What is a Non Slam Check Valve?

Non-slam check valves are check valves used to prevent reverse fluid flow. Also, these valves are meant to eliminate or reduce water hammer and their associated effects. A water hammer is a high-pressure shock wave that happens when the fluid flow stops abruptly because of a pump or valve closing quickly in a piping system. When water hammer happens, the fluid flow reversal causes high stress on the piping system which endangers its structural integrity and may cause damage or rupture. Non-slam check valves are used to prevent water hammers and ensure fluid flows in one direction only. Non slam check valve manufacturers produce this valve without a handle or actuator but it works mechanically to stop the fluid flow from reversing.

How does a Non Slam Check Valve work？

The opening and closing parts open or close by themselves depending on the flow and force of the medium, so as to prevent the reverse flow of the medium, the valve is called non slam check valve. Non-slam check valve belongs to automatic valves. It is mainly used in pipelines with a one-way flow of the medium. It allows medium to flow in one direction only to prevent accidents.

Types of Non-slam Check Valve

Non-slam check valves can be divided into three types according to their structure: lifting non-slam check valves, swing non-slam check valves and butterfly non-slam check valves.

• 1. Lifting non-slam check valve is divided into vertical and horizontal.
• 2. Rotary non-slam check valve can be divided into three types: single-lobe, double-lobe, and multi-lobe.
• 3. Butterfly non-slam check valve is straight-through.

The above non-slam check valves can be divided into threaded connection, flange connection, welding connection, and clamp connection.

Structure of Non-slam Check Valve

According to the structure, it can be divided into three types: lifting non-slam check valve, swing non-slam check valve, and butterfly non-slam check valve. The lifting non slam check valve can be divided into two types: vertical and direct. Rotary non-slam check valve can be divided into three types: single-lobe, double-lobe, and multi-lobe. The butterfly non-slam check valves are butterfly double-lobe, butterfly single-lobe and the above non-slam check valves can be divided into four types in connection form: threaded connection, flange connection, welding, and clamping connection.

Differences Between Non-Slam and Swing Check Valves

Some styles of check valves are specifically designed to allow their disc, or flapper, to slam shut in certain conditions, such as the reversal of fluid flow. This sudden shutting, or slamming, creates a wave of pressure in the liquid that reverberates throughout the system and, depending on the precise application, can ultimately lead to reduced process efficiency, valve damage, gasket joint leaks, and other issues. This inevitable — but controllable — phenomenon is commonly referred to as a water hammer.

Non-slam check valves are designed specifically for use in these situations. As their name implies, these valves close without slamming, meaning no excess pressure spikes are created. The disc of a non-slam check valve has an internal spring opposing the opening fluid flow pressure. When the flow of a media is strong enough, the spring compresses and the valve opens; the disc is smoothly pushed back toward the seating surface in the valve by the spring as the flow decreases and stops, but before flow direction reverses.

Often called flapper style check valves, swing check valves are a more traditional variety. The disc of a swing check valve is secured to the body of the valve by a trunnion and hinge arm, without the aid of a spring. Unlike a non-slam check valve, which opens and closes at rates comparable to the pressure of the fluid flow, a swing check valve opens and closes more suddenly, relying on the installation orientation, gravity, and reversing flow to close the valve.

Applications of Non-slam Check Valves

• Non-slam check valves are used in chemical industries.
• These valves are used in the foods and beverages industries.
• They are used in pharmaceutical applications.
• These valves are used to prevent the backflow of water or steam in boiler applications.
• They are used to prevent water contamination in the freshwater supply.
• These valves are used in the oil and gas industries.
• They are used in wastewater treatment.

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Its function is to prevent the medium backflow in the pipeline. The bottom valve of the pump suction closure also belongs to the non slam check valve class.

The non slam check valve is generally divided into lifting type, swing type, butterfly type, and diaphragm type.

Lifting non-slam check valve

Lifting non-slam check valve is similar to a globe valve. Its disc moves reliably along the line of the passage, but the main force of the fluid is larger. It is suitable for smaller caliber occasions.

Straight-through non-slam check valve

The straight-through non-slam check valve can only be installed in the horizontal pipeline, while the vertical non-slam check valve is usually installed in the vertical pipeline. Piping.

Rotary non-slam check valve

The rotary non-slam check valve disc rotates around the rotating axis, and its resistance is generally less than that of the lifting non-slam check valve. It is suitable for larger caliber applications.

Butterfly non slam check valve

Butterfly non slam check valve is similar to a butterfly valve in structure, which has a simple structure and small flow resistance.

Diaphragm non-slam check valve

Diaphragm non-slam check valve has many structural forms. The diaphragm is used as an opening and closing parts. Its waterproof hammer has good performance, simple structure, and low cost. However, the temperature and pressure of the diaphragm-type non-slam check valve are limited by the diaphragm material.

