10 Operating types

All regulators maintain a pre-determined outlet pressure to control the quantity of gas flow. They are pressure operated, and no other power source is required for their operation. All regulators are one of these two operating types:

• Direct-operated
• Pilot operated

Direct-operated regulators

Direct-operated regulators, also known as self-operated regulators, are the simplest type of pressure regulator and are the most common. Direct-operated regulators are a self-contained valve and actuator combination (Figure 19). They use the actual downstream pressure directly in the actuator to position the valve accordingly and match the gas demand.

Figure 19 Direct operated regulator

In operation, a direct-operated, pressure regulator senses the downstream pressure through either internal port or an external control line. This downstream pressure opposes a spring which moves the diaphragm and valve plug to change the size of the flow path through the regulator.

Pilot-operated regulators

Pilot-operated regulators are used for high flow rates or where precise pressure control is required. A pilot-operated regulator can be simplified by viewing it as two independent regulators connected together (Figure 20). The smaller of the two is generally the pilot. The pilot is a pressure amplifier as it senses to downstream pressure to then create the necessary loading pressure to the main regulator diaphragm. This improves the overall sensitivity and accuracy of the regulator.

Figure 20 Pilot-operated regulator

As these regulators are primarily used on larger commercial, institutional and industrial applications they are covered in greater detail in the Class “A” training.