Type of valve range, its structure, manufacturing materials, drive and connection type are different. Fire pumps Valve in daily activities and industrial and agricultural production in all aspects of people's daily lives have been widely used. As a control valve element fluid line, its main role is to isolate equipment and piping systems, and adjusting the flow rate, and adjust the pressure to prevent reflux, its basic function is to change the line of medium flow direction and flow rate to ensure that the pipeline safe and smooth operation of the system is turned on or off the flow of the pipeline media.
 

As a control valve element fluid line, its main role is to isolate equipment and piping systems, and adjusting the flow rate, and adjust the pressure to prevent reflux, its basic function is to change the line of medium flow direction and flow rate to ensure that the pipeline safe and smooth operation of the system is turned on or off the flow of the pipeline media.

First, the main technical performance of the valve
 

1, strength properties

Strength properties of the valve is the valve's ability to withstand the media pressure. Valve is a pressure of mechanical products, and therefore must have sufficient strength and rigidity to ensure the long-term use without breakage or deformation.
 

2, the sealing performance

The sealing performance of the valve is the valve part of the sealing ability to prevent media leaks, it is the valve most important technical performance indicators. Sealing valve has three parts:

(1) opening and closing member and the valve seat sealing surface between the contact points;

(2) filler stem and the stuffing of the distribution and office;

(3) the valve body and bonnet connection.
 

The first one is called the leak within the leak, also known as loose relationship, it will affect the ability of the valve cut off media. For the cut valve, the internal leakage is not allowed. The latter two called the leak leak, that media leaks from the valve to the valve outside. Leakage will result in material losses, environmental pollution, can also cause serious accidents. The explosive, toxic or radioactive medium, leakage is allowed, and therefore, the valve must have a reliable sealing performance.

When we select valve, the valve seal is necessary to emphasize. During use, the valve sealing surface should not be any erosion, wear is also very small, not afraid to wear, excellent sealing performance can be achieved within and outside the sealed zero leakage, save energy, protect the environment and improve work efficiency.
 

3, the flow of the medium
 

Will produce medium flow through the valve after the pressure loss (both before and after the valve pressure difference), which is the flow valve on the media have a certain resistance, medium to overcome the resistance of the valve, it takes some energy. From the conservation of energy considerations, to minimize the resistance of the valve on the flow medium.
 

4, opening and closing force and closing torque
 

Hoisting force and hoisting moment is the valve to open or close the force or torque must be imposed. Close the valve, the need to open and close between the two pieces with the fat seat sealing surface of the seal formed between certain specific pressure, but also to overcome between the stem and the packing between the stem and the nut thread between the stem end bearing at and other friction parts of friction, and therefore must apply the closing force and closing moments, in the valve opening and closing process, the need to stop force and the opening and closing moments of change, and its maximum is close to the final instant or open the initial transient. Valves should strive to reduce the closing force and closing moments.
 

5, the opening and closing speed
 

Hoisting speed is used to open or close the valve to complete a movement time required to represent. Valves open and close the general speed is not critical, but some conditions have special requirements for opening and closing speed, the prompt to open or close, to prevent accidents, and some asked slowly shut down to prevent water hammer, etc., this should be taken into account in the selection of valve type.
 

6, movement sensitivity and reliability
 

This refers to the valve for the medium parameters, and make the appropriate degree of sensitivity for the throttle valve, reducing valve, regulating valve used to adjust the medium parameters of the valves and safety valves, steam traps and other valves have a specific function its functional sensitivity and reliability is very important technical performance indicators.
 

7, The use of life
 

It indicates the durability of the valve, the valve is an important performance indicators and has great economic significance. Usually guarantee the number of seals required to open and close that can also be used to indicate the time.
 

Second, the direction and position
 

Many directional valve, such as closing valves, throttle valves, check valves, if installed anti-flip, it will affect the use of effects and life, or simply does not work (such as valve), and even dangerous. Usually valves, directional signs on the body; there is no case, should be based on the valve works correctly identified. Cut-off valve left-right asymmetry of the valve chamber, the fluid through the valve port to make its bottom-up, so fluid resistance (determined by the shape), open the effort, after the closure of the media do not pressure filler for easy maintenance. That is why the non-stop valve An anti-truth. Other valves have their own characteristics. Installation position of the valve must be easy to operate; even with some temporary difficulties, but also for the sake of the operation of permanent staff.
 

Third, the construction work
 

Installation must be careful to avoid the impact of brittle material valve. Before installation, you should make a check valve, check the specifications, identification of damage, especially for stem. Also a few turns to see if skewed, because the transport process, most likely to hit the crooked stem. But also to clear the debris inside the valve. The valve lifting, rope not tied hand wheel or stem to avoid damage to these parts, it should be tied to the flange. For pipe valve is connected, it must be cleaned. Available compressed air to remove iron oxide particles, silt, welding slag and other debris. These sorts of things, not only easy to scratch the sealing surface of the valve, wherein large particles of debris (such as weld slag), also blocked a small valve, it can be disabled. When installing the valve screw should be packing (leaded hemp oil or Teflon tape), including on the pipe threads, do not get inside the valve, the valve in order to avoid memory product, the impact medium flow.
 

Fourth, protection facilities
 

Some valve must have external protection, which is heat and cold. Sometimes within the insulation layer plus heating steam line. What kind of valve should be heat or cold, according to the production requirements. Principle to say, Where a valve medium temperature is reduced too much, it will affect production efficiency or nipped valve, you need heat, even heating; where the valve nudity, production caused by adverse or negative phenomena such as frost, it needs cold. Asbestos insulation materials, slag wool, glass wool, perlite, diatomaceous earth, Vermiculite, etc.; cold materials cork, perlite, foam and plastics. Long without water, steam valve must let go of water.
 

Five, packing replacement
 

Stock valves, some filler has been so bad, and some do not match with the use of the media, which need to replace the packing. Valve manufacturer can not consider the use of units of one thousand million class different media, always packed stuffing box packing ordinary, but when used, must be allowed to adapt the filler and the media. When replacing the packing, to circle around pushed. Each lap joints 45 degrees is appropriate, ring and ring joints staggered 180 degrees. Continue to consider the height of packing gland pressing room, now we have to let the lower part of the gland packing chamber pressure proper depth, this depth is generally 10 to 20% of the total depth of the packing room.
 

For advanced-valves, joint angle of 30 degrees. Joints staggered 120 degrees between the coils. In addition to the Office of the filler, also depending on the circumstances, the use of rubber O-ring (natural rubber resistant to 60 degrees Celsius weak base, NBR oil resistant to 80 degrees Celsius, fluorine rubber resistant to many corrosive media 150 degrees Celsius) three stacked PTFE ring (resistant to 200 degrees Celsius and strong corrosive media) nylon bowl rings (resistant to 120 degrees Celsius ammonia, alkali) and other forming filler.