Dave’s Corner: Shaft Cushions

Lately we have seen several pump failures due to improperly installed shaft cushions (p/n 770582). We have noticed that the problem occurs when a shaft cushion is installed in a pump that does not require it.

For instance, the shaft cushion is used on all NDP-40 and NDP-50 pumps with rubber diaphragms, including Santoprene® and Hytrel® elastomers. However, the shaft cushions are not to be used on NDP-40 and NDP-50 pumps with PTFE diaphragms or any NDP-80 series pump.

The purpose of the shaft cushion is to prevent the center disk from impacting the air chamber wall when operating at the far right of the performance curve. This isn’t an issue with the NDP-40 and NDP-50 pumps outfitted with PTFE diaphragms because the pumps are destroked and will not travel far enough to impact the chamber. This can, however, happen with the NDP-80 series pumps. A shaft cushion cannot be used because it will interfere with the center disk as it makes contact with the pilot valve.

Lastly, if you have a rebuilt NDP-80 pump and cannot get it to cycle, check to see if it was rebuilt (incorrectly) with shaft cushions. Below is a quick reference guide to follow when determining whether you can install shaft cushions in your pump.

shaft cushion

Dave’s Corner: EX-Air Valves

When we refer to EX-Air Valves we are talking about electrically controlled shuttle valves as opposed to a pump that uses a c-spool piloted by an air signal from the pilot valve. The EX-Air Valve is available on all pumps except the NDP-5 and NDP-15 series pumps.

This type of valve can be directly mounted on the pump or remotely mounted. It is available in single or dual solenoid versions and is available in 12VDC, 24VDC, and 115VAC.

A pump equipped with this type of valve is used for metering and batch control. It is used with our YSC-3 controller or can also be used with a PLC.

The standard valve that is used with our YSC-3 controller is 12VDC, single solenoid. Below is a matrix for selecting the appropriate valve for your EXAir application.

EX-air valves

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