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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Structure And Installation Of Wafer Check Valve

A wafer check valve is also called countercurrent valve, check valve, back pressure valve, and one-way valve. This kind of valve is automatically opened and closed by the force generated by the flow of the medium itself in the pipeline and belongs to an automatic valve. Check valves are used in pipeline systems. Their main functions are to prevent medium backflow, reverse pumps and their driving motors, and release of the medium in containers. Check valves can also be used in pipelines to supply auxiliary systems where the pressure may rise to more than the pressure of the main system. Check valves can be used in pipelines of various media according to different materials.

The structure of the wafer check valve:

• 1. The layout length is short, and the layout length is only 1/4~1/8 of the traditional flange check valve.
• 2. Small size and lightweight, the weight of which is only 1/4~1/20 of the traditional flange check valve.
• 3. Disc closure speed, low water hammer pressure
• 4. Horizontal or straight pipes can be used with convenient installation.
• 5. Smooth runner and low fluid resistance
• 6. Active collateral activation and good sealing function

Installation Notes Of Wafer Check Valve:

• 1. When installing the pipeline, attention should be paid to making the direction of flow through the check valve and the flow direction of the fluid common.
• 2. Install in a straight line. As for the horizontal pipeline, place the check valves in straight line; use an elastic tube between the check valves and butterfly valves and never connect them directly with other valves; prevent joints and blockages within the operating radius of the valve plate; and do not install a front or rear device on the check valves. Variable diameter pipe.
• 3. When the elbow is adjacent to the clamp-type check valve, attention should be paid to leaving enough space for the clamp-type check valve; when the pump outlet device is opposite to the clamp-type check valve, at least six times the valve diameter should be flowed out to ensure that the butterfly end is affected by the fluid effect.

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Ball Valve ZECO Product Line: Floating Ball Valve, Trunnion Mounted Ball Valve, Top Entry Ball Valve & Full Weld Ball Valve/ GET VALVE PRICE >

Gate Valve ZECO Product Line: Wedge Gate Valve & Through Conduit Gate Valve/ GET VALVE PRICE >

Butterfly Valve ZECO Product Line: Center Line Butterfly Valve, Double Eccentric Butterfly Valve & Triple Eccentric Butterfly Valve/ GET VALVE PRICE >

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Forged Steel Valve ZECO Product Line: Forged Gate Valve, Forged Ball Valve, Forged Globe Valve & Forged Check Valve/ GET VALVE PRICE >

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This post will focus on explaining different types of industrial valves, their mechanism, their application in the oil and gas industry as well as API and ASME standards for oil and gas valves.

What are Valves in Oil and Gas?

A valve is a device used to regulate the flow of oil and gas. Opening or closing an aperture controls the amount of liquids and gases allowed through pipes. The valve controls the flow of fluids by stopping and starting, adjusting the amounts, controlling the direction, regulating pressure, or relieving pressure.

Types of Valves Used in the Oil and Gas Industry

1. Ball Valves

Ball valves are available in various materials and sizes. They are used for the broadest spectrum of isolation applications and are available in full flow and full through conduits.

Advantages: low-pressure drop, quick-acting, straight through flow in either direction, easily actuated, bubble tight shut off & operating torque.
Disadvantages: long “relative” face to face dimension and temperature limitations on seating material.

2. Gate Valves

The function of the gate valve is to start or stop a flow when a straight-line flow of fluid and minimum flow restriction is needed.

During use, gate valves are kept either fully open or fully closed. The disc of the gate is completely removed when turned open, allowing contents to pass through.

Advantages: a straight-through flow of fluid in either direction, low-pressure drop.
Disadvantages: slow-acting, takes a lot of space. Not drip tight shut off.

3. Globe Valves

If you want to stop the flow of air, you can close the globe valve using a plug-like piston. When the actuator is turned, the linear valve opens and closes. It is possible to open this valve to a variety of levels due to the threading on the stem. The popularity of this sort of valve in the petrochemical industry can be traced back to this very fact. Depending on how much throttling is required, the opening size can be reduced.

