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The Fluid Systems Engineering and Management Blog

by Swagelok Northern California

Pressure Regulators Control Outlet Pressure Not Fluid Flow

by Jeff Hopkins, on 6/23/17 9:00 AM

How pressure reducing regulators maintain outlet pressure as inlet pressure and flow varies


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A pressure regulator is a fluid system component designed to control outlet pressure under a given set of inlet pressure and flow conditions. 


Two types of pressure regulators

There are two broad categories of pressure regulators: pressure reducing regulators and back pressure regulators. Two of our webinars focused on the more common of the two types: the pressure reducing regulator. A pressure reducing regulator maintains outlet pressure as inlet pressure and flow varies.

The primary reasons for regulating pressure is to provide accurate, consistent, and repeatable delivery pressures to processes and process equipment in order to reduce the likelihood of process variability and to protect sensitive equipment.

In order for processes and pressure sensitive equipment to work properly, high pressure process fluid must be reduced to an acceptable pressure before entering the point of use, this pressure reduction may be achieved through the use of one pressure regulator or through a series of pressure regulators. If pressure is not reduced and controlled, the process may shut down or sensitive equipment may be damaged.

Three main components

A typical regulator has an inlet where fluid enters the regulator, an outlet where fluid exits the regulator, and an orifice through which the flow of the fluid is directed. 

Regulator components are manufactured using a variety of designs. Although, there are many design options on the market, most pressure regulators contain three main components that perform similar functions regardless of design: the control element, the sensing element and sensing chamber, and the loading mechanism.

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Control

The first component to mention is the control element, often referred to as the main valve, valve stem, or poppet, it is used to control the outlet pressure of the fluid by moving into and out of the orifice.

When the poppet moves into the orifice, fluid flow is restricted and outlet pressure decreases, conversely, when the poppet moves out of the orifice, fluid flow and outlet pressure builds.

 

Most pressure regulators contain three main components that perform similar functions regardless of design

 

Sensing

The second component is composed of two parts, the sensing element and the sensing chamber.  

The sensing chamber is the area just below the sensing element. The sensing element responds to pressure changes in the sensing chamber.

The stem of the control element is in constant contact with the sensing element. The sensing element and control elements move together as pressure changes in the sensing chamber. 

Loading

The third component is the loading mechanism. The loading mechanism exerts force on the sensing element to counterbalance the pressure of the fluid inside the chamber.

The loading mechanism is set or adjusted to provide the desired outlet pressure of the regulator.

Summary

There are three key elements that allow a pressure reducing regulator to function.

  • The control element governs flow by moving into and out of the orifice.
  • The sensing element detects changes in outlet pressure.
  • The loading mechanism exerts force on the sensing element to counterbalance the pressure of the fluid inside the chamber.

It is important to remember that pressure regulators control only pressure, not fluid flow. Pressure regulators react to changes in fluid flow, but control only pressure. 

 

additional resources

 

Download our Pressure Regulator Selection & Sizing Guide

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Topics:Regulators

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