Check valve is to rely on the media itself to flow and automatically open and close the valve, to prevent the backflow of the media, also known as check valve, reversing valve, and back pressure valve. 

Check valve is an automatic valve, its main role is to prevent the media back, to prevent the pump and drive motor reversal, as well as the release of the container medium. The check valve can also be used to provide a supply of pressure which may rise to more than the pressure of the system. 

Check valve can be divided into swing check valve and lift check valve. The role of this type of valve is only allowing the media to flow in one direction, and stop the flow direction. Usually the valve is automatically work, fluid pressure flow in one direction, the valve open; the opposite direction of fluid flow by gravity, fluid pressure and valve closing effect on the valve seat, thereby cutting off flow. 

The sanitary check valve belongs to this type of valve, which includes swing check valves and lift check valves. Swing check valve has a hinge mechanism. In order to ensure that the valve flap can reach the appropriate position of the valve seat every time, the valve flap design in the hinge mechanism, so that the valve flap is sufficient to have a swing space, and make the valve real, comprehensive contact with the valve seat. 

Valve can be all made of metal, can also be placed on the metal leather, rubber, or synthetic coverage, depending on the performance requirements. Swing check valve in the fully open condition, the fluid pressure is almost unimpeded, so the pressure drop through the valve is relatively small. Lift check valve is located on the valve seat sealing surface. In addition to this valve disc is free to lift, like the rest of the cut-off valve, the fluid pressure valve from the valve seat sealing surface lift, medium return led down to the valve seat, and cut off the flow. According to the conditions of use, the valve flap can be all metal structure, you can also be on the valve frame mounted rubber pad or rubber ring form.

The same as the sanitary shut off valve, lift check valve fluid through the channel is narrow, so the check valve by lifting the pressure drop than the swing check valve a little bigger, and swing check valve flow restrictions very little.

According to its structure and installation, check valve can be divided:

One, swing check valve: swing check valve to the disc valve seat is rotated around the channel axis, because the valve channel is streamlined, but not for the pulsating flow, the sealing performance is less than lift. Swing check valve is divided into single, double valve, the main form of these three points to the valve diameter, the purpose is to prevent the media to stop the flow or back, weakening the hydraulic impact.

Two, lift check valve: the valve flap is along the vertical centerline of the valve sliding check valve, lift check valve can only be installed in the horizontal pipe, small bore check valve can be used on the high-pressure ball. The body of the lift check valve is the same as the globe valve (which can be used as a globe valve), so that the fluid resistance coefficient is larger. The structure is similar to the cut-off valve, the valve body and disc with the same cut-off valve. The lower part of the upper valve and the valve cover processing guide sleeve, the valve in the valve lift free guide simple light driven, when the medium downstream, the valve thrust open by the media, when the media stopped flow, the valve is vertical landing on the seat, preventing the media from the upstream effect. Straight through lift check valve direction of medium inlet and outlet channel direction is perpendicular to the seat; vertical lift check valve, the media import and export channel in the direction of the same direction with the valve seat, the flow resistance is smaller than the straight through.

Three, disc check valve: the valve seat is rotated around the valve pin. Disc check valve structure is simple, can only be installed in the horizontal pipe, poor sealing.

Check valve products, classification is also very detailed:

1 in accordance with the structure, it can divided into lift check valve, swing check valve and butterfly valve, diaphragm valve, the corresponding products are: pressure from the tight seal lift check valve, swing check valve, flange butterfly valve buffer.

(1) the pressure tight seal lift check valve structure is generally similar to the cut-off valve, the valve flap along the line for the lifting movement, reliable action, but the fluid resistance is large, suitable for light and small caliber occasions. Lift check valve can be divided into straight through lift check valve and vertical lift check valve.

(2) swing type flange check valve disc is rotated around the shaft, the fluid resistance is generally less than the lift check valve, it is suitable for large caliber occasions. Its applicable media include water, steam, oil, nitric acid, strong oxidizing medium, urea, etc.. 

Sanitary check valve is widely used in power plants, petroleum, chemical, pharmaceutical, food and other industries, can be directly used with imported equipment. Swing check valve according to the number of disc can be divided into single swing type, double valve swing and multi disc swing type three. Single swing check valve is generally applicable to medium caliber occasions. Large diameter pipeline single swing check valve, in order to reduce water hammer pressure, it is best to use to reduce the water hammer pressure slow closing check valve. Double disc swing check valve is suitable for medium and large diameter pipeline. Double disc swing check valve structure is small, light weight, is a rapid development of the check valve; multi disc swing check valve for large diameter pipeline.

