Pumping Sodium Hypochlorite 1

[pumpking]

Just a quick survey of peoples thinking:

Pumping low concentration Sodium Hypochlorite at ambient temperatures, the material corrosion charts shows Polypropylene to be quite suitable, however, long term you get lots of brittleness at sharp corners in components such as pump casings etc.

Our preferred option is either ETFE or PFA lined, but we regularly come up against Polypropylene which is also much cheaper.

My question to the pump users in this forum is when would you opt to use a known inferior material on such applications, would you simply add this to your routine maintenance lists to check pump robustness ?

Unfortunately cost savings are being driven more and more into Industry, and i'm guessing these decisions are all side effects to 'cutting costs'

Ash Fenn

http://www.cdrpumps.co.uk

 

[MikeHalloran]

If you hit the pump with a forklift, its material doesn't matter.

So, surround the pump with a sturdy barricade, properly support the pipes around it, and budget to replace it every N years, or when it develops cracks or other evidence of material degradation.



Mike Halloran
Pembroke Pines, FL, USA

 

[bimr]

Many end users of hypochlorite make the same decision and periodically replace components that degrade over time because the material is hard to handle.

As a pump supplier (which you appear to be) that is a difficult recommendation to make. You do not know what type of plant system (spill containment, backup pumps, maintenance quality, etc.) that the pump will be part of. For example, if there are backup pumps, then breakdown of one pump is not a problem. Down the road, you would not want to be blamed for some problem that is out of your control.

I would survey other users and find some common ground among them.

 

[pumpking]

Thanks for the replies people, bimr has hit the nail on the head - making such a recommendation about an inferior material is a real problem for us, and compromises our Engineering advice, but the other problem is that many of our competitors put such inferior material into such applications all the time, so technically we offer the technically superior and 'correct' material, but commercially we are pushed down a road that we really dont want to go down. Thanks for your input folks

Ash Fenn

http://www.cdrpumps.co.uk

 

[MikeHalloran]

To prevent 'blowback', don't use words like 'inferior' in reference to a competitor's work, in front of a customer.

Instead say 'perfectly satisfactory for a limited time', or something like that.



Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

I see that laundry bleach is packaged in HDPE bottles. For what it is worth.

 

[pumpking]

That sounds like a very good voice of experience there Mike, absolutely correct, dont get me wrong, if you were really brave (and stupid !) there would be all kinds of things you would REALLY like to say sometimes...

But your post made me chuckle to myself - commercial suicide !!

Ash Fenn

http://www.cdrpumps.co.uk

 

[moltenmetal]

pumpking: there are plenty of applications where long service life without maintenance isn't an absolute requirement. A PP pump in room temperature hypochlorite service could last 10 years or more before you have problems, assuming it's seal-less and contains no otherwise incompatible materials for shafts, bushings/bearings etc. A small magdrive in PP might cost 1/4 to 1/3 what an ETFE or PTFE-lined pump would cost, so the savings aren't minor. The smallest lined pump isn't very small, either- the little Iwaki or March magdrives are available in sizes much smaller. PP can be brittle and notch-sensitive at room temperature even without hypochlorite present, such that threaded parts can snap off due to vibration etc., but that doesn't mean it's not a useful material as long as you know this property.