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I am having a problem with methanol injection pumps, these are mRoy ‘s diaphragm type . as they could not deliver methanol at 6à bars discharge pressure (system back pressure) In fact they start kicking methanol till 20 bars then they start making a strange noise and abruptly stop. Just to say that methanol is under 3 barg pressure and 40-65 C during summer with fuel gas blanketing. This is why I suspect dissolved gas to cause cavitation for the pumps, since pure methanol bubble point is around 100 C under this pressure.
However I could not find a solution ..
Thanks for your help

[sgkim]

> ..(snip).. In fact they start kicking methanol till 20 bars then they start making a strange noise and abruptly stop.

Hi Sabrina,

I guess the discharge check valve do not work properly. The methanol seems to flow back and forth due to the malfunction of the discharge valve. If so, the temperature of methanol in the pump will rise above the boiling point of methanol.

Check the discharge valve first. If my guess is correct, then you may probly require "spring-return check valves" on both (suction and discharge) side.

Stefano/050805