About the use of check valves

Usage of check valve

1、 Swing check valve: the disc of the swing check valve is in a disc shape and rotates around the rotating shaft of the valve seat channel. Because the channel in the valve is streamlined, the flow resistance ratio increases

The drop check valve is small, which is suitable for large-diameter occasions with low flow rate and infrequent flow change, but it is not suitable for pulsating flow, and its sealing performance is not as good as the lift check valve. Swing check valve is divided into single disc type, double disc type and multi half type. These three forms are mainly divided according to the valve diameter, in order to prevent the hydraulic impact from being weakened when the medium stops flowing or flows back.

2、 Lift check valve: a check valve whose disc slides along the vertical centerline of the valve body. The lift check valve can only be installed on the horizontal pipeline. On the high-pressure small-diameter check valve, the disc can use a ball. The body shape of lift check valve is the same as that of stop valve, which can be used with stop valve, so its fluid resistance coefficient is large. Its structure is similar to the stop valve, and the valve body and disc are the same as the stop valve. The upper part of the valve disc and the lower part of the valve cover are processed with a ring sleeve Jane. The valve disc guide Jane can rise and fall freely in the valve disc guide Jane. When the medium flows downstream, the valve disc is opened by the medium thrust. When the medium stops flowing, the valve disc falls on the valve seat vertically to prevent the reverse flow of the medium. The direction of medium inlet and outlet channel of straight through lifting check valve is perpendicular to the direction of valve seat channel; For vertical lift check valve, the direction of inlet and outlet channel of Sri Lanka is the same as that of valve seat channel, and its flow resistance is smaller than that of straight through type.

3、 Disc check valve: a check valve whose disc rotates around the pin shaft in the valve seat. Disc check valve has simple structure and can only be installed on horizontal pipeline with poor sealing.

4、 Pipeline check valve: a valve whose disc slides along the center line of the valve body. Pipeline check valve is a new type of valve. It has the advantages of small volume, light weight and easy processing

Good workmanship is the development direction of check valve -. However, the fluid resistance coefficient is slightly larger than that of swing check valve.

5、 Compression check valve: This valve [] is used as a boiler feed water and steam shut-off valve. It has the comprehensive function of lifting check valve, stop valve or angle valve.

In addition, there are some check valves that are not suitable for pump outlet installation, such as bottom valve, spring type, Y-type and other check valves.

Working principle of check valve

Check valve refers to the valve that automatically opens and closes the valve disc depending on the flow of the medium itself to prevent the backflow of the medium, also known as check valve, one-way valve, backflow valve and back pressure valve. The check valve belongs to an automatic valve, which is mainly used to prevent medium backflow, reverse rotation of pump and driving motor, and discharge of container medium. The check valve can also be used on the pipeline to supply the auxiliary system in which the pressure may rise above the system pressure. Check valves can be mainly divided into swing check valves, which rotate according to the center of gravity and lift check valves move along the axis. Check valve this type of valve] is used to only allow the medium to flow in one direction and prevent the flow in the opposite direction. Usually, this valve works automatically. Under the action of fluid pressure flowing in one direction, the valve disc opens; When the fluid flows in the opposite direction, the fluid pressure and the self weight of the valve disc act on the valve seat, so as to cut off the flow. The check valve belongs to this type of valve, which includes swing check valve and lift check valve. The swing check valve has a medium hinge mechanism, and a valve disc like a door freely rests on the inclined seat surface. In order to ensure that the valve clack can reach the appropriate position of the valve seat surface every time, the valve clack is designed in the hinge mechanism, so that the valve clack has enough swing space and makes the valve clack really and comprehensively contact with the valve seat. The valve disc can be made of metal, or inlaid with leather, rubber or synthetic coverage, depending on the requirements of service performance. When the swing check valve is fully open, the fluid pressure is almost unimpeded, so the pressure drop through the valve] is relatively small. The disc of the lift check valve is located on the sealing surface of the valve seat on the valve body. In addition to the free lifting of the valve disc, the phase part of the valve is like a stop valve. The fluid pressure lifts the valve disc from the sealing surface of the valve seat, and the medium backflow causes the valve disc to fall back to the valve seat and cut off the flow. According to the service conditions, the valve disc can be of all metal structure or inlaid with rubber pad or rubber ring on the valve disc frame. Like the stop valve, the passage of fluid through the lift check valve is also narrow, so the pressure drop through the lift check valve is larger than that of the swing check valve, and the flow of the swing check valve is rarely limited.

Main function of check valve

-- purpose of wafer check valve:

The check valve is installed in the pipeline system and its main function is to prevent medium backflow. The check valve is an automatic valve opened and closed by medium pressure. Wafer check valve is applicable to nominal pressure PN1.0MPa ~ 42.0mpa and class150 ~ 25000; Nominal diameter DN15 ~ 1200mm, nps1 / 2 ~ 48; On various pipelines with operating temperature of - 196 ~ 540 ° C, it is used to prevent medium backflow. By selecting different materials, it can be applied to water, steam, oil, nitric acid, acetic acid, strong oxidizing medium, uric acid and other media

2、 Main materials of wafer check valve:

There are carbon steel, low temperature steel, dual phase steel F51 / F55, titanium alloy, aluminum bronze, Inconel, SS304, ss304l, SS316, SS316L, chromium molybdenum steel, Nair 400 / 500, 20# alloy, Hastelloy and other metal materials. Application and structural characteristics of wafer check valve

3、 Standards and specifications for wafer check valves:

1. Design and manufacturing: api594, API6D, JB / t8937, JB / t3595,

2. Structure length: api594, API6D, din3202, JB / t8937, ANSI / ASME B16.10

3. Excitation and temperature class: ANSI B16.34, din2401, GB / t9124, hg20604, hg20625, sh3406, JB / T74

4. Test and inspection: API598, JB / t9092, GB / t13927

5. Piping flange: JB / T74 ~ 90, GB / t9112-9124, hg20592 ~ 20635, sh3406, ANSI / ASME B 16.5, din2543-2548

GB/T13402、API605、 ASMEB17

4、 Structural features of wafer check valve:

1. The structural length is short, and its structural length is only 1 / 4 ~ 1 / 8 of that of traditional flange check valve

2. Small size, light weight and heavy weight, only 1 / 4 ~ 1 / 20 of the traditional flange check valve

3. The valve disc closes quickly and the water hammer pressure is small

4. Both horizontal and vertical pipes can be used for easy installation

5. The flow channel is unobstructed and the fluid resistance is small

6. Sensitive action and good sealing performance

7. The valve disc has short stroke and small closing impact

8. The overall structure is simple, compact and beautiful

9. Long service life and reliable performance

The function of check valve in the water supply system of water pump is to prevent the impact of high-pressure water return on the impeller of water pump. During the operation of the system, when the water pump suddenly stops running for some reason, the pressure in the pump disappears, and the high-pressure water connected with the outlet of the water pump will flow back to the water pump in reverse. When a check valve is installed at the outlet of the water pump, it will be closed immediately to prevent the reverse flow of high-pressure water back to the water pump. The function of check valve in hot water system is to prevent hot water from flowing back into the pipeline. If it is PVC pipe, it is likely to burn the pipe and even hurt people, especially in the solar water heater system.