Advantages and disadvantages of valve installation

1. Valves used on water supply pipes are generally selected according to the following principles:

When the pipe diameter is not more than 50mm, a cut-off valve should be adopted. When the pipe diameter is larger than 50mm, gate valves and butterfly valves are used.
Need to adjust the flow, water pressure should be used when regulating valve, globe valve.

For areas where the resistance to water flow is small (such as on the suction pipe of a pump), gate valves should be used.
Pipe valves and butterfly valves shall be used on the sections of the water that require two-way flow, and no stop valves may be used.
The small installation space should adopt butterfly valve and ball valve.
In the often open and closed pipe segment, shut-off valves should be adopted.
Multi-purpose valves should be used on the outlet pipe of the larger diameter pump.
2. The valve should be set on the following parts of the water supply pipe:

The residential community water supply pipe is introduced from the pipe section of the municipal water supply pipe.
The nodes of the outdoor circular pipe network in the residential area shall be set according to the separation requirements. When the annular pipe section is too long, a sectional valve should be set.
From the residential area, the branch pipe that is connected to the main water pipe starts or ends.
Inlet pipe, water meter and branch risers (at the bottom of the riser and at the upper and lower ends of the vertical ring pipe riser).
The branch pipe of the ring pipe network and the connection pipe of the branch pipe network.
The indoor water supply pipe starts at the end of the water distribution pipe connected to the occupant and the public toilet, and the water distribution point on the water distribution pipe is set at 3 or more.
The outlet pipe of the pump, the suction pump of the irrigation pump.
Water tank inlet and outlet pipes and discharge pipes.
Equipment (such as heaters, cooling towers) fill the water supply pipe.
Plumbing fixtures (such as large and urinals, washbasins, showers, etc.).
Some accessories, such as automatic exhaust valve, pressure relief valve, water hammer eliminator, pressure gauge, sprinkler, etc., before and after the pressure relief valve and backflow preventer.
The drain valve should be set at the lowest point of the water supply network.
3. The check valve should generally be selected based on factors such as the installation location, the water pressure before the valve, the closed performance requirements after closing, and the size of the water hammer caused when closing:

When the water pressure before the valve is small, swing type, ball type and shuttle type check valves should be selected.
When close tightness is required after closing, a check valve with spring closing should be used.
When it is required to weaken the closing of the water hammer, a quick-closed muffler check valve or slow-closing check valve with damper device should be used.
The check valve or spool of the check valve should be able to close by itself under the action of gravity or spring force.
4. Check valves should be provided on the following sections of the water supply pipeline:

Into the pipe; closed water heater or water equipment on the water inlet pipe; pump out of the water pipe; in and out of the water pipe combined with a pipe tank, water tower, high water tank on the outlet pipe section.
Note: Pipe sections equipped with pipe backflow preventers do not need to be fitted with check valves.

5. The following parts of the water supply pipeline should be equipped with an exhaust device:

For intermittently used water supply networks, automatic exhaust valves should be provided at the end of the pipe network and at the highest point.
The water pipe network has obvious undulations that accumulate air, and automatic exhaust valves or manual valve exhaust have been set at the peaks of the segment.
In the air pressure water supply device, when the automatic air pressure type water tank is used, the highest point of the water distribution network shall be provided with an automatic exhaust valve.
Second, the advantages and disadvantages of various valves:

Gate valve: A gate valve is a valve in which the closing member (the gate plate) moves in the vertical direction along the axis of the channel, and is mainly used as a cutting medium on the pipeline, that is, fully open or fully closed. In general, the gate valve cannot be used as a regulating flow. It can be applied to low temperature pressure can also be applied to high temperature and high pressure, and according to the different materials of the valve. However, gate valves are generally not used to convey fluids such as mud.

advantage:
1 The fluid resistance is small; 2 The required torque for starting and closing is small; 3 It can be used on the ring network pipeline where the medium flows in both directions, that is to say the flow direction of the medium is not limited; 4 When the full open, the sealing surface is affected by the working medium. The erosion is smaller than the shut-off valve; the structure of the 5-shaped body is relatively simple and the manufacturing process is good; 6 the structure is relatively short.