(3) butterfly check valve structure is similar to sanitary butterfly valve. The structure is simple, the flow resistance is small, and the water hammer pressure is small.

(4) diaphragm type check valve has a variety of structural forms, the diaphragm is used as the opening and closing parts, because of its good performance, simple structure and low cost, the water hammer has developed rapidly in recent years. However, the use of diaphragm check valve temperature and pressure by the diaphragm material restrictions.

2 according to the main material, it can be divided into cast iron check valve, brass check valve, stainless steel check valve, etc., the corresponding products are H64W brass welding swing check valve, vertical pure nickel check valve, check valve, etc..

3 in accordance with the function, it can be divided into silent check valve, Muffler check valve, etc., the corresponding products of our company have Muffler check valve, brass on the clip, such as noise check valve.

The basic function of the liquid trap is to condense the condensed water, air and carbon dioxide gas in the steam system as soon as possible. Many varieties traps have different performance. Steam traps, its characteristics should be selected to best meet the steam heating equipment operation before considering other objective conditions, such choices you need to trap is the correct and effective.

The main components of the double metal sheet trap are bimetal temperature sensing elements, which is heated and deformed with the steam temperature. Bimetallic trap is provided with an adjusting bolt, can adjust the temperature according to the needs of the general undercooling range is lower than the saturation temperature is 15 DEG -30 DEG C, back pressure is higher than 70%, to row non condensing gas, not afraid of cold, small size, resistant to water hammer, high pressure, can be installed anywhere.

The working principle of bimetallic trap

When the device has just started, the pipeline appears low temperature condensate water, double metal sheet is flat, the valve core spring in the spring, the sanitary valve is in the open position. When the condensate water temperature gradually increased, the bimetal sheet temperature sensitive components began to bend deformation, and the valve core to the closed position. In the condensate to saturation temperature before the trap began to close. Double metal sheet is switched with the steam temperature control valve.

The advantages of common gate valve structure

1, the valve opening and closing needs more effort. Is compared with the cut-off valve, because whether it is opened or closed, the direction and the movement of the gate and the media flow direction is perpendicular.

2, the height is big, open and close time is long. Gate opening and closing stroke is larger, the decline is carried out through the screw.

3, water hammer phenomenon is not easy to produce. The reason is the closing time is long.

4, the media can flow in any direction on both sides, easy to install. Gate valves are symmetrical on both sides of the channel.

5, the length of the structure is smaller.

6, sealing surface is easy to wear and tear, affect the service life. When the sanitary valve is opened and closed, the two sealing surfaces of the gate plate and the valve seat are mutually friction and sliding, so as to produce the abrasion under the pressure of the medium, and the sealing performance and the service life can be shortened.

7, the price is more expensive. Contact sealing surface is more complex processing, especially the gate seat sealing surface and more parts are not easy to process.

8, the body is simple, the structure of short length, good manufacturing process, wide application.

9, compact structure, good rigidity, smooth channel, small flow resistance, sealing surface of stainless steel and carbide, long service life, the use of PTFE packing.

Stainless steel sanitary diaphragm valve

Manual or pneumatic operation, especially applied for the hygienic and aseptic processes in the pharmaceutical industry. The valve is ideal for fluid control and on / off tasks. Diaphragm provides body seal and valve seat seal. There is no path to the external environment, so the diaphragm is suitable for aseptic processes. 

When the valve is closed, the pressure pad supported the diaphragm moves toward the sealing surface of the valve body. When the pressure plate moves, the diaphragm bends and is forced into the valve seat area in the center of the valve body, thereby closing the fluid path to the valve body. The sanitary diaphragm valves can be operated manually or pneumatically, and can be controlled by a controller and an electromagnetic valve.

Welded sanitary check valves are used in stainless steel piping systems to prevent fluid backflow.

Technical data of welding sanitary check valve:

If the check valve is installed in a vertical pipe, open the valve required pressure is about 300-600kpa, the maximum conveying pressure of 800kpa, temperature ranged according to the seal material selection.

Welded sanitary check valve material:304 stainless steel

Sealing ring: silicone rubber (VMQ), fluorine rubber (FPM) three ethylene propylene (EPDM)

Welding type sanitary check valve is installed in a vertical pipe, open the valve required pressure is about 300-600kpa, the maximum conveying pressure is 800kpa, temperature range according to the seal material selection.