Air trapping through suction pipe w

[moideen]

Air trapping through suction pipe when switch off the condenser pump. During switch off all water reurened to the cooling tower, Cannot be possible to change the piping configuration. Thinking an idea by fitting NRV closed to cooling tower outlet pipe to hold the water in suction pipe during the off period. Pipe size 16 inch. Any other suitable ideas…find the approximated sketch

 

[Artisi]

Is the sketch indicative of the installation - the pump inlet is lower than the cooling tower?

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]

An NRV or sometimes called a foot valve is one way, but over time they have a tendency to leak and hence an isolation valve is better. To prime the pump you can use a vacuum pump or a self priming pump.

The back flow though must be accompanied by inflow of air from somewhere so try and stop that happening.

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

 

[bimr]

Install a small 1-Inch or 2-Inch manual valve at the high point in the suction piping. Open the valve to release the air to atmosphere when refilling the suction piping.

 

[moideen]

Thanks to all commented, I think self priming pump is suitable option as little inch advised, then i can avoid that much pressure drop in suction line if i not fix a nrv or isolation valve.

 

[bimr]

If this is an existing application, then the air release valve will be much less expensive than replacing the pump. The air release can even be automated.

The self-priming pump is less efficient energy wise and will also be more expensive to repair.

 

[moideen]

bimr: i didnt think about the replacement of existing pump. what i thought tat the self priming pump waork as ancillary for only a limited time that using for only removing air for supporting main pump.after running the main pump it will be switched off. i am not familiar with this pump..

 

[LittleInch]

moidenn,
You haven't really given us much to go on here.

Please add some levels and dimensions to your sketch and explain how the operation works now or doesn't work.

Type of pump, how do you fill the pipe, how often does this happen, that sort of thing.

I assume your high point is above liquid level, but your sketch is a little bit too basic. ?if it's higher than the cooling tower liquid level then bimrs idea won't work, but your sketch is open to interpretation.

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

 

[bimr]

bimr: i didnt think about the replacement of existing pump. what i thought tat the self priming pump waork as ancillary for only a limited time that using for only removing air for supporting main pump.after running the main pump it will be switched off. i am not familiar with this pump.

Less expensive option (than a pump) is to use an eductor powered by air or steam to clear the piping.

https://cdn.wartsila.com/docs/defau...mps-centrifugal-priming-systems.pdf?sfvrsn=11

Or use a priming system:

http://www.dezurik.com/download-file/apco-priming-valves-psv-sales-608.pdf/234/

 

[moideen]

The suction pipe routed to cooling tower l like serpent. See the attached pipe images taken from outside the plant room. Right now, the condenser pump is running without any problem, but when switch off part of the maintenance, suddenly air is trapping to the suction pipe and as per the site info, the water will reach to the cooling tower and overflowing.

 

[LittleInch]

moideen,

You seem to be approaching this issue in a bit part manner.

first off, you need to define your problem.

Is it that water flows back and overflows the cooling tower?
Or that you have difficulty on re-start?
Was it always like this?
Or has it just started?
Ha something changed?
find the P&ID and the operating procedure / philosophy to work out what should be happening
See if a HAZOP or other review was undertaken as to how the system should operate
Get a properly dimensioned route plan of the pipework.

Are there no NRVs in the system (e.g. on pump outlet?) Have they failed?
Where is the air coming from?

If you can fit an NRV, then why don't you?

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

 

[Artisi]

Lovely photos, but do nothing to establish what the problem is. A lot of expertise available to help, but very little crystal-ball experience.
At the moment you are wasting your time as well ours and as LittleInch has advised, DEFINE the problem.

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.)

 

[wayne3298]

The easiest way to solve your problem is to install a motor operator on the isolation valve near the pump and one on the isolation valve near where you show the foot valve. On shut down delay the pump shut down until both valves are closed. On start up start the pump and then open the valves. I have seen this piping error before and this solution works.