4. Check Valves

Gas refineries find check valves extremely helpful as the device opens under pressure and does not allow backflow of fluid or material. Because of the restricted backflow, cross-contamination of the product is prevented. That is, different materials can use the same pipeline. There is no need for an actuator as required in other valve types. However, it does need precise installation to ensure the response to fluid pressure occurs as required.

5. Plug Valves

A plug valve is also a linear valve but it has a wider piston than a globe valve. While it may not be ideal for throttling, it can hold its own in high pressure or a high-temperature pipeline. The wider surface area of the plug provides enough room for the pressure to be distributed and dissipated along the plug while maintaining fluid flow control.

6. Butterfly Valves

A butterfly valve makes up for a lot of what a gate valve lacks in terms of performance. Open channels allow media to flow freely, even if they contain solid particles. Since the stem at the base of a butterfly valve holds its disc in place, it can be used in high-pressure pipelines. Its low-torque operation is also a result of these design attributes.

7. Control Valves

Control valves are valves that provide process control over flow rate, pressure, and temperature in the oil and gas industry. They work by varying the size of the flow passage way as directed by either a hydraulic, pneumatic, or electrical signal sent from a controller. The automatic operation of these valves gives them the ability to be operated remotely, rather than having an operator constantly monitoring and adjusting.

Case of ZECO Oil and Gas Valves

North Pars Gas Field

From 2011 to 2013, ZECO Valve Group provided API 6D valves such as wedge gate valves, swing check valves and ball valves for North Pars Gas Field, providing a solid foundation for the normal operation of pipelines.

Sudan National Strategic Oil Tank

From 2011 to 2013, ZECO Valve Group provides pipeline solutions for wedge gate valves, check valves and ball valves for Sudan national strategic oil tank.

Samsung C&T Engineering & Construction Group

ZECO Valve Group provided API 6D products and other water system products such as backflow preventors for water systems for oil pipeline projects contracted by Samsung C&T Engineering & Construction Group.

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Ⅰ. Introduction of check valve

The function of the check valve is to only allow the medium to flow in one direction and prevent the flow in the opposite direction. Usually this kind of valve works automatically. Under the action of the fluid pressure flowing in one direction, the valve flap opens; when the fluid flows in the opposite direction, the fluid pressure and the self-coincidence of the valve flap act on the valve seat, thereby cutting off the flow.

Ⅱ. The failure of the check valve and its treatment method

Common failures of check valves include:

①The valve disc is broken;

1The reason for the disc breaking is: the pressure of the medium before and after the check valve is close to equilibrium and they are in a state of “seeing” each other. The disc often beats against the valve seat, and some brittle materials (such as cast iron, brass) are made of The finished valve disc was broken. The preventive method is to use a non-return check valve whose disc is a flexible material.

②The medium flows back.

The reasons for the backflow of the medium are:

1. The sealing surface is damaged;
2. Clamp in impurities.

Repairing the sealing surface and cleaning impurities can prevent backflow.

Ⅲ. The principle of check valve

A check valve is a valve that automatically opens and closes the disc depending on the flow of the medium itself, and is used to prevent the medium from flowing back. It is also called a check valve, a one-way valve, a reverse flow valve, and a back pressure valve. Its main function is to prevent the medium from flowing backwards, to prevent the pump and drive motor from reversing, and to discharge the container medium. Check valves can also be used to supply pipelines for auxiliary systems where the pressure may rise above the system pressure.

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1. The Gate Valve: 

Conditions are that the rated water working pressure shall be above 175 PSI and that the body and bonnet shall be of cast bronze alloy as per the ASTM standard with a structure of threaded connection. Available valves are the gate valve and the high stem gate valve. Conditions are that the rated water working pressure is no less than 300 PSI and that the bonnet and body shall be made of cast iron alloy as per B standard with a structure of flange connection, of which the flanges shall be 250 or 300 pound.

2. The Ball Valve: 

Conditions are that the rated water working pressure shall be above 175 PSI, that it has a teflon seat and climate independent gear actuators, that it is applicable for indoor / outdoor use and that it has a structure of threaded or slotted connection with rising position indicators and two built-in monitoring switches. Available standard port valves are ball valves (with threaded connections) , ball valves (with slotted connections), which are pipe control valves of DN65 or above and in accordance with valve and fitting manufacturer’s standard.

