Figure 1: Many different valve types in an industrial chiller and boiler system.
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HVAC valves are important in every heating, ventilation, and air conditioning system for controlling how fluids, both liquids and gasses, move. There are various types of valves in HVAC systems, such as hvac gas valves and hvac control valves, and understanding the different HVAC valve types will help system design. This article covers the different types of valves and example applications for each type.
Solenoid valves are electrically controlled valves that open or close based on the electric current passed through a solenoid coil, allowing for precise fluid flow control. HVAC solenoid valves are commonly used in HVAC systems where automatic control is essential, such as controlling refrigerant flow in an air conditioning system based on signals from the thermostat. Learn more in our solenoid valves for hvac-r applications article.
Figure 2: A stainless steel solenoid valve
Butterfly valves are commonly utilized in both regulating the flow of fluid and in large commercial HVAC systems, where high flow rates are needed. With a rotating disk in the middle, they can either block or allow fluid to pass through. HVAC butterfly valves are frequently used in applications such as cooling towers, chillers, and air handling units, where they control the flow of water or refrigerant.
Figure 3: A cast iron electric butterfly valve
Disc valves are similar to butterfly valves because they control flow with a rotating disc. However, their design is not identical. A disc valve has two discs, one remains stationary and acts as the valve seat, and the other disc rotates to control the size of the orifice opening. Therefore, disc valves offer on/off and proportional control. Finally, because these valves operate quickly (approx. 4 seconds), typical disc valve HVAC applications are temperature control, zone control, regulation within air handling units, variable air volume systems, ventilation systems, radiant heating systems, domestic hot water systems, and in the control of boilers and furnaces.
Figure 4: A brass disc valve with an electric actuator.
Globe valves are known for their excellent shut-off capability and fluid flow regulation. These are often used in applications requiring precise flow control, throttling, and frequent operation. A prime example of their use is controlling water flow in a hydronic heating or cooling system.
Figure 5: A manual globe valve
Ball valves are renowned for their durability, excellent sealing capability, and strength. These valves feature an internal ball that can be turned to either block or allow flow. Typical ball valve HVAC applications include refrigeration systems to isolate specific components for maintenance or during a system shutdown, in natural gas applications, and in systems where a tight shut-off is required.
Figure 6: A brass ball valve
Check valves are important parts of HVAC systems. They let fluid (gas or liquid) flow in one direction and stop it from going the other way. HVAC check valves are useful in many areas, like ensuring refrigerant flows correctly, preventing water from flowing backward in heating systems, and stopping air from going the wrong way in ductwork.
Figure 7: A PVC check valve
Gate valves in HVAC systems control how fluid (gas or liquid) flows. They're used when a fluid needs to flow straight and unrestricted or needs to be stopped entirely. HVAC gate valves are common in larger pipes but aren't good for controlling the flow speed as it can damage the valve. They're best used in systems where you don't need to turn the valve on and off a lot.
Figure 8: A brass gate valve
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Zone valves are utilized in zoning systems. These valves control water flow, allowing for independent control of heating or cooling to different zones within a building. HVAC zone valves are typically used in large or zoned HVAC systems where different rooms or areas may have varying heating or cooling needs, facilitating independent temperature control in each zone.
Pressure relief valves in HVAC systems are safety devices. They open when the system's pressure is too high to prevent damage, then close when pressure is normal again. When they open, they vent to a safe location, either the atmosphere or a containment system if necessary. HVAC pressure relief valves help avoid problems like broken parts or blockages. For example, they stop boilers from exploding due to too much pressure.
Figure 9: A stainless steel pressure relief valve
Various valves are used in HVAC systems, including solenoid, ball, gate, zone, check, and pressure relief valves.
In HVAC systems, three way valves control the mixing of hot and cold liquids through a system.
The role of the valve is to control and guide the flow and direction of refrigerant in the system, cut off and conduct the connection between the equipment and the equipment or the equipment and the outside world. Improper operation of the valve can cause unsafe factors or cause accidents, so the operation of the valve must strictly abide by the operating rules to avoid accidents. Cold storage valves mainly include globe valves, expansion valves, and safety valves according to their uses. There are two types of globe valves: straight-through valves and angle valves. The safe operation of the valve should do the following work:
1) The operator must be sure about the operation of the valve and do not accidentally open other valves to cause human accidents.
2) When opening the suction valve of the compressor, the discharge valve of the condenser or the accumulator, it must be carried out slowly, and sometimes it should be started and stopped alternately, so as to avoid the wet stroke accident of the compressor due to too fast opening speed.
3) During the opening of each valve, especially when it is close to the maximum opening, you must slowly pull the handwheel without excessive force, so as to avoid the phenomenon that the valve core is caught by the valve body and the valve is pulled off. When the valve is at the maximum opening (limited to the handwheel can not move), the handwheel should be rotated one or two times.
4) The operator should pay attention to the proper force during the closing of each valve, and not use too much force, so as not to damage the valve.
5) For pipes and equipment with liquid refrigerant, it is strictly forbidden to close the valves at both ends at the same time, so as to avoid the expansion of the liquid due to the absorption of external heat and the explosion of the pipeline or equipment caused by ammonia leakage. Under normal circumstances, most liquid bursts crack at the valve. The correct way to prevent a liquid explosion is to evacuate the liquid in the tube when closing the valve of the liquid tube. Under special circumstances, when the liquid pipe cannot be evacuated, only the valve at one end of the liquid pipe should be closed, so that the valve connected to the equipment at the other end is in the open state. If the compressor is completely stopped, the supply of the liquid reservoir should be closed first. Liquid valve, wait for the system and liquid pipe to evacuate, then close the main liquid supply valve to the regulating station.
Particular attention should be paid to the parts where liquid explosion may occur in the refrigeration system. These parts are the liquid pipeline between the condenser and the reservoir, the pipeline from the high-pressure reservoir to the expansion valve, the liquid pipeline with shut-off valves at both ends, the liquid level gauge of the high-pressure equipment, and the liquid between the ammonia container Balance pipe, liquid distribution station, the pipeline below the outlet valve of the circulating liquid reservoir to the double suction end of ammonia, the liquid supply pipeline of the ammonia pump, the pipeline from the liquid reservoir to the emergency ammonia drain, and all pipelines that may cause a liquid explosion.
6) Valves that do not open and close for a long time should be regularly checked for opening and closing flexibility.
7) The safety valve in the refrigeration system must be corrected once a year, and the safety valve in question should be repaired or replaced in time.
8) Add the red and yellow opening and closing plates made of color steel plate to the handwheel of the valve to avoid misoperation as much as possible.
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