Low Side Float Valves
The low side float type of the throttling valve is usually used in the flooded type of the refrigeration plants. In industrial refrigeration plants the evaporators are of shell and tube type. In the plants with medium capacity the refrigerant is filled in the tube side and the substance to be chilled is filled in shell side such as in the water chilling plants. But when very low temperature is required for large quantity of the substance the refrigerant is filled in the shell side and the substance to be chilled is on tube side. Such types of evaporators are called as the flooded evaporators.
The float valve maintains the constant level of the liquid in the flooded evaporator irrespective of the pressure and the temperature inside it. The float of the low side float valve is placed in the evaporator, which is at low pressure. The construction and the working of the low side refrigeration float valve are similar to the float valve used in the water tank used for maintaining the level of the liquid.
In the water tank the float keeps floating inside on the water and its arm is connected to the water connection. When the level of the water drops down the arm of the float valve moves to open the water connection and allows the flow of the water to the tank. When the tank gets filled the float rises up and the arm closes the water connection. The float valve in the refrigeration plant also works in a similar manner.
The valve assembly of the low side float valve comprises of the hollow ball, a float arm, needle valve and the seat (refer the images below). The valve seat and the needle forms the orifice opening of the valve that provides the throttling effect to the refrigerant passing through it and through which the regulated amount of the refrigerant can pass. The valve seat and the needle are located inside the chamber of the float valve which is connected to the evaporator.
The hollow ball or float floats on the refrigerant inside the evaporator and moves up and down as per the level of the liquid. The hollow ball is connected to the needle and valve seat via the float arm. Thus as the ball moves up and down the float arm also moves that allows for the opening or the closing of the orifice.
When the level of the refrigerant drops inside the evaporator due to high refrigeration load the float moves down, this allows for the opening of the orifice of the valve increasing the flow of the refrigerant. When the sufficient amount of refrigerant enters the evaporator the level of the float rises due to which moves the float valve closes. The movement of the float and the opening of the float valve is in accordance to the refrigeration load on the evaporator.