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On the Principle of Cut Off Valve

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On the Principle of Cut Off Valve

Source:www.flowxgroup.com/Update Time:2014-04-03Hits:

Valve is one of the most widely used valve, with the development of ball valve and butterfly valve, stop valve applications part to be replaced, but the characteristics of a cut-off valve itself, the selection principle is:

Piping or equipment 1, high temperature, high pressure media should use cut-off valve. Such as thermal power plant, nuclear power plant, high temperature, high pressure pipeline in petrochemical system.

2, some of the flow resistance pressure loss is not considered.

3, adjusting flow rate or pressure regulation, but the regulation accuracy is not high, and the pipe diameter is small, such as the nominal pipe through ≤ 50mm, should use.

4, the choice of a small needle valve, instrument valves, sampling valves, pressure gauge valve.

5, synthetic industrial production of small and large chemical fertilizer should use high-pressure angle type valve or high pressure angle type throttle valve.

Line 6, Bayer alumina production desiliconization workshop, easy to coke, easy to use separate body hard alloy type, can place the seat, sealing pair of DC type or DC type throttle valve.

7, in the construction of city water supply, heat supply engineering, nominal pipe by small, can use cut-off, balancing valve or piston valve pneumatic actuators .

Stop valve has the advantages of simple structure, cheap price, which makes it so far is almost no "competitors". Only with a stop valve is diaphragm valve called competition. But the diaphragm valve because the price is too high, although more than technical advantage of cut-off valve is better, but it is still difficult to compete with the cut-off valve.

When you need to use the corrugated in horizontal pipe in pipe valve electric valve is a relatively new type of valve type, it has some advantages of the unique structure of its own, such as the switch without friction, seal is not easy to wear, hoist torque small. This reduces the actuator with the specifications. With multi turn electric actuator, which can be realized on the media regulation and tight shutoff. Widely used in petroleum, chemical industry, city water supply and drainage requirements strictly cutting condition, it must ensure that in accordance with bellows globe valve manufacturer specified angle installation of stainless steel gate valve in the level line, or in the process equipment operation, the diaphragm of the empty encounter some problems, can not be completely discharged body in the media. However, different types of diaphragm valves, different manufacturers of corrugated pipe diaphragm valve, different nominal flow of the installation angle is different, brought great trouble often to the design and manufacture of sterile process equipment. In the T type structure of corrugated pipe valve, the performance of the empty body problem more clearly.

Selection criteria:

Piping or equipment 1, high temperature, high pressure media should use cut-off valve; fire power plants, petrochemical system of high temperature, high pressure pipeline valve selection is appropriate;

2, the flow resistance on the line not strict pipeline, the pressure loss is not considered;

3, a small needle valve can be used as the cut-off valve, needle valve, instrument valves, sampling valves, pressure gauge valve;

4, adjusting flow rate or pressure regulation, but the regulation accuracy is not high, and the pipe diameter is small, such as the nominal pipe diameter ≤ 50mm, should use cut-off valve or throttle valve;

5, in the construction of city water supply, heat supply engineering, nominal diameter smaller Road, the choice of cut-off valve, balance valve or piston valve, such as nominal pipe diameter less than 150mm;

6, application of DN200 medium following steam pipe;

7, do not apply to the medium viscosity;

8, do not apply to contain particles precipitated medium;

9, not for the vent valve and low vacuum valve.

The most obvious advantage of cut-off valve:

(L) in the opening and closing process, because the valve flap and valve sealing surface friction forces between the gate is small, and therefore wear

(2) generally only open seat height channel diameter l/4, so much smaller than the gate.

(3) usually in the valve body and the valve flap is only one sealing surface, thus comparison of manufacturing processes is good, easy to repair. However, the cut-off valve defects can not be ignored. Its main drawback is the relatively large flow resistance coefficient, the resulting pressure loss, especially in the hydraulic device, this pressure loss is particularly evident.

Compared with the electric ball valve, bellows valve is not such a problem, regardless of the corrugated pipe cut-off valve body is what kind of structure, process equipment in the run-time load will not appear "dead", to ensure strict to cut off pipeline. Moreover, it can be installed according to different installation of equipment in a sterile process piping systems.

In the pharmaceutical manufacturing, sterile process equipment by a number of horizontal pipe and vertical pipe, in the pharmaceutical equipment design, due to the pipeline location and technical reasons, must be installed using this bellows valve in a specific location. For example, if in a vertical pipe bellows globe valve installation, it shall be connected to a 90 degree bend in the same horizontal plane. The diaphragm valve type T structure and high production costs, compared with the diaphragm valves of different body shape, bellows valves in size and appearance, pipeline connection with the installation advantages. The structure of two types of valve type is different, therefore, in the early days of aseptic process equipment design, it should choose should choose which type of valve good parts.

An output device in medicine, food and biotechnology in the field of the needs of a large number of disinfection of the pneumatic ball valve. The large valve, in which situations require disinfection is almost no play. Because, in these devices in the process, requires less and less transport of medium quality, the less traffic, people almost invariably chose the diaphragm valve. And the thin flange ball valve new has a smaller size, can be equipped with different pipe diameters used, in this more competitive than the diaphragm.

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