The valve which is used to prevent backflow while a drilling operation in an oil field is termed as Float Valve. Backflow is a unique mechanism that regulates the flow of fuel. Float valve is more videly used in Water Tanks. The filling of water tanks is generally checked by a hollow ball that floats in the water.
Float valves prevent backflow of mud into drill pipes and hence play a vital role in oil and gas industries. Float valves are basically check valves which are installed in the drill stem pipes which allow the mud to be pumped down and prevent the backflow of mud. As far as oil and gas industries are concerned, they use two different types of Float Valves :
- Flapper type float valves
- Plunger type float valves
Spring loaded float valves which remain in closed position and thus provide qan internal well controled barrier inside the coiled tubing bottom hole assembly are known as Flapper type float valves. If this type of valve is opened completely, it gives a large internal passage and full flow. This type of valve is designed for highly abrasive fluids.
The second type i.e., Plunger type float valves offer positive and instant shut off characteristics which make them more efficient and durable than Flapper type float valves.
The Working of a Float Valve :
The float valve is generally used in a reserve water tank and baasically it has three parts, the Valve, the Stem and the Float Device. The valve creats a tight seal by blocking the water through the pipe as the stem rises. The valve is connected to the float device through the stem. In certain applictions the stem is also used to adjust when the water flow will be blocked. The float device is generally round and is filled with air. This device is air tight and is attached to the stem. Because of the trpped air in the float device it has buoyancy and will float atop the water. As soon as the water is released from the reserve, the float device drops, paving the way for the valve to open. The valve will remain open until the float device is raised to a pre – fixed level by the rising water. As a result the valve will be shut off.
Common Use of Float Valve :
The standard household toilet is the most common application of the Float Valve. On the back of the toilet, the float valve is fixed inside the reserve tank. Mejority of the toilet models have a baloon shaped float valve fixed to a stem, which extends across the tank to the float device. When the toilet is flushed, the float drops as the water is released and the valve becomes activated. Again the valve will be closed, as the tank will refill. Now, the toilet can be flushed again.
Ball Float Valve :
Ball Float Valve is another type of Float valve. In this application the valve seals a vent line, insteade of shutting the flow of liquid. A ball float is held in place by a bracket which keeps it properly positioned below a vent line. The ball will float up and will cover the vent pipe opening as soon as the water or other liquid rises. Therefore it prevents any liquid from moving up the vent line. This application can also ristrict the entry of more liquid into the reserve tank if the seals are working properly.