Safety valve professional terminology Analysis
back pressure
The back pressure is due to the discharge system after safety valve has pressure and is the pressure exists in the valve outlet, back pressure can be fixed or changeable. The back pressure is the sum of additional back-pressure and accumulation back pressure.
Additional back pressure: When the valve is not started, due to other valve emissions that exists in the safety valve outlet static pressure, it may be fixed or changeable.
Accumulation back pressure: When the valve opens, the increased pressure in the main pipe due to emissions.
opening height
it is the actual lift height of disc leaves the closed position.
flow channel area
It is the minimum cross-sectional area of flow channel from the disc inlet end to closed part sealing surface, it is used to calculate the theoretical displacement with no impact of resistance.
flow channel diameter
It means the diameter used in the flow channel area.
curtain area
It means when the disc above the seat, the cylindrical-shaped or cone-shaped channel surface area which formed between its sealing surface.
discharge area
It means the minimum cross-sectional area of flow channel when the valve discharges. To the fall lift safety valve, discharge area is equal to flow channel area; to the low lift safety valve, discharge area is equal to curtain areas.
theoretical displacement
It is the calculated displacement of flow channel cross-sectional area and the safety valve flow channel area equal ideal nozzle.
discharge coefficient
It refers to the ratio of actual emissions and theoretical displacement.
rated discharge coefficient
The product of dischage coefficient and reduction coefficient ( take 0.9).
rated displacement
It refers to the part that is permitted to use as a safety valve applicable benchmark in the actual diplacement
equivalent calculated displacement
It refers to the safety valve calculated displacement when pressure, temperature, media properties and other conditions are the same to the rated displacement applicable conditions.
Frequency jump
It means the disc rapidly back and forth movement, and contacts the seat when moving.
shimmy
It means the disc rapidly back and forth movement, and not contact the seat when moving.
