Safety valve selection for the hottest industrial

2022-07-31
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Type selection of safety valves for industrial boilers

at present, there are many kinds of boiler safety valves commonly used in industrial boiler houses in China: lever type, spring type, dead weight type, pulse type and composite type

I. lever type boiler safety valve

lever type safety valve is divided into single lever type and double lever type. Because they act on the valve core through the heavy torque of lever and heavy hammer, they are also called heavy hammer safety valve to balance the steam (water) pressure

lever type (heavy hammer type) safety valve is mainly composed of valve core, valve seat, lever, heavy hammer, limit device, etc. It uses the weight of the heavy hammer to press the valve core on the valve seat through the lever, and moves the position of the heavy hammer to change the size of the heavy torque, so as to adjust the opening pressure of the safety valve. When the boiler pressure exceeds the pressure exerted by the heavy hammer on the upper part of the valve core, the valve core is jacked up and left the valve seat, and the steam is discharged. When the boiler pressure is lower than the pressure exerted by the heavy hammer on the upper part of the valve core, the valve core drops and the boiler stops steam exhaust

this safety valve has simple structure, convenient adjustment and reliable working performance, so it is widely used in boilers. General horizontal bar safety valves are applicable to low-pressure boilers, and parallel bar safety valves are applicable to medium and high-pressure boilers

II. Spring type boiler safety valve

spring type safety valve is mainly composed of valve core, valve seat, valve rod, spring, adjusting screw, etc. The safety valve mainly uses the spring force to press the valve core on the valve seat. When the boiler pressure exceeds the pressure acting on the upper part of the valve core by the spring, the valve core and valve rod are jacked up and the steam is discharged; When the boiler pressure is lower than the pressure applied by the spring on the upper part of the valve core, the valve core drops and presses on the valve seat, and the boiler stops steam exhaust. Different combinations of force measuring and force adding methods for connecting the valve core and valve seat result in different styles of horizontal tensile testing machine. The contact surface is conical, and there is a little protruding around the edge of the valve core. When the steam pushes open the valve core, the edge of the valve core is also affected by the steam pressure, which suddenly increases the entire action area, and the safety valve immediately opens; When the pressure drop is reduced, the steam force is suddenly reduced, so that the valve core is closed at one time to prevent the valve core from jumping repeatedly

the main parameters of spring safety valve are opening pressure and steam exhaust capacity, which depends on the diameter of valve seat and the lifting height of valve core. Due to the different lifting height, it can be divided into three types: Micro open, medium open and full open safety valves

the spring-loaded safety valve has a compact structure, and the volume coating contains a large amount of VOC (volatile organic compounds), which is small and portable; It has good tightness, convenient adjustment, can withstand vibration, and rarely leaks. Therefore, it is sensitive and reliable. It is the most widely used one

III. dead weight boiler safety valve

it is composed of valve core, valve seat, annular iron plate, valve cover, anti flying screw, etc

this kind of safety valve mainly uses the weight of the annular iron plate to make the valve core press on the valve seat. When the boiler pressure exceeds the pressure of the iron plate acting on the upper part of the valve core, the valve core is jacked up and the steam is discharged: when the boiler pressure drops below the pressure of the iron plate acting on the upper part of the valve core, the valve core drops and the steam is stopped

the dead weight safety valve is simple in structure and easy to manufacture, but it is bulky and bulky, difficult to adjust and low in sensitivity. It is only suitable for low-pressure small boilers. "However, the specific provisions of this' Document No. 46 'are problematic. At present, it is rarely used in industrial boilers in China.

IV. the pulse type boiler safety valve is mainly composed of pulse spring safety valve and impulse tube main safety valve. The working principle of the pulse type safety valve is: when the pressure of the steam drum or superheater exceeds the specified value for aligning with a level ruler, the steam enters the pulse spring safety valve through the impulse tube and valve, and When the valve core is pushed open, the steam flows into the upper part of the main safety valve piston through the pulse spring safety valve, so that the piston moves downward and the main safety valve is opened, so that the steam is discharged and relieved. When the pressure returns to the normal pressure, the pulse spring safety valve is closed, so that the steam on the upper part of the main safety valve piston is interrupted, and the valve core of the main safety valve is closed under the action of steam and spring

this safety valve device has an electrical control system as electrical protection. When the boiler is overpressured, the contact of the pneumatic pressure gauge is closed, and the electromagnet of the pulse spring safety valve is connected to make it work and open the valve; When the reseating pressure is too low or the valve fails, the electrical control switch can also be operated to turn on the electromagnet coil and turn off the electromagnet to close the valve

the impulse of this safety valve during operation is connected to the valve on the conduit, which should be kept fully open, so lead sealing should be added. This safety valve is applicable to high-pressure boilers

v. composite boiler safety valve

composite safety valve is composed of two identical or different safety valves, which are connected to one valve seat at the same time to reduce the number of openings

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