Valve Selection and Setting Position
(1) Valve Selection Principle for Water Supply Pipeline
1. When the pipe diameter is not more than 50 mm, globe valve should be used. When the pipe diameter is greater than 50 mm, gate valve and butterfly valve should be used.
2. When flow and water pressure need to be regulated, adjusting valves and globe valves should be adopted.
3. Locations requiring low flow resistance (e.g. on suction pipes of pumps), gate valves should be used.
4. Sluice valves and butterfly valves shall be used in pipelines where water flow requires bidirectional flow, and globe valves shall not be used.
5. Butterfly valve and ball valve should be used in small installation space.
6. Cut-off valves should be used in frequently opened and closed pipelines.
7. Multifunctional valves should be used in the outlet pipes of large-caliber pumps.
(2) Valve location in water supply pipeline
1. Water supply pipeline of residential district is introduced from municipal water supply pipeline
2. Nodes of outdoor circular pipe network in residential area should be set up according to the requirements of partition. When the annular pipe section is too long, it is advisable to install sectional valves
3. The beginning of branch or household pipes connected from the main water supply pipes in residential districts
4. Household pipe, water meter and branch riser (bottom of riser, upper and lower end of vertical annular pipe network riser)
5. The branch pipe of the ring pipe network and the connecting pipe through the branch pipe network
6. The starting point of the distribution pipe connected by the indoor water supply pipeline to the household and the public toilet, and the water distribution point on the distribution branch pipe shall be set when there are three or more water distribution points.
7. Outlet pipe of water pump, suction pump of self-irrigation pump
8. Inlet and outlet pipes and discharge pipes of water tanks
9. Water supply pipes for equipment (such as heaters, cooling towers, etc.)
10. Distribution pipes for sanitary appliances (such as large, urinal, washbasin, shower, etc.)
11. Some accessories, such as automatic exhaust valve, relief valve, water hammer eliminator, pressure gauge, sprinkler plug, front and rear of relief valve and backflow preventer, etc.
12. Drainage valve should be installed at the lowest point of water supply network
(3) Choice of Check Valves
Check valves should generally be selected according to their installation location, water pressure in front of the valve, sealing performance requirements after closing and the size of water hammer caused by closing.
1. When the water pressure in front of the valve is small, swing type, ball type and shuttle type check valves should be selected.
2. When the sealing performance after closure is strictly required, check valves related to the closing spring should be selected.
3. When it is required to weaken the closing water hammer, it is advisable to select a quick-closing silence check valve or a slow-closing check valve with a damper.
4. Check valves should be self-closing under the action of gravity or spring force when the valve is broken or the spool is broken.
(4) Installation of check valves in water supply pipelines
On the inlet pipe; on the inlet pipe of the sealed water heater or water equipment; on the outlet pipe of the pump; on the outlet pipe of the water tank, water tower and the outlet pipe section of the highland pool where the inlet and outlet pipes share one pipe.
Note: No check valve is required in the section with pipeline backflow preventer.
(5) Location of exhaust devices in water supply pipelines
1. The automatic exhaust valve should be installed at the end and the highest point of the intermittent water supply network.
2. The pipe section with obvious fluctuation and accumulation of air in the water supply network has been set up with automatic exhaust valve or manual valve at the peak of the section.
3. Pneumatic water supply device. When using automatic air-filling pneumatic water tank, the highest point of its distribution pipe network should be equipped with automatic exhaust valve.
Advantages and Disadvantages of Various Valves
1, Gate valve
2. Butterfly valve
3. Ball valve
4. Globe Valve
5. Plug /Cock valve, Safety valve, Steam trap, Pressure relief valve, Check valve