More back pressure regulator questions and answers

Written by Jeff Hopkins | 8/29/13 4:30 PM

Extra information our webinar audience wanted from field engineer Eric Kayla.

In this 3 minute clip from the webinar "Back Pressure Regulators Made Simple", Eric Kayla discusses the differences between back pressure regulators and relief valves and the type of applications each are best suited for. Download Kayla's webinar presentation slide deck:

Eric Kayla, Swagelok's roaming expert on regulators, puts a lot of preparation and rehearsal time into his webinars. His expertise shines even more, however, when the formal part of the program ends and he opens the floor to questions. There's no telling what the audience will toss at him, yet he always has the right information at his fingertips, and the right slide to go with it. Here are a few questions tossed his way at our Aug. 22 webinar on back pressure regulators.

Q: For lower pressure, less than 15 psi, is the dome or spring better when controlling only back pressure?

A: Both designs are going to do well controlling to a specific pressure. The big difference with a spring loaded design or a dome loaded design is going to be the flow curve. The accumulation is going to be more for a spring loaded regulator than for a dome loaded regulator. So if precise pressure control is required, for example if you need to hold 15 psi with very little variability on either side of it across a fairly broad flow range, then a dome loaded regulator would be a better option. If you've got more flexibility on the tolerance of that 15 psi, or if you have a fairly narrow flow requirement, then a spring loaded regulator would work just fine.

Q: What is the most common failure in back pressure regulators?

A: The most common failure is going to be in the seat area. You've got a metallic poppet, you've got a plastic seat. Any sort of contaminant or particulate in the system is going to interrupt the seal between the poppet and the seat. Once you have contamination in the seat region, it's going to cause the regulator not to seal when it goes to close, so it may not hold the back pressure on the upstream side as closely as you need it to. So good filtration is important for back pressure regulators as well as pressure reducing regulators to prevent damage to that seat-sealing area.

Q: If the design is similar, why is a relief valve imprecise as compared to a back pressure regulator?

A: The big difference between the relief valve and the back pressure regulator is the sensing mechanism. In the relief valve we are relying on the poppet to be our sensing mechanism. And it's very imprecise compared to the back pressure regulator, where we've got a much larger diameter diaphragm, in most cases, or a larger diameter piston.

Q: Which type of regulator is better for high pressures - 3,000 psi or greater?

A: If you have a high pressure system, using a pressure reducing regulator or a back pressure regulator is really going to depend on where you need the precise pressure control. If you have a high-pressure supply -- let's imagine it's 4,500 psi into this 3,000 psi system, you would need to use a pressure reducing regulator to cut the pressure into your system. However, if you do have a fairly stable 3,000 psi supply into your system, but you have a number of valves and instruments between your supply and the outlet, you are going to get pressure drop through your system. So having a back pressure regulator on the outlet of the system would allow you to build pressure in the system, holding at 3,000 psi across the system before the back pressure regulator goes into dynamic operation, allowing excess pressure to pass downstream but holding that 3,000 psi upstream.

Regulator assemblies

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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We have regulators to fit almost any situation: back-pressure dome-loaded; back-pressure spring-loaded; pressure-reducing dome-loaded; pressure-reducing spring-loaded; high purity; sanitary; and tank-blanketing regulators.

Get all Swagelok regulators literature plus the Swagelok Pressure-Reducing Regulator Flow Curves Technical Bulletin.