An axial check valve is a preferred solution for critical non-return applications such as the protection of rotating equipment and systems where low pressure loss, stable operation, and dynamic behavior are essential.

What is an Axial Flow Check Valve?

Axial flow check valves are a type of non return valve, designed to avoid the quick reverse of a flow in a pipe known as a “water hammer” that may cause severe damage to the different equipment of a piping system. This kind of valve close fast enough without creating excess pressure spikes, avoiding slamming.

The streamlined design of the axial flow check valve permits it’s fully opening at low flows and fluid velocities, getting a low pressure drop. Its spring assisted system and metal-to-metal sealing features provide a non-slam closing and little maintenance.

Working Principle of Axial Flow Check Valve

When the pressure differential between the upstream and downstream sides of the valve exceeds the cracking pressure of the spring, the obturator will move and allow flow. The flow area of the valve decreases steadily down to the seat diameter; this is the venturi design.

As a result of the venturi design, the reduced flow area increases the kinetic pressure and reduces the static pressure allowing the valve to fully open quickly. The spring is selected so that the disc is fully opened and stable against its backstop under normal flow conditions.

When a noticeable reduction in flow occurs, the spring reacts early against the force of the reducing flow.

Why is an Axial Flow Check Valve used?

When flow is reversed in a pipe, this can cause hydraulic shock waves to pass through (also known as water hammer). This can cause severe damage to equipment in the pipeline if measurements are not taken to prevent this. The introduction of the correct check valve, in a fully closed position during reverse flow can prevent this from occurring and causing severe issues at the site.

Valves that prevent water hammer and close rapidly without slamming are called non-slam check valves.

How are Axial Flow Check Valves used?

Axial check valves are specifically designed for fast-reversing systems where backflow is a constant concern. It is categorized as a non-slam check valve as the valve closes without slamming meaning no excess pressure spikes are created. Most axial flow check valves are spring-loaded, with a single low-mass disc, which facilitates fast, dynamic response to a reduction in flow. Due to having a single disc and spring when the disc is opening, the force is balanced resulting in an even flow.

Features of Axial Flow Check Valves

Axial flow check valves offer several advantages over other types of check valves, such as:

• Rapid closing action (prevents water hammering)
• The ability to be properly sized for each application
• Durability
• Increased valve longevity
• The ability to accommodate low-pressure drops and high flow
• Non-slamming opening and closing action
• Tight shut-off leading to zero leakage
• Various end-to-end options
• The ability to be installed in both horizontal and vertical orientation

Axial flow check valves offer many advantages over other types of check valves. Axial flow check valves can save time and money by preventing damage and increasing the lifetime of your pumps, valves, pipes, and other system parts.

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What is an Axial Flow in the Check Valve?

Axial flow in the check valve means the fluid or gas flowing parallel to the axis. It is an axial flow shuttle structure design, and the disc assembly with spring has cushioning and anti-vibration functions. When the medium flows downstream, it will push open the disc and the fluid through the body via axial flow channel circulation. And the spring here has a cushion effect to avoid the impact vibration between the disc and the body when a standard check valve opens. When the medium flows in the opposite direction, the disc closes very quickly, and the disc and the valve seat are tight-fitted to cut off the fluid from the reverse flow direction.

The axial flow check valves have a fast response and silent non-slam issue against pressure surge or damage from water hammer and are particularly designed for fast-reversing systems where backflow is a regular crisis.

What is an Axial Flow Check Valve?

An axial flow check valve is a kind of silent check valve. The check valve is driven by the medium itself and automatically opens and closes the valve disc. Generally, it is used to prevent the backflow of fluid or gases. A flow check valve can be called a one-way valve, non-return valve, backflow valve, backstop valve, and back pressure valve. An axial flow check valve has been a popular industrial valve since 2008. This valve has the function of the general check valve and is designed with a shock-absorbing spring, combined metal seat, and soft seat structure, which is easy for end-user maintenance on site.

