Valve and the pipeline or the connection between the equipment is the right choice, will have a direct impact on the pipeline valve running, running, dripping, leakage probability of the phenomenon. Common valve connections include: flange connection, the folder connection, butt welding, screw connections, ferrule connection, clamp connections, self-sealing connections and other forms of connection. 1, the flange connection Flange connection is a flange with two ends of the valve body, corresponding to the flange on the pipe, and is installed in the pipe by a bolt fixing flange. Flange connection is the most used form of connection in the valve. Flange has a convex surface (RF), plane (FF), convex and concave surface (MF) of the points. According to the shape of the junction can be divided into the following categories: 1) smooth: for the valve is not high pressure. Processing more convenient 2) Bump: high pressure, can be used in the hard washer 3) Mortise groove: available plastic deformation larger washers, used in a more extensive corrosive media, the sealing effect is better. 4) trapezoidal groove: with oval ring for gaskets, used for working pressure ≥ 64 kg / cm2 valve, or high temperature valve. 5) Lens type: Gasket is a lens shape, made of metal. For working pressure ≥ 100 kg / cm high pressure valve, or high temperature valve. 6) O-ring: This is a newer form of flange connection, which is developed with the advent of various rubber o-rings. It is more reliable in sealing effect than conventional flat washers. 2, the folder connected to the valve installed in the middle of two flanges, the valve body usually has a positioning hole to facilitate the installation of positioning, the valve and the two ends of the pipe directly with the clamp through the connection form. 3, the welding connection Butt welding connection: both ends of the valve body welded into the butt weld bevel welding requirements, corresponding to the pipe welding bevel, fixed on the pipe by welding. Socket welding connection: both ends of the valve socket by welding requirements processing, and pipe welding socket connection. 4, threaded connection Threaded connection is a simple method of connection, commonly used in small valves. Body according to the standard thread processing, there are two kinds of internal thread and external thread. Corresponds to the thread on the pipe. Thread connection in two cases: 1) direct seal: the internal and external threads directly from the sealing effect. In order to ensure that the joints do not leak, often with lead oil, linen and PTFE raw material filled with tape; which polytetrafluoroethylene raw material tape, the use of a wide range of day; this material is very good corrosion resistance, sealing effect pole Good, easy to use and store, when removed, it can be completely removed because it is a layer of non-sticky film, superior than lead oil, linen is much better. 2) Indirect seal: Thread tightening force, passed to the gasket between the two planes, so that the gasket sealing effect. There are five commonly used thread categories: ordinary rice thread; English ordinary thread; thread sealing pipe thread; non-thread sealing pipe thread; American standard pipe thread. The general introduction is as follows: ①International standards ISO228 / 1, DIN259, internal and external parallel threads, code G or PF (BSP.F); ② German standards ISO7 / 1, DIN2999, BS21, Code BSP.P or RP / PS; ③ British Standard ISO7 / 1, BS21, internal and external tapered thread, code-named PT or BSP.Tr or Rc; ④ American Standard ANSI B21, internal and external tapered thread, code NPT G RP (PS), Rc (PT) dental angle of 55 °, NPT dental angle of 60 ° BSP.F, BSP.P and BSP.Tr collectively referred to as BSP teeth. There are five types of American standard pipe threads: NPT for general purpose pipe threads, NPSC for straight pipe threads for pipe joints, NPTR for tapered pipe threads for guide bar connection, NPSM for straight pipe threads for mechanical connection, NPSL (free- Loose with a lock nut with mechanical connection). Belonging to non-thread sealing pipe thread (N: American national standard; P: pipe; T: tapered 5, ferrule connection ferrule connection, developed in China in recent years, its connection and sealing principle is that when tightening the nut , The sleeve is under pressure to bite the edge of the pipe into the outer wall of the tube and the outer conical surface of the ferrule is in tight contact with the conical surface of the fitting body under pressure so as to reliably prevent leakage such as meter valve.The advantage of this form of connection : 1) small size, light weight, simple structure, easy disassembly; 2) strong connection, wide range of use, can be resistant to high pressure (1000 kg / cm), high temperature (650 ℃) and shock vibration; A variety of materials, suitable for anti-corrosion; 4) machining accuracy is not high; 5) to facilitate high-altitude installation. At present, the form of sleeve connection has been adopted in some small-caliber valve products in China. 6, the clamp connection This is a fast connection method, it only requires two bolts, for low-pressure valve often disassembled. Such as the health valve. 7, within the tight connection from the various forms of connection, are the use of external force to offset the media pressure, to achieve sealed. The following describes the use of media pressure self-tight connection. Its sealing ring is installed at the inner cone, with the media facing the side of an angle, the media pressure transmitted to the inner cone, and passed to the ring, at a certain angle of the cone, resulting in two components, one with Valve body center line parallel to the outside, the other pressure to the valve body wall. Behind this force is self-tightening. The larger the media pressure, the greater the self-tightening force. So this form of connection, suitable for high-pressure valve. It is connected to the flange, to save a lot of material and manpower, but also need some pre-tightening force, so that when the valve pressure is not high, the use of reliable. The use of self-tight sealing principle of the valve, usually high-pressure valve. There are many forms of valve connection, for example, some do not have to remove the small valve, with the pipe welding together; some non-metallic valves, the socket connection, and so on. Valve users should be based on the situation with the specific treatment. Vortex flowmeter 8, there are many other forms of valve connection, for example, some do not have to remove the small valve, with the pipe welding together; some non-metallic valve, the socket connection, and so on. Valve users should be treated according to the situation with the specific treatment Remark: 1) All connection methods must refer to the appropriate standards, the need to clearly understand the standards of users to avoid the selection of the valve can not be installed. 2) Usually large diameter pipe and valve connection flange connection, small diameter pipe and valve threaded connection. More Keywords Search: Valves, Pipes
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