Dave’s Corner: Diaphragm for NDP-20/25 Series Pumps

In August of 2008 the NDP-20 / NDP-25 series pumps came with a new style diaphragm which has an o-ring molded into the air side. This change was made for two reasons:

To prevent air leaks where the diaphragm contacts the air chamber. To prevent a diaphragm from pulling out of place if there is excessive air pressure.

On the thermoplastic diaphragms (TPO, TPE, PTFE), there is no o-ring molded in the diaphragm. Instead a separate o-ring is used to fill the o’ring groove in the air chamber wall.

The new style diaphragms cannot be used in the old style pumps, however the old style diaphragms can be used in the new style pump when used with the air chamber wall o-ring. The old style diaphragm will continue to be available for a few more years.

new diaphragm

Jim Nelsons Helpful Hints: Diaphragm Cycle Life vs. Maximum Flow Rate

I often receive phone calls from end users about diaphragm cycle life and the first few questions I ask are:

  1. What pump are they using?
  2. What chemicals are they using and at what temperature?
  3. Is it a suction lift application or a flooded suction?
  4. At what flow rate are they operating the pump?

After discussing these questions I find that several customers are running the pump at full throttle instead of selecting a larger pump in the beginning process of the pump selection.

Operating a larger pump at half throttle would extend the diaphragm life, consume less air consumption and overall provide less wear and tear on the equipment.