What are the Types of Check Valves Used in the Gas Industry?

Check valves are used in pipelines, hoses, and tubing to prevent backflow of liquids and gases. In the gas industry, this helps protect equipment from damage, reduce excessive vibration, and maintain steady production.

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A major use for check valves is normalizing the flow of gas during reciprocating compressor discharge in long-distance pipelines. Other natural gas production uses include directing gas flow on metering pumps, hydraulic and air lines, pump discharge, and pressure letdown processes. Check valves are also widely used with gases in oil refineries, chemical and petrochemical plants, and manufacturing facilities.

Here, we’ll look at what check valves are, factors to consider when specifying them, and how they benefit gas industry applications. 

What is a Gas Check Valve?

A check valve keeps liquids or gases flowing in a desired direction while preventing them from flowing backward (also called the non-return direction). They are available in many configurations, including threaded, flanged, and space-efficient wafer designs.

In an axial flow check valve, gas moves parallel to the axis of rotation through the center of the valve. In-line check valves are placed at predetermined points along a pipeline or tubing system. The valve contains a spring-loaded disc pressed against a gasket to keep the valve closed in its default resting state. When sufficient gas pressure is applied to the disc, it opens and the gas flows through. When pressure drops, the disc closes to prevent the gas from flowing back in the opposite direction. A stem and bushing guide the disc to keep it properly aligned. Nozzle-style check valves are a type of axial flow valve designed specifically for use with low-pressure or intermittent flow liquids or gases. 

In natural gas production, check valves are critical for reciprocating compressor discharge. DFT® Inc.’s PDC valve is an ideal solution due to its pulse-dampening chamber, which keeps the disc open during discharge, even as pressure and flow rate may vary. It is a nozzle-style valve with durable carbon or stainless steel construction, a Durlon gasket, Teflon and Rulon guiding elements, and an Inconel x750 spring for durability and a long service life. As a result, the PDC valve is suitable for a range of uses in the oil, gas, and other industries.

Important Specifications in the Gas Industry

Key factors in specifying gas check valves include:

• Gas Characteristics and Composition. This includes fluid viscosity and specific gravity, corrosiveness, particulate matter, and elemental composition, all of which influence valve size and materials.
• Gas Flow Rate. This influences the size and design of the check valve needed, such as threaded or flanged models. High-flow systems often require larger or multiple valves.
• Temperature. Extreme and/or fluctuating gas and ambient temperatures influence decisions about materials, especially for thermal shock resistance.
• Pressure. Check valves are rated for different operational and maximum pressures in the overall system and in the specific location of the valve.
• Cracking Pressure. This is the minimum pressure needed to open the valve and permit gas flow. If cracking pressure is too high, the valve is harder to open and may slow the flow rate, causing chatter. If it is too low, the time to close the valve increases, since back pressure must overcome forward pressure to close it. 
• Operating Environment. This includes horizontal or vertical orientation; accessibility for maintenance in remote locations; gas flow path; vibration, shock, or pulsation in the system; temperatures; and corrosiveness of the environment (e.g., offshore or salt spray exposure).
• Valve Materials. Materials impact the valve’s resistance to environmental conditions and durability over the lifetime of production. They may also affect its ability to stay open or closed for a prolonged time. 
• Regulatory Compliance. Check valves used in the oil and gas industry must comply with standards set by the American Petroleum Institute (API), the American Society of Mechanical Engineers (ASME), and the International Organization for Standardization (ISO). 

Benefits of Check Valves

Check valve technology benefits natural gas production and other processes that use gases in daily operations in these ways:

• Protecting Equipment. Check valves protect pumps and compressor equipment from damage caused by backflow or reverse flow, ensuring systems operate smoothly and without interruption.
• Minimizing Chatter from Turbulence or Pressure Drop. Properly sized and located check valves minimize chatter from the disc opening and closing repeatedly, which contributes to wear on the valve. Chatter is caused by turbulence or drops in flow pressure, and valves that are oversized or too close to the discharge port may not receive adequate pressure to remain open consistently. 
• Preventing Slam and Water Hammer. Using the right size valve protects against slamming and hammering from sudden pressure drops, which can damage equipment and pipes or tubing.
• Low Maintenance. Axial flow valves have no external components which protects them from damage and associated repair or replacement.
• Spring-Assisted Design. The spring-assisted design holds the valve disc closed reliably. 
• Versatile Installation. Check valves can be oriented vertically or horizontally.
• Tight Shutoff. The spring and gasket ensure a tight seal to prevent leaks.
• Reducing Downtime. Correctly sized check valves help reduce downtime and expenses associated with equipment maintenance or replacement.
• Custom Sizing. Custom sizing is available for certain applications, pressures, and flow rates.

Gas Check Valves from DFT® Inc.

Check valves play a crucial role in the efficiency, safety, and reliability of gas production, oil refining, and similar operations. DFT® check valves offer superior performance, lower maintenance costs, and reassurance against equipment damage due to backflow.

To learn more, visit our DFT® Gas Transmission page to see our PDC and other gas and oil check valve solutions. 

What is a stainless steel dual disc check valve?

Check valves are a type of valve that make sure water flows only one way through a pipe. The main purpose of the stainless steel dual disc check valve is to prevent backflow, which can occur when the water pressure inside a pipe is greater than the pressure in the surrounding area.

A check valve is a type of valve that allows fluid to flow in only one direction. The valve closes automatically to prevent backflow or reverse flow when the fluid in the pipeline changes direction or stops flowing. Check valves are designed to operate without human intervention, relying mainly on the back pressure of the fluid to close the valve.

