Booster pump with Jockey pump for potable water network of the plant

[Vysakh1700]

In our project the specification call for 2 booster pump(1 duty+1standby) with one jockey pump arrangement for the potable water ring network.
But In our understanding and experience in other projects, the hydropneumatics tank is necessary and provides a well-studied performance in potable water systems. The hydropneumatics tank avoids the delay to the consumer and constant start/stop of the main pumps if a low demanding consumer is activated. Without the tank, we understand that jockey pump will always be functioning, which from an energetic point of view doesn’t seem favorable.
Can you please help me the system will work with jockey pump or not without any delay with consumer?

Please provide some supporting reference to discuss with client.

31m3/Hr flow & 88m head for the booster pump and 1% flow considered for the jockey pump

 

[LittleInch]

Not enough data.

You are talking two different things and without knowing what the demand curve over time looks like no one can say what is going to happen.

Jockey pumps tend to be used for pressurising things like fire water mains to account for things like small leaks or small usage of water.

Only you know what the flows look like and how to balance out a big pump starting and stopping - 31m3/hr looks quite alot.

You often see some sort of cascading pump system so that you have a range of pump sizes to cope and a decent sized pressurised tank to smooth it all out.

"Please provide some supporting reference to discuss with client." - Sorry - I don't provide free engineering services.

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

 

[bimr]

To add to LittleInch's comments, you need to provide enough information. Is your potable water network one building, or is it several square miles? Is the source of water onsite or offsite.

Jockey pumps have been commonly used in this application for years in process plants on fire water systems. The potable water systems are generally smaller and don't require jockey pumps.

It is probably more common today to use a VFD pump for this application.

 

[Vysakh1700]

@ bimr,
This potable water network for Desalination plant.
Which includes following common tap,shower,kitchen sink,toilet,Urinals,emergency shower,drinking fountain for almost 11 buildings and total point of 1043.
It is several square miles.
The specificaion strictly to be followed,they ask 2 booster pump with jockey pump for potable water supply.We affraid that the system will work without any delay and no pressure tank in the system.

 

[FMJalink]

I was writing an extensive reply, but realized writing, that the jockey pump requirement may come from hygiene requirements.
With accumulators, which are basically dead ends, there is a lot of risk of bacteria growth. Above drinking fountains are mentioned, which would require drinking water quality and not just sweet water.
Good luck with finding a good approach.

 

[georgeverghese]

1% of main pump flow for the jockey pump seems too low. Which perhaps explains why the main pump kicks in more often than it should. Why not say 10% = 3m3/hr at 88m of head for the jockey pump? That would mean fewer events when the main pump kicks in. To save power on the jockey pump which runs all the time, you could use a 2speed electric motor, and trigger higher speed when header pressure drops. You could ask for the main pump to run on a 2 speed motor also, if you find VFD too much of a bother.

One can cook up a scheme for this accumulator tank, but I would try selling the client the above scheme first.

 

[LittleInch]

Whether this will work depends on many things such as predicted range of flow rates over a day, ability of the main pumps to run at low flows, Is it 2 x 50% or?, what control system you're using to turn the pumps on and off or otherwise control the flow.

Having two 1% pumps for a system which sounds like it will have a constant flow from somewhere unless there are literally no people on site for certain times.

but 11 buildings, over 1000 connections and spread over several square miles sounds quite different to a fire main system which is where you commonly see such small jockey pumps.

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

 

[Valvecrazy]

Pumps are made to run 24/7/365. I have some systems like this with very small pressure tanks where the jockey pumps have not turned off in over 30 years. If you control all the pumps to vary the flow rates to match the demands there will be no cycling. With a system like this very little if any pressure tank is needed. If the jockey pump is not way oversized it is also an efficient way to handle continuous small flow rates.

 

[pierreick]

Hi,
An issue with this set up (accumulation tank +jockey pump) is the risk of legionella. Be aware of!
Good luck
Pierre