What is the restricting element on a direct-operated regulator?

What is the restricting element on a direct-operated regulator?

• A. Piston
• B. Valve, disk or plug
• C. Spring
• D. Diaphragm

Answer: (B)

In a direct-operated regulator, the part that actually throttles the gas is the valve assembly—the disk or plug seating against its valve seat. This is the restricting element that controls flow to maintain the desired downstream pressure. The diaphragm or piston acts as the sensing/actuating member, translating pressure differences into movement to open or close the valve, while the spring provides the reference force that sets the regulator’s setpoint. The valve’s position directly changes how much flow is allowed, making it the restricting element, whereas the diaphragm, piston, and spring set and transmit the force but do not themselves restrict the flow.

In a direct-operated regulator, the part that actually throttles the gas is the valve assembly—the disk or plug seating against its valve seat. This is the restricting element that controls flow to maintain the desired downstream pressure. The diaphragm or piston acts as the sensing/actuating member, translating pressure differences into movement to open or close the valve, while the spring provides the reference force that sets the regulator’s setpoint. The valve’s position directly changes how much flow is allowed, making it the restricting element, whereas the diaphragm, piston, and spring set and transmit the force but do not themselves restrict the flow.