Installing a 4zk94 Regulator having blowback

Hello Bill,

I am installing a 4zk94 onto our compressor line to regulate air flow to our tools. Once I install the regulator according to the instructions and apply the air I can not get the regulator to work properly. I have incoming air at 160psi and want to regulate the outgoing air to around 85-90psi, but each time I turn on the system the regulator vibrates and blows air out the top of the unit. I have checked the flow and verified the maximum inlet pressure, but I can't get the system to stabilize. What could I be doing wrong during the installation?

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Sep 18, 2015
Another thought about the regulator... Dale
by: Bill

Of course, if the regulator is installed backwards, with the arrow pointing towards the compressor instead of away from it, the regulator will blow off continuously too.

Double check that, won't you?

Sep 18, 2015
Regulator having blowback
by: Bill

Dale, there may be nothing wrong with the regulator.

How long are the air lines downstream of the new regulator and how long is the regulator blowing off?

If they are long or there are lots, then you have a whole system of air with 160 PSI in it, and when you dial the regulator down to 85-90, all of the downstream air that is higher in PSI than that 85-90 will blow back out through the regulator (that's why it's called a relieving regulator) until the downstream pressure is at or below the regulator new set point.

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