Manual expansion valves, needle valves with manual control, which are widely used in industrial process applications with relatively constant load cooling. The parties expansion valves are very similar in operation of conventional valves used in water supply systems. Needle (pin) valve plug firmly into the valve's seat ring die to stop the flow of refrigerant. Seat hardened metal ring is located above the hole in the body of the valve, which modulate refrigerant flow. Seat allows the needle to firmly stop the flow without deformation of soft metal brass valve body. The diameter of the hole in die seat size to ensure the required flow at design there is a pressure drop across the ring. Valve connects the plug / socket connector (needles) with manual drive. Movement of the barrel position the needle in the center seat holes to modulate refrigerant flow. The stem has the exact thread processed in mine precisely adjusted his position and velocity of the flow. Packing, located around the smooth surface of the valve prevents the leakage of refrigerant from the system.
When the valve is seated, no flow through its ports.
As it is cracked, the needle is moving very short distance from the seat and refrigerant begins to flow through the valve ports. Flow rate changes in response to changes in distance that the needle away from the seat. It also varies as a pressure difference via valves, ports changes. As
needle departs from the chair, the flow rate through the port increases. Exactly the same as the differential pressure ports increases the refrigerant mass flow also increases. If the arrow is in regulation s and pressure drop across the valve remains constant, the speed of the flow through the expansion valve hand also remains the same. The main disadvantage of the hand of the expansion valve is responding to their nature of changes in the cooling load, requiring dosing valve adjusted whenever the load on the system changes. If changes are not made evaporator will work with insufficient refrigerant (hunger) or too much refrigerant (overfed). Manual dosing valves must also be closed each time when the compressor is cycled off. Because of these limitations hand expansion valves are designed for use only in large industrial systems, which have a relatively constant load and operating engineer is always on duty.
Although not often used as expansion valves in commercial systems, these metering devices are installed in systems as a secondary refrigerant management devices. They are installed in the bypass line for the smooth operation of the system during the internship. Their precise modulating capacity allows the valve to control the flow of lubricating oil in divorce. They are also used in combination with float management in large industrial ammonia systems to keep limits on consumption. In refrigeration plants, which are subject to frequent load fluctuations, automatic refrigerant metering device you want...
Industrial