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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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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