4 replies to this topic

[Bill B]

When is it appropriate to consider a modulating valve, vs. a non-modulating pilot valve? I have two vendors - one recommending the modulating, the other vendor not. Thanks in advance, bill

[rxnarang]

A modulating Pilot operated PSV has some advantages viz, the inlet and outlet laterals can be sized for the required flow, rather than for the rated flow.

I suspect this comes at the expense of reliability as compared to pop-acting, but I do not have the reliability data to back this statement.

If required, I normally recomend a modulating, non-flowing type pilot operated PSV, specially if the pilot is remote.

Regards

[ankur2061]

When is it appropriate to consider a modulating valve, vs. a non-modulating pilot valve? I have two vendors - one recommending the modulating, the other vendor not. Thanks in advance, bill

Bill B,

Could you be more specific by providing the details of the application where you need a pilot operated relief valve. The above details are too insufficient to provide a meaningful answer.

However, you can look up the following link to get an overview of pilot-operated relief valve:

http://en.wikipedia....ed_relief_valve

Hope to get more details from you.

Regards,
Ankur.

[fallah]

When is it appropriate to consider a modulating valve, vs. a non-modulating pilot valve?

As a general response,when operating pressure is much close to design (set) pressure.

[Bill B]

Thanks for the input. My question was mainly a general one. Ankur, I am presently looking at two cases. In the first, we are protecting against blocked flow from a compressor (process air). The back pressure is high and I will replace the existing conventional valve with either a bellows or pilot. One down the road issue is that process pressure may be raised to closer to the set point.

In the other case same issue with back pressure - syn gas vapor stream. In this case there is some possibility of mild deposition of material.

One of our reps sent me quotes for both bellows and non-modulating pilots. Another gave quotes for modulating pilot valves. I was basically looking for a checklist of things to consider when making the bellows vs. non-modulating pilot vs. modulating.

Thanks again. Bill