# What is a good axial piston pump for this application (ballast pump in a submersible)

So I posted yesterday about appropriate pumps for pumping water out of a ballast tank in a manned submersibles at a depth of 1000m. I decided to switch to an axial piston pump. I got that the require pump head is approx. 410 m and the required power input provided by the pump is approx. 18 000W. My inlet diameter is 2.6 cm and my outlet diameter is 2 cm.

What would be a good axial piston pump I could use?

Thanks!

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## Answers and Replies

anorlunda
Staff Emeritus
So I posted yesterday about appropriate pumps for pumping water out of a ballast tank in a manned submersibles at a depth of 1000m. I decided to switch to an axial piston pump. I got that the require pump head is approx. 410 m and the required power input provided by the pump is approx. 18 000W. My inlet diameter is 2.6 cm and my outlet diameter is 2 cm.

Whoa! 18000 watts is far too much if your purpose is only to maintain constant depth with a "trim tank". But if you're talking about diving and surfacing that's a different thing.

What is the flow rate in gallons or ft3 or m3 per second?

One you know the pressures, the flow rates, and the power requirements, why can't you just search the Internet for pumps meeting your specifications? Learning how to use research tools available to you may be part of the lesson your professor wants you to learn.

russ_watters and berkeman
russ_watters
Mentor
So I posted yesterday about appropriate pumps for pumping water out of a ballast tank in a manned submersibles at a depth of 1000m. I decided to switch to an axial piston pump. I got that the require pump head is approx. 410 m and the required power input provided by the pump is approx. 18 000W. My inlet diameter is 2.6 cm and my outlet diameter is 2 cm.

What would be a good axial piston pump I could use?
In the previous thread you never nailed down the assumptions much less calculated the operating requirements. Please post a summary of the work you've done to get those answers so we know we aren't just providing meaningless help to move forward with bad critera/calculations.

Whoa! 18000 watts is far too much if your purpose is only to maintain constant depth with a "trim tank". But if you're talking about diving and surfacing that's a different thing.

What is the flow rate in gallons or ft3 or m3 per second?

One you know the pressures, the flow rates, and the power requirements, why can't you just search the Internet for pumps meeting your specifications? Learning how to use research tools available to you may be part of the lesson your professor wants you to learn.

Hi Anorlunda! My flow rate is 50 l/min or 0.000833333 m^3/s. I did look look online for a dc pump to meet my specifications but the one I found for that power was like 800 lbs lol...So I thought perhaps I was doing something wrong but I guess for that amount of power it would be quite large? Its odd though because how would small manned submersibles be able to accommodate such massive motors.

In the previous thread you never nailed down the assumptions much less calculated the operating requirements. Please post a summary of the work you've done to get those answers so we know we aren't just providing meaningless help to move forward with bad critera/calculations.

Yes, I apologize I didnt want to clog up the post with my calculations but I'll try to be clearer next time

anorlunda
Staff Emeritus
OK, I must have been wrong in what your application is. I thought it was just trim to maintain constant depth.

An 18kw BLDC motor is similar to those used in electric cars. A quick search for those on alibaba showed some 20 kw weighing 39 kg. It might be similar to the motors used for propulsion.

Tom.G
Gold Member
How about using compressed gas instead of a pump for gross buoyancy control. A full compressed Nitrogen tank is at 2200psi and a high pressure SCUBA tank is in the 3300-3500psi range.

russ_watters
A caution: be sure to thoroughly dry such air lest an urgent tank-blow cause icing in the lines...
IIRC, this was the probable cause of tragic loss of submarine USS Thresher...

Tom.G
Tom.G