(1) When the gate valve is fully opened, the resistance coefficient is the smallest of all valves, and the applicable range of caliber, pressure and temperature is very wide. Compared with the stop valve of the same caliber, its installation size is smaller, so it is the most widely used type in chemical production equipment.
(2) The handle of gate valve can be divided into two types: clear stem and dark stem. When the open stem gate valve is used for the alternate switching of more than two sets of the same equipment, it is particularly advantageous. Its open stem can clearly indicate the opening and closing of the valve.
(3) When the gate valve is half open, the valve core is easy to vibrate, so the gate valve is only suitable for the situation of full open or full close, not suitable for the situation where the flow needs to be adjusted.
(4) Gate valve body has grooves, so it is not suitable for fluid containing solid particles. In recent years, the gate valve with blowing port can be used in this situation.
(1) Ball valve is widely used in chemical plant. Its sealing performance is reliable, and it is also suitable for regulating the flow. It is generally installed at the pump outlet, upstream of the bypass flowmeter of the regulating valve and other places where the flow needs to be regulated.
(2) When the fluid flows through the valve core, it changes the flow direction, so the pressure drop is large, and it is easy to deposit solids on the valve seat, so it is not suitable for suspension.
(3) Compared with gate valve of the same caliber, stop valve has larger volume, which limits its maximum caliber (maximum dn150-200)
(4) Compared with the common through valve, the pressure drop of Y-type stop valve and angle stop valve is smaller, and the angle valve also has the function of changing the flow direction.
(5) Needle valve is also a kind of stop valve. The valve core is tapered, which can be used for small flow fine adjustment or sampling valve.
Cock, plunger valve, ball valve
(1) The three functions are similar. They are all valves that can be opened and closed quickly. The valve core has transverse opening, the liquid passes through directly, the pressure drop is small, suitable for suspension or viscous liquid. The valve core can be used as L-shaped or T-shaped channel to become a three-way or four-way valve. It is easy to make jacketed valves with regular shape for the situations requiring heat preservation. These valves can be easily made into pneumatic or electric valves for remote control.
(2) The difference between the three is that the 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, and the use temperature is limited by the sealing material.
(1) Check valve is used to prevent reverse flow of fluid. Generally used to prevent pollution, temperature rise or mechanical damage caused by fluid backflow.
(2) Commonly used are swing type, lift type and ball type. The diameter of swing type is larger than the latter two, which can be installed on horizontal pipe or vertical pipe. When installed on vertical pipe, the fluid should flow from bottom to top. The lifting type and ball type have smaller caliber and can only be installed on the horizontal pipeline.
(3) Check valve can only be used to prevent sudden backflow but poor sealing performance. Therefore, other measures should be taken for strictly prohibited materials.
(4) When the inlet of centrifugal pump is in suction state, the bottom valve installed at the inlet pipe end 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 diaphragm valve and pipe clamp valve are used, the fluid only contacts with diaphragm or hose and does not touch other parts of valve body, especially for corrosive fluid or viscous liquid, suspension, etc. However, the range of use is limited by the material of diaphragm or hose.