3. The Block / Angle Valves: 

Conditions are that the rated water working pressure is no less than 175 PSI and that the valve should be provided with rubber seat disc and thread-ended connections.

4. The Check Valve: 

Conditions are that the rated water working pressure is no less than 175 PSI, that the valve is furnished with the rubber seat disc and thread ended connections that the valve should be Y-shaped and horizontal swing and that it shall comply with the MSS standards. Available valves are KT-403-W check valves. These check valves should be rated for no less than 175 PSI with bronze internals and rubber-metal seats.

5. The Butterfly Valve: 

Conditions are that the rated water pressure should not be less than 175 PSI, that the valve is climate independent with indoors and outdoors use and that it has a hand-gear actuator, a bulged position indicator and two built-in monitoring switches.

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First, selection and installation of valves.

1. Principles of valve selection for water supply pipelines.

• The block valve shall be used in pipelines with a diameter less than 50mm. While the gate valve and the butterfly valve shall be used for ones with a diameter more than 50mm.
• The control valve and the block valve shall be used in need of volume and pressure regulation.
• The gate valve shall be used in request of the low resistance (like the pump suction pipe).
• The gate valve and the butterfly valve shall be used for the commuted flow. Never is it the case for the block valve.
• The butterfly valve and the ball valve can be applied to limited installation space.
• The block valve shall be used for the pipeline frequently switched on-and-off.
• The multi-function valve shall be used for the outlet pipe of large caliber water pumps.

2. Parts of the water supply pipeline shall be provided with valves.

• The inlet pipe between residential quarters and the municipal water supply.
• Long pipes. The residential outdoor ring pipe network shall be set node according to the separation requirements. Valves shall be provided to separate into the short.
• The head of branch pipes and household pipes connected the main water supply pipe in the residential quarter.
• Inlet pipes, water meters and branch standpipes (the bottom of standpipe and the two ends of vertical loop standpipe).
• Branch pipes of ring pipe network and connecting pipes of branch pipe network.
• The head of the distribution pipes of the indoor water supply, like households, public toilets, etc. Valve should be provided in the case of 3 or more distribution points.
• The outlet pipe of the pump and the suction of the self priming pump.
• The inlet, the outlet and drain pipes of the water tank.
• The inlet supply pipes for equipment (like heaters, coolers, etc.).
• Water distribution pipes for sanitary appliances such as urinals, toilets, washbasins, showers, etc. .
• Some accessories. For example, valves shall be installed in front of the automatic exhaust valve, pressure relief valve, water hammer eliminator, pressure gauge, sprinkler and at both ends of the relief valve and the back-flow preventer.
• The lowest part of the water distribution system. Drain valves here is a better choice.

3. Factors of check valve selection are its installation site, the upstream pressure, sealing requirement, the hydraulic ram size and so on.

• Low upstream pressure. Swing, ball and shuttle check valves are preferable.
• An excellent sealing performance requested. Spring check valves are preferable.
• The weakened hydraulic ram. Quick-closing silent check valves or damping closure-delayed check valves are preferable.
• A self-closing flap or spool by gravity or spring.

4. Sections of the water supply pipeline should be provided with check valves.

Sections are the leading-in pipes, inlet pipes of sealed water heaters or water equipment and outlet pipes of the water pump, one-way cisterns, water towers, or upland cisterns.

Note: No check valve for pipe sections with a back-flow preventer.

5. Sections of the water supply pipeline shall be equipped with exhaust devices.

• The end and the highest point of the intermittent pipe network shall be equipped with automatic exhaust valves.
• The peak point of the pipe section with obvious air inflation shall be equipped with automatic exhaust valves or manual valves.
• The highest point of he water distribution network with air pressure water supply devices shall be equipped with automatic exhaust valves in the case of automatic supply pressure tank.

Second, merits and drawbacks of various valves:

1. The Gate Valve:

The gate valve is a valve whose closing part (the gate) moves vertically along the axis of the passage.It is mainly used for blocking medium in the pipeline, that is, being a wide open or a sealed close, it generally can not be used as a throttle. It can be applied to extreme temperature and pressure based on the valve material, except mud pipelines and the like.

