Special stainless steel ball valve for liquid ammonia
Time: March 26, 2020 11:13:58 Source: Yonglong Valve Reading: zero second
Special stainless steel ball valve for liquid ammonia
The opening and closing parts of stainless steel liquid ammonia special ball valve are balls with circular through-hole, and the ball rotates with the valve stem to realize opening and closing. The ball valve has simple structure, quick opening and closing, convenient operation, small volume, light weight, few parts, small fluid resistance, good sealing and convenient maintenance.
1、 Key points for selection of stainless steel liquid ammonia special ball valve:
1. Clarify the use of valves in equipment or devices:
Determine the working conditions of the valve: the nature of the applicable medium, working pressure, working temperature, operation and control mode, etc.
2. Correct selection of valve type:
The correct selection of valve type is based on the designer's full grasp of the entire production process and operating conditions. When selecting the valve type, the designer should first master the structural characteristics and performance of each valve.
3. Determine the end connection of the valve:
The first two are most commonly used in threaded connection, flange connection and welded end connection. Threaded valves are mainly those with a nominal diameter of less than 50 mm. If the diameter is too large, it is very difficult to install and seal the connection. Flange connected valves are easy to install and disassemble, but heavier and more expensive than threaded valves, so they are suitable for pipe connection of various diameters and pressures. The welding connection is applicable to the conditions with relatively high load and is more reliable than the flange connection. However, the valve connected by welding is difficult to disassemble and reinstall, so its use is limited to the occasions where it can normally operate reliably for a long time, or where the service conditions are severe and the temperature is high.
4. Selection of valve material:
When selecting the materials of the valve shell, internals and sealing surface, in addition to considering the physical properties (temperature, pressure) and chemical properties (corrosivity) of the working medium, the cleanliness of the medium (whether there are solid particles) should also be mastered. In addition, the relevant regulations of the country and the user department should also be referred to. Correct and reasonable selection of valve material can obtain the most economical service life and the best service performance of the valve. Valve body material selection sequence: carbon steel - stainless steel, seal ring material selection sequence: PTFE, carbide
5. Others:
In addition, it is also necessary to determine the flow rate and pressure level of the fluid flowing through the valve, use existing data (such as valve product catalog, valve product samples, etc.) to select appropriate valves, add pneumatic actuators, electric actuators and regulating functions, and realize remote automatic control system.
2、 Selection description of stainless steel liquid ammonia special ball valve:
globe valve It is suitable for medium with low temperature, high pressure and high viscosity. Most ball valves can be used in media with suspended solid particles, and can also be used in powder and granular media according to the sealing material requirements; The full channel ball valve is not suitable for flow regulation, but it is suitable for occasions requiring quick opening and closing, which is convenient for emergency shutdown; Generally, ball valves are recommended for pipelines with strict sealing performance, wear, necking channel, rapid opening and closing, high pressure cut-off (large pressure difference), low noise, gasification, small operating torque and low fluid resistance.
Ball valve is suitable for light structure, low pressure cut-off and corrosive medium; The ball valve is also the most ideal valve for low-temperature and cryogenic media. The low-temperature ball valve with valve cover should be selected for pipeline systems and devices for low-temperature media; When floating ball valve is selected, its valve seat material shall bear the load of ball and working medium. Large diameter ball valve requires large force during operation. DN≥ 200mm ball valve shall be driven by worm gear; The fixed ball valve is suitable for the occasions with large diameter and high pressure; In addition, the ball valve used for the pipeline of highly toxic materials and combustible media in the process should have a fireproof and anti-static structure.
The strength test of electric liquid ammonia ball valve and pneumatic liquid ammonia ball valve shall be conducted when the ball is half open.
1. Sealing test of floating ball valve: keep the valve half open, introduce test medium at one end, and close the other end; Rotate the ball several times, open the closed end when the valve is closed, and check the sealing performance of the packing and gasket, without leakage. Then introduce the test medium from the other end and repeat the above test.
2. Tightness test of fixed ball valve: before the test, rotate the ball several times without load, and the fixed ball valve is closed, and introduce the test medium from one end to the specified value; Check the sealing performance of the inlet end with a pressure gauge. The accuracy of the pressure gauge is 0.5~1, and the range is 1.5 times of the test pressure. It is qualified if there is no pressure drop within the specified time; Then introduce the test medium from the other end and repeat the above test. Then, keep the valve half open, close both ends, fill the cavity with medium, and check the packing and gasket under the test pressure to ensure that there is no leakage.
3. The three-way ball valve shall be tested for tightness at all positions.
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