Float valves are mechanisms or machines used for filling tanks, reservoirs, or other containers for liquids. Also referred to as a ballcock, as the hollow float is often shaped like a ball, it’s essentially the same mechanism as one would find in flushing toilets, and helps prevent overflow or backflow. Consisting of a valve connected by a lever to a hollow and sealed float, they are mounted close to the top of the tank. The valve connects to the pipe bringing in the liquid, opening and closing as the lever raises or lowers the float. Once it reaches a certain level, the mechanism causes the lever to close the valve, cutting off the flow. Selecting a stainless steel float valve requires consideration of several factors, such as style and material. Keep reading to learn how to choose the best float valve for your application!
What is a Float Valve & How Does it Work?
A float valve serves a simple purpose. It controls the flow of liquid from a source supply, such as a tank, and rising as the level of liquid in the tank rises. Float valves consist of three parts: the float device, float valve, and stem.
The valve connects to the float device through the stem, which acts as a lever to control the flow of liquid when the valve opens or closes. Generally, float valves are used in reserve tanks to keep liquid from flowing through piping, creating a leak-free seal when the stem rises. As the stem rises, the valve seals off the flow.
The float device normally contains air to give it buoyancy and is airtight. When liquid leaves the tank, the float device sinks with the liquid while the valve remains open until the floating device is again raised to a certain level, allowing liquid to refill the tank. Float valves prevent overflow or overfilling of tanks, diverting the liquid instead of draining it away. The valve and float move with each other as the tank empties and refills and can operate mechanically or hydraulically.
Types of Float Valves
As a simple mechanical device controlling the level of liquids in tanks or reservoirs, float valves serve many purposes. Often used in domestic water systems, one application includes use in cold water header tanks to regulate pressure in hot water heaters. Smaller float valves fit into many toilets as well to regulate water flow. Depending on the application, valves work under high-pressure or low-pressure conditions. Below are a few of the many types of float valves used.
High-Pressure Float Valves
High-pressure float valves work in single-evaporator flooded systems. These are essentially containers used for storing liquid refrigerant, with float valves fitted to direct drained liquid from the condenser to the evaporator. It acts as a steam trap, working with refrigerants like ammonia or carbon dioxide.
High-Temperature Float Valve
Used for heaters, heat exchangers, boilers, and other high-temperature applications, these maintain the level of liquids at a precise level with the float triggering the valve’s opening or closing.
Balanced Float Valve (Equilibrium Float Valves)
Sometimes called equilibrium float valves, these valves help resolve high operating torque. It consists of a single valve and a balance piston. The balance piston’s seal introduces a bit of friction, even with the reduction of operating torque, but as this can decrease modulation produced by waves it can offer significant benefit.
Large Float Valves
Used for filling over overflow control, these types of valves can reach 12 meters (approximately 40 feet) in diameter. These valves are most often used in reservoirs, operating either mechanically or via hydraulically actuated small pilot float valves.
Combination Float Valves
Used to control the water level in steam condensers, depending on the water level this valve will either supply or dump water. The valve’s body is bolted to the condenser wall, with all parts of the mechanism subjected to the condenser’s vacuum and the combination consisting of two piston valves on different systems.
Drill Pipe Float Valves (Non-Return Valves)
Also known as non-return valves, these are used in oil and gas fields to prevent unwanted fluids from flowing up the drill string. These valves halt the flow while others on the crew make or break connections.
Why Use a Stainless Steel Float Valve?
Stainless steel offers numerous advantages over other materials. A stainless steel float valve will keep liquid levels constant through the use of their floats. Because of their corrosion resistance, they can be used not only for fresh water but also for seawater, corrosive liquids, harsh chemicals, and other special fluids.
Some benefits of using stainless steel float valves include:
- Higher graded alloys of stainless steel are useful in industrial and other environments with elevated alkaline, acid, or chloride levels, even at high pressures and temperatures, while lower grades resist atmospheric corrosion well.
- Most stainless steels can be easily formed, machined, welded, cut, or otherwise fabricated.
- Resistant to extremes in temperature, some grades maintain their strength when exposed to excessive heat while also resisting scaling, while others hold up well in very cold temperatures.
- Stainless steel is easy to maintain and keep clean.
- Stainless steel is more durable than other materials used for float valves, so is often the less expensive option over its life cycle.
- The properties of many stainless steels allow it to harden well during cold working, so as to reduce thickness and weight of components or products, along with costs, while other types of stainless steel become stronger when treated with heat.
Stainless steel float valves are often used to maintain water levels in industrial-grade tanks and water treatment plants. Float valves typically use T303 or T316 stainless steel alloys, with the former offering better machining properties and the latter offering better corrosion resistance.
Stainless Steel vs. Plastics & Other Materials
Float valves can be made from a variety of different materials. As they are exposed to environments with different levels of corrosive substances, temperatures, and pressures, durability is a major issue. Stainless steel offers a variety of properties that make it a better option than other materials.
Materials vary and may be combined, depending on the manufacturer and application. Floats can be constructed from stainless steel, copper, plastic, or other materials, while the bodies often are constructed from stainless steel, bronze, or cast iron. Sometimes floats that are used in vertical rod systems employ counterweights to keep them submerged and provide better performance.
Plastic
Using plastic reduces manufacturing costs, though most higher quality products will use stainless steel float valves rather than plastic, as they last longer and are generally more durable.
Cast Iron
Both cast iron and stainless steel work well in high temperature and high-pressure environments, and cast iron’s low carbon content makes it more corrosion resistant than other ferrous metal alloys. The main advantage stainless steel has over cast iron is its chromium content of at least 10.5%, which reacts to oxygen to create a protective layer against corrosion.
Brass
Stainless steel offers much better protection against corrosion than brass, an alloy made from zinc and copper, and holds up better in environments high in chlorine. Stainless steel is especially resistant to corrosion from seawater and other harsh fluids, along with having a better pressure rating than brass. Brass conducts heat better and, as a softer metal than stainless steel, it also shapes more easily. Given brass alloys that include lead have been largely banned for plumbing applications, stainless steel is often a less expensive option as well.
Bronze
Made mostly of copper combined with varying amounts of tin, bronze looks similar to brass, though it has certain unique benefits. It resists cracking and corrosion better but is less expensive than brass. Commonly used in the petrochemical industry, like stainless steel it also holds up well in marine environments and in high-performance applications.
Stainless Steel Float Valve Applications
Along with their use in toilets, stainless steel float valves are used in many industries for a variety of applications.
Applications for which stainless steel float valves can be used include:
- Basins
- Carburetors
- Condensate tanks
- Industrial refrigeration system
- Open and closed storage tanks
- Refrigeration systems
- Remote tanks
- Reservoirs
- Sump pumps
- Swimming pools
- Toilet tanks
- Watering troughs and tanks
As float valves operate mechanically, without the need for power, they are capable of working in remote locations. Their versatility makes them valuable for many industrial and other applications, with stainless steel float valves used in some of the harshest environments.
Stainless Steel Float Valves from Arthur Harris
Arthur Harris offers more than 100 years of experience, with the capability to manufacture our floats in a variety of shapes, sizes, gauges, metals, and connections. To learn more about our stainless steel float valve selection, view our products here!