"When we talk about matching a pressure regulator to the job, one of the primary tools is the flow curve"
- From Flow Control: Don't let pressure regulators throw you a curve
The most useful tool in selecting a pressure regulator is a flow curve. That's a simple graph that shows you how much pressure that a specific model of regulator can maintain at various flow rates. The vertical axis shows the amount of pressure on the downstream side of the regulator. The horizontal axis shows the flow rate. You'll get a different curve for each set pressure. (We have a technical bulletin devoted to the subject if you want to dive deeper.)
What you're looking for is the regulator with the flattest flow curve for your conditions, meaning that the pressure won't change much when the flow rate changes.
But a page full of flow curves can be daunting. It's a lot of lines to keep track of. Comparing a curve on one graph with a similar curve on another graph can get tricky.
Now Swagelok has an online tool that simplifies the process: The Swagelok Regulator Flow Curve Generator. This tool will give you a unique flow curve based on a set of user-specified application parameters for three dozen RHPS series regulators. That's a series engineered for applications in the chemical/petrochemical, oil and gas, power, biopharmaceutical, semiconductor, and alternative fuels industries.
All you have to do is fill in a series of boxes for parameters such as pressure and temperature and the type of gas you plan to run through the regulator. Some of the boxes feature dropdown menus, making it easy to click on factors such as the specific model of regulator you want to compare. It works for back-pressure regulators as well as pressure-regulating regulators.
Our online tool will even automatically fill in the outlet tube/piping ID and maximum line velocity, though you also can edit those fields. The tool also will fill in the molar mass and specific heat for your chosen gas type.
Then all you have to do is click the "calculate" button (and make sure your device allows pop-ups), and you'll get a custom-made graph. You'll see two pieces of information for each regulator chosen: a solid line for the flow curve itself, and a dotted line marking the point at which the downstream gas will exceed the specified velocity.
While the graph will not show you the lock-up pressure for a given application, remember that lock-up is factory tested to be not more than 10 percent of the maximum control pressure of a regulator configuration.
So click on the link and give the Regulator Flow Curve Generator a test drive. If you want some additional advice, we're here to help.
Come see pressure regulators in action in our Customer Briefing Center.
Swagelok Northern California has a great deal of exposure to all aspects of fluid system design and engineering. Whether you have a simple question or a complex challenge, we're glad to hear from you.
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