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Among them, non slam check valve belongs to this type of valve, which includes swing non slam check valve and lifts non slam check valve. The swing non-slam check valve has an intermediate hinge mechanism and a door-like disc rests freely on the inclined seat surface. In order to ensure that the disc can reach the proper position of the seat surface every time, the disc is designed in a hinge mechanism so that the disc has sufficient swing space and makes the disc truly and comprehensively contact with the seat. Valve discs can be made entirely of metal or can be metal inlaid with leather, rubber, or synthetic coverage, depending on the performance requirements. The swing-type non slam check valve has almost no hindrance to the fluid pressure when it is fully opened, so the pressure drop through the valve is relatively small. The lift non slam check valve disc seat is located on the seating face of the valve body. In addition to the valve, the disc can rise and fall freely, the rest of the valve is like a globe valve. The fluid pressure causes the disc to rise from the seating surface, and the medium reflux causes the disc to fall back to the seat and cut off the flow. According to service conditions, the disc can be all-metal structure, or it can be in the form of rubber pads or rubber rings embedded on the disc rack. Like globe valves, fluids are narrow through lifting non-slam check valves, so the pressure drop through lifting non-slam check valves is larger than that of swing non-slam check valves, and the flow of swing non-slam check valves is limited very little.

Non-slam check valve common faults and treatment methods

Common failures are:

Disc smashing and medium backflow.

The reason for disc breakage is that the medium pressure before and after non-slam check valve is close to equilibrium and mutual “saw” state, the disc often beats with the seat, and the disc made of some brittle materials (such as cast iron, brass, etc.) is broken. The precaution is to use non slam check valve with the disc as tough material.

The reasons for medium backflow are as follows:

The sealing surface is damaged and the impurities are clamped in. Repairing the sealing surface and cleaning the impurities can prevent backflow.

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What are Non Slam Check Valves?

The non-slam check valve is a kind of automatic valve, its main function is to prevent the backflow of the medium, prevent the pump and drive motor from reversing, and discharge the container medium. The check valve can also be used to supply the auxiliary system whose pressure may rise above the system pressure.

Non-slam check valves are check valves used to prevent reverse fluid flow. Also, these valves are meant to eliminate or reduce water hammer and their associated effects. A water hammer is a high-pressure shock wave that happens when the fluid flow stops abruptly because of a pump or valve closing quickly in a piping system. When a water hammer happens, the fluid flow reversal causes high stress on the piping system which endangers its structural integrity and may cause damage or rupture. Non-slam check valves are used to prevent water hammers and ensure fluid flows in one direction only. Non slam check valve manufacturers produce this valve without a handle or actuator but it works mechanically to stop the fluid flow from reversing.

How does a Non-Slam Check Valve work?

A non slam check valve works based on differential pressure. When the upstream pressure is high, it provides enough pressure energy that is used to open the valve disc. The disc is supported by the use of a spring. As such, the pressure energy compresses the disc to open. When the disc opens, fluid flows through the valve from the inlet to the outlet port and finally to the piping system. The valve closes when fluid pressure reduces.

The fluid pressure reduces for example when the pump is closed. As such, fluid attempts to reverse flow direction because upstream pressure is lower than downstream pressure. In the instance the fluid attempts to reverse, the valve disc closes immediately due to the low-pressure drop.

Purpose of Non Slam Check Valves

The purpose of the non slam check valve is to prevent the flow in the opposite direction, allowing only the media to flow in one direction. Usually, this valve is automatic, The valve disc opens under the pressure of the fluid flowing in one direction; when the fluid flow in the opposite direction, due to the fluid pressure and the self-coincidence of the valve disc, the valve disc acts on the valve seat, thereby cutting off the flow. It is not suitable for media containing solid particles and high viscosity.

Types of Non Slam Check Valves

1. Metallic seated non-slam check valve
   • This is a non-slam check valve that is meant for use in high-pressure and high-temperature applications. This type of check valve has its seat made of metallic materials such as carbon steel, stainless steel, ductile iron, brass, and bronze among other materials. These materials are used to make which makes it suitable for high-temperature applications. In addition, metallic seats have high strength which helps to enhance high strength against high pressure. Such valves are resistant to corrosive products.
2. Soft-seated non-slam check valve
   • This is a check valve in which the seat is made of soft materials such as rubber or plastic. However, the valve body is made of strong metallic materials to ensure the valve is strong against high pressure and impact damage. These materials have low melting temperatures and thus are recommended for use in temperatures below 60oC. These materials have low strength and thus they can work well in medium and low-pressure applications. Also, soft seated non-slam check valves are used in corrosive applications because they are highly resistant to corrosion relative to their metallic seated counterparts.

