Pump Suction Design

[pmcrowell]

I would like to obtain an opinion on a pump suction design.

I have an existing 24" pump suction out of a chest that run approximately 3 ft to a LR 90 into reducer to a 12" pump inlet. The flow is about 3,600 gpm.

I adding a new pump and may not have a long enough shutdown to install another suction on the chest. I am thinking about adding a 12" connection on the straight piece to feed another pump rated at 1,200 gpm.

All total I have 4,800 gpm which is under 3.75 ft/sec velocity.

My concern is the how close the original pump will be to the new connection.

What is everyone thoughts?

Thanks,

Paul Crowell

 

[BigInch]

What's a chest?
What is a "a long enough shutdown"?
3.75 fps velocity is total flow in what?
Where is the new connection?
What is it connecting to, the chest, the ell, the reducer?
Your system as described is totally not clear to me.


"Make everything as simple as possible, but not simpler." - Albert Einstein (1879-1955)
***************

http://virtualpipeline.spaces.live.com/

 

[Artisi]

Chest is a typical paper industry term- ie tank containing water or stock.
Agree we need more detail - preferably a sketch.

 

[786392]

Are we up sizing the chest as well?
Two pumps(proposed)side by side suction may create internal vortex and possible air -inflow and cavitation!
Vortex breakers might be needed to take care of such situation.
It is also important that whole material inflow into the chest should match with outflow through propsed pumps with sufficient liquid level(head)always available above NPSHR of each of the pumps.
Hope this helps

Best Regards
Qalander(Chem)

 

[MikeHalloran]

Chest means big tank with open top, usually equipped with impellers for mixing/ shredding stuff dumped in by forklift, or just to keep the stock moving so the fibers don't settle.

Shutdown is not a piping term here- he's talking about down time available to modify the chest. Paper mills run 24/7, so there isn't any.

I think he's talking about splicing a branch onto the existing 24" dia x 3 ft run of straight pipe, turning it into a tee or wye, through which both pumps would draw from the chest through the same 24" dia aperture at the stated flow and velocity.

I've seen uglier rigs work. I've seen prettier rigs not work.

The problem with doing it this way on a temporary basis is that unless it has huge problems immediately, it will still be there in a hundred years, every problem anywhere downstream will be blamed on it, and it will always be called "Paul's butt-ugly pipe" or something equally complimentary.

I don't think it will have huge problems immediately, but I think it will have subtle problems indefinitely, so the next three or four generations of papermakers will curse Paul for all of their quality problems.

I.e., I'd go ahead and do it as described...
... for any fluid except paper stock.




Mike Halloran
Pembroke Pines, FL, USA

 

[Artisi]

Some of the ugliest pipe work you can see will be found in and around paper machines usually resulting from immediate needs and upgrades in very confined areas - yes, and that goes against all logic as far as correct pipework configuration can quiet often work whereas text book installations can give no end of problems - especially when pumping air entrained pulp.

More detail on what is being pumped and an idea of what it looks like could help - however, a wye would be a prefered option over a 'T" for comnnection into the 24" pipe.

 

[Artisi]

Correction

"and what goes against"

 

[786392]

A 'Wye' is definitely preferable on 'T' connection in general terms.
However I still believe that whole Material in and out balance should be carried-out afresh considering
post modification scenario and 24/7 continuous operation.

Best Regards
Qalander(Chem)

 

[Artisi]

786392 - you are correct - but nothing back from the OP so we are crystal ball gazing at the moment.

 

[pmcrowell]

To begin with, thanks for everyone's comments.

I forget that in my industry (Paper) we tend to assume that everyone talks the same.

The chest is a 10 ft x 12 ft tile concrete tank.

The fluid is 2% consistency paper stock which on the boarder line between pulp stock and white water. We treat white water as the same as water. Pulp stock in a non-Newtonian fluid and every so much fun to deal with.

Existing pump flow 3,300 gpm (24" pipe)
New pump flow 1,500 gpm (12" pipe)
Total new flow 4,800 gpm (thru exisitn 24" suction)

As typical in the Paper industry I have to put another pump (jam into a small place) on a chest and I only have 48 hrs to install a new insert in the chest. My question would be if a lateral into an existing 24 suction pipe do you feel this would be very bad?

This is my one shot at this and if I attach onto the existing pipe it will be become the permanent solution.

I have attached a quick sketch of what is being proposed.

I am willing to take my punishment on this from all. I have had a few things name in my honor over the years (Fort Paul, Paul's "f"ing pump etc) My skin has become very thick as with my brain at times.

Thank You,

Paul

 

[MikeHalloran]

I fear that one will make you a legend....



Mike Halloran
Pembroke Pines, FL, USA

 

[Artisi]

For an on the run installation in a paper mill it almost looks civilised - some I have seen are diabolical in comparison.

My only concern would be the mixer which is close up to the tank exit - you need to ensure that you are not beating air into the white water, this might call for increasing the level in the chest.

You are correct in treating the 2% stock as water which in most case is the same for all stocks upto 6%. See thread 378-226658 for more detail on stock consistancies.