Low-pressure valves and switches
Flooded evaporators require constant level of liquid, so that the tubes remain wetted. A simple float valve enough, but must be positioned outside the float evaporator shell, since the surface of the boiling liquid excited and constant movement can lead to increased wear of the mechanism. Float, therefore, is contained in a separate chamber, combined with the balance line shell (see Fig. 8.7).
Such a valve metering device, and may not provide positive shut-off when the compressor is stopped. In such circumstances, the refrigerant would continue to flow into the evaporator, until the pressure is equalized, and the fluid level can rise too close to the suction outlet. To verify this, gate valve, electromagnetic valve, the needs of the liquid line.
With low pressure float needs solenoid valve for tight closure, this valve can be used as on-off control in combination with pre-opening and controlled by a float switch (Fig. 8.8). Common form of float metal level sensor was carrying iron rod, which rises and falls in the sealing sleeve.
An induction coil surrounds sleeve and is used to determine the position of the kernel. The resulting signal is amplified to the switch, solenoid valve, and can be adjusted to the level and sensitivity. Butterfly valve pressure reducing device.
If the float control fail, a level in the shell can rise and fluid pass into the compressor suction. To prevent this, the second float switch, usually set at higher levels, to operate alarm and cut.
Where flooded coil is located in a tank of liquid refrigerant, its level will be within the tank, and this makes it difficult to position the management level. In such cases, gas trap or siphon can be formed in the lower balance of the trumpets, to make subsequent level in the float chamber. Siphons or trap can also be arranged to contain non-volatile liquids, such as oil, so that the balance of pipes remain free from frost.....
|
Expansion valves 
