Q&A with Eric Kayla: Answers to 5 pressure regulator questions
by Jeff Hopkins, on 11/2/12 11:00 AM
Answers to 5 questions posed to regulator expert Eric Kayla. Plus, get his slides.
When we hosted the webinar "The Theory and Operation of Pressure-Reducing Regulators," participants sent in questions to Swagelok field engineer and webinar presenter Eric Kayla. Below is some of the material from the robust Q&A that followed Kayla's presentation.
Q: What happens if you oversize a regulator?"
A. If it's too big for the application, your poppet and seat will be too large, allowing too much flow. Every time that regulator opens, it will allow more flow than you expect. The regulator will do more work than it should need to. You'll see more fluctuations and spikes in your downstream pressure.
Q: What about if you undersize it?
A: Instead of having a seat and poppet too large, you'll have one too small. It will open as much as it can to let through as much flow as it can. You are probably going to operate closer to the choke flow range. You are also probably going to erode the seat faster than with a properly sized regulator.
Q: Discuss the difference between liquids and gasses in regulators.
A: Liquids are more straightforward because they are not compressible. Gasses are a little different, so there are different sizing methodologies. And if you are using a liquid with some particulates, it could increase wear on the seats over time.
Q: Does the supply-pressure effect happen with both liquids and gasses?
A: Yes. If we aren't changing anything on the loading force, our sensing mechanism will work to balance out against that loading force. If the inlet pressure force goes down, the only way to counterbalance it is an increase in outlet pressure force.
Q: Can you use a backpressure regulator for overpressure protection?
A: Yes, they can be used for overpressure protection. It probably requires a deeper discussion than a few sentences here. Some people choose to use a relief valve, but there are probably applications where it is more important to use a backpressure regulator. A relief valve is designed to stay closed, and to open only in an emergency. A back pressure regulator is designed as a dynamic component and will react constantly to keep upstream pressure constant.
Additional webinar Q&A
We will post again with more answers stemming from the briefing, including Kayla's answer to, "How does a two-stage regulator manage supply pressure effect?"
Swagelok Northern California’s regulator assemblies provide the most-requested configurations for gas bottle or inline service utilizing the KPR-Series pressure reducing regulator (KLF for 0-10 psig control range). Click through for literature covering technical data for pressure, temperature, and flow, information on KPR regulator features, and ordering information.
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