fluid change

[VikingUK]

I'm trying to think of a reason why I should NOT use a positive displacement pump which was previously used to pump glycol to pump water.
I can't think of a reason why I should not, anyone have any thoughts ?

 

[Latexman]

Use it for WHAT?

Good luck,
Latexman

 

[VikingUK]

The pump is designed to pump glycol. I want to use it to pump water instead.

 

[Latexman]

We need some details on the PD pump and the water, especially the lubricity of the water and the internal drive function of the pump, if any.

You really need to put more effort and detail into your posts, who do you think we are, the Amazing Kreskin?

Good luck,
Latexman

 

[VikingUK]

Well the water is simply tap water (it comes from the same supply as the canteen)
The pump is a small variable stroke piston pump. It flows from 20-100 litres/hour at a discharge pressure of 150 barg.
Sorry if I was a bit vague I was just looking for a general idea of opinions when you change pumping fluids of differing viscosities and densities.

 

[Latexman]

Tap water. Good. We had issues with deionized water in an internally driven SS gear pump. It galled like crazy. We use a lot of piston pumps with several dilute aqueous solutions. They are flushed with tap water or deionized water after every batch. I think you are okay.

Good luck,
Latexman

 

[jmw]

Of course, you may decide that a positive displacement pump is a bit of overkill for water where you would more usually use a cheaper centrifugal pump (or since it is drawn from the potable mains water supply to the canteen, rely on the mains pressure - but I assume there is some reason to believe mains pressure inadequate for the purpose and which is why you want a pump).

If you need a PD pump in future then you might wish you had this available.

Also, if the water pipework was originally set up anticipating a centrifugal pump or to operate on mains pressure (e.g. 80pisg?)then it may not be suitable for a PD pump, especially one capable of 150bar.

For example, if someone closes a valve on a PD pump it may cause some serious problems or damage.

It should have either an internal or external pressure relief valve to protect the pipework and fitting and if it has, the settings may need to be adjusted.

If it doesn't you might want to think about adding some protection.

That the pump is capable of 150Bar suggests this would be a very sensible precaution.

A fast closing valve could generate water hammer at up to 4 times line pressure - that could be quite a bit to manage in a pipeline designed for low pressure potable water supply.



JMW

http://www.ViscoAnalyser.com

 

[ApC2Kp]

VikingUK,

The PD pump could get you around a possible requirement for a back flow preventer to avoid process fluids reversing from the 150 Barg system into the canteen's water supply.

Maybe you want to have a food grade certified pump?

 

[mbt22]

Potable water may well be chlorinated, so watch out for stress corrosion cracking on atainless steel.

Not to try to teach you to suck eggs, but there are rather a lot of regulations around connecting potable water to process applications. A break tank to introduce an 'air gap' may be required.

 

[VikingUK]

No prob using potable water supply. The header tank will be filled by hose so no physical connection.
I intend to change from glycol injection for hydrate prevention to using a KHI chemical. This means I wil reduce from 400 litres/hour MEG injection to 2 litres/hour KHI.
Therefore I need to use water as a carrier fluid. I simply want to use the same pumps instead of buying new ones.
The PD pump is needed as ApC2Kp points out to prevent back pressure problems.