Brass safety valve is a special branch of the brass valve family. Its particularity is because the brass safety valve is different from other brass valves and only acts as a switch, and more importantly, it protects the safety of the equipment. .

The brass safety valve is in a normally closed state under the action of external force on the opening and closing parts. When the pressure of the medium in the equipment or pipeline rises beyond the specified value, it discharges the medium to the outside of the system to prevent the medium pressure in the pipeline or equipment from exceeding the specified value. Numerical special brass valve.

Brass safety valve is an automatic valve, mainly used in boilers, pressure vessels and pipelines, the control pressure does not exceed the specified value, and plays an important role in protecting personal safety and equipment operation. Brass safety valves must be pressure tested before they can be used. With the rapid development of global economic construction, there are more and more equipment projects with pressure control. In view of the need for equipment pressure relief, brass safety valves play a vital role in protecting equipment.

Brass safety valves are mainly used in: steam boilers, liquefied petroleum gas truck tankers or liquefied petroleum gas railway tankers, oil production wells, high pressure bypass of steam power generation equipment, pressure pipelines, pressure vessels, etc.

The diameter of brass safety valve is generally not large, and the commonly used ones are between DN15mm-DN80mm. If it exceeds 150mm, it is generally called large-diameter brass safety valve.

Brass safety valve is divided into full-opening brass safety valve and micro-opening brass safety valve. According to the overall structure and loading method of the brass safety valve, it can be divided into four types: static weight type, lever type, spring type and pilot type. According to the connection with the pipeline, it can be divided into threaded brass safety valve and flanged brass safety valve.

When the working temperature is high and the pressure is not too high, the lever type is more suitable; the high-pressure equipment should use the spring type; the spring type brass safety valve is commonly used.

As part of the commissioning of the entire equipment system, when the brass safety valve is first opened, the valve seat is often damaged due to the constant presence of dirt and debris in the system. In order to ensure that foreign impurities do not enter the brass safety valve, the entire system should be fully flushed before the brass safety valve is installed, and the brass safety valve should be installed in a place where dirt, rust and debris will not accumulate.

In steam applications, it is also important to reduce the leakage tendency through the installation of brass safety valves, which should be installed so that condensate does not collect upstream of the disc. This is done by installing a brass safety valve above the steam line as shown below.

When the brass safety valve is properly installed above the steam pipeline, the inlet pipe of the brass safety valve can function as self-draining.

The temperature brass safety valve should be installed with the top or side of the water heater, as shown below:

The correct flow of fluid in the brass safety valve is shown in the figure below

1) Install vertically upwards.

2) The installation location should be as close as possible to the protected equipment or pipeline.

3) Install in a place where it is easy to repair and adjust, and there is enough space around.

4) The brass safety valve of the pressure vessel is installed in the gas phase space above the liquid level of the container body, or can be installed on the pipeline whose connection point is located in the gas phase space of the pressure vessel.

5) For containers and equipment containing flammable, toxic and viscous media, a stop valve can be installed in front of the brass safety valve, but the flow area of the stop valve shall not be less than the minimum flow area of the brass safety valve, and lead shall be installed. to ensure that the globe valve is fully open and normally open.

6) The brass safety valve should be installed in the opposite direction to the globe valve to reduce the influence of the self-gravity of the brass valve and avoid stress fatigue and exhaust vibration fatigue.

7) For the brass safety valve that may be blocked or corroded by the material, a bursting disc is installed in front of its inlet, and a check valve is installed between the brass safety valve and the bursting disc, and back-purging, Anti-blocking measures such as heat tracing or insulation.

8) The brass safety valve installed on the pipeline should be installed in a place where the fluid pressure is relatively stable and there is a certain distance from the fluctuation source, and cannot be installed in the dead corner of the horizontal pipeline.

9) For the pipelines, heat exchangers or pressure vessels of liquid medium, when the brass valve is closed, thermal expansion may occur, causing the problem of high pressure, the brass safety valve can be installed horizontally to discharge the liquid directly downward.

10) For emergency air discharge, the nozzle should be flat, not sharp, and free of burrs to prevent electrostatic discharge.

11) The installation point of the brass safety valve should not allow the brass safety valve to withstand excessive back pressure, and should be within the specified allowable range.

12) The valve body of the brass safety valve should be supported smoothly.

13) For containers with extremely and highly hazardous or flammable and explosive media, the outlet of the brass safety valve should be led to a safe place and properly handled. If two or more brass safety valves share one discharge pipe, the cross-sectional area of the discharge pipe shall not be less than the sum of the cross-sectional areas of the outlet of all brass safety valves, except that oxygen or combustible gas and other two kinds of substances that can produce chemical reactions with each other are not allowed. Gases cannot share a single exhaust pipe.

