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What are the most common Types of Valves and Scope of Application

What are the most common Types of Valves and Scope of Application

In the face of so many classifications of valves and a variety of complex working conditions, to choose the most suitable valve products for pipeline installation system, first of all, also understand the characteristics of the medium working condition, and the function and scope of application of different valves.

I. Medium

(1) Material state

  1. The material state of the gas material, including the physical properties of the data, pure gas or mixture, whether there are liquid droplets or solid particles, whether there is easy to condense the ingredients.
  2. Liquid material material state includes: the physical properties of data, pure components or mixtures of volatile components or dissolved gases (pressure reduction can be precipitated to form two-phase flow), whether or not it contains solid suspensions, as well as the viscosity of the liquid, the freezing point or pouring point and so on.

 

(2) Other properties

 Including corrosivity, toxicity, solubility of the valve structure materials, whether flammable and explosive properties. These properties sometimes not only affect the material, but also cause special requirements on the structure, or the need to improve the pipeline grade.

II. Operating conditions under operating conditions

(1) Temperature and pressure under normal operating conditions, but also need to be combined with the opening and closing or regeneration of the working conditions.

  1. The pump outlet valve should be considered the maximum closing pressure of the pump and so on.
  2. When the system regeneration Sølve is much higher than the normal temperature, while the pressure is reduced, for this type of system, to consider the combined effect of temperature and pressure.
  3. The degree of continuity of operation: that is, the frequency of opening and closing the valve, also affects the degree of wear resistance requirements, switching more frequent system, should consider whether to install double valve.

(2) The allowable pressure drop in the system

Allowable pressure drop in the system is small, or allow pressure drop is not small but do not need to adjust the flow, the pressure drop should be selected smaller valve such as gate valves, straight through the ball valve.


Need to regulate the flow, it should be selected to regulate the performance of better, with a certain pressure drop of the valve type (pressure drop accounted for the proportion of the pressure drop of the entire pipeline and the sensitivity of the regulation).

(3) The environment in which the valve: outdoor in cold areas, especially for chemical materials, the valve body material generally can not be cast iron and should be used cast steel (or stainless steel).

III. Valve function

(1) Cut off: almost all valves have cut off function. Simply used to cut off the flow without regulating the choice of gate valves, ball valves, etc., the requirements of rapid cut-off, the plug, ball valves, butterfly valves, etc. is more appropriate. Globe valve can both regulate the flow and cut off. Butterfly valve can also be suitable for large flow regulation.

(2) Change the direction of flow: the use of two-way (channel L-shaped) or three-way (channel in order to shape) ball valve or plug, you can quickly change the direction of flow of materials, and because of a valve to play a role in more than two through the valve, can simplify the operation, so that the switching is accurate and can reduce the space occupied.

(3) Regulation: globe valve, plunger valve can meet the general flow regulation, needle valve can be used for a small amount of fine-tuning; in the larger flow range for stable (pressure, flow) regulation, it is appropriate to throttle valve.

(4) Check: need to prevent backflow of materials can be selected check valve.

(5) Different production processes can choose to have additional features of the valve, such as with a jacket, with a clean port and with a bypass valve, with blowing port valves used to prevent solid particles from settling, and so on.

 

IV. Switching valve power

The vast majority of valves operated in situ with a handwheel, with a certain distance from the operating belt, can use a chain wheel or Distance, can use a sprocket or extension rod. Some large calibre valves due to excessive starting torque in the valve design with a motor. In the explosion-proof area to use the appropriate level of explosion-proof motor.

Remote control valves: take the type of power pneumatic, hydraulic, electric, etc., of which electric can be divided into solenoid valves and motor-driven valves. Should be based on the need and the energy available to choose.

IV. Various types of valve features and scope of application

(1) Fluid flow through the gate valve does not change the flow direction, when the gate valve is fully open resistance coefficient is almost the smallest of all valves, and the applicable calibre range, pressure and temperature range are very wide. Compared with the same diameter globe valve, its installation size is smaller, so it is a type of chemical production plant used most often.

 (2) Gate valve handle is divided into two kinds of open stem, dark stem: open stem gate valve for more than two sets of the same equipment for alternate switching, especially favourable, its open stem can be clearly marked out the valve switching.

 (3) When the gate valve is half-open, the spool is prone to vibration, so the gate valve is only suitable for fully open or fully closed, not suitable for occasions where the flow rate needs to be regulated.

 (4) Gate valves have grooves in the valve body, so they are not suitable for fluids containing solid particles. In recent years, there are gate valves with blowing port can be applied to this situation.

(1) Globe valves are widely used in chemical plants. Its sealing performance is reliable and it is also suitable for regulating flow. It is generally installed at the pump outlet, upstream of the regulating valve bypass flow meter, etc. where the flow needs to be adjusted.

 (2) Fluid flow through the valve spool to change the flow direction, thus the pressure drop is large, and easy to deposit solids on the valve seat, so it is not suitable for suspension.

 (3) Globe valves and gate valves of the same diameter compared to the larger size, thus limiting its maximum calibre (maximum DNl50 ~ 200).

 (4) Y-type globe valves and angle globe valves have a smaller pressure drop compared with ordinary straight-through valves, and angle valves also have the function of changing the flow direction.

 (5) Needle valve is also a globe valve, the spool is conical, can be used for small flow fine-tuning or as a sampling valve.

 (1) Valves that can be opened and closed quickly. The spool has a transverse opening, the liquid flow through, small pressure drop, suitable for suspension or viscous liquid. Spool and can be made into a top or d-shaped channel and become a three-way, four-way valve. The shape of the regular, easy to make into a jacketed valve for the need for insulation, these types of valves can be more easily made into pneumatic or electric valve for remote control.

Have a certain regulatory function, especially for large flow regulation, the use of temperature by the sealing material restrictions.

 (1) Check valve is used to prevent the reverse flow of fluid valve. Generally used to prevent contamination, temperature rise or mechanical damage caused by the backflow of fluid.

 (2) Commonly used spinning, lifting and ball type three types. The diameter of the rotary type is larger than the latter two, and it can be installed on the horizontal pipe or vertical pipe, and the fluid should flow from bottom to top when it is installed on the vertical pipe. Lift and ball type diameter is smaller, and can only be installed in the horizontal pipe.

 (3) Check valve can only be used to prevent sudden backflow but the sealing performance is not good, so strictly prohibit the mixing of materials, other measures should be taken.

 (4) Centrifugal pump inlet for the suction state, in order to keep the pump liquid in the inlet pipe end installed bottom valve is also a check valve. When the container is open, the bottom valve can be with a strainer.

These two types of valves in use, the fluid only contact with the diaphragm or hose without touching other parts of the valve body, especially for corrosive fluids or viscous liquids, suspensions and so on. However, the scope of use is limited by the material of the diaphragm or hose.

Piping systems in various industries, valve applications, operating frequency and services vary greatly, to control or eliminate even the slightest leakage, the most important and critical equipment or rely on the valve. The ultimate control of the pipeline is the valve, and valves are unique in their service and reliability across a wide range of industries. Valve model selection is critical and is based on specific operating conditions.

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