The axial flow check valve adopts a particular sealing structure. Whether the downstream pressure is high or low, the valve is permanently closed tightly and has excellent shutoff performance. It overcomes the disadvantage of the lack of shutoff performance of the general check valve at low back pressure. ZECO Valve produced an axial flow check valve that has a unique axial flow shuttle structure. It has the advantages of small flow resistance, significant flow coefficient, compact design, etc. It is the best valve for oil and gas gathering and transmission pipeline systems, especially for the outlet of oil transmission pumps.

Specifications of Axial Flow Check Valve

• VALVE DESIGN
  • based on API 6D and customer requirements
• TEMPERATURE RANGE
  • -150 to 662°F (-101 to 350°C)
• SIZE
  • NPS 2 – 56 (DN 50-1400)
• PRESSURE RATING
  • ASME 150 – ASME 2500
• FACE-TO-FACE
  • As per API 6D standard
• END CONNECTIONS
  • RF, RTJ as per B16.5 &B16.47
  • BW, Butt Welded as per B16.25
• BODY DESIGN
  • Cast one piece / bolted two pieces for size >20 inch.
  • Forged bolted one-piece/ three-piece
• SEAT DESIGN
  • Metal-seated with hard facing on disk and seat

How are Axial Check Valves used?

Axial check valves are specifically designed for fast-reversing systems where backflow is a constant concern. It is categorized as a non-slam check valve as the valve closes without slamming meaning no excess pressure spikes are created. Most axial flow check valves are spring-loaded, with a single low-mass disc, which facilitates fast, dynamic response to a reduction in flow. Due to having a single disc and spring when the disc is opening, the force is balanced resulting in an even flow.

Features of Axial Check Valves

• Axial flow
  • Streamlined flow path through full-port expanded body avoids turbulence and prevents erosion and vibration. Process downtime and maintenance costs are eliminated.
• Low pressure loss
  • The full opening flow passage and high-pressure recovery of the venturi-shaped body result in very low pressure loss and reduced operating costs of pumps and compressors.
• Tight shut-off
  • Tight shut-off is obtained by means of metal-to-metal sealing between the disc and the seat. This sealing is not affected by erosion and deformation of material (like with a soft seal).
• Low cracking pressure
  • The stability of a compressor system during startup benefits from low cracking pressure. This is achieved with a large disc that has identical effective pressure areas on both sides (line contact sealing).
• Easy opening and stable operation
  • The low static pressure in the venturi-shaped throat area creates a pressure differential over the disc, resulting in an easy opening. The axial check valve responds smoothly to changes in flow and remains stable when it is supposed to be.
• Non-slam operation
  • The spring-assisted design ensures ultra-fast closing with virtually no backflow and pressure surges in critical applications such as multi-pump systems or LNG trains.
• Maintenance free
  • Internal construction is based on the application of sound basic mechanical engineering principles. Consequently, ZECO axial check valves do not require any maintenance.
• Reliable performance prediction
  • Both the pressure drop and the dynamic behavior can be predicted with great accuracy, based on full-scale laboratory flow tests and a mathematical model developed in cooperation with a recognized fluid hydraulics laboratory.

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Consisting of 2 discs attached to the valve body by a pin and operated by the action of springs, which immediately start closing the valve, when the fluid stops, dual plate check valves are used to prevent back flow and also work as a prevention for water hammer.
Dual Plate Check Valves are made from a wide range materials including cast iron, special stainless steels, ect. They can be soft seat or metal seat construction and also have the ability to adjust the spring torque according to the application, which makes it a product suitable for general and special purposes.

Features of Dual Plate Check Valve:

1. Patented retainer-less design – High integrity sealing, facilitates quick disassembly at site;
2. Two independent seats – Consistent sealing even in uneven flow;
3. Raised profile of the soft seat enhances sealing;
4. Integrally moulded liner;
5. Stopper pin prevents the discs from coming into contact with each other and thus prevents disc damage. The stopper pin also prevents spring failure by ensuring that the discs don’t travel beyond the full-open position;
6. For sizes 6” and above, lifting eyebolt option is provided;
7. Drain connections provided on demand

Material of Dual Plate Check Valve:

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How does a Wafer Swing Check Valve work?

