How It Works: Check Valves

Varieties of Check Valves

Swing (tilting-disc) check valves feature a clapper with a disc that boasts a convex shape on the upstream inlet side and a flat design on the downstream outlet side. According to API Spec 600, the disc pivots on a hinge attached to the bottom of the valve bonnet. For valves that conform to API Spec 6D, the typical construction includes a cast pocket within the valve body, accommodating a drop-in shaft or pin-and-bushing that allows the clapper to rotate. This design necessitates a restraint to secure the clapper within the pocket. The latest design enhancements bring forth improved modularity, simplifying assembly and enabling diverse configurations with a foundational design.

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Nozzle (axial flow) check valves incorporate a spring-loaded disc that translates horizontally. The spring mechanism facilitates a nonslam design that mitigates the repercussions of water hammer. These valves remain fully open even at minimal flow rates, guaranteeing optimal performance. They are suitable for both buried and above-grade applications, particularly for gas applications.

Ball check valves utilize a spherical ball clapper, which can sometimes be spring-loaded to ensure sealing at pressures below the cracking threshold. Due to the spherical structure, these valves may experience wear over time, necessitating regular maintenance; thus, they should be placed in accessible areas for repair crews.

Diaphragm check valves feature a rubber diaphragm clapper that expands when upstream pressure exceeds downstream pressure, effectively closing when this pressure equalizes or drops below a certain differential.

Stop check valves are generally constructed like swing check valves but include external control mechanisms—such as actuators, levers, or handwheels—that enable deliberate closure independent of flow pressure.

Duckbill valves allow flow through a soft tube leading into the downstream side, with backpressure resulting in the collapse of the tube, effectively halting flow.

Advantages of Check Valves

The primary benefit of check valves lies in their straightforward design. They are typically smaller and simpler to install compared to other valve types, enhancing maintenance efficiency. Various check valves can be customized with specific nonslam features to minimize noise and reduce wear on the seal. Notably, ENTECH nozzle check valves are frequently selected for their nonslam features in LNG pump stations and gas compressor stations. Additionally, the streamlined design of TOM WHEATLEY and ENTECH check valves ensures reduced pressure drops (under 1 psi), outperforming comparable piston check valves.

Several industries rely heavily on various check valve types within their process systems. The diversity of check valves available meets unique application requirements, ensuring reliable, efficient performance while maintaining safety and smooth operation.

The innovative Frank P Cotter created a simplistic, self-sealing check valve that adapts easily to pipe connections. The benefit of Cotter's design lies in its ability to connect without needing special fittings, along with easy repair and inspection capabilities.

Renowned inventor Nikola Tesla also made strides in check valve designs, presenting a straightforward one-way valve. The versatility and extensive history of these valves underscore their valuable contributions.

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Diverse Check Valve Types Utilized Across Industries

1. Bronze Swing Check Valves

The widely-used Bronze Swing Check Valve performs effectively in both industrial and commercial settings. They open in response to forward flow and close to prevent or lessen reverse flow, safeguarding pumps and pipelines from damage due to backflow. Swing Check valves produce minimal pressure loss, suitable for hot and cold water, low-pressure steam, HVAC, compressed air, and various utility applications.

2. Cast and Ductile Iron Swing Check Valves

Ideal for high and low-pressure environments, Cast and Ductile Iron Swing Check Valves are known for their durability and longevity. Their unrestricted flow path leads to improved flow capacity and lower pressure losses, attributed to their solid construction and uncomplicated design.

3. Tilting Disc Check Valves

Tilting Disc check valves were specifically engineered for pumping stations that handle drinking water and other neutral liquids. Their compact closing angles provide enhanced closing performance, reducing slams and pressure surges during pump shutdowns. They are typically installed in environments with multiple pumps discharging into shared header pipes, maintaining low-pressure loss.

4. Dual Plate Check Valves

Manufacturers produce an array of Dual Plate Check valve designs, including retainer and retainer-less styles, wafer, lug, and double-flanged configurations. Available in various body and trim materials, these high-performance valves provide exceptional reliability and versatility.

5. Ball Check Valves

Characterized by their reliability and simplicity, Ball Check Valves utilize one moving spherical ball to block reverse flow. They incorporate either reduced or full-ported valve seats, ensuring that the ball creates a leak-tight seal without becoming wedged.

Check Valve Applications

Designed as self-actuating devices, check valves allow media to flow in one direction while preventing backflow. These valves find utility primarily in potable water, wastewater, and irrigation systems; however, they are also crucial in various other applications, including processing, mining, food and beverage, oil and gas, pharmaceuticals, power production, and HVAC systems.

Selecting the Right Check Valve

To achieve efficient and safe operations, choosing the appropriate check valve is critical. Factors to consider include flow characteristics, fluid compatibility, nonslam features, pressure loss, and overall ownership cost. Assessing system requirements and installation costs will guide the decision-making process. It's vital to understand the distinct characteristics of each check valve type before purchasing and installing.

The Best Check Valve for Your Needs

With many varieties of check valves tailored for specific applications, some are engineered for high-pressure-temperature solutions, while others mitigate slam and pressure surges that may arise during pump shutdowns. These innovations have profoundly enhanced safety and productivity across numerous industries.

For inquiries about the most suitable check valves for your business or industry, contact John Valves.