At present, there are many boiler safety valves used in industrial boiler room in our country: lever boiler safety valve, spring type boiler safety valve, static heavy boiler safety valve, pulse boiler safety valve and composite boiler safety valve. Here we introduce several kinds of boiler safety valve.
First, the classification of boiler safety valve
1, lever boiler safety valve
Lever type safety valve is divided into single lever and double lever two. They are also known as heavy hammer safety valves because they balance the pressure of the steam (water) by acting on the spool through the moment of leverage and weight.
Lever (hammer type) safety valve mainly by the valve core, seat, lever, hammer, limit devices and other components. It is the weight of the hammer, through the lever to the spool on the valve seat, move the weight of the position to change the size of the weight moment to adjust the relief valve opening pressure. When the boiler pressure exceeds the pressure at the top of the spool, the spool is lifted off the seat and the steam is vented. When the boiler pressure is lower than the pressure at which the hammer acts on the upper part of the valve plug, the valve spool falls and the boiler stops exhausting. This safety valve structure is simple, easy to adjust, reliable performance, so the boiler is quite common. General single lever safety valve for low pressure boilers, double lever safety valve for medium and high pressure boilers.
2, spring-type boiler safety valve
Spring-loaded safety valve is mainly composed of valve core, valve seat, valve stem, spring, adjusting screw and so on. This safety valve is mainly the use of spring force, the spool pressure on the seat. When the boiler pressure exceeds the spring pressure in the upper part of the valve core, the valve core and the valve stem are jacked up and the steam is discharged. When the pressure of the boiler is lower than the pressure of the spring acting on the upper part of the valve core, The boiler stopped exhausting. Spool valve seat and the contact surface of the cone, the spool around the edge of a little out. When the steam valve top open, the valve core edge is also affected by the steam pressure, so that the entire role of a sudden increase in area, safety valve suddenly open; when the reduction of force, due to a sudden decrease in steam force, so that a closed spool, Prevent the valve core from beating repeatedly.
The main parameters of the spring-loaded safety valve is the opening pressure and exhaust capacity, while the exhaust capacity depends on the caliber of the valve seat and the lifting height of the valve core. Due to the different height of lift, it can be divided into three types of micro-Kai type, medium type and full type safety valve. Spring-loaded safety valve has the advantages of compact structure, small size and light weight. The tightness is good, the adjustment is convenient, the vibration can be tolerated, and there are few leaks. Therefore, sensitive and reliable. It is the most widely used, is the most commonly used one.
3, static heavy boiler safety valve
Static heavy boiler safety valve is the valve core, seat, ring iron, valve cover, anti-fly screws and other components.
This safety valve is mainly the use of annular iron weight, so that the valve core pressure on the valve seat, when the boiler pressure exceeds the pressure on the role of iron in the valve core, the valve is jack, steam discharge: boiler pressure dropped to low In the role of iron in the upper spool pressure, the spool landing, stop the exhaust. The static heavy-duty safety valve has the advantages of simple structure, easy manufacture, bulky bulkiness, difficult adjustment and low sensitivity, which is only applicable to low-pressure small boilers. At present, China's industrial boilers rarely used.
4, pulse boiler safety valve
Pulsed boiler safety valve mainly by the pulse spring safety valve, impulse catheter main safety valve and other components. Pulse relief valve works: When the drum or superheater pressure exceeds the specified value, the steam through the impulse conduit, the valve into the pulse spring safety valve, the valve top open, the pulse spring safety valve, the steam entered The upper part of the main safety valve piston, the piston moves down, open the main safety valve, the steam discharge pressure relief. When the pressure is restored to normal pressure, the pulse spring safety valve is closed and the steam in the upper part of the main relief valve piston is interrupted. The main relief valve spool is closed by the action of steam and spring.
This safety valve device has an electrical control system as electrical protection. When the boiler overpressure, then, gas pressure gauge contacts closed, connected to the pulse spring safety valve solenoid, so that work, the valve open; when the pressure is too low back seat or the valve fails, you can also operate the electrical control Switch, turn on the solenoid coil, turn off the solenoid, the valve closed. This safety valve in operation impulse access catheter on the valve, to maintain the fully open state, which should be sealed. This safety valve is suitable for high pressure boilers.
5, composite boiler safety valve
Composite safety valve consists of two identical or different safety valve integrated at the same time connected to a valve seat to reduce the number of openings.
In the selection of boiler safety valve, we must carefully compare the advantages and disadvantages of various types of boiler safety valve, reference to the relevant technical staff to choose the most suitable boiler safety valve.
Second, boiler safety valve selection
Safety valves are important safety accessories on boilers, pressure vessels and other pressurized equipment. The reliability and performance of its movement is directly related to the safety of equipment and people, and with energy conservation and environmental protection are closely related. And some users and design department in the selection, always choose the wrong model.
From the operating pressure to determine the nominal pressure of the safety valve, the operating temperature of the safety valve to determine the temperature range from the calculated value of the constant pressure relief valve spring or lever to determine the pressure range, and then decide on the use of safety valve material and Structure type, according to the relief valve discharge valve to calculate the throat diameter, summed up the following general safety valve selection rules:
(l) General use of hot water boilers are not closed with a micro-valve wrench safety valve;
(2) steam boiler or steam pipe is generally not enclosed with a wrench full open safety valve;
(3) water and other liquid incompressible medium commonly used closed micro-valve, or safety relief valve;
(4) high pressure water supply is generally closed full Kai safety valve, such as high pressure water heaters, heat exchangers;
(5) compressible gas and other gases generally use closed-type safety valve, such as gas tanks, gas pipelines;
(6) Class E steam boilers are generally used static heavy safety valve;
(7) large-caliber, large displacement and high pressure systems generally use pulse safety valve, such as temperature and pressure relief devices, power station boilers;
(8) General purpose built-in safety valves for tank trucks, tank trucks and storage tanks for transporting liquefied gas;
(9) The top of the tank with hydraulic safety valve, need to cooperate with the breathing valve;
(10) Downhole drainage or gas pipelines generally use pilot-operated safety valves;
(11) LPG tank pump outlet of the liquid return pipe with a general safety valve;
(12) Negative pressure or negative pressure may be generated during operation of the system generally with vacuum safety valve;
(13) Bellows safety valves are generally used for container or piping systems with large back pressure fluctuations and toxic flammability;
(14) medium freezing point lower system generally use insulation jacket safety valve.
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