Control Valve

What is a float valve and how does it work

What is a float valve and what does it do

This valve can be used to control the water level in a tank, this valve is capable to open and close itself as the liquid level changes. A float is used to mechanically operate this valve. These valves are liquid level control valves and they are mostly used in the industrial refrigeration system. In a large refrigeration system, the float valves are used as a throttling device. Float valves are actuated lever valves that are designed to control the level of the liquids.

What is the use of a float valve

  • These valves are used in water tanks and in cisterns so that it can maintain the proper water level and prevent overflow
  • The flow of the water is controlled by the rise and fall of the ball
  • These valves are suited for low pressure, high pressure, and for medium pressure applications
  • It is used as a throttling device in large industrial refrigeration plants

How does a float valve work

Float valves are used in many industrial applications, float valves can be used with other valves. Float valves open and closes according to the liquid level that is sensed by the float. The float could be hollow metal or plastic ball. An example of the float valve operation would be the use of a float valve in, flow pressure reducing valves. By using a sub-valve the float valve can control the main valve. The sub valve would set a water level in the tank, if the water level exceeds this level then it will close and thus the back pressure chamber in the main valve would handle this pressure quickly. So the float valve can be used to control the water level in heavy industrial plants.

How to select a float valve

  • According to the size of the valve
  • Connections
  • Media
  • Globe or angle pattern
  • Maximum operating pressure
  • The discharge pressure of the valve if other than the atmosphere
  • Maximum temperature

How float valves are constructed

The float rods in the float valves are made up of brass, stainless steel, or galvanized pipe. The trim in the float valve, main valve, and the seat is made up of stainless steel. Swivel adaptor, vertical operation of the float rod, replace rosette, and joins the lever and float rod. Teflon is used in the discs and cups for high-temperature purposes. Design considerations include providing high flow rates at a low head loss. By properly designing the valve seat cavitation and noise can be minimized, minimize frictional resistance, and shut-off loads, and ensuring the float. These valves are designed to pilot operated or standard, with small and large orifices, long levers, small floats, or short levers. In order to obtain a proper valve life, the float valves must not be overrated in terms of flow or pressure.

How to install float valves

Float valve must be installed in a horizontal position, it must not be installed in a vertical discharge position. In order to do the proper maintenance, an isolation valve should be installed before the automatic float control valve so that maintenance can be done without draining the pipe system. The installation of the float valve must be done only by an experienced person.

While installing remove the bulkhead fitting from the tank. Remove the drain plug and install the valve assembly. Float valves when installing in water tanks should be located near the surface of the water with the float where it will be least disturbed by the waves. The waves would be prevented by the discharge pipes by the discharge pipes. In order to avoid the friction on the inner valve sliding the stem of the valve must be vertical.

What are the types of the float valve

The float valve is divided into two types depending upon the location of the float chamber. Float type valve can be either a low side float valve or a high side float valve.

Low side float valves

These valves are mostly used in the flooded type of refrigeration plants. This valve would maintain a constant liquid level in a flooded evaporator or a float chamber attached to the evaporator. So if the load increases then the refrigerant would evaporate from the evaporator. Because of this, the liquid level in the evaporator or the low side float level drops momentarily. After that, the float moves and helps to increase the valve opening so more amount of refrigerant flows into the evaporator, and the liquid level will be normal again. Low side valves are mostly used in the industrial control system.

The high side float valve

In the low side float, the float chamber is placed in the evaporator, but in the high-pressure side float valve, the float chamber is placed on the high-pressure side between the condenser and evaporator. So as the load increases, the refrigerant would evaporate and condenses. So the float chamber liquid level would increase. The valve would be opened more by the float so that the refrigerant would flow and the liquid level would be normal. The reverse would happen if the liquid level is low.

What are the applications of the float valve

  • Water heaters
  • Condensate tanks
  • Reservoirs
  • Sprinkler services
  • Swimming pools
  • Cooling tower
  • Open or closed storage tanks

To get more info about the control valve check the following link


post-graduate in Electronics & communication.

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