Non Return Valve

What are the applications of a non-return valve?

• They are used for industrial purposes such as
  • Chemical industries
  • Power plant industries
  • Dump lines
  • Wastewater management plants
• They are used for pumping systems
  • Water pumping
  • Metering pumps
  • Feed pumps
• They are used for domestic purposes
  • Irrigation sprinklers
  • Solar installation
  • Hydraulic pump jacks

How does a non-return valve work?

Firstly for the functioning of the non-return valve it requires a minimum pressure or the upstream pressure is required for the opening of the valve. The pressure at which the valve opening takes place is called cracking pressure. The cracking pressure of each such valve depends upon the size and diameter of the valve. They could also be varying upon the upstream pressure required for the functioning; high-pressure types of equipment may require a greater cracking pressure.

 

What if the upstream pressure falls below the cracking pressure? This will lead to the backflow of the fluid. In this situation, the non-return valve will get closed. The closing of the valve may depend upon the prevailing situation such as pressure on the gate, ball, diaphragm, etc.

What are the various types of non-return valves?

Ball non-return valve

A ball non-return valve uses a free-floating or a spring-loaded ball that rests on the sealing seat to close the office. This ball is used to check and stop the backflow of fluid when the pressure of the fluid in the inlet side exceeds the cracking pressure; the ball is dislodged from its seat and allows

flow to occur. When the inlet pressure doesn’t exceed the cracking pressure, or there is

back pressure, the ball will close with the

backpressure or via the spring, effectively closing the orifice. The free-floating ball is used for low-pressure applications and the spring-loaded ball is used for high-pressure applications.

 

What are the applications of ball non-return valves?

• • Pumping stations
  • Metering pumps
  • Chromatography pumps

Spring-loaded inline non-return valve

In-line spring-loaded is one of the most common types of non-return valve used. When flow enters from the input port of the valve it has more pressure than the cracking pressure and the spring pressure. Due to which it pushes the disc and allows the fluid to move ahead through the valve, once the input pressure is less than the cracking pressure or there is the backflow of fluid it will again back press the disk against the orifice to create a sealing application. They are also called nozzle non-return valves or silent check valves. 

What are the applications of spring-loaded in-line non-return valves?

• • Pumping stations
  • Firefighter water pumps
  • Hydraulic pumps

Spring-loaded y non-return valve

They are very similar to the in-line spring-loaded. They both tend to work on the same lines of working principles. The only difference between both of them is the placement of the disc. Here in spring-loaded y type, the disc is placed at an angle to the fluid flowing direction. This helps in maintaining the non-return valve from the pipeline.

What are the applications of spring-loaded y type?

• • Used in pumping systems
  • Chemical industries
  • Pipelines

Diaphragm

The diaphragm non-return valve consists of Diaphragm which opens when there is inlet pressure. The Diaphragm is very soft and elastic. It has a normal opening which means it does not require any cracking pressure. When the inlet pressure incurs