The valve’s wafer-like profile makes it a great choice for systems requiring short takeout lengths. Wafer check valves work much in the same way as swing check valves. Like swing check valves, wafer check valves are comprised of a disc and a seating arrangement. When material flows in one direction, the flow lifts the disc from the seating arrangement. This allows the material to flow through the valve. If and when flow reverses direction through the valve, the flow of material pushes the disc back into the seating arrangement, thus closing the valve off from the flow of material.
Wafer check valves are designed to be slim and unlikely to clog. This design makes them ideal for use with materials containing solid particles or debris. This type of valve can be mounted either vertically or horizontally, as long as the back pressure required to seat the check valve is sufficient. Mechanisms are available to help provide assist valves in case back pressure is insufficient.

Applications of Wafer Swing Check Valve

• Steam
• Hot & Cold Water
• Power & Heat Engineering
• Pressurized Air
• Industrial Technologies
• Fluids without Acidity or Alkalinity Properties

Advantages of Wafer Swing Check Valve

• Minimizes piping support with the compact wafer-style body. This range of wafer check valves is two to three times lighter than traditional full-bodied check valves.
• To meet special applications and service conditions, These valves can be offered with many different options, such as silicone-free cleaning, oxygen-cleaning, vertical service, left-hand operation, levers, weights, and cushions.
• For media containing fibrous matter or caustics, These offer an external spring that eliminates the spring from the flow path. This will prohibit the possibility of fiber wrapping around the spring or a chemical attack on the spring.
• Maintenance is minimal with the field-replaceable O-ring seat, available in all styles and sizes.

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This valve can be installed at the water outlet of the pump or the water outlet pipe to prevent backflow of the medium.

Features：

1. The switch can be up to 100,000 times;
2. Full flow area, low flow resistance;
3. Less likely to accumulate debris;
4. Simple structure and convenient maintenance.

Principle：

The sealing ring of this valve adopts the tilting design, and the closing time is short, which can reduce the water hammer pressure.

Installation and Commissioning：

This valve can be installed in sewage. For specific use, please consult Zeco Valve Group.

Product scope, Standards & Materials

Size Range: 2″~48″

Pressure Rating: 150LB~2500LB

Face-to-Face Dimensions: AMSE B16.10, EN558-1

Flange End Dimension :AMSE B16.1/16.42, AS4087, EN1092-2

Inspection and Test: API 598

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Backflow Preventers

Festures of Backflow Preventers

• The double check valve is designed as a whole, with small structure；
• Body is streamlined with little resistance loss；
• Combination of a double check valve and safety drain valve can completely prevent backflow pollution under any working condition；
• All moving parts are made of non-rust and wear-resistant materials with long service life.

Backflow Preventers Working Principle

Backflow preventers for two check valve series, when one of the seal damage, the other also ACTS as a seal to prevent backflow. However, when the sealing of two check valves is broken at the same time, the check function is lost. Backflow preventers on the common type of foundation in the middle of the drain, so even if two check valve sealing at the same time damage, it can also play a role in preventing backflow pollution.

Backflow Preventers Installation and Commissioning

This valve must be installed horizontally, the environment of the installation site should be clean, there should be sufficient maintenance space, the main degree of safety drain or (air barrier) outlet is more than 300mm above the ground, and it should not be flooded by water or debris, and the installation area should be equipped with drainage facilities. For specific use, please consult ZECO Valve Group.

Backflow Preventers Material and Standard

Size Range: 2″~12″
Pressure Rating: 10bar ~ 25bar
Face to Face Dimensions: AMSE B16.10, EN558-1
Flange End Dimension: AMSE B16.1/16.42, AS4087, EN1092-2
Coating: Fusion Bonded Epoxy Coating
Inspection and Test: ISO 5208 / EN 12226-2

Part	Material	Standard
Body	Ductile Iron	EN 1563/DIN 1693
Bonnet	Ductile Iron	EN 1563/DIN 1693
Seat	CuZn39Pb1 / C37000	EN12167/ASTM B135
Stem	Stainless Steel 431	EN10088-1/ASTM A959
Spring	Stainless Steel 431	EN10088-1/ASTM A959
Seal	EPDM / NBR	ISO 4633
For the materials options not listed, consult factory. ZECO manufactures valves in more than 50 different alloys.

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