(1) The newly installed brass safety valve should be accompanied by a product qualification certificate. Before installation, it should be recalibrated, sealed with lead and issued with a brass safety valve calibration.

(2) The brass safety valve should be installed vertically and installed at the gas-phase interface of the container or pipeline.

(3) The outlet of the brass safety valve should have no resistance to avoid back pressure. If a drain pipe is installed, its inner diameter should be larger than the outlet diameter of the brass safety valve. The discharge port of the brass safety valve should be protected from freezing. For containers with flammable or toxic or highly toxic media, the discharge pipe should be directly connected to an outdoor safe place or have facilities for proper disposal. No brass valves are allowed to be installed on the discharge pipe.

(4) No brass valve shall be installed between the pressure-bearing equipment and the brass safety valve. For containers containing flammable, explosive, toxic or viscous media, a stop valve can be installed to facilitate replacement and cleaning. Orifice size should not interfere with the proper operation of the brass safety valve. During normal operation, the globe valve must be fully opened and sealed with lead.

(5) For pressure vessels with flammable, explosive or toxic media, the media discharged from the brass safety valve must have safety devices and recovery systems. The installation of the lever type brass safety valve must be maintained in a vertical position, and the spring brass safety valve is also best installed vertically so as not to affect its action. During installation, attention should also be paid to the fit, the coaxiality of the parts and that each bolt should be evenly stressed. The cross-sectional area of the connecting short pipe between the brass safety valve and the boiler pressure vessel shall not be less than the flow cross-section of the brass safety valve. The entire brass safety valve is installed on a pipe at the same time, and the cross-sectional area of the pipe shall not be smaller than that of the brass safety valve. 1.25 times the sum of the flow cross-sectional areas.

(1) When there are gas and liquid two-phase materials in the container, the brass safety valve should be installed in the gas phase part.

(2) When the brass safety valve is used to discharge flammable liquid, the outlet of the brass safety valve should be connected to the accident storage tank. When the discharged material is high-temperature combustible, its receiving container shall have corresponding protective facilities.

(3) Generally, the brass safety valve can be vented on the spot, and the vent should be more than 1 meter (m) higher than the operator and should not be directed to the open flame location, sparking location and high temperature equipment within 15 meters (m). The vents of the brass safety valves of indoor equipment and containers should be led out of the roof and should be more than 2 meters (m) above the roof.

(4) When there is a block valve at the entrance of the brass safety valve, the block valve should be in a normally open state and be sealed with lead to avoid errors.

(5) The cross-sectional area of the through holes of the connecting pipes and fittings between the brass safety valve and the boiler or pressure vessel shall not be less than the inlet cross-sectional area of the brass safety valve; if several brass safety valves share an inlet pipe, The flow cross-sectional area of the inlet pipe shall not be less than the sum of the inlet cross-sectional areas of the brass safety valve.

(6) Generally, between the brass safety valve and the steam drum and header of the boiler, no brass shut-off valve, or a steam outlet pipe shall be installed. Generally, it is not suitable to install shut-off brass valves or other outlet pipes between the brass safety valve and the pressure vessel; for pressure vessels containing extremely high, high, moderate hazard, flammable, corrosive, viscous media or precious media , Only with the approval of the technical person in charge of the pressure vessel of the user unit and the formulation of reliable preventive measures, a stop valve can be installed between the brass safety valve and the pressure vessel. During normal operation of the pressure vessel, the shut-off valve must be kept fully open, sealed or locked. The structure and diameter of the globe valve shall not hinder the safe discharge of the brass safety valve.

(7) The spring-type brass safety valve with threaded connection should be connected with the short pipe with threads, and the short pipe should be connected by welding between the simplified pipe and the header.

(8) The brass safety valve must be equipped with a discharge pipe. The discharge pipe should avoid twists and turns as much as possible to minimize drag. The discharge pipe should go straight to the safe place and have enough cross-sectional area to ensure smooth exhaust. For brass safety valves that can interact and produce chemical reactions, a discharge pipe cannot be shared; when the brass safety valve is installed on equipment with corrosive and flammable gases, anti-corrosion or fire and explosion prevention measures should be taken when discharging; When there is a toxic medium in the equipment where the brass safety valve is installed, and the steam density of the medium is greater than that of air, the medium and steam discharged from the brass safety valve should be introduced into a closed system, and recovered from the closed system to production used in.

(9) The discharge pipe of the brass safety valve should be fixed to avoid excessive additional stress or vibration of the brass safety valve.

