entirevalveHow to connect with the pipeline or equipment, this problem cannot be ignored, because most of the valve’s running, dripping, dripping and leaking occur here.How many connections do you know?
Flange connection is the most commonly used connection form between valve and pipeline or equipment.means byflangegaskets and bolts are connected to each other as a detachable connection of a group of combined sealing structures.
Pipe flange refers to the flange used for piping in the pipeline installation, and used on equipment refers to the inlet and outlet flanges of the equipment. Flange connection is easy to use and can withstand greater pressure.
Flange connection can be applied to valves of various nominal sizes and nominal pressures, but there are certain restrictions on the operating temperature. Under high temperature conditions, the connection bolts of the flange are prone to creep and cause leakage. The blue connection is recommended to be used at a temperature of ≤350℃.
According to the shape of the joint surface, it can be divided into the following types:
Smooth: for valves with low pressure.Processing is more convenient
Concave-convex type: high working pressure, medium hard washer can be used
Tongue and groove type: gaskets with large plastic deformation can be used, which are widely used in corrosive media and have better sealing effect.
Trapezoidal groove type: use an oval metal ring as a gasket, used for valves or high temperature valves with a working pressure of ≥60kg/square centimeter
Lens type: The gasket is a lens shape and is made of metal.For working pressure ≥ 100 kg/cm²High pressure valveor high temperature valve
O-ring type: the newer flange connection type, the sealing effect is more reliable than the general flat washer
The connection form in which the valve and the two pipes are directly clipped together with bolts.
Welded connection refers to a form of connection in which the valve body has a welding groove and is connected to the piping system by welding.
GB/T 12224, API600, ASME B 16.34 and other standards stipulate the welding groove. ,
The welding connection between the valve and the pipeline is divided into the butt welding connection (BW) and the socket welding connection (SW). Butt welding connection (BW) can be applied to various sizes, various pressures and high temperature conditions, and socket welding connection (SW) is generally suitable for valves ≤ DN50.
This is an easy connection method and is often used for small valves. There are two cases:
Direct sealing: The inner and outer threads directly play a sealing role. In order to ensure that the connection does not leak, it is often filled with lead oil, thread hemp and PTFE raw material tape, among which PTFE raw material tape is widely used.
This material has good corrosion resistance, excellent sealing effect, and is easy to use and store. When disassembling, it can be removed completely because it is a non-sticky film, which is much better than lead oil and thread hemp.
Indirect sealing: The force of thread tightening is transmitted to the gaskets on the two planes, so that the gaskets play a sealing role.
The working principle of the ferrule connection is that when the nut is tightened, the ferrule is under pressure, so that the edge of the ferrule bites into the outer wall of the pipe, and the outer cone surface of the ferrule is in close contact with the inner cone surface of the joint under pressure, so it can reliably prevent leakage. .
The advantages of this form of connection are:
Small size, light weight, simple structure, easy disassembly and assembly;
Strong connection force, wide range of use, can withstand high pressure (1000 kg/cm 2 ), high temperature (650 ° C) and shock and vibration;
Can choose a variety of materials, suitable for anti-corrosion;
The requirements for machining accuracy are not high;
Easy to install at high altitude.
At present, the ferrule connection form has been adopted in some small-diameter valve products in my country.
This is a quick connect method that requires only two bolts and is suitable for low pressure valves that are frequently disassembled.
Internal self-tightening connection
Internal self-tightening connection is a form of self-tightening connection using medium pressure. Its sealing ring is installed at the inner cone and forms a certain angle with the side facing the medium. The pressure of the medium is transmitted to the inner cone and then to the sealing ring. On the cone surface of a certain angle, two component forces are generated, one with The center line of the valve body is parallel to the outside, and the other is pressed against the inner wall of the valve body.
The latter force 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. Compared with flange connection, it saves a lot of material and manpower, 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 using the principle of self-tightening sealing are generally high-pressure valves. There are many forms of valve connection, for example, some small valves that do not need to be removed are welded with the pipe; some non-metallic valves are connected by socket and socket, and so on. Valve users should be treated according to the specific situation.
There are many other valve connection forms, for example, some small valves that do not need to be removed are welded together with the pipe; some non-metallic valves are connected by socket and socket, and so on. Valve users should be treated according to the specific situation.