What is a float valve?

A float valve is a valve that shuts off the flow of fluid when the desired level is reached by means of a float or buoy.

We are all familiar with valves of this type in our bathroom cisterns. They are not only valves for industrial applications, but can also be found in the most everyday things in our lives.

Basically a float valve consists of two parts, the valve body and the float.

They can have a straight or angled body. They can also be direct-operated, where the float applies force through a rod, or pilot-operated, where a small level float can be used to operate large diameter valves for high flow rates.

The operation of the float valve is a simple mechanical liquid level controller. A float detects elevation changes in the free liquid surface and opens or closes a valve accordingly.

Caution should be exercised when fitting direct acting float valves, as they can create problems with the tank walls. The arm can produce considerable torque to close the valve, this torque must be resisted by the tank wall. Thin-walled tanks and fibreglass tanks may need reinforcement to cope with the loads. The problem increases as both valve size and inlet pressure increase. Torque can be estimated using seat area and inlet pressure.

Flanged float valves are generally available in sizes DN15 to DN300.

Standard materials include cast iron, bronze and stainless steel. More exotic materials can be used, but the problem of float fabrication must be considered. Working pressures up to PN20 are normal.

APPLICATIONS AND RECOMMENDATIONS:

This type of valve is recommended when we want to control the level of a tank in a simple and economical way.
The fluids must be clean.
It is important to know the flow rate of the valve in order to calculate the filling time.

Both valve bodies and floats are made of different materials such as: brass, cast iron, steel, stainless steel, plastic body and copper, brass, stainless steel, plastics, expanded polystyrene for buoys.

We can also find different types of buoys: spherical, cylindrical, flat, etc.

FLOAT SWITCH

We can achieve the same purpose of controlling a level in a tank with a level switch and an electrically operated valve or with a solenoid valve.

These level switches are also known colloquially as pear switches, due to the fruit-like appearance of most of them.

Float switches can be used as alarm devices or as control ON-OFF switches, to turn something on or off, such as a pump, also to send a signal to a valve actuator. Level switches have a switched output and can be electromechanical, normally open or normally closed.