Triplex pump in series with a ... ?

[Tommyasdf]

Hi everyone, I'm trying to figure out the feasibility of addressing this particular problem. I am far from an expert when it comes to pumps so thank you in advance for putting up with any stupid questions.

The simplified version is that there is a triplex pump taking fluid from one storage tank and pumping it through several thousand feet of pipe into another storage tank (which is actually located very close to the first tank). The majority of this 'pipeline' is essentially inaccessible, the beginning and end of the line are the only parts open to modification. The triplex pump is limited to 4,000 psi regardless of liner size. The flowrate is limited to 200 GPM because at higher flowrates, the pressure drop across the entire system exceeds that 4,000 psi limit.

I'd like to be able to increase the flowrate to at least 250 GPM but at a bare minimum cost (surprise!). I haven't done the math but let's assume this would increase the pressure drop by 800-1,000 psi. This spawned the idea of adding a smaller pump in series with the existing triplex. I only have the beginning and end of the line to play with but any additional pump would have to be downstream of the triplex due to inlet pressure restrictions.

My initial thought was to use a rotary PDP immediately downstream of the triplex (with some sort of buffer in between) but this additional pump would need to be capable of an internal pressure of up to 5,000 psi even though the actual differential across it would only be 1,000 psi right? Is there any other obvious solution that I'm missing here? Thanks for the help everyone.

-Tommy

 

[zdas04]

If your pipe is rated for that kind of pressure, the idea can work. I'm not familiar with a pump designated PDP unless that just means "positive displacement pump" and you are talking about something like a progressing cavity pump (PCP) which can certainly be purchased with that kind of discharge pressure ability.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[Tommyasdf]

Yeah, that's what I meant by PDP. I'm guessing it would be easier to match the flowrate of the existing triplex with another positive displacement pump as opposed to a centrifugal pump. I wasn't thinking specifically of a progressive cavity pump but I was curious if anyone had any thoughts on what type of pump would be best for this kind of application. Thanks for the input David.

 

[zdas04]

PD pumps are affected much less by changing conditions than a dynamic pump is. A dynamic pump like a centrifugal is fine as a charge pump for a PD pump, the reverse is absolutely not true and will cause problems from day 1 through day 2 (when the centrifugal finally eats itself).

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[Pumpsonly]

If it take 4000PSI to push 200gpm through the pipe line, a quick calculation will need more than 6000 PSI to push 250 gpm assuming all friction losses as you suction the 1st tank is very close to the 2nd tank.
Can your pipe line take the pressure?
Can your present triplex pump afford you the increased flow rate?

As point out by David, you can only put the centrifugal booster pump, before the triplex pump. But it has inlet pressure limitation..

You have a real problem.

 

[SREisme]

If you are just pumping from one tank to another in close vicinity, why not install a pump that can do 50gpm with a separate pipe run? Why do you need thousands of feet of pipe to go next door? What is the pressure at the outlet of your existing pipe with the 4000psi pump pressure? This sounds more like you are supplying fluid to a manifold and discharging the excess to the second tank, but if you really are going through a few thousand feet of pipe to go 50 feet, you might look into the energy savings of redesigning the system to transfer 250gpm at minimal discharge pressures. 4000psi of line losses seems shameful.

 

[Tommyasdf]

Hey guys, thanks for the input. The application is a drilling rig pumping drilling fluid down the drill string and back up the annulus. I didn't mention it initially because I was trying to be as concise as possible in my first post, which I think I failed at anyway .

To answer your questions, yes the line can handle the additional pressure and the triplex pump can definitely supply the additional flow. The higher flowrate would translate to cost savings, I'm just trying to figure out how complicated and expensive that higher flowrate is going to be. Thanks again.

-Tommy