain flow, and the pump will not lose prime while cleaning the tank.

 

[Dezsi1982]

Thanks for all, for answering.
Apologies, should have started with a sketch, I provide it now:

The tank being washed needs to be empty, otherwise there will be no impact from the sprayball where I have liquid coverage.
So avoiding air entertained in the water cannot happen, I also cannot return the water back to the being washed, or fill it.
The recommended pumps for these applications are scavenging pumps, or liquid ring pumps, using PD pumps would go against the hygienic design recommendations, they are also considerably more expensive. We also have some of these pumps, different manufacturers, they don't exhibit this behaviour.
Unfortunately the only information I have is what is there on the website, we bought this pump second-hand.
I have contacted the manufacturer, but the only thing they said it is normal for this pump to be noisy, when it handles air in the liquid.
I kind of expected that, but sometimes it shakes really violent, according to the production team.
We tested different scenarios, but so far no reliable connection to inlet flow rate. We tried to use a silo being washed, so air would be in the flow, with low and high flow rates. We also tried when the inlet flow is from a filled tank no air in the liquid, reducing available flow rate or going to the maximum. We didn't manage to reproduce the violent vibration, only the normal amount we'd expect.
I was thinking to install maybe an automatic dearetor on the air separator, but according to their website the air is getting evacuated through the casing. And in fairness, monitoring the sight glass, I don't see air in the outlet pipe, only little air bubbles.
Thanks

 

[pierreick]

Hi,
Cavitation!
Pierre

 

[Artisi]

little air bubbles in the inlet line become big bubbles in the eye of the impeller.

Air entrainment is not cavitation.

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.)

 

[LittleInch]

What slope is the 20m long suction line? Or elevation from tank exit to pump inlet?

My guess is that you're getting some slugging of liquid at times when you're running out of water. Slugging is difficult to replicate and can be quite violent at times.

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

 

[Artisi]

To solve your problem I suggest you use a vacuum assisted self-priming pump.
A few life times ago I was involved with supplying pumps for emptying and cleaning refinery heavy crude oil tanks using vac assist self-priming pumps, this followed the contractor to the job trying many unsuccessful and disastrous approaches before they made contact, this was so successful they went on to become the go-to company for this work.
look for a pump hire company that can supply a small vac assist pump and give it a try




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.)

 

[pierreick]

Hi Artisi,
We have no indication about the suction line and the management of the level of the tank. I don't see the reason you rule out the possible cavitation.
Pierre