Reducing Air Pressure

The air pressures needed for applications in different areas of the plant are often less than the pressure available from the main compressed air supply. To reduce the pressure in these areas, a pressure regulator valve is used. The pressure regulator valve controls the pressure downstream from its outlet. It is designed to maintain a constant downstream pressure. You find that regulators are located at almost every station in a manufacturing plant to allow each station to operate at the exact pressure needed for each application.

This is the pressure regulator that we will use on our trainers. If you remember from when we talked about filters, some air preparation units are combined to form FR units (Filter Regulator Units). The top of the unit, which is circled in yellow in the picture below, is where we control the pressure going to the system.

Parker Hannifin Corporation. (1980). Industrial Pneumatic Technology. Parker Hannifin Corp. DOI: 1557690154

The pressure regulator consists of a body, poppet, springs, piston, and a means of adjustment. The poppet opens and closes to provide the correct pressure downstream (at the outlet) by restricting the air flow. There are two springs: one for the adjustment and the other to make the poppet close. The adjustment knob changes the compression on the spring, which controls the level of downstream pressure. The piston is attached to one end of the poppet to provide a surface for the spring to push on.

To understand how this works, here's what happens: when air is allowed to flow through the downstream line, the pressure on the outlet side of the regulator drops slightly. Since there is now less air pressure on the piston, the adjustment spring pushes it down, opening the poppet. This allows air to flow from the inlet side. The poppet will continue to open wider to allow the air flow to increase until the pressure at the outlet reaches the regulator's pressure setting. At this point, the poppet is open part way. As air flows through the line, the poppet will adjust the amount of its opening to provide a balance between air pressure and air flow.

Parker Hannifin Corporation. (1980). Industrial Pneumatic Technology. Parker Hannifin Corp. DOI: 1557690154

A pressure regulator allows a facility to have a common supply of air. This common supply of air is referred to as shop air or plant air. Shop air or plant air is what the compressor is set at (typically not any higher than 150 psi). Once the shop air gets to the various machines, a pressure regulator at that machine allows the air pressure to be set by restricting the flow. This allows the needed air pressure to overcome whatever opposing force is needed in order to do the work at that particular machine.

Quiz Preparation

Study the following diagram. You will need to know the parts in order to answer the following quiz.

Parker Hannifin Corporation. (1980). Industrial Pneumatic Technology. Parker Hannifin Corp. DOI: 1557690154

The following is the schematic symbol for a pressure regulator:

Parker Hannifin Corporation. (1980). Industrial Pneumatic Technology. Parker Hannifin Corp. DOI: 1557690154

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