Advantages of Gate Valves

• ①Minor fluid resistance. 
• ② Less torque required for on-and-off. 
• ③ Non-restricted medium flow in the circular network pipelines. 
• ④ Less erosion of the sealing surface by medium than that of the block valve. 
• ⑤Simple structures with excellent technique. 
• ⑥ Shorter structure length.

Disadvantages of Gate Valves

• ①More installation space needed for its size and opening height. 
• ② Relative friction of sealing surfaces. They will be worse scratched under high temperature. 
• ③ Difficulties in processing, grinding and maintenance of two sealing surfaces.
• ④ Long time required for on-and-off.

2. The Butterfly Valve:

The butterfly valve is a flow regulated valve with disc pieces rotating back and forth about 90° to control its on-and-off.

Advantages of Butterfly Valves

• ①Simple structures, miniature size, light weight and less consumption. Never for large-diameter valves. 
• ②A quick switch with minor fluid resistance. 
• ③ Plenty applications. It can be used for media with suspended solid particles, powder and particulates referring to the strength of the sealing surface. It is perfect for two-way flow regulating of ventilation pipelines. Therefore, it is widely used in gas pipeline and water channels of metallurgy, light industry, electric, petrochemical system, etc. .

Disadvantages of Butterfly Valves

• ①Narrow regulatory range. With 30% opened, it runs more than 95% of the flow. 
• ②Limited temperature and pressure conditions. Due to its structure and confined sealing material, it can not be used in pipeline systems of high temperature and high pressure. Its general working conditions is below 300 °C and PN40. 
• ③ Inferior sealing performance as to the ball valve and the block valve. It can be applied to pipes of low sealing requirements.

3. The Ball Valve:

The ball valve evolved from the plug valve is a ball switched one with the ball rotating 90° to achieve its on-and-off. The ball valve is mainly used to disconnect, distribute and direct the medium flow in the pipeline and it is an excellent regulator for its V-shape opening.

Advantages of Ball Valves

• ①Minimum flow resistance (Actually is 0). 
• ② Reliable applications in corrosive media and low boiling point liquids. It never tends to get stuck ( even without lubricant). 
• ③ An excellent sealing performance under a wide range of pressure and temperature. 
• ④ Rapid on-and-off without impact. Some structures, of which the switch time of is only 0.05 ~ 0.1 s, can be used in the automation system of the test bench. 
• ⑤ An automatic location ability at the boundary position of the ball switch. 
• ⑥ Two-way sealed media. 
• ⑦ Isolated ball body and sealing surface of the seat from media. No erosion caused by the high-speed media rush will happen to the sealing surface during its on-and-off. 
• ⑧ A compact structure of light weight. It is a best choice for low-temperature medium systems. 
• ⑨ A symmetry welded body structure. It can bear the stress from the pipeline. 
• ⑩ A high-differential bearing ability of the switch parts. ⑾ An overall welded body. It can be directly buried without etching internals and therefore its maximum service life is up to 30 years, which make it an ideal one for oil and natural gas pipelines.

Disadvantages of Ball Valves

• ①The Teflon sealing ring. Advantaged with minor friction coefficient, stable characteristic, anti-aging ability, wide temperature application and excellent sealing performance, it is inert to almost all chemicals. However, its physical properties is difficult to deal with. Disadvantaged with high coefficient of expansion, sensitivity to cold flow and poor thermal conductivity, the sealing surface should be constructed in consider of all these difficulties. Therefore, the harder it becomes, the less the sealing reliability is. Furthermore, the Teflon can not withstand a high temperature thus only be used below 180 °C. Otherwise, it will age. For a long-term use, 120 °C is recommended. 
• ② Inferior regulation performance to the block valve, especially to the pneumatic valve (or electric valve).

4. The Block Valve:

The block valve is a valve of which the switch device (the disc) moves along the center line of the seat. As a result of the motion trail, the size of the seat opening is proportional to the disc stroke. The direct proportion, together with its relatively short stroke and reliable disconnect ability, enables it to be a good flow regulator. Therefore, the block valve is very versatile in disconnecting, regulating and throttling.

