02 May 2018Email

Valve is line attachments used to open and close lines, control flow, and regulate and control the parameters (temperature, pressure, and flow rate) of the medium being transported. According to its function, it can be divided into shut-off valve, check valve, regulating valve and so on.

The valve is a control component in the fluid delivery system, with functions such as cut-off, regulation, diversion, anti-backflow, regulation, shunt or overflow relief. Valves for fluid control systems range from the simplest shut-off valves to the extremely complex self-control systems used in a wide variety of sizes and sizes.

Valves can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metals, and radioactive media. According to the material, the valve is also divided into cast iron valve, cast steel valve, stainless steel valve (201, 304, 316, etc.), chrome molybdenum steel valve, chrome molybdenum vanadium steel valve, duplex steel valve, plastic valve, non-standard custom valve.



(1) Shut-off valve
This type of valve is open and closed. Standing on the inlet and outlet of cold and heat sources, equipment inlet and outlet, and pipeline branch lines (including risers), it can also be used as drain valve and bleed valve. Common shut-off valves include gate valves, globe valves, ball valves, and butterfly valves.
Gate valves can be divided into open and dark rods, single and double gates, wedge gates and parallel gates. The tightness of the gate valve is not good, and the opening of the large-diameter gate valve is difficult; the size of the valve body is small along the direction of the water flow, the flow resistance is small, and the nominal diameter of the gate valve is large.
The shut-off valve is divided into three types according to the flow direction of the medium straight flow, right angle type and direct current type, and there are clear poles and dark poles. The shut-off valve is tighter than the gate valve, the valve body is long, the flow resistance is large, and the maximum nominal diameter is DN200.
The spool of the ball valve is an open spherical ball. The plated valve stem is fully open when the spherical opening is facing the axis of the pipe, and is fully closed by 90°. The ball valve has a certain adjustment performance, and the closing is tight.
The valve spool of the butterfly valve is a circular valve plate that rotates along the vertical axis of the vertical pipe axis. When the plane of the valve plate coincides with the axis of the pipe, it is fully open; when the plane of the ram is perpendicular to the axis of the pipe, it is fully closed. The butterfly valve body has a small length and a small flow resistance, which is higher than the price of the gate valve and the globe valve.


(2) Check valve
These valves are used to prevent backflow of the medium, open it by the kinetic energy of the fluid itself, and automatically shut down in the reverse flow. Standing at the pump outlet, steam trap outlet, and other places where fluid flow is not allowed. The check valve is divided into three types: swing type, lift type and clip type. For swing-type check valves, when the fluid can only flow from left to right, it automatically closes when flowing in the reverse direction. For the lift check valve, when the fluid flows from left to right, the spool rises to form a passage, and when the flow is reversed, the spool is pressed against the valve seat to be closed. For the wafer type check valve, when the fluid flows from left to right, the spool is opened to form a passage. When the flow is reversed, the spool is pressed against the valve seat and closed, and the clip type check valve can be multi-position. Installation, small size, light weight and compact structure.


(3) regulating valve
The pressure difference between the valve and the valve is constant. When the opening degree of the ordinary valve changes within a large range, the flow rate does not change much, and when it reaches a certain opening degree, the flow rate changes abruptly, that is, the adjustment performance is not good. The regulating valve can change the spool stroke according to the direction and size of the signal to change the resistance of the valve, so as to achieve the purpose of regulating the flow. The regulating valve is divided into a manual regulating valve and an automatic regulating valve, and the manual or automatic regulating valve is divided into many types, and the regulating performance is also different. The automatic regulating valve has a self-operated flow regulating valve and a self-operated differential pressure regulating valve.


(4) Vacuum class
Vacuum types include vacuum ball valves, vacuum flap valves, vacuum inflation valves, pneumatic vacuum valves, and the like. The function of the vacuum system used in the vacuum system to change the direction of the air flow, adjust the flow of the gas, and cut or close the pipeline is called a vacuum valve.


(5) Special purpose categories
Special purpose categories include pigging valves, venting valves, blowdown valves, exhaust valves, filters, etc.
The exhaust valve is an indispensable auxiliary component in the pipeline system and is widely used in boilers, air conditioners, oil and gas, and water supply and drainage pipes. It is often installed at the commanding heights or elbows to eliminate excess gas in the pipeline, improve the efficiency of the pipeline and reduce energy consumption.


According to the nominal pressure:
(1) Vacuum valve: refers to a valve whose working pressure is lower than the standard atmospheric pressure.
(2) Low pressure valve: refers to the valve with nominal pressure PN ≤1.6Mpa.
(3) Medium pressure valve: refers to the valve with nominal pressure PN of 2.5Mpa, 4.0Mpa and 6.4Mpa.
(4) High pressure valve: refers to a valve with a nominal pressure PN of 10.0Mpa to 80.0Mpa.
(5) Ultra-high pressure valve: refers to the valve with nominal pressure PN≥100.0Mpa.


According to working temperature:
(1) Ultra-low temperature valve: for valves with medium working temperature t<-101°C.
(2) Normal temperature valve: used for valves with medium working temperature -29 °C < t < 120 °C.
(3) Medium temperature valve: used for valves with media working temperature 120 °C < t < 425 °C.
(4) High temperature valve: used for valves with medium working temperature t>425°C.

According to the driving method, it can be divided into automatic valve type, power driven valve type and manual valve type.
(1) Small-diameter valve: a valve with a nominal diameter of DN≤40mm.
(2) Medium diameter valve: a valve with a nominal diameter DN of 50 to 300 mm.
(3) Large-diameter valve: a valve with a nominal diameter of DN of 350 to 1200 mm.
(4) Extra large diameter valve: valve with nominal diameter DN≥1400mm

The structural characteristics of the valve are divided according to the direction in which the closure member moves relative to the valve seat:
(1) Truss shape: the closing member moves along the center of the valve seat;
(2) cock and ball: the closing member is a plunger or a ball that rotates around its centerline; such as a plug valve, a ball valve
(3) Gate shape: the closing member moves along the center of the vertical valve seat; such as gate valve, gate, etc.
(4) Swing shape: the closing member rotates around the shaft outside the valve seat; such as a swing check valve, etc.
(5) Butterfly shape: the disc of the closing piece rotates around the shaft in the valve seat; such as butterfly valve, butterfly check valve, etc.
(6) Spool shape: The closing member slides in a direction perpendicular to the passage.

Connection method
(1) Threaded connection valve: The valve body has internal or external thread, which is connected with the pipe thread..
(2) Flange connection valve: The valve body is flanged and connected to the pipe flange.
(3) Welded connection valve: The valve body has a welding groove and is welded to the pipe.
(4) Clamp connection valve: The valve body has a clamping port and is connected with the pipe clamp.
(5) ferrule connection valve: connected with the pipe with a ferrule.
(6) Matching the connecting valve: The connection form in which the valve and the two pipes are directly clamped together by bolts.

According to the valve body material
(1) Metal material valve: The valve body and other parts are made of metal material. Such as cast iron valves, cast steel valves, alloy steel valves, copper alloy valves, aluminum alloy valves, lead alloy valves, titanium alloy valves, Monel alloy valves.
(2) Non-metallic material valves: Parts such as valve bodies are made of non-metallic materials. Such as plastic valves, enamel valves, ceramic valves, glass steel valves and so on.

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