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Safety Valve Knowledge
- Mar 07, 2018 -

Safety valves are devices, devices, and pipelines that are used as security devices to prevent pressure exceeding the specified value in the medium of equipment, devices, and piping. When the working pressure in the equipment, devices and piping exceeds the specified value, the relief valve is automatically opened, the excess media is discharged, and when the pressure returns to normal, the relief valve shuts itself down and prevents the media from continuing to drain from the device.

Since the safety valve is an automatic valve, there are many differences in structure and performance parameters with general purpose valves, and some special terminology is easy to confuse. In order to make the majority of readers more clearly understand the safety valve, and the correct selection of the following will be some of the main terminology to explain.

1. Safety Valve Terminology

1) Relief valve: An automatic valve, it does not use any external force, but use the force of the medium itself to discharge a rated amount of fluid, to prevent the system pressure exceeding the predetermined safety value, when the pressure back to normal, the valve again closed and prevent the media continue to flow out.

2) Direct Load type safety valve: A direct use of mechanical load such as heavy hammer, lever heavier hammer or spring to overcome by the disc under the pressure of the media force caused by the relief valve.

3 Driving force auxiliary device's safety valve: the safety valve by means of a powerauxiliary device, can be opened under normal opening pressure, even if the auxiliary device fails, such valves should still be able to meet the standard requirements

4. Safety valve with supplemental load: This safety valve maintains an additional force of an enhanced seal before pressure reaches the opening pressure at its inlet. This additional force (supplemental load) can be provided by external energy sources and should be released reliably when the safety valve reaches the opening pressure. The size should be set, that is, assuming that the additional force is not released, the safety valve can still be imported pressure does not exceed the state regulation of the opening pressure percentage of the premise to achieve the rated discharge.

5 Pilot type safety valve: a safety valve which relies on the discharge of media from the guide valve to drive or control. The guide valve itself shall be a direct load type safety valve which meets the standard requirements.

6 opening pressure (pressure): relief valve Disc under the operating conditions of the beginning of the rise of the import pressure, under the pressure, began to have a measurable opening height, the media can be visual or auditory perception of the continuous discharge state.

7 Discharge pressure: the valve to meet the requirements of the opening height of the import pressure. The ceiling of the discharge pressure shall be subject to the requirements of the relevant national standards or norms.

8) Exceeding the pressure: the difference between the discharge pressure and the opening pressure, usually expressed as a percentage of the open pressure.

9 Back seat pressure: After the release of valve flap contact with the seat, that is, open height into zero import pressure.

10 opening and closing pressure difference: open pressure and back seat pressure difference, usually with the open pressure of the percentage, only when the opening pressure is very low only with MPA "said."

11 Back pressure: relief valve outlet pressure.

12 Rated discharge pressure: The CAP value of the standard prescribed discharge pressure.

13 Seal test pressure: the inlet pressure of the seal test, the leakage rate of the sealing surface of the closed part is measured under the pressure.

14 Open Height: The actual lift of the disc leaving the closed position.

15 Flow Path Area: Refers to the valve inlet end to the closed part of the sealing surface of the Flow channel | In the minimum sectional area, used to calculate the theoretical displacement without any resistance effect.

16 runner Diameter: corresponding to the diameter of the runner area.

17 Curtain Area: The area of a cylindrical or conical channel formed between its sealing surfaces when the disc rises above the seat

18 Emission area: valve discharge when the minimum section area of the fluid channel for the QUANQI type safety valve, the discharge area is equal to the flow path area; for the micro-opening safety valve, the discharge area is equal to the curtain area.

19 Theoretical Displacement: the calculated displacement of the ideal nozzle with the same flow section area as the relief valve flow path area.

20 displacement coefficient: the ratio of actual displacement to theoretical displacement

21 rated displacement coefficient: the product of displacement coefficient and reduction coefficient (take 0.9).

22 Rated Displacement: The actual displacement is allowed as a safety valve to use the basis of the part.

23 equivalent calculation of displacement: the pressure, temperature, the nature of the medium and other conditions and the applicable conditions of the rated displacement, the calculation of the discharge valve.

24 Frequency Jump: The relief valve flap moves back and forth rapidly and abnormally, in motion the valve seat is contacted.

25 Flutter: The relief valve flap moves back and forth quickly and abnormally, and the disc does not contact the valve seat in motion.