Many valves will be encountered in the construction of tapping under pressure, and some types of valves can be used for tapping under pressure. Therefore, if you want to manufacture a more suitable pressure tapping valve, you need to understand the pressure tapping principle and the valve manufacturing principle. The following briefly introduces the types of valves and commonly used pressure-opening valves.
1. Overview of the valve
A valve is a control device for a fluid pipeline. Its basic function is to connect or cut off the flow of the pipeline medium, change the flow of the medium, change the flow direction of the medium, adjust the pressure and flow of the medium, and protect the normal operation of the pipeline equipment.
A large number of industrial valves are used after Watt invented the steam engine. In the past two to three decades, due to the needs of petroleum, chemical industry, power station, metallurgy, shipbuilding, nuclear energy, aerospace, etc., higher requirements have been placed on valves. Its working temperature ranges from ultra-low temperature -269°C to high temperature 1200°C, even as high as 3430°C. The working pressure ranges from ultra-vacuum 1.33x10-8Mpa (1x10-1 ㎜ Hg) to ultra-high pressure 1460MPa. The valve diameter ranges from 1mm to 600mm, even reaching 9750mm. . The materials of the valves have developed from cast iron, carbon steel to titanium and titanium alloys, high-strength corrosion-resistant steel, etc., and the driving methods of the valves have developed from manual to electric, pneumatic, hydraulic, program control, numerical control, and remote control.
With the continuous development of modern industry, the demand for valves continues to grow. A modern petrochemical plant needs tens of thousands of valves of all kinds, and the amount of valves used is large. Frequent opening and closing, but often due to improper manufacturing, use, selection, and maintenance, running, emitting, dripping, and leaking occur, resulting in flame, explosion, poisoning, scalding accidents, or the valve manufacturer's product quality is inferior, and energy consumption is increased , Equipment corrosion, increased material consumption, environmental pollution, and even cause accidents such as production shutdowns are not uncommon. Therefore, people want to obtain high-quality valves, and at the same time require improved valve use and maintenance. At this time, new requirements are put forward for valve operators, maintenance personnel, and engineering and technical personnel. In addition to careful design, reasonable selection, and correct operation of the valve, the valve must be replaced, maintained and repaired in time to minimize the "running, leaking, dripping, leaking" and various accidents of the valve.
2. Classification of valves
Valves have a wide range of uses, many types, and many classification methods. The total can be divided into two categories:
The first type of automatic valve: a valve that relies on the ability of the medium (liquid, gas) to act on its own. Such as check valves, safety valves, regulating valves, traps, pressure reducing valves, etc.
The second type of drive valve: a valve that is operated manually, electrically, hydraulically, and pneumatically. Such as gate valve, globe valve, throttle valve, butterfly valve, ball valve, plug valve, etc.
In addition, the classification of valves has the following methods:
2.1 According to structural features, according to the direction of movement of the closing member relative to the valve seat, it can be divided into:
a. Truncated door shape: The closing piece moves along the center of the valve seat, as shown in Figure 1-1.
b. Gate shape: The closing piece moves along the center of the vertical valve seat, as shown in Figure 1-2.
c. Cock and ball: The closing part is a plunger or a ball, which rotates around its own centerline, as shown in Figure 1-3.
d. Swing shape; the closing piece rotates around the axis outside the valve seat, as shown in Figure 1-4.
e. Dish shape: The disc of the closing member rotates around the axis in the valve seat, as shown in Figure 1-5.
f. Slide valve shape: The closing piece slides in the direction perpendicular to the channel, as shown in Figures 1-6.
2.2 According to the purpose, according to the different purposes of the valve can be divided into:
a. For breaking: used to connect or cut off pipeline media, such as globe valves, gate valves, ball valves, butterfly valves, etc.
b. Non-return use: used to prevent the medium from flowing back, such as a check valve.
c. Adjustment: used to adjust the pressure and flow of the medium, such as regulating valves and pressure reducing valves.
d. Distribution: used to change the flow direction of the medium and distribute the medium, such as three-way cock, distribution valve, slide valve, etc.
e. Safety* full valve: When the medium pressure exceeds the specified value, it is used to discharge excess medium to ensure the pipeline system and equipment
Equipped with safety valves, such as safety valves and emergency valves.
f. Other special purposes: such as traps, vent valves, drain valves, etc.
2.3 According to the driving mode, it can be divided into different driving modes:
a. Manual: With the help of handwheel, handle, lever or sprocket, etc., it is driven by human power. When the transmission torque is large, it is equipped with
Reduction devices such as worm gears and gears.
b. Electric: driven by a motor or other electrical devices.
c. Hydraulic: driven by (water, oil).
d. Pneumatic; driven by compressed air.
2.4 According to the pressure, according to the nominal pressure of the valve, it can be divided into:
a.Vacuum valve: For valves with pressure <0.1Mpa that is 760mm mercury column height, usually mm mercury column or mm
The water column represents pressure.
b. Low pressure valve: valves with nominal pressure PN≤1.6Mpa (including steel valves with PN≤1.6MPa)
c. Medium pressure valve: a valve with a nominal pressure of PN2.5—6.4MPa.
d. High-pressure valve: a valve with a nominal pressure of PN10.0-80.0MPa.
e. Ultra-high pressure valve: a valve with a nominal pressure of PN≥100.0MPa.
2.5 According to the temperature of the medium, according to the temperature of the medium when the valve is working, it can be divided into:
a. Ordinary valve: suitable for valves with a medium temperature of -40°C to 425°C.
b. High temperature valve: suitable for valves with a medium temperature of 425°C to 600°C.
c. Heat-resistant valve: suitable for valves with medium temperature above 600℃.
d. Cryogenic valve: suitable for valves with medium temperature -40℃～ -150℃.
e. Ultra-low temperature valve: suitable for valves whose medium temperature is below -150℃.
2.6 According to the nominal diameter, according to the nominal diameter of the valve can be divided into:
a. Small diameter valves: valves with nominal diameter DN<40mm.
b. Medium-caliber valves: valves with a nominal diameter of DN50~300mm.
c. Large diameter valves: valves with a nominal diameter of DN350~1200mm.
d. Extra large diameter valves: valves with nominal diameter DN ≥ 1400mm.
2.7 Divided according to the connection mode with the pipeline, according to the connection mode of the valve and the pipeline;
a. Flange connection valve: The valve body has a flange and is connected to the pipeline by a flange.
b. Threaded connection valve: the valve body has internal thread or external thread, and the valve is connected with the pipeline by thread.
c. Welded connection valve: The valve body has a welding port and is connected to the pipeline by welding.
d. Clamping clamp connection valve: a valve with clamps on the valve body and clamp connection with the pipeline.
e. Card sleeve connection valve: the valve is connected with the sleeve and the pipeline.