What is a check valve and what are its uses?
A check valve is a one-way valve or non-return valve. They open with the movement and pressure of the fluid and close to prevent pressure from returning to the equipment connected downstream of pumping and compressors. These valves allow fluid to flow in only one direction.
The check valve is usually in the closed position and opens when fluid flows through it. It also can shut down the flow if the pressure in the sliding direction is greater than the pressure in the rising direction. In this sense, they are used to flow in one direction only. Thus, they prevent flow back through the valve. Since the flow of liquid through the valve is allowed in only one direction. Check valves must be installed properly by observing the normal direction of flow. An arrow printed on the outside of the valve body indicates the direction of flow.
What is a Check Valve?
A check valve is an automatic safety device designed to allow the flow of liquids and gases in one direction and prevent backflow. Under pressure, fluid enters the valve at the inlet. It pushes the disc off its seat in the valve and exits through the outlet.
The flow continues stably as long as the pressure is maintained to maintain the disc opening. A wide range of these valves exist, ranging from standard valves to those specifically designed to meet the needs of unique applications. With many check valves, the descriptive factors are similar in all types.
Materials used in making check valves:
Most Check Valves are made of durable materials that can withstand high pressures. Common materials used to make check valves include PVC, CPVC, bronze, brass, iron and stainless steel:
- Polyvinyl chloride (PVC): PVC is resistant to corrosion and flexibility. The smooth surface of PVC allows the check valve parts to move easily.
- Chlorinated polyvinyl chloride (CPVC): CPVC has the same properties as PVC but withstands higher temperatures.
- Bronze: Bronze can be used in low and medium-pressure applications, can be cast in complex configurations, and is resistant to corrosion.
- Copper: Copper has the same capabilities as bronze, in addition to being easier to work with and being cheaper than bronze.
- Cast Iron: Cast iron check valves are used in hot and cold water, heating, air conditioning, steam, gas, and municipal services due to their excellent corrosion resistance.
- Ductile Iron: Ductile iron contains more than 3% carbon, which makes it easily bendable and shaped. It is stronger than cast iron and easier to machine than check valves.
- Iron: Iron is used in steam, water, oil, and gas applications. It can withstand a wide range of temperatures and pressures. Its excellent performance is balanced by its high cost.
- Stainless Steel: Stainless steel is resistant to corrosion and withstands harsh conditions, including chemical applications.
- Polypropylene (PP): PP is used to make check valves because of its exceptional corrosion resistance. It is superior to that of CPVC and PVC.
- Polyvinylidene difluoride (PVDF): PVDF plastic is used in applications that require exceptional clarity and resistance to acids, solvents, and hydrocarbons, for example.
- Cast Steel: Cast steel is used to produce check valves because of its resistance to sudden shocks without deformation, breakage, or bending. It can also be easily formed into any type of check valve.