Advantages of Block Valves

• ①Wear-resistance. There is less friction between the disc and the sealing surface of the body than that of the gate valve. 
• ② A shorter opening height than that of the gate valve. It is only 1 / 4 of the seat passage. 
• ③ Only one sealing surface on the body and the disc. Therefore, it is easy made and convenient to repair. 
• ④ The high temperature withstand ability. Its filler, which is generally a mixture of asbestos and graphite enables it to be a valve for general steam pipelines.

Disadvantages of Block Valves

• ①High flow resistance. Even its minimum resistance is greater than that of most others due to the direction change of media flow inside. 
• ② A slow switch-on based on the long stroke.

5. The Plug Valve:

The plug valve refers to a rotary valve with a plunger-shaped switch. By 90°rotation, it connects or separates the channels of the plug and the valve body to achieve the om-and-off. The plug can be cylindrical or conical in shape. Being similar to each other, the ball valve is evolved from the plug valve, which is mainly used in oil field production and petrochemical industry.

6. The Safety Valve:

The safety valve refers to an over-pressure protection valve on the pressure vessels, equipment or pipelines. For a safe operation, the valve automatically opens to discharge and closes to reserve when the pressure in the equipment, container or pipeline is out of the allowable value.

7. The Steam Trap:

The steam trap is a drain device for the transmission of steam, compressed air or others, in which generates useless condensed water. It ensures the efficiency and safety of the system by timely discharging the harmful media. 

It has the following functions. 

• ① Quickly drain the condensed water. 
• ② Seal the steam. 
• ③ Remove air or other non-condensable gas.

8. The Pressure Relief Valve:

The pressure relief valve is an adjustment valve, that is, the inlet pressure is reduced by it to a certain needed outlet pressure. Supported by the energy of the medium itself, the outlet pressure is automatically stable.

9. The Check Valve:

It is also known as the back-flow valve, the check valve, the back pressure valve, the one-way valve and an automatic one for it is forced by the flow of the medium itself in the pipeline to be switched on-and-off. The check valve is used in piping systems to prevent reversed media flow, rotation pumps and drive motors, and to discharge media in the container. It can also be used for supply lines of secondary systems in which the pressure may rise above the system pressure. The check valve can be sorted into swing ones (rotation by the gravity) and lift ones (motion along the axis).

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Ⅰ. Introduction of check valve

Check valve is an automatic valve. It relies on the pressure of the flowing medium in the pipeline to push the disc to close and open the valve. When the medium stops flowing, the check valve disc closes, it can be effective to prevent the medium in the pipeline from flowing back, which plays a great role in ensuring the safety of the pipeline.

 Ⅱ. The installation position of the check valve

The check valve is installed to ensure the flow direction of the water flow inside the water pump, so as to ensure the normal operation of the water pump. Therefore, regarding the installation position of the non-return check valve, whether it is installed before the pump or after the pump, there are two situations:

• 1. One is installed at the end of the vertical suction pipe in front of the water pump, also called a bottom valve. The purpose is to fill the pump without pumping water once, because when there is no water in the pump and the suction pipe in front of the pump, the pump can only run idling and cannot pump water, so the pump must be filled with water to pump out water. The installation of this kind of water pump is a method when it is higher than the liquid level, also called negative pressure method.
• 2. The other is installed behind the pump. This installation method is that when the liquid level is higher than the water pump, it is convenient to start and stop the water pump without closing the water pump outlet valve, especially for the main control water pump system to prevent backflow.

The non-return check valve must be installed at the outlet of the pump and before the outlet control valve in order to check the check valve. Generally, the first outlet of the pump is the soft connection (shock absorber), the next is the check valve, and then the isolation valve (such as butterfly valve, gate valve, stop valve)

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What is a Check Valve?

The valve that is used to prevent backflow in a piping system is known as a check valve. It is also known as a non-return valve or NRV. The pressure of the fluid passing through a pipeline opens the valve, while any reversal of flow will close the valve.

It allows full unobstructed flow and automatically shuts as pressure decreases. The exact operation will vary depending on the mechanism of the valve.

