1/2" & 1" All-Flo air valve assembly (air motor) 42000-60 symptoms:

• Air releasing out of air valve incorrectly and hissing sound.
• Pump not pumping with these concurrent symptoms reminder: Regulator supplied by PWP should be set to 80 psi maximum.

       Viton diaphragms are not the best choice because of the following reasons according to All-Flo: Santoprene and other thermal plastic elastomers (TPE) will have a very long flex life due to the nature of the material. This is especially apparent when comparing them to FKM and PTFE diaphragms, which tend to have a low flex life.

       When selecting a diaphragm, the chemical compatibility and the natural flex life should be considered. In most cases, a “B” rated Santoprene or other TPE will outlast an “A” rated FKM (Viton) or PTFE diaphragm.

       This is because both the “A” and “B” rated diaphragms will normally fail due to their natural flex life before they experience chemical issues. PTFE should predominantly be used when a TPE is not chemically compatible with the process fluid, and FKM (Viton) is traditionally used for high temperature applications that go above the other materials maximum temperature limits.

       In short, Santoprene has a high flex life and FKM (Viton) has a very low flex life with flex life being its weakness.