Evaporator pressure control valves
Evaporator pressure control (EPR), valves (Fig. 9.7) can be used in suction line, and their function is to prevent the evaporator pressure drops below a certain or controlled value, although the compressor suction pressure may be lower.
Application of EPR valve:
- Prevent damage to the liquid cooling evaporator, which may arise as a result of freezing of the liquid.
- To prevent freezing of the formation of cooling evaporator where it is close to freezing point, or where a temporary fault can not be allowed to interrupt the operation in time.
- Placing two or more evaporators, working at different load, temperature, working with a single compressor.
- To regulate the pressure in the evaporator under variable load, temperature controlled load.
- Act as a solenoid valve, controlled pilot solenoid valve.
The simplest EPR valve spring, balancing thrust spring, plus atmospheric pressure, on the same side of the diaphragm or piston against the evaporator or pressure.
For the working pressure below atmospheric, assistant spring installed below the diaphragm. The slight deviation of the result from changes in atmospheric pressure, but they are too small to significantly affect the refrigeration control system.
Room sensor is installed, in most cases, adjacent to the valve or as part of the valve Assembly to promote the creation or reorganization. Above approximately 40 mm pipe size, chief EPR valve is used as a pilot operation the main servo performance. Another pilot signals can be used on the same servo and many management functions are possible.
Fig. 9.7 shows the main electrical actuator pilot who responds to the signal from the controller to maintain constant temperature load and a high level of accuracy. Constant pressure pilot evaporator temperature prevents too low and solenoid pilot for on/Off.
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