Types of Check Valve

• Swing Check Valves.
• Tilting Disk Check Valves.
• Wafer Check Valves.
• Spring Check Valves.
• Piston Check Valves.
• Ball Check Valves.
• Duo-Check Valves.
• Non-Slam Check Valves.

What is Spring Check Valve?

Spring Check Valve. Valves are versatile devices used for controlling the flow of liquids or gases. They play an important role in countless piping and process systems, typically serving to regulate flow and pressure, start or stop the flow, or prevent the occurrence of backflow within a system.

What is UPVC Spring Check Valve?

UPVC Spring Check Valve is suitable for plastic industrial applications; delivering excellent environmental and chemical resistance. A simple to install and maintain PVC valve, configurable as a Spring Check or Foot Valve offers a number of benefits where space and weight savings are not only required but play an important factor within the pipeline.

Key features of UPVC Spring Check Valve

• Available in Spring or Foot, connections: Imperial Solvent Socket, Metric Solvent Socket, and Screwed BSP.
• Sizes: 3/8″ to 4″ (Imperial Solvent Socket and Screwed BSP) and 16mm to 110mm (Metric Solvent Socket).
• Pressure rating: PN10/16 (Spring Check and Foot Valve).
• PVC-U body with EPDM ‘O’ rings.
• 100% factory tested.

PTFE Spring Check Valve Seat

PTFE Seats are manufactured using extrusion technology and can be cut and supplied in a wide range of standard sizes or can be supplied in custom-made shapes and colors.

Commonly PTFE Seats are used for fluid and gas transport seals, medical equipment, food and beverage equipment (e.g. coffee machines), and water delivery systems.

Standards of Check Valves

• Face to Face dimensions as ANSI B16.10
• End flange dimension as ANSI B16.5
• Pressure-temperature ratings as ANSI B16.34
• Pressure test as API 598
• Applicable Medium: water, gas, oil,and another causticity medium.

Spring Check Valve vs Swing Check Valve

The difference between swing check valves and spring check valves. The flapper in a swing check valve ‘swings’ off the seat to allow forward flow and then swings back onto the seat when the flow is stopped. In contrast, a spring-loaded check valve incorporates a spring to assist in closing the check valve.

Swing check valves are limited in the orientation in which they can be installed. Swing check valves can only be installed in horizontal flow applications, which greatly limits the installation orientation. While swing check valves do offer a larger flow capacity (larger CV value assuming the valve is fully open), they do not always fit in existing piping configurations. On the other hand, spring-loaded check valves can be mounted in any flow orientation with the right spring selections. So if you have a skid system, a difficult space with challenging dimensions, or even a unique direction of piping, choosing a spring check valve with the right spring setting (a.k.a spring cracking pressure) creates more possibilities for finding the right solution for your specific pumping system.

A spring-loaded check valve will help minimize the effects of the water hammer, while a swing check valve can exacerbate the issue. Any water hammering effects present in a piping system can potentially be amplified by a swing check valve. Let’s consider this basic example to explain the concept of a water hammer: say you have a line with water in it and you have a check valve. Downstream of that check valve, you have a quarter turn ball valve (this is one of the most commonly used types of control valves used for smaller line sizes). Let’s say water is flowing and someone shuts the quarter turn ball valve abruptly. This can produce a pressure wave flowing through the piping – this is what is known as a water hammer. With a swing check valve specifically, the flapper on that valve will be open until that pressure wave returns back to the swing check. The pressure wave causes the flapper to slam shut, which is very much audible and causes excessive wear within the swing check valve and other piping system components.

Conversely, a spring-loaded check valve will help minimize, and in some cases, eliminate the effects of a water hammer. How? When we think about that same pressure wave that closed the swing check valve, the spring in the spring check closes before the pressure wave gets there. Spring check valves are considered “silent check valves” by utilizing a spring to assist the poppet in closing the check valve prior to fluid flow reversal.

Applications of Check Valves

Valve is used for preventing the back-going of the medium in pipelines and equipment, and the pressure of the medium will bring the result of opening and closing automatically.

When the medium is back-going, the valve disc will automatically be closed to avoid accidents.

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