Vilter 440 compressor

[RANGER1]

Has anyone really looked at a Vilter internal relief valve?

I'm wondering if they actually work in a working system, that is
obviously out of control to have head pressure of 300psi.

Sabroe worked it out after 50 yrs with a retrofit balanced port internal relief, Vilter I'm not sure.

The Vilter is so small, so whats its purpose & is it back pressure affected?

[NH3LVR]

I always assumed it was to protect the compressor, especially if it was started with the discharge valve closed. The pressure might build so rapidly that the machine could over pressure even after the motor had shut off. I know of one case where this happened, although it was a a diesel powered screw.

Vilter does make some machines that unload 100%, If they were started with the discharge closed they could come up to speed and a high pressure condition could occur when they loaded.

The valve operates on differential pressure, if that is what you mean by back pressure affected.

As to the size I believe it is adequate from the standpoint of effectively reducing the capability of the machine to overpressure. I base this on guesswork, from observations of compressors with broken discharge valves

[RANGER1]

I always assumed it was to protect the compressor, especially if it was started with the discharge valve closed. The pressure might build so rapidly that the machine could over pressure even after the motor had shut off. I know of one case where this happened, although it was a a diesel powered screw.

Vilter does make some machines that unload 100%, If they were started with the discharge closed they could come up to speed and a high pressure condition could occur when they loaded.

The valve operates on differential pressure, if that is what you mean by back pressure affected.

As to the size I believe it is adequate from the standpoint of effectively reducing the capability of the machine to overpressure. I base this on guesswork, from observations of compressors with broken discharge valves

Thanks NH3LVR, it would be interesting if they actually work. Of course I'm not going to wind discharge pressure
up to it relieving pressure though.
For many years we assumed a lot or relief valves worked when outlet of relief was plped back into system.
But we all eventually found out that outlet pressure is added to relief set relieving pressure effecting its operation.
Thats why I question the Vilter one, that's all.
It appears the Vilter one may be more of a static relief, not really big enough for when compressor is running, unloaded or if discharge stop valve is left closed on start up.
In Australia & Europe we are recommended to use a valve from discharge to suction that can handle the flow if discharge is closed etc.
These valves are not downstream pressure affected & are like 2,3,4" in size
Sabroe made the change about 10 years ago on their recip compressors.