This paper mainly introduces the product selection, design principles, the precautions for selecting the HVAC system valve, the setting of the check valve, and the selection of the check valve for the valves for HVAC refrigeration and ventilation pipes.
Selection and design of valves for HVAC pipelines
1. Butterfly valve for chilled water unit and cooling water inlet and outlet;
2. Pump front butterfly valve, filter, pump back check valve, butterfly valve;
3. Differential pressure bypass valve between set and water separator;
4, set, water separator inlet and return pipe butterfly valve
5. Horizontal dry tube butterfly valve;
6. Air treatment unit gate valve, filter, electric two-way or three-way valve
7, fan coil gate valve (or plus electric two-way valve)
Note: When the butterfly valve is generally used, the handle type butterfly valve (D71X, D41X) is used when the diameter is less than 150mm; the worm gear type butterfly valve (D371X, D341X) is used when the diameter is larger than 150mm.
Note on the use of HVAC valves:
1. Pressure reducing valve, balance valve, etc. must be added with a bypass valve;
2. It is best to use ball valve and gate valve for full opening and closing.
3. Use a shut-off valve as little as possible for the HVAC pipeline;
4, the resistance calculation of the valve should attract attention;
5, electric valve must be selected.
Selection principle of valves used on water supply pipes
1. When it is necessary to adjust the flow rate and water pressure, it is advisable to use a regulating valve or a shut-off valve;
2. It is recommended to use a gate valve for parts with small water flow resistance (such as water pump suction pipe);
3. For places with small installation space, butterfly valves and ball valves should be used;
4. On the pipe section where the water flow needs to flow in both directions, the stop valve shall not be used;
5. For pumps with larger diameters, multi-function valves should be used on the outlet pipes.
Check valve setting requirements:
1. Introduce into the tube;
2. Closed water heater or inlet pipe of water equipment;
3. The water pump outlet pipe;
4. The inlet and outlet pipes are combined with a water tank, a water tower and a discharge pipe section of the highland pool.
Note: The pipe section with the pipe backflow preventer does not need to be equipped with a check valve.
Valve type selection for check valves:
It should be determined according to the installation position of the check valve, the water pressure before the valve, the sealing performance after closing, and the size of the water hammer caused by the closing. The following requirements should be met:
1. For the part with small water pressure before the valve, the swing check valve, the ball check valve and the shuttle check valve should be used.
2. If the sealing performance is tight after closing, the check valve with closed spring should be used.
3. It is required to weaken the part that closes the water hammer. It is advisable to use a quick closing anti-slip check valve or a slow-closing check valve with a damping device.
4. The valve or spool of the check valve should be able to close by itself under the action of gravity or spring force.
The following parts of the water supply pipe should be provided with exhaust:
1. The water supply network used in the intermittent cycle shall have an automatic exhaust valve at the end and the highest point of the pipe network.
2. The water supply network has a pipe section with obvious undulations to accumulate air. An automatic exhaust valve or manual valve exhaust has been set at the peak point of the section.
3. The air pressure water supply device should be equipped with an automatic exhaust valve at the highest point of the water distribution network when the automatic air supply pressure water tank is used.