Check valves are commonly used in applications where backflow or reverse flow can lead to contamination of the fluid, damage to the equipment, loss of product, or safety hazards. Examples of rubber disc check valve applications include water and wastewater treatment systems, HVAC systems, oil and gas processing, and chemical processing.

There are different types of check valves, including swing, lift, ball, and diaphragm check valves. Each type is designed for specific applications depending on the fluid properties, pressure, temperature, and flow rate.

Application of swing check valve:

Check valves have numerous applications across various industries, but some of the most common applications of check valves include:

1. Water treatment systems: Check valves are extensively used in water treatment systems to prevent the backflow of contaminated water into the clean water supply.

2. Pumps and compressors: Check valves to prevent fluid that has already been pumped or compressed from flowing back through the system, which could damage the equipment.

3. HVAC systems: Check valves are used in HVAC systems to prevent the backflow of refrigerant and other fluids, which can cause damage to the equipment and increase costs.

4. Oil and gas industry: Check valves are important components of oil and gas pipelines, where they are used to prevent the backflow of oil or gas, which could create safety hazards and reduce the efficiency of the system.

5. Chemical and food processing: Check valves are used in chemical and food processing systems to maintain the flow of fluid in one direction and prevent cross-contamination between different fluids or processes.

6. Fire protection systems: Check valves are used in fire protection systems to ensure that water can only flow in one direction, from the water source towards the fire, preventing contamination of the fire suppression system.

Are you interested in learning more about Check Valve Manufacturers? Contact us today to secure an expert consultation!

Overall, check valves play a vital role in maintaining the safety and efficiency of fluid systems in various industries.

Ball check valves have many advantages over other types of valves:

1. They can withstand high pressures without leaking or breaking. This means they can be used in high-pressure situations where other types of valves would fail due to excessive pressure.

2. Check valves can be used with any type of liquid or gas that flows through them. They do not require electricity in order to operate and do not require any special equipment such as pumps or compressors for operation.

3. The only moving part of a check valve is its ball valve which opens when there is an increase in pressure inside the pipe so that it can allow fluid through but closes when there is a decrease in pressure so that it does not allow any more fluid through it until it has time to adjust again and open again.

Some disadvantages of stainless steel dual disc check valve are mentioned below:

1. Check valves cannot be used for fluids having a high viscosity or density.

2. When there is a pressure difference between two sides, then it can cause leakage through the valve.

3. When there is a large differential pressure across a check valve, then it can cause wear and tear to the body of the valve and also cause damage to the sealing ring inside it.

The check valve should be operated in such a way as to avoid the occurrence of excessive impact pressure and rapid oscillating action of the valve closing member due to the valve closing.

To avoid the formation of excessive impact pressure due to the closure of the check valve, the valve must be closed quickly, thereby preventing the formation of a great backflow velocity, the backflow velocity is the root cause of the impact pressure when the valve is suddenly closed, so the closing speed of the valve should be correctly matched with the velocity decay of the downstream medium.

However, the velocity decay of the downstream medium may vary greatly in the liquid system. For example, if the liquid system uses a group of parallel pumps, and one of the pumps suddenly failed, the check valve at the outlet of the failed pump must be closed almost simultaneously. However, if the liquid system has only one pump, and this pump suddenly failed, and long delivery pipeline, and its outlet back pressure and pumping pressure are low, the use of a smaller closing speed check valve is better.

The rapid oscillating motion of the valve closing member must be avoided to prevent early failure due to excessive wear of the valve moving parts. The rapid oscillating motion can be avoided by determining the valve passage diameter based on the flow rate that is calculated to generate the force that makes the valve closing member move. If the medium is a pulsating flow, the check valve should be placed as far away from the source of the pulsation as possible. Rapid oscillation of the closing member may also be caused by violent media disturbance, and when this exists, the check valve should be placed where the media disturbance is minimal.

Therefore, the first step in selecting a check valve is to determine the working conditions in which the valve is located.

1. The assessment of the fast closing check valve

In most practical use, the check valve can only be used qualitatively for a fast closing, the following can be used as a basis for judgment.

1) The stroke of the closing member from fully open to the closed position should be as short as possible. Therefore, from the point of closing speed, small check valves are faster to close than large check valves of similar construction.

2) The check valve should be closed from the fully open position at the maximum possible downstream media velocity before backflow to get the longest closing time.

3) The inertia of the closing member should be as small as possible, but the closing force should be appropriately increased to ensure the fastest response to the downstream media velocity reduction. From this point of low inertia, the closing member should be made of lightweight materials, such as aluminum or titanium. In order to balance the lightweight structure and the large closing force, the closing force generated by the weight of the closing member can be enhanced by spring force.

4) Around the closing member, the limiting factor that delays the free closing action of the closing member should be removed.

2. Check valve operation of mathematical applications

The application of mathematical methods to the normal operation of the check valve is developed in recent years. For check valves with articulated flaps, foreign check valve manufacturers such as POOL, Porwit, and Carlton provide a calculation method that involves the establishment of the equation of motion of the valve flap and the application of the deceleration characteristics of the fluid medium in the system. Before the equation of motion of the valve flap can be established, some physical constants of the valve must be known. Calculations can be made to determine the backflow velocity of the valve during sudden closure, and also to calculate the impact pressure of the backflow medium caused by the sudden closure of the valve.

Valve manufacturers can use mathematical methods to design and predict the impact pressure according to the important applications of check valves, and it is important for valve users to know this.

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