Regulator Pressure Adjustment Screws

“I’ve read that we should always back-off the pressure adjusting screw on our oxy-fuel pressure regulators after use, and I was wondering why this is important.”

A pressure reducing regulator is a critical device that is designed to reduce the high cylinder pressure to a working pressure suitable for safe use and regulate the flow of gas to the torch.  For oxy-fuel operations the regulator will have a gauge that shows the cylinder (inlet) pressure, and a working pressure (outlet) gauge with a pressure adjustment screw.

The two common types of regulators used in our industry are the single-stage and the two- or double-stage type, with the single stage being less expensive (and subsequently more common) and the double-stage regulators offering better control of the outlet pressure.  The single-stage regulators drop the high cylinder pressure directly to the working pressure; the two-stage regulators have high, intermediate, and low internal pressure sections.  The basic components of these regulators are illustrated below.

When using pressure-reducing regulators with an outlet pressure adjustment screw, after the gas cylinder has been closed, the user must then release (bleed) the residual pressure from the regulator and the lines by opening the torch valves.  Following this step, the pressure adjustment screw must be turned counterclockwise (outward) to remove the loading on the internal load spring and diaphragm.  The screw (or dial) should then be gently retightened (clockwise) until it has a slight resistance to hold it in-place.

When the load spring is continually compressed by tightly engaging the pressure-adjusting screw the non-metallic diaphragm is pushed inward and the poppet valve is left in an open position, as shown in the lower illustration of the single-stage regulator.  When the high-pressure cylinder is opened for the next use, there will be a shock inrush of pressure which can damage the regulator, and in extreme cases can even cause the bonnet to fail and blow-outwards.  This is the reason that when opening the gas cylinder, the operator should always first double-check to ensure that the pressure adjusting screw is released, open the cylinder valve slowly, stand to the side of the gauge faces, and make sure that other personnel are also in a safe position.