Double diaphragm pneumatic pumps

[MedicineEng]

Dear All:
I have in my site some applications with plastic double diaphgram pneumatic pumps. We have chosen these due to the fact that they can run dry and can handle some degree of solids in suspension. Besides that, we also use it since these areas are Exproof.
Our requirements demand a quite stable flow and to reduce the unstability of the flow our pumps have an equalizer.
Our common setting is pump the suspension from level 1 to level 4 (around 15 meters level difference) and then this flow is splitted in two, one part will go to another equipment and the other will recirculate back to Level 1.

The problem is that this service is provoking several problems with the pumps namely leaks on the chambers and deformation of the plastic. I believe that this is due to the restriction of the outgoing flow that is provoking a overpressure inside the pump, but I wanted to hear your oppinion regarding this.
I would also wanted to seek your advice on how could I improve the lifespan of these pumps.

Replacing it by metal pneumatic pumps is not an option, at least for now.

Thanks a lot for your help.

PR

 

[notnats]

The pumping pressure is related to the air pressure supplied to the pump. Do you have a regulator on the air supply?

Jeff

 

[MedicineEng]

Yes, I have. I would like to see if there was any way that I could regulate better the flow.

Thanks

PR

 

[ccfowler]

I would pay some serious attention to NPSH issues giving special attention to all the details of the acceleration effects of the pulsations in the flow rates. Increasing line sizes and locating pulsation dampers close to the pump on both the suction and discharge lines are likely to be very helpful. The actual maximum and minimum pressures experienced at the liquid sides of the pump diaphrams may be much greater than you may expect from simplified assumptions.

Since you are pumping some solids, it would be wise to pay close attention to the possibility of partial clogging of the valves. If you now have ball valves, it may be very helpful to change to flapper valves. If you can increase the valve sizes, this may be helpful, too.

 

[quadtracker]

By increasing the size of the diaphram pump, you can operate the pump at a much lower rate of speed for the same gpm. Thus reduce the acceration rate, pulsation frequency and less wear and tear on the pump.