(4) Trapezoidal groove type: use oval metal ring as a gasket, used for valves with working pressure ≥ 64 kg/square centimeter, or high temperature valves;

The overview is as follows:

(1) International standard ISO228/1, DIN259, for internal and external parallel threads, code G or PF (BSP. F);

(2) German standards ISO7/1, DIN2999, BS21, for outer teeth tapered, inner teeth parallel thread, code BSP.P or RP/PS;

(3) British standard ISO7/1, BS21, internal and external tapered thread, code PT or BSP.Tr or Rc;

(4) American standard ANSI B21, internal and external tapered thread, code NPT G (PF), RP (PS), RC (PT) TOOTH SHAPE ANGLE IS 55°, NPT TOOTH ANGLE IS 60°BSP. F、BSP. P and BSP.Tr are collectively referred to as BSP teeth.

The American standard pipe thread includes five types: general purpose conical pipe thread NPT, straight pipe internal thread NPSC for pipe fittings, cone pipe thread NPTR for guide rod connection, straight pipe thread NPSM (free fit mechanical connection) and NPSL (loose fit mechanical connection with lock nut) for mechanical connection. It belongs to non-threaded sealed pipe threads (N: American National Standard; P: tube; T: conical)

5. Ferrule connection

Ferrule connection, only developed in recent years in China, its connection and sealing principle is that when the nut is tightened, the ferrule is pressured, so that its edge bites into the outer wall of the tube, and the outer cone of the ferrule is sealed with the cone in the joint under pressure, so that it can reliably prevent leakage. Such as instrument valves. The advantages of this form of connection are:

(1) Small size, light weight, simple structure, easy to disassemble and assemble;

(2) Strong connection force, wide range of use, can withstand high pressure (1000 kg/square centimeter), high temperature (650 °C) and shock vibration;

(3) A variety of materials can be selected, suitable for corrosion prevention;

(4) The processing accuracy requirements are not high;

(5) Easy to install at height.

At present, the ferrule connection form has been adopted in some small-diameter valve products in China.

6. Clamp connection

This is a quick connection method that requires only two bolts and is suitable for low-pressure valves that are frequently disassembled. Such as hygienic valves.

(5) American standard pipe thread.

7. Internal self-tightening connection

The above various connection forms are used by external force to offset the pressure of the medium to achieve sealing. The following describes the connection form of self-tightening using medium pressure. Its sealing ring is installed at the inner cone, and the side opposite the medium at a certain angle, the medium pressure is transmitted to the inner cone, and then transmitted to the sealing ring, on a certain angle of the cone, two components are generated, one parallel to the center line of the valve body outward, the other pressure to the valve inner wall. The latter component is the self-compacting force. The greater the pressure of the medium, the greater the self-tension. Therefore, this connection form is suitable for high-pressure valves. It saves a lot of materials and manpower than flange connection, but it also requires a certain preload so that it can be used reliably when the pressure in the valve is not high. Valves made of self-tightening sealing principle are generally high-pressure valves. There are many forms of valve connection, such as some small valves that do not have to be removed, welded together with the pipe; Some non-metallic valves use socket connections and so on. Valve users should be treated according to the situation of the rest.

Concentrate:

(1) All kinds of connection methods must refer to the corresponding standards, and it is necessary to clearly understand the standards required by users to avoid the selection of valves that cannot be installed.

(2) Usually the connection between large diameter pipes and valves adopts flange connection, and small diameter pipes and valves are connected with threads.

, often filled with lead oil, hemp and PTFE raw meal tape; Among them, PTFE raw material belt, which is widely used day by day; This material has good corrosion resistance, good sealing effect, easy to use and preserve, and when disassembled, it can be completely removed, because it is a non-sticky film, which is much superior to lead oil and hemp.

(2) Indirect sealing: the force of thread tightening is transmitted to the gasket between the two planes, so that the gasket can play a sealing role.

There are five main categories of commonly used threads:

(1) Metric ordinary thread;

(2) Imperial ordinary thread;

(3) Thread sealing pipe thread;

(4) Non-threaded sealing pipe thread;

(5) American standard pipe thread.

The overview is as follows:

(1) International standard ISO228/1, DIN259, for internal and external parallel threads, code G or PF (BSP. F);

(2) German standards ISO7/1, DIN2999, BS21, for outer teeth tapered, inner teeth parallel thread, code BSP.P or RP/PS;

(3) British standard ISO7/1, BS21, internal and external tapered thread, code PT or BSP.Tr or Rc;

(4) American standard ANSI B21, internal and external tapered thread, code NPT G (PF), RP (PS), RC (PT) TOOTH SHAPE ANGLE IS 55°, NPT TOOTH ANGLE IS 60°BSP. F、BSP. P and BSP.Tr are collectively referred to as BSP teeth.

The American standard pipe thread includes five types: general purpose conical pipe thread NPT, straight pipe internal thread NPSC for pipe fittings, cone pipe thread NPTR for guide rod connection, straight pipe thread NPSM (free fit mechanical connection) and NPSL (loose fit mechanical connection with lock nut) for mechanical connection. It belongs to non-threaded sealed pipe threads (N: American National Standard; P: tube; T: conical)

5. Ferrule connection

Ferrule connection, only developed in recent years in China, its connection and sealing principle is that when the nut is tightened, the ferrule is pressured, so that its edge bites into the outer wall of the tube, and the outer cone of the ferrule is sealed with the cone in the joint under pressure, so that it can reliably prevent leakage. Such as instrument valves. The advantages of this form of connection are:

(1) Small size, light weight, simple structure, easy to disassemble and assemble;

(2) Strong connection force, wide range of use, can withstand high pressure (1000 kg/square centimeter), high temperature (650 °C) and shock vibration;

(3) A variety of materials can be selected, suitable for corrosion prevention;

(4) The processing accuracy requirements are not high;

(5) Easy to install at height.

At present, the ferrule connection form has been adopted in some small-diameter valve products in China.

6. Clamp connection

This is a quick connection method that requires only two bolts and is suitable for low-pressure valves that are frequently disassembled. Such as hygienic valves.

7. Internal self-tightening connection

The above various connection forms are used by external force to offset the pressure of the medium to achieve sealing. The following describes the connection form of self-tightening using medium pressure. Its sealing ring is installed at the inner cone, and the side opposite the medium at a certain angle, the medium pressure is transmitted to the inner cone, and then transmitted to the sealing ring, on a certain angle of the cone, two components are generated, one parallel to the center line of the valve body outward, the other pressure to the valve inner wall. The latter component is the self-compacting force. The greater the pressure of the medium, the greater the self-tension. Therefore, this connection form is suitable for high-pressure valves. It saves a lot of materials and manpower than flange connection, but it also requires a certain preload so that it can be used reliably when the pressure in the valve is not high. Valves made of self-tightening sealing principle are generally high-pressure valves. There are many forms of valve connection, such as some small valves that do not have to be removed, welded together with the pipe; Some non-metallic valves use socket connections and so on. Valve users should be treated according to the situation of the rest.

Concentrate:

(1) All kinds of connection methods must refer to the corresponding standards, and it is necessary to clearly understand the standards required by users to avoid the selection of valves that cannot be installed.

(2) Usually the connection between large diameter pipes and valves adopts flange connection, and small diameter pipes and valves are connected with threads.