Air-Operated Double Diaphragm Pump Sizing

Whenever sizing an Air-Operated Double Diaphragm pump (or any pump in
that matter), do you size for just the discarge head?  Or do you size
the pump (determine operating point on pump curve) by using:

Head=Discharge head-Suction head.
We use a lot of these pumps.  Almost all of ours are 1" pumps.  We use
them in all kinds of intermitant services.  We have pressure regulators
on the compressed air to the pumps.  That controls the total allowable
discharce pressure (Discharge=Supply) and we also have a ball valve on
the air line that we throttle to slow or speed up the pump.   It is
pretty crude but effective for what we do.   If you actually have a standard application maybe you
would be more interested in a vane pump or centrifugal pump but for
miscellaneous pumping needs the 1" or 2" diaphragm pumps work well.
You may want to switch pumps as MikeHalloran suggested.  You will be
happier with something like an LMI pump for real small flows or a
Pulsafeeder pump for larger flows.  Then control based on the number of
strokes, or time which ever is easier for you.   The diaphragm pump is
not going to give you what you want.  Maybe you could fill an
intermediate tank from the tote and then pump the whole intermediate
tank into the reactor but that is more operator intensive.
From the original1CheckValve
.