Disadvantages:
1 The external dimensions and opening height are large, and the space required for installation is also large; 2 In the process of opening and closing, the sealing surface is relatively frictional and wear-resistance is large, and it is even easy to cause scratches at high temperatures; 3 General gate valve There are two sealing surfaces, which add some difficulties for processing, grinding and maintenance; 4 long opening and closing time.

Butterfly Valve: A butterfly valve is a type of valve that opens, closes, and regulates fluid passages by reciprocating a disc about 90°.

advantage:
1 simple structure, small size, light weight, consumables, do not use in large-diameter valves; 2 rapid opening and closing, small flow resistance; 3 can be used for media with suspended solid particles, can also be used for powder according to the strength of the sealing surface And granular media. It can be applied to the bidirectional opening and closing of ventilation and dust removal pipelines and is widely used in gas pipelines and water in metallurgy, light industry, electric power, and petrochemical systems.

Disadvantages:
1 The flow adjustment range is not large. When it is opened up to 30%, the flow rate will be more than 95%. 2 Due to the restrictions of the structure of the butterfly valve and the sealing material, it is not suitable for high temperature and high pressure piping systems. The general operating temperature is below 300°C and below PN40. 3 The sealing performance is poor with respect to the ball valve and the cut-off valve, so the sealing requirements are not very high.

Ball valve: It is evolved from the plug valve. Its opening and closing part is a ball. It uses the ball to rotate 90° about the axis of the valve stem to open and close. The ball valve is mainly used for cutting, distributing and changing the flow direction of the medium on the pipeline. The ball valve designed as a V-shaped opening also has a good flow regulation function.

advantage:
1 has the lowest flow resistance (actually 0); 2 because it does not get stuck during operation (in the absence of lubricant), it can be reliably applied to corrosive media and low-boiling liquids; 3 at higher pressures And within the temperature range, can achieve a complete seal; 4 can achieve fast opening and closing, some structures open and close time is only 0.05 ~ 0.1s, to ensure that can be used in the test bench automation system. When opening and closing the door quickly, there is no impact on the operation. 5Spherical closing parts can be automatically positioned at the boundary position; 6The working medium is sealed reliably on both sides; 7 When fully open and fully closed, the sealing surfaces of the ball body and the valve seat are isolated from the medium, so the medium that passes the valve at high speed will not Cause the sealing surface erosion; 8 compact, light weight, can be considered that it is the most reasonable valve structure for low temperature medium system; 9 valve body symmetry, especially welded valve body structure, can well withstand the stress from the pipe ;10 The closure can withstand the high pressure difference when it is closed. Fully welded valve body ball valve, can be buried directly in the ground, so that the valve internals are not eroded, the maximum service life of up to 30 years, is the best oil, natural gas pipeline valve.

Disadvantages:
1 Because the ball valve's most important seat sealing material is PTFE, it is inert to almost all chemical substances, and it has a small friction coefficient, stable performance, not easy to age, a wide temperature range and excellent sealing performance. The comprehensive features. However, the physical properties of Teflon, including its high coefficient of expansion, cold flow sensitivity, and poor thermal conductivity, require that the design of the seat seal be performed around these characteristics. Therefore, when the seal material hardens, the reliability of the seal is impaired. Moreover, PTFE has a low temperature rating and can only be used at temperatures less than 180°C. Above this temperature, the sealing material will age. Considering long-term use, it is generally not used at 120°C. 2 Its regulation performance is worse than the shutoff valve, especially the pneumatic valve (or electric valve).

Cut-off valve: It refers to the valve that the closing member (valve) moves along the centerline of the valve seat. According to this kind of movement of the valve flap, the change of the valve seat port is in direct proportion to the valve stroke. Because the valve stem of this type of valve has a relatively short opening and closing stroke and a very reliable cutting function, because the change of the valve seat port is proportional to the stroke of the valve disc, it is very suitable for regulating the flow rate. Therefore, this type of valve is used to cut off or regulate and throttling.

advantage:
1 During the opening and closing process, the friction between the valve flap and the sealing surface of the valve body is smaller than that of the gate valve and is therefore wear-resistant. 2 opening height is generally only 1/4 of the seat channel, so much smaller than the gate valve 3 usually has only one sealing surface on the valve body and valve, so the manufacturing process is relatively good, easy to maintain. 4 Because its filler is generally a mixture of asbestos and graphite, it has a higher temperature rating. General steam valve use cut-off valve.

