Pressure Regulator and Relief Valve Sizing Flashcards
What is Setpoint in terms of pressure regulators?
the desired outlet pressure
What is Droop in terms of pressure regulators?
deviation from the setpoint at a given flow, Droop curves indicate the useful regulating capacity
What is capacity in terms of pressure regulators?
flow rate, which is a function of droop
What is Lockup in terms of pressure regulators?
pressure above the setpoint that is required to stop flow
How does a pressure regulator work?
operates by controlling a valve with a spring, weight or pressure force which is opposed by the outlet pressure over a piston or diaphragm area.
What are pressure relief valves?
a device actuated by static inlet pressure and designed to open to prevent a rise of internal pressure in excess of a specified value.
What is accumulation in terms of Pressure Relief Valves?
The pressure increase over the MAWP of the vessel during discharge through a pressure relief device
What is back pressure in terms of Pressure Relief Valves?
The pressure that exists at the outlet of a pressure relief device as a result of pressure in the discharge system.
What is Curtain Area in terms of Pressure Relief Valves?
The area of the cylinder or conical discharge opening between the seating surfaces … created by lift of the disc.
What is huddling chamber in terms of pressure relief valves?
An annular pressure chamber located beyond the seat for the purpose of generating rapid opening
What is lift in terms of pressure relief valves?
Travel of the disc away from the closed position when a valve is relieving
How do you determine the volumetric flow rate of a gas for a relief valve?
The volumetric flow rate of a gas is inversely proportional to the square root of the specific gravity and absolute temperature. The stated capacity in air can be corrected for other gases or temperatures by multiplying the capacity by the correction factor relative to air
State some relief valve inlet criteria.
Inlet piping should not be smaller than the relief valve inlet fitting size. Long inlet systems need to be sized and analyzed to keep the pressure drop below 3% of set pressure when flowing at stamped capacity
State some relief valve outlet criteria.
Vent system should not be smaller than the relief valve outlet fitting size. Long vent systems need to be analyzed to ensure back pressure doesn’t exceed 10% of set pressure when flowing at stamped capacity. A vent system from more than one PSV should be considered for effects of one PSV on another.
