How Pressure Regulators work…

Why is it important to regulate Pressure in a Piping System?

Pressure is one of the most important aspects of ANY piping system. If pressure is too low, for example, the system is powerless. And if it is too high…

Just as high blood pressure damages the vital organs in your “piping system,”

overpressure affects filters, tools, sprayheads, instruments…any vital tool in a liquid piping system.

Purpose of a Pressure Regulator…Imagine having an employee who continuously monitors a single pressure gauge, and constantly tweaks a valve as downstream pressure rises or falls past a pre-determined point.

A Pressure Regulator Works Automatically

…and it won’t get carpal-tunnel. It simply reacts to changes in pressure.

Uses of a Pressure Regulator:

1. As a control element, to ensure that downstream pressure does not exceed a set point.

2. As a safety device, to protect equipment from harmful overpressure.

3. Regulate to the correct pressure range so that a flow system or piece of equipment can operate safely and effectively.

Remember this simple definition:

• A pressure regulator is a normally-open valve that takes a high inlet pressure and converts it to

a lower, pre-set downstream pressure.

A Set Screw

is used to set the desired pressure. It does this by controlling the force of non-wetted steel springs

The springs are attached to, and the force of the springs presses down, the main shaft

The valve seat

is part of the main shaft, and thus is held “open” by the force of the springs.

How it Works continues…

How it Works…

INLET OUTLET

While the spring is holding the valve open and liquid is flowing through, a small tube near the valve outlet – called the “sensing orifice” – transmits downstream pressure into a chamber.

Because pressure is equal in all directions, the pressure in the chamber is identical to downstream pressure.

SENSINGORIFICE

PRESSURECHAMBER

SENSINGORIFICE

PRESSURECHAMBER

VALVE OUTLET

ROLLING DIAPHRAGM

The key to this pressure chamber is a large Rolling Diaphragm. It rolls upward as pressure increases, and back down as pressure decreases…

In other words, it moves up and down in direct response to changes in downstream pressure.

SENSINGORIFICE

PRESSURECHAMBER

VALVE OUTLET

ROLLING DIAPHRAGM

The Rolling Diaphragm is attached to the Main Shaft that we mentioned earlier – which as you recall, is held down by spring force, which in turn holds the valve open.

SPRINGFORCE

M AIN SHAFT

VALVE IS HELD OPEN

But when pressure at the outlet increases…

…as downstream pressure increases, the force on the rolling diaphragm increases, in direct opposition to the spring force...

When downstream pressure exceeds the spring force, the rolling diaphragm overpowers the springs.

This compresses the springs and forces up the main shaft...

The valve seat, as part of the main shaft, closes against the main internal orifice, preventing additional pressure downstream.

It will remain closed as long as downstream pressure exceeds the set point, as determined by the set screw controlling the force on the springs.

When downstream pressure falls below the set point, the valve begins to re-open as the springs again force the main shaft down. Flow resumes.

.

Although accurate, the preceding explanation is overly simplified. In most applications, a properly set pressure regulator quickly finds a “balance” – as long as inlet pressure is higher and relatively constant, and downstream conditions are stable. The valve stays partially open, with the force of the downstream pressure against the rolling diaphragm and the force of the internal springs in a state of equilibrium.

As events occur downstream…

When a faucet is closed downstream, pressure will build in the downstream pipeline – and at the outlet of the regulator. If the closed faucet causes downstream pressure to build to the set point, the regulator will close until the pressure drops.

When the faucet is re-opened, pressure will drop in the downstream pipeline – and at the outlet of the regulator. The spring will force the regulator open, and pressure will seek the desired level downstream. Actual downstream pressure will depend on many variables, including flow rate, inlet pressure, and other factors.

Similarly…

What a Pressure Regulator WON’T Do:

(common misconceptions)

1. It can’t convert a low inlet pressure to a higher downstream pressure – it won’t function like a pump.

2. It won’t control backpressure.

Advantages of Plast-O-Matic Pressure Regulators…

• Most pressure regulators impede flow while sensing pressure. The sensing orifice and pressure sensing chamber in a Plast-O-Matic regulator are not in the flow path – flow is unrestricted and much higher than competitive designs.

• Large sensing area of the rolling diaphragm provides smoother, more accurate control.

Advantages, continued…• U-cups used in place of o-rings provide smooth, non-sticking movement of the main shaft.

• Greater accuracy & repeatability achieved via springs matched to the pressure range of the application.

• Overall design – large flowpath, large sensing area, more sensitive springs – all combine to provide the best performing pressure regulators since 1967.

• No wetted metals. All-plastic wetted designs are essential for corrosive and ultra-pure applications.

End of part I…stay tuned for sizing and selecting regulators!