Disadvantages:
1 Because the flow direction of the medium through the valve has changed, the minimum flow resistance of the shutoff valve is also higher than most other types of valves; 2 Because the stroke is longer, the opening speed is slower.

Reducing valve: It is a valve that regulates the inlet pressure to a certain required outlet pressure and relies on the energy of the medium to keep the outlet pressure automatically stable.

Check valve: also known as reverse flow valve, check valve, back pressure valve and check valve. These valves are automatically opened and closed by the force generated by the flow of the medium in the pipeline, and belong to an automatic valve. The check valve is used in the piping system. Its main function is to prevent the back flow of the medium, prevent the reverse rotation of the pump and the drive motor, and discharge the container medium. Check valves can also be used on pipelines where the pressure may rise above the system pressure to provide supplemental systems. Can mainly be divided into swing-type (depending on the center of gravity rotation) and lifting (moving along the axis).

1. Valves used on water supply pipes are generally selected according to the following principles:

When the pipe diameter is not more than 50mm, a cut-off valve should be adopted. When the pipe diameter is larger than 50mm, gate valves and butterfly valves are used.
Need to adjust the flow, water pressure should be used when regulating valve, globe valve.

For areas where the resistance to water flow is small (such as on the suction pipe of a pump), gate valves should be used.
Pipe valves and butterfly valves shall be used on the sections of the water that require two-way flow, and no stop valves may be used.
The small installation space should adopt butterfly valve and ball valve.
In the often open and closed pipe segment, shut-off valves should be adopted.
Multi-purpose valves should be used on the outlet pipe of the larger diameter pump.
2. The valve should be set on the following parts of the water supply pipe:

The residential community water supply pipe is introduced from the pipe section of the municipal water supply pipe.
The nodes of the outdoor circular pipe network in the residential area shall be set according to the separation requirements. When the annular pipe section is too long, a sectional valve should be set.
From the residential area, the branch pipe that is connected to the main water pipe starts or ends.
Inlet pipe, water meter and branch risers (at the bottom of the riser and at the upper and lower ends of the vertical ring pipe riser).
The branch pipe of the ring pipe network and the connection pipe of the branch pipe network.
The indoor water supply pipe starts at the end of the water distribution pipe connected to the occupant and the public toilet, and the water distribution point on the water distribution pipe is set at 3 or more.
The outlet pipe of the pump, the suction pump of the irrigation pump.
Water tank inlet and outlet pipes and discharge pipes.
Equipment (such as heaters, cooling towers) fill the water supply pipe.
Plumbing fixtures (such as large and urinals, washbasins, showers, etc.).
Some accessories, such as automatic exhaust valve, pressure relief valve, water hammer eliminator, pressure gauge, sprinkler, etc., before and after the pressure relief valve and backflow preventer.
The drain valve should be set at the lowest point of the water supply network.
3. The check valve should generally be selected based on factors such as the installation location, the water pressure before the valve, the closed performance requirements after closing, and the size of the water hammer caused when closing:

When the water pressure before the valve is small, swing type, ball type and shuttle type check valves should be selected.
When close tightness is required after closing, a check valve with spring closing should be used.
When it is required to weaken the closing of the water hammer, a quick-closed muffler check valve or slow-closing check valve with damper device should be used.
The check valve or spool of the check valve should be able to close by itself under the action of gravity or spring force.
4. Check valves should be provided on the following sections of the water supply pipeline:

Into the pipe; closed water heater or water equipment on the water inlet pipe; pump out of the water pipe; in and out of the water pipe combined with a pipe tank, water tower, high water tank on the outlet pipe section.
Note: Pipe sections equipped with pipe backflow preventers do not need to be fitted with check valves.

