How Your Regulator Balances Four Different Forces

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This article and accompanying video are an excerpt from the Swagelok® Regulator Selection & Optimization Webinar presented by Swagelok Field Engineer Supervisor Jon Kestner.

There are four forces that we care about within a pressure regulator. They are:

1. Loading force. When we compress the spring or allow that spring to relax, that loading force is going to change.

2. Inlet spring force. Almost every regulator will have some sort of spring that keeps the poppet pushed against the seat if there's low or no inlet pressure to help do that. That spring is extremely light, but it is something we should consider.

3. Outlet pressure force. That's the force created by the outlet pressure acting on the underside of that sensing mechanism.

4. Inlet pressure force. While the area is smaller on the poppet, there is some force that's created by that inlet pressure.

Balancing the Forces

You could probably tell what the equation might look like just based on the arrows in the diagram above, but the F1 (loading force) has to balance out against F2 (inlet spring force), F3 (outlet pressure force), and F4 (inlet pressure force). The regulator is going to constantly self-adjust to maintain that balance as best it can.

If we turn the handle clockwise, we're compressing that spring. The F1 (loading force) goes up because we've compressed the spring and increased the force. The only other thing we assume is that our inlet pressure or inlet source is large enough that it's not going to change by any appreciable amount. In that case, F4 (inlet pressure force) is the same. The only thing that can change too much within the regulator is F3 (outlet pressure force). F3 (outlet pressure force) has to also rise by some proportional amount.

That's how regulators work. When any of the inputs change the balance of forces, the regulator works to equalize itself.

To learn more about regulators, watch the Swagelok Regulator Selection & Optimization Webinar, visit our Swagelok regulators product page, or contact us at 412.761.3212.