Valve types of connection

Flange connection

1: Flange connection is the most commonly used connection form between valves and pipelines or equipment. It refers to a detachable connection which is connected by flanges, gaskets and bolts as a group of combined sealing structures. Pipe flange refers to the flange of the pipe distribution pipe in the pipeline device, used in the equipment refers to the import and export flange of the equipment. The flange connection is easy to use and can withstand greater pressure. Flange connection can be applied to a variety of nominal size, nominal pressure of the valve, but there are certain restrictions on the use of temperature, in high temperature conditions, due to the flange of the connection bolt prone to creep caused by leakage, under normal circumstances, flange connection is recommended to be used at ≤350℃ temperature.

According to the shape of the joint surface, it can be divided into the following types:

Smooth: for valves with low pressure. Easy to process

Concave and convex type: high working pressure, can use a hard washer

Mortise and groove type: The gasket with large plastic deformation can be used widely in corrosive media, and the sealing effect is better

Trapezoidal groove type: with oval metal ring as a washer, used for working pressure ≥60kg/ cm2 of valves or high temperature valves

Lens type: The gasket is a lens shape and is made of metal. For high pressure valves or high temperature valves with working pressure ≥100 kg/cm2

O-ring type: the new flange connection form, the sealing effect is more reliable than the general flat washer

Clamp connection

A type of connection in which the valve and two pipes are directly threaded together by bolts.

Welded connection:

Welded connection refers to a connection form in which the valve body has a welded groove and is connected to the pipeline system by welding.

GB/T 12224, API600, ASME B 16.34 and other standards for welding groove provisions.

The welding connection between valve and pipeline is divided into butt welding connection (BW) and socket welding connection (SW), and the socket welding end shall comply with the provisions of JB/T 1751. Butt welding connection (BW) can be applied to various sizes, various pressures and high temperature conditions, socket welding connection (SW) is generally suitable for ≤DN50 valves.

Threaded connection

This is a simple connection method, often used for small valves. There are two cases:

Direct sealing: the internal and external threads directly play a sealing role. In order to ensure that the joint is not leaking, it is often filled with lead oil, thread linen and polytetrafluoroethylene raw material belt, of which polytetrafluoroethylene raw material belt is widely used. This material has good corrosion resistance, good sealing effect, convenient use and preservation, and can be removed completely when disassembly, because it is a non-viscous film, which is much superior to lead oil and linen.

Indirect sealing: The force of screw tightening is transmitted to the two planes of the washer, so that the washer plays a sealing role.

Bushing joint

The working principle of the sleeve connection is that when the nut is tightened, the sleeve is under pressure, so that its edge bites into the outer wall of the pipe, and the outer cone of the sleeve is tightly closed with the inner cone of the joint under pressure, so that leakage can be reliably prevented.

The advantages of this form of connection are:

1) Small size, light weight, simple structure, easy disassembly;

2) Strong connection, wide range of use, can withstand high pressure (1000 kg/cm2), high temperature (650℃) and shock vibration;

3) Can choose a variety of materials, suitable for corrosion prevention;

4) Machining accuracy requirements are not high;

5) Easy to install at high altitude.

At present, the sleeve connection form has been used in some small-caliber valve products in our country.

Clamp connection

This is a fast connection method that requires only two bolts and is suitable for low pressure valves that are often removed.

Internal self-tightening connection

Internal self-tightening connection is a form of connection that uses medium pressure for self-tightening. Its sealing ring is installed in the inner cone, with the opposite side of the medium at a certain Angle, the medium pressure is transmitted to the inner cone, and is transmitted to the sealing ring, on the cone of a certain Angle, two components are generated, one is parallel to the center line of the valve body, and the other is pressed to the inner wall of the valve body. The latter component is the self-tightening force. The greater the medium pressure, the greater the self-tightening force. Therefore, this connection form is suitable for high pressure valves. It is more than the flange connection, to save a lot of materials and manpower, but also requires a certain preload force, so that when the pressure in the valve is not high, the use of reliable.

Valves made of self-sealing principle are generally high-pressure valves. There are many forms of valve connection, such as small valves that do not need to be removed and welded together with pipes; Some non-metal valves, using socket connections, and so on. Valve users should be treated according to the specific situation.

other

There are many other valve connection forms, such as small valves that do not need to be removed and welded together with pipes; Some non-metal valves, using socket connections, and so on. Valve users should be treated according to the specific situation.