(10) Brass safety valves installed in the open air should be provided with reliable measures to prevent the moisture in the medium in the valve from freezing and affecting the discharge of the brass safety valve when the temperature is lower than 0oC.

(11) When the crystallization temperature of the brass safety valve medium is higher than the minimum ambient temperature, the brass safety valve must be equipped with a thermal insulation jacket, and a thermal insulation purging steam shall be installed to prevent the medium crystallization from clogging the brass safety valve and affecting the performance of the brass safety valve. Normal operating performance. The inlet and outlet pipes of the brass safety valve must also be designed with steam insulation jacketed pipes or additional insulation steam accompanying pipes to prevent the medium from crystallizing and blocking the pipes.

(12) The brass safety valve must have a device to prevent the weight from moving by itself and a guide frame to limit the lever's deviance. The spring-type brass safety valve must have a lifting handle and a device to prevent the adjustment screw from being arbitrarily twisted.

(13) It should be installed vertically at the highest position of the boiler and the header. Between the brass safety valve and the drum or header, there shall be no outlet pipes and brass valves for taking steam.

(14) For boilers with rated steam pressure less than or equal to 3.82MPa, the throat diameter of brass safety valve shall not be less than 25mm; for boilers with rated steam pressure greater than 3.82MPa, the throat diameter of brass safety valve shall not be less than 20mm.

(15) The brass safety valve of the pressure vessel is preferably installed directly on the highest position of the pressure vessel body. The brass safety valve of the liquefied gas storage tank must be installed in the gas phase. Generally, a short pipe can be used to connect with the container, so the diameter of the short pipe of the brass safety valve should not be smaller than the valve diameter of the brass safety valve.

(16) For boilers with rated evaporation greater than 0.5t/h, at least two brass safety valves shall be installed; for boilers with rated evaporation less than or equal to 0.5t/h, at least one brass safety valve shall be installed. Brass safety valves must be installed at the outlet of the separable economizer and the outlet of the steam superheater.

(17) The outlet of the brass safety valve should have no resistance to avoid the phenomenon of back pressure. If a drain pipe is installed, its inner diameter should be larger than the outlet diameter of the brass safety valve. The discharge port of the brass safety valve should be protected from freezing. For containers with flammable or toxic or highly toxic media, the discharge pipe should be directly connected to an outdoor safe place or have facilities for proper disposal. No brass valves are allowed to be installed on the discharge pipe.

Strengthen daily maintenance and maintenance, keep clean, prevent corrosion and blockage of grease and dirt; check the lead seal frequently to prevent others from arbitrarily moving the heavy hammer of the lever-type brass safety valve or twisting the adjusting screw of the spring-type brass safety valve; In order to prevent the valve and the valve seat from sticking firmly, a regular hand-pull (or hand-lift) discharge system should be formulated according to the actual situation of the pressure-bearing equipment. For example, the brass safety valve of the steam boiler drum should generally be artificially discharged once a day, and the discharge pressure should preferably be within the specified range. More than 80% of the maximum working pressure; if the leakage is found, it should be repaired or replaced in time, and it is strictly forbidden to increase the load (such as the lever-type brass safety valve moves the heavy hammer outward or the spring-type brass safety valve over-tightens the adjusting screw) to eliminate leakage.

Brass safety valves are regularly inspected at least once a year. The inspection contents include dynamic inspection and disassembly inspection. The steps of dynamic inspection are divided into assembly, boosting (to the working pressure), maintaining pressure (there should be no leakage within 3-5 minutes), boosting action (immediate action under the opening pressure), reducing pressure and returning to the seat, and re-maintaining the pressure (returning to the seat). Then keep it under working pressure for 3min without leakage).

1)  For corrosive media, brass safety valve should be installed in combination with bursting disc.

2)  For highly toxic media, choose a type of brass safety valve with good sealing performance.

3)  For the high temperature medium brass safety valve, the high temperature has a great influence on the spring, and the spring type brass safety valve should be avoided.

4)  For important brass safety valves, or brass safety valves that are easily affected by fire, sprinkler protection should be provided.

5)  For the brass safety valve for spherical tank, double brass safety valve should be installed, and the pressure relief capacity of any one of the brass safety valve can meet the safety pressure relief requirements of spherical tank.

6) Brass safety valve should be set with electrostatic jumper.

7) In order to prevent the brass safety valve from repeatedly opening and closing, resulting in flutter and damage to the brass valve, it is necessary to reduce the pressure drop of the brass safety valve inlet pipeline, that is, increase the inlet pipe diameter and shorten the inlet pipe section.