Check valve 101: What is a check valve?

A check valve is a type of valve that allows fluid (liquid or gas) to flow through it in only one direction. Check valves have two ports: one for the fluid to enter and the other for the fluid to exit. The primary function of a check valve is to prevent backflow in the system, ensuring that the fluid flows in the desired direction only.

Here are some key characteristics and uses of check valves:

1. One-Way Flow: Check valves are designed to allow fluid to flow freely in one direction but automatically close to prevent flow in the opposite direction.
2. Non-Return Valve: They are also known as non-return valves or one-way valves because they block reverse flow.
3. Types:
   • Swing Check Valve: Utilizes a swinging disc/clapper that opens with forward flow and closes against a seat to prevent backflow.
   • Lift Check Valve: Uses a disc that moves up and down within a guide to allow or prevent flow.
   • Axial Flow: Uses a spring and disc/piston in the center of the bore with flow passes around the disc. When flow drops the spring energizes and pushes the disc closed.
   • Ball Check Valve: Employs a ball that is pushed away from the seat by the forward flow and returns to the seat to block reverse flow.
   • Diaphragm Check Valve: Features a flexible diaphragm that opens and closes to control flow.
4. Applications:
   • Piping Systems: Used in water, oil, and gas pipelines to prevent backflow and protect equipment such as pumps & compressors.
   • Industrial Processes: Applied in chemical processing, power generation, and manufacturing industries to maintain system integrity.
   • Household Uses: Found in everyday items like plumbing systems, HVAC systems, and fuel systems in vehicles.
5. Benefits:
   • Automatic Operation: Operate without the need for human intervention or external control.
   • Simple Design: Often compact and straightforward, requiring minimal maintenance.
   • Cost-Effective: Typically inexpensive and reliable components in fluid handling systems.

In short, check valves are essential in many systems to help ensure proper flow direction and protect equipment from damage due to reverse flow.

Why are check valves used in oil and gas?

Check valves play a critical role in the oil and gas industry for several important reasons:

1. Prevent Backflow: In oil and gas systems, it is crucial to ensure that the flow of fluids, such as oil, gas, and water, moves in the intended direction. Check valves prevent backflow, which can cause contamination, damage to equipment, and safety hazards.
2. Protect Equipment: Pumps, compressors, and other equipment can be damaged by reverse flow. Check valves help protect this equipment by ensuring that fluids flow only in the correct direction.
3. Maintain Pressure: Check valves help maintain pressure within the system. By preventing reverse flow, they ensure that pressure remains stable, which is essential for the efficient and safe operation of oil and gas facilities.
4. Safety: Safety is a paramount concern in the oil and gas industry. Check valves contribute to the overall safety of operations by preventing accidents caused by reverse flow, such as leaks, bursts, and explosions.
5. Environmental Protection: Preventing backflow can also help protect the environment. For example, in the case of a pipeline rupture, a check valve can prevent oil or gas from flowing backward and causing a spill.
6. Operational Efficiency: By ensuring that fluids flow in the intended direction, check valves help maintain the efficiency of processes in oil and gas operations. This can lead to more efficient production and reduced downtime.
7. Applications in Various Systems:
   • Pipelines: In oil and gas pipelines, check valves prevent backflow that could lead to pressure surges and pipeline damage.
   • Wellheads: Check valves are used in wellhead equipment to ensure the proper flow of hydrocarbons from the well.
   • Storage Tanks: They are used in storage tanks to prevent reverse flow when filling or emptying tanks.
   • Processing Plants: In refineries and gas processing plants, check valves are used to maintain flow direction and protect equipment.

Check valves are indispensable in the oil and gas industry due to their ability to prevent backflow, protect equipment, maintain pressure, enhance safety, and contribute to operational efficiency and environmental protection.

A Crown-Europa non-slam nozzle check valve, left, and Crown check valve, right, prepare to be painted inside the main Stream-Flo manufacturing facility in Edmonton, AB.

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What components are found in a check valve?

A check valve consists of several key components that work together to allow fluid to flow in one direction and prevent backflow. The specific design and components can vary depending on the type of check valve, but the common components typically include:

1. Body: The main structure of the valve, which houses the internal components and provides the pathway for fluid flow. It is typically made of metal or plastic, depending on the application.
2. Seat: The surface within the valve body against which the closing mechanism (disc, ball, or diaphragm) seals to stop reverse flow. The seat must be precisely machined to ensure a tight seal.
3. Disc/Clapper, Ball, or Diaphragm: The moving part that opens to allow forward flow and closes to prevent backflow.
   • Disc / Clapper: In swing check and lift check valves, a disc pivots or lifts to allow flow.
   • Ball: In ball check valves, a ball moves away from the seat to permit flow and returns to the seat to block reverse flow.
   • Disc / Piston: Uses a spring and disc in the center of the bore with flow passes around the disc. When flow drops the spring energizes and pushes the disc closed.
   • Diaphragm: In diaphragm check valves, a flexible diaphragm moves to open or close the flow path.
4. Hinge or Guide: In swing check valves, a hinge pin allows the disc to pivot. In lift check valves, guides or cages keep the disc aligned and allow it to move up and down.
5. Spring (in some designs): Some check valves, such as spring-loaded check valves, incorporate a spring to help close the disc or ball more quickly when flow stops or reverses, providing a quicker response to prevent backflow.
6. Cover (or Cap): The cover or cap is a removable part of the valve body that allows access to internal components for maintenance and inspection.
7. Seal or Gasket: A seal or gasket is used between the body and the cover to ensure a leak-tight connection.
8. End Connections: These are the points at which the valve connects to the piping system. Common end connections include threaded, flanged, or welded ends.

A check valve ensures unidirectional flow and prevents backflow in piping systems, protecting equipment and maintaining operational efficiency and safety.

A 48″ Stream-Flo Crown swing check valve awaits shipment after being manufactured in Edmonton, AB.