Features of Non Slam Check Valves

• Powerful spring for ultra-fast closing action
• Venturi pattern design
• Minor friction between moving parts to eliminate any chance of jamming
• Spring-assisted and short stroke
• No chattering effects to minimize pressure fluctuation during normal conditions
• Low-pressure drop
• High dynamic response and zero reverse flow
• Nozzle design if the valve size>20 inches. for better flow regulation
• Short pattern design compact face-to-face option for weight and space savings

Applications of No Slam Check Valves

The following lists some of the many typical applications where Non-Slam Check Valves should be used:

• Centrifugal Compressor Discharge
• Reciprocation Compressor Discharge (Sizing is critical for this application)
• Rapid Closure requirements
• Low-Pressure Drop Requirements
• Salt Water Fire Safety Systems Due To Critically Of This Service
• Desalination Reverse Osmosis Process
• Critical Applications
• Non Serviceable Locations
• High system deceleration applications
• Elevate Valve Slamming applications
• High-Temperature critical applications
• Cryogenic Application
• Competitive Pricing
• Delivered Worldwide
• High-Quality Engineering
• Suitable for Critical Applications

Common Faults of Non Slam Check Valves

• The valve disc is broken;
  • The pressure of the medium before and after the non-slam check valve is close to balance and they are in a state of “seeing” each other. The valve disc often beats against the valve seat, and the disc made of some brittle materials (such as cast iron, or brass) is broken. The preventive method is to use a check valve whose disc is a flexible material.
• The medium flows back.
  • The damage to the sealing surface or the inclusion of impurities. After repairing the sealing surface and cleaning impurities, backflow can be prevented.

ZECO Valve Group is a professional non slam check valve manufacturer. For each spring in the non-slam check valve, we use a caliper to measure the geometric size and use a spring tester to test the load force to ensure that the check valve is opened and closed in a normal state.

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What is a Nozzle Check Valve?

A type of non-slam check valve, nozzle check valves are high performance and self-actuated regulating devices. These reliable non-return valves are designed specifically with demanding applications in mind. As such, this means they can react promptly to high deceleration rates with a non-slam performance, which minimises water hammer in reverse flow conditions.

Compared to other check valve types, nozzle check valves offer unrivalled high flow, energy efficiencies and non-slam performance. They come with a selection of valve body and internal orifice designs and springs that are specifically optimised for the flow conditions of any given application. In addition, they also feature a built-in diffuser, which recovers head losses unlike any other non-return valve and minimises energy consumption.

Nozzle check valves also feature a spring assisted, short stroke disc action that closes the valve within mere fractions of a second. This function is able to protect pipework, expensive pumping and related equipment from any high reverse velocities and damaging surge pressures.

Structure of a Non Slam Nozzle Check Valve

The axial flow check valve has a simple structure and is mainly composed of a valve body, seat, disc, spring, guide sleeve, guide cover, and internal structure. See as bellow picture.

Design Features of Nozzle Type Check Valves

The nozzle check valves characterise for an effective dynamic response under various flow deceleration conditions.

Generally compared to other traditional check valves, the valve design is superior in performance, lower pressure drop ( depending size and form) and response.

The axial movement of the disc is giving a streamlined flow path obtaining the Venture effect.

Generally spoken the axial graded nozzle formed check valves have presently a much better dynamic performance compared to other conventional.

Its application on high pressure pumping equipment is not only allowing a better dynamic performance but also a more durable design compared well other conventional check valves.

As the flow is streaming smoothly through the valves it is not exposed to continuous movements.

How does a Nozzle Check Valve work?

The opening and closing of the flap for axial flow check valve is determined by the pressure difference between the inlet end and the outlet end of the valve. When the pressure at the inlet end is greater than the sum of the spring forces at the outlet end, the valve flap is opened; when the sum of the outlet end pressure and the spring force is greater than the inlet end pressure difference, the flap is closed. The structures in valve opening and closing.

Technical Data of Nozzle Check Valves

• RANGE: DN 100 to DN 900
• Design: EN16767(EN12516-1) / API594 (ASME B16.34)
• Connections: Flanged PN10 to PN100 ACC. to EN1092-1 / ISO7005-1 / BS 4504 sect. 3.2 ANSI125#/600# ACC. to ASME B16.1/B16.5.
• Face to Face: API594 (300#-600#) others no standard.
• Operating temperatures: -20ºC +200ºC (rubber seated) others inquire.
• Testing: EN12266 (ISO5208) / API598. Minimum pressure for tightness: 0.2 bar.
• Materials: Ductile Iron, Steel, Stainless steel, superduplex, brz -alu.

Features of Axial Nozzle Check Valves

Nozzle check valves have been designed to provide reliable backflow prevention for the Petrochemical, Gas & Water divisions.

ZECO’s Engineering department has create Nozzle check valve with dymanic quick closing which reduces the flow return speed. The Axial movement of the disc produces a streamlineflow with venturi effect which reduces the pressure drop with minimal seat leakage and with minimum turbulences.

Our design needs only a very low flow to completely open the valve and guarantees the highest fluid dynamic performances reacting fast to flow alteration.

Nozzle check valves are available with multiple spring torques increasing considerably its purposes. it has also been conceived to have really low maintenance costs and high serviceability.

Advantages of Nozzle Check Valves

• Low pressure loss
• Unique dual-spring design for fast, dynamic, non-slam response
• Reliable, maintenance-free operation
• One-piece, all-metal valve body—fire safe and no fugitive emissions
• Reliable, leak-free, and integral metal-tometal seat
• Suitable for low and high flow rates
• Springs replaceable without major valve disassembly
• Lightweight moving parts and minimized disc stroke to optimize the closing time
• Low friction bearings

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