Pressure relief valve is by opening and closing of throttling and adjustment, the medium pressure is reduced, and through the direct effect of medium pressure after the valve, make the valve after pressure automatically to meet the requirements of the book.
The relief valve is also a kind of automatic valve door, in institutions and the performance parameters of the common valve door have many differences, the name of some professional terms, is easy to confuse.
In order to make readers more clear understanding of the pressure relief valve, and can choose correctly, will now be the main terms and pressure relief valve.
The name of the relief valve term 1.
Direct acting pressure relief valve: using the outlet pressure change, direct control of the valve disc movement and pressure relief valve.
Pilot operated relief valve: is composed of main valve and pilot valve, main valve outlet pressure changes by magnifying control action and pressure relief valve.
Diaphragm pressure relief valve, the diaphragm as sensitive element to drive the valve disc decompression valve 4 of the movement.
Piston type pressure relief valve, piston as sensitive element is used to drive the valve disc movement of the relief valve.
Bellows type pressure relief valve, corrugated pipe as sensitive element is used to drive the valve disc movement of the relief valve.
Static seal: export flow is zero, and pressure relief valve sealing state.
Dynamic seal: export medium by the cutoff, and pressure relief valve sealing state.
Regulating characteristics: inlet pressure must be, continuous adjusting export pressure, pressure relief valves, resistance and vibration phenomenon.
Features: pressure steady flow state, the outlet flow must, inlet pressure changes, a function of the pressure of export and import.
Flow feature: the steady flow state, the inlet pressure is constant, a function of pressure and flow of export.
Maximum flow: under a given outlet pressure, its deviation can achieve the maximum flow within the specified scope.
Pressure characteristic deviation: export flow must, inlet pressure, outlet pressure changes in value.
Usually after decompression valve valve pressure Pc should be less than 1/2 before the valve, the Pe and pressure relief valve are more widely application scope, in the industrial steam, compressed air, gas or water, by many other liquid medium and xiao equipment and can be used on the pipeline.
Medium flow path and pressure relief valve exit quantity, mass flow rate is commonly used in qm (
Or volume flow qv (
There are many kinds of the types of the relief valve and pressure relief valve, but can be roughly divided into direct acting (
And indirectly (
Two kinds big.
Direct acting pressure relief valve, it is using the energy of the medium itself to control the pressure required.
Indirect role type pressure relief valve, the use of external power, such as pneumatic, hydraulic or electric to control the pressure required.
Compared the two kinds, the former mechanism is simple, the precision is higher.
At present, the mass production and use are direct acting pressure relief valve.
According to the pressure relief valve group also can be divided into: 1.
Piston type pressure relief valve: it is through the piston to balance the pressure, to drive the valve disc.
As shown in figure 2 -
As shown in 106.
This kind of pressure relief valve is small in size, allowed by the piston stroke is bigger, but because of the piston in the cylinder friction is bigger, so the sensitivity is lower than diaphragm pressure relief valve.
In addition, the strict manufacturing processes, especially the piston, piston ring and cylinder block, the deputy valve and other parts, because of the use on the steam pressure relief valve, the expansion of the heated clearance is not easy to control these parts, are prone to get stuck or steam leakage phenomenon, more affect its sensitivity.
Nevertheless, this kind of institution and pressure relief valve is widely used, especially when the medium temperature is higher, diaphragm pressure relief valves due to the heat resistance of the film material is difficult to solve, is still a lot of choose piston type pressure relief valve;
For a medium such as water, air, also can choose.
Diaphragm pressure relief valve: film as sensitive element is used to drive the valve disc movement and pressure relief valve, as shown in figure 2
As shown in 107.
The sensitivity of the diaphragm pressure relief valve is higher, because it has no piston friction force.
Compared with piston type pressure relief valves, film trip is small, and easy to damage;
General film made of rubber, so using temperature is limited.
When using a high temperature and pressure, the film will need to use copper or stainless steel.
So, the diaphragm in the water, air temperature and pressure relief valve is not high under the conditions of use for the common.