Diaphragm Pumps Wearing Fast 1

[cjhut]

I am an elcetrical guy so bear with me. We are a steel foundry that uses a Corewash paint made by Ashland Chemical Corp. The paint is Velaplast ZWTXB 8090 Coating. We are using a double diaphragm pump to transfer this liquid paint into a corewash station which has jets to spray and coat our cores.I have been told that this paint has abrasives in it, and we are experiencing short life out of our pumps.The pumps quit pumping about once a week. The diaprhagm pumps have two balls and seats for cycling, these are beaking down fast. Are there any suggestions on another type of pump to transfer the liquid, or what do other companies use for corewash? Oh, I forgot to mention the prime mover of the pump is compressed air.

 

[CH5OH]

that type of pump is used in various application.The important thing is to look at the materials its made of.
SS housing (liquid side), all plastic,alu,...
also the valves (the 4 balls): SS,plastic,...
you might want to try a SS pump with SS balls.

 

[ione]

AODD (air operated double diaphragm) pumps seem to be a standard for processes involving paint transport. It would be interesting to know what you mean by "experiencing short life".

Have attached a paper in which using an inlet stabilizer the pump life has increased from three weeks to one year.

 

[moltenmetal]

Your pump selection needs replaceable check valve seats. It's often the valve seats that wear, and the cheap pumps have the valve seats machined into the body of the pump such that they're non-replaceable. The better quality ones have replaceable seats that you can retrofit with harder, more wear resistant materials OR elastomeric materials which will wear less rapidly.

Hose (peristaltic) pumps are another option.

 

[cjhut]

Moltenmetal,
We do have the better pump with replaceable seats. As I said before the paint we use has an abrasive quality to it. I have just found out two important facts: We have switched to a new paint, and we are buying our pumps and rebuild kits from Grainger. The signifigance of where we are buying our parts is that we are probably not using the appropriate internal pump materials for this process. The balls and seats are worn in about three days, when we used to get a month out of our pumps. I just found out that we used to get our pumps from someone else who had proprietary components inside to handle this process. The people who build the pump for our application won't disclose what the balls and seats are made of. I appreciate everyone's input, hope everyone has a wonderful holiday!

 

[ione]

These are some material used for seats in those application where abrasion is an issue (maybe it can help).

RTFE (Reinforced PTFE) is filled with fiber glass filler to improve strength and resistance to abrasive wear. Not to be used in applications that attack glass, such as hydrofluoric acid and hot strong caustics.

Stainless Filled PTFE. It Offers excellent abrasion resistance with higher pressure and temperature ratings than RTFE.

PEEK (PolyEtherEtherKetone). Excellent choice for high pressure, high temperature service and excellent abrasion and corrosion resistance.

 

[FACS]

I worked for a Paint dispenser company for many years, and pumping paint was always an issue regarding the seals. I spent several years experimenting with different seal materials, and there never was a real solid solution to the problem.

We used Graco diaphram pumps for the large volume filling. They had the most experience with abrasive issues at the time. The White Dioxide paint had "Zeospheres" in it, and was horribly abrasive. However, the pumps held up very well. Usually it was only the check valves that had to be replaced periodically.

We used positive displacement pumps for the tinting machines. (The abrasive is in the tint) Hardened shafts with mechanical seals for larger pumps (3 gpm) and hardened shafts with three sets of Teflon lip seals for the smaller pumps.

None of these lasted forever, it was said that we were in the pump repair business instead of the paint dispensing business.

If you want to discuss the issue, feel free to EMail me. I can tell you what I remember, and maybe even give you a company to talk to.

Charlie

http://www.facsco.com

 

[moltenmetal]

You can have tungsten carbide or silicon carbide or machinable ceramic parts made for these pumps too. The balls are relatively easy to come by.

 

[msquared48]

"The people who build the pump for our application won't disclose what the balls and seats are made of."

That is unacceptable and ridiculous as you are the purchaser and user. I would look elsewhere for a new supplier whoi is more forthcoming and helpful. There are a lot of hungry people out there now.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[micalbrch]

cjhut,

I think there is an issue that has not been considered yet. Most of the answers so far refer to the materials of ball and seats. But do the balls and/or seats wear out or are they chemically attacked? If they are chemically attacked,a change of materials will be the best option. But if they really wear, the velocity through the valves might be too high and that means the pump might just be too small.

 

[JRLAKE]

As someone mentioned before, nearly every time I have had a wear issue in a diaphragm pump it was because the pumps were too small and run too fast. Before I looked at exotic materials I would buy a larger pump and slow it down, the same thing you would probably due with a centrifugal pump.

I also agree that it is completely unacceptable for a vendor to not disclose the material of construction. I would drop them like a bad habit.

I recommend contacting a pump distributor. That's why I don't buy from Grainger. Zero support.

 

[robs68charger]

Another option is using and ARO AODD pump. They have the option of Santoprene balls and seats. I believe they also offer the option of 400 series stainless steel balls and seats. The advantage with the ARO pump is it uses less air and does not freeze over. The air section has a design that makes it very efficient. As for the "liquid end" portion of the pump that can be done in a Stainless, Cats Iron, Hastelloy C, and some others that I cannot recall off the top of my head.