Refrigeration system commonly used valves are: globe valve, throttle, safety valve, pressure gauge valve, check valve, liquid level indicator
Function of globe valve-put through or cut off system pipeline-regulate and control the flow of fluid and flow direction globe valve type, structural characteristics and working principle-ammonia and fluorine-straight through valve and right angle valve-thread connection and flange connection globe valve seal, packing seal between stem and bonnet, positive seal between lower end of disc and upper end of seat, reverse seal between upper end of disc and lower end of Bonnet
Throttle capillaries-throttle valves for small fluorine installations-manual standby float ball valves-thermal expansion valves for automatic fluid supply in ammonia systems-throttle orifice plates for fluorine systems (used sparingly in ammonia systems)-lithium bromide absorption chillers and centrifugal chillers with small pressure differences
The pressure difference before and after the capillary throttling is related to the inner diameter and length of the tube. After shutdown, the low-pressure part of the pressure rises quickly, which is beneficial to the compressor starting again (starting current is small) and the installation process is simple, easy to operate self-regulation, regulation range is small, can not adapt to the drastic changes in load system maintenance operation requirements
The external structure of the throttle valve is the same as that of the globe valve
The difference between the internal structure and the globe valve-stem thread throttle valve for fine thread-help to adjust the globe valve for coarse thread-switch function-disc throttle valve for needle-type (small size) , plug-type (medium size) and window-type (large size) globe valve for flat-head type
Float valve function:-throttling pressure-to maintain the stability of the liquid level in the container type-straight-through-non-straight-commonly used
Thermal expansion valve working principle-use temperature-sensitive package to feel the size of the evaporator outlet overheating, automatically adjust the opening of the valve core, control refrigerant flow overheating, indicating the lack of liquid supply, refrigerant flow is too small, therefore increase the valve opening degree of little or no overheating, indicating that the refrigerant flow is too large, so reduce the valve opening degree
Type:
internal balance-evaporator resistance hours use (ignore this resistance)
external balance-evaporator resistance when the use of large (considering the flow resistance in the evaporator)
Safety valve-function: when the pressure exceeds the limit, automatically open and eliminate excess pressure gauge valve-function: set in the pressure gauge and pressure vessel or regulating station between the stop valve, when to replace the pressure gauge, this valve can be closed after the old table to remove the role of the new table
Check valve-prevents refrigerant backflow, also known as check valve or one-way valve
Installation of check valve-check valve installed in the refrigerant compressor exhaust pipe and liquid pump out of the liquid line-installation to pay attention to the direction of the valve body to be consistent with the direction of refrigerant flow
Level indicators glass tube and plate level indicators-high pressure reservoirs and oil collectors-ball valve oil-filled level indicators-low temperature differential pressure level indicators for cryogenic equipment
The difference between Freon system and ammonia system freon system compared with ammonia system, their refrigeration principle and the main components of the system are basically the same. They differ significantly in: 1) Freon systems have a dry filter, ammonia systems do not; 2) Freon systems use a thermal expansion valve for liquid supply, ammonia systems use a floating ball control valve for liquid supply; 3) Freon systems have refrigerant liquid from the upper part of the evaporator into the lower exhaust, ammonia systems are the opposite; 4) some Freon systems use a regenerative cycle, ammonia systems do not.