5. The following parts of the water supply pipeline should be equipped with an exhaust device:

For intermittently used water supply networks, automatic exhaust valves should be provided at the end of the pipe network and at the highest point.
The water pipe network has obvious undulations that accumulate air, and automatic exhaust valves or manual valve exhaust have been set at the peaks of the segment.
In the air pressure water supply device, when the automatic air pressure type water tank is used, the highest point of the water distribution network shall be provided with an automatic exhaust valve.
Second, the advantages and disadvantages of various valves:

Gate valve: A gate valve is a valve in which the closing member (the gate plate) moves in the vertical direction along the axis of the channel, and is mainly used as a cutting medium on the pipeline, that is, fully open or fully closed. In general, the gate valve cannot be used as a regulating flow. It can be applied to low temperature pressure can also be applied to high temperature and high pressure, and according to the different materials of the valve. However, gate valves are generally not used to convey fluids such as mud.

advantage:
1 The fluid resistance is small; 2 The required torque for starting and closing is small; 3 It can be used on the ring network pipeline where the medium flows in both directions, that is to say the flow direction of the medium is not limited; 4 When the full open, the sealing surface is affected by the working medium. The erosion is smaller than the shut-off valve; the structure of the 5-shaped body is relatively simple and the manufacturing process is good; 6 the structure is relatively short.

Disadvantages:
1 The external dimensions and opening height are large, and the space required for installation is also large; 2 In the process of opening and closing, the sealing surface is relatively frictional and wear-resistance is large, and it is even easy to cause scratches at high temperatures; 3 General gate valve There are two sealing surfaces, which add some difficulties for processing, grinding and maintenance; 4 long opening and closing time.

Butterfly Valve: A butterfly valve is a type of valve that opens, closes, and regulates fluid passages by reciprocating a disc about 90°.

advantage:
1 simple structure, small size, light weight, consumables, do not use in large-diameter valves; 2 rapid opening and closing, small flow resistance; 3 can be used for media with suspended solid particles, can also be used for powder according to the strength of the sealing surface And granular media. It can be applied to the bidirectional opening and closing of ventilation and dust removal pipelines and is widely used in gas pipelines and water in metallurgy, light industry, electric power, and petrochemical systems.

Disadvantages:
1 The flow adjustment range is not large. When it is opened up to 30%, the flow rate will be more than 95%. 2 Due to the restrictions of the structure of the butterfly valve and the sealing material, it is not suitable for high temperature and high pressure piping systems. The general operating temperature is below 300°C and below PN40. 3 The sealing performance is poor with respect to the ball valve and the cut-off valve, so the sealing requirements are not very high.

Ball valve: It is evolved from the plug valve. Its opening and closing part is a ball. It uses the ball to rotate 90° about the axis of the valve stem to open and close. The ball valve is mainly used for cutting, distributing and changing the flow direction of the medium on the pipeline. The ball valve designed as a V-shaped opening also has a good flow regulation function.

advantage:
1 has the lowest flow resistance (actually 0); 2 because it does not get stuck during operation (in the absence of lubricant), it can be reliably applied to corrosive media and low-boiling liquids; 3 at higher pressures And within the temperature range, can achieve a complete seal; 4 can achieve fast opening and closing, some structures open and close time is only 0.05 ~ 0.1s, to ensure that can be used in the test bench automation system. When opening and closing the door quickly, there is no impact on the operation. 5Spherical closing parts can be automatically positioned at the boundary position; 6The working medium is sealed reliably on both sides; 7 When fully open and fully closed, the sealing surfaces of the ball body and the valve seat are isolated from the medium, so the medium that passes the valve at high speed will not Cause the sealing surface erosion; 8 compact, light weight, can be considered that it is the most reasonable valve structure for low temperature medium system; 9 valve body symmetry, especially welded valve body structure, can well withstand the stress from the pipe ;10 The closure can withstand the high pressure difference when it is closed. Fully welded valve body ball valve, can be buried directly in the ground, so that the valve internals are not eroded, the maximum service life of up to 30 years, is the best oil, natural gas pipeline valve.

Disadvantages:
1 Because the ball valve's most important seat sealing material is PTFE, it is inert to almost all chemicals and has a low coefficient of friction and