Views: 211 Author: Site Editor Publish Time: 2020-11-03 Origin: Site
Valves are piping accessories used to open and close the pipeline, control the flow direction, adjust and control the parameters (temperature, pressure, and flow) of the conveying medium. According to its function, it can be divided into shut-off valve, check valve, regulating valve and so on. Today, we will mainly introduce the characteristics and application of six major types of valves, such as gate valves and check valves.
1) The fluid does not change its flow direction when passing through the gate valve. When the gate valve is fully opened, the resistance coefficient is almost the smallest among all valves, and the applicable caliber range, pressure and temperature range are very wide. Compared with the same caliber shut-off valve, its installation size is smaller, so it is the most used type in chemical production equipment.
2) There are two types of gate valve handles, visible rod and hidden rod. The gate valve with visible rod is particularly useful for alternate switching of two or more identical devices. The visible rod can clearly indicate the valve opening and closing conditions.
3) When the gate valve is half-open, the valve core is prone to vibration, so the gate valve is only suitable for the situation of full opening or full closing, and it is not suitable for the occasion that needs to adjust the flow.
4) The gate valve has a groove in the valve body, so it is not suitable for fluids containing solid particles. In recent years, a gate valve with a blow port can be applied to this situation.
1) The shut-off valve is a valve type widely used in chemical plants. Its sealing performance is reliable, and it is also suitable for regulating the flow rate. Generally, it is installed at the outlet of the pump, upstream of the bypass flow-meter of the regulating valve, and other places where the flow rate needs to be regulated.
2) When the fluid flows through the valve core, the flow direction is changed, so the pressure drop is large, and at the same time, it is easy to deposit solids on the valve seat, so it is not suitable for suspension.
3) Compared with a gate valve of the same caliber, a shut-off valve has a larger volume, which limits its maximum caliber (maximum DNl50 ~ 200).
4) Y type shut-off valve and angle shut-off valve have smaller pressure drop compared with ordinary straight valve, and angle valve also has the function of changing flow direction.
5) Needle type valve is also a type of shut-off valve. Its spool is tapered, which can be used for small flow fine adjustment or used as a sampling valve.
1) The functions of these three types are similar, all are valves that can be quickly opened and closed. The valve core has a lateral opening, and the liquid flows directly. The pressure drop is small, and it is suitable for suspensions or viscous liquids. The valve core can be made into an upper or J-shaped channel to become a three-way or four-way valve. The shape is regular, and it is easy to be made into a jacketed valve for the situation requiring heat insulation. These types of valves can be more conveniently made into pneumatic or electric valves for remote control.
2) The difference between the three is that working pressure of the plunger valve and the ball valve is slightly higher.
It has a certain adjustment function, especially suitable for large flow adjustment. The use temperature is limited by the sealing material.
1) A check valve is a valve used to prevent fluid from flowing in the reverse direction. Generally used to prevent contamination, temperature rise or mechanical damage caused by fluid backflow.
2) There are three types: swing type, lifting type and ball type. The diameter of swing type is larger than the latter two, and can be installed on horizontal or vertical pipes. When installed on vertical pipes, the fluid should flow from bottom to top. Lifting and ball calibers are small and can only be installed on horizontal pipelines.
3) The check valve can only be used to prevent sudden backflow, but the sealing performance is not good.
4) When the inlet of the centrifugal pump is sucked up, the bottom valve installed at the end of the inlet pipe to keep the liquid in the pump is also a check valve. When the container is open, the bottom valve can be equipped with a strainer.
When these two valves are in use, the fluid only contacts the diaphragm or hose without touching other parts of the valve body. It is especially suitable for corrosive fluids or viscous liquids and suspensions. However, application is limited by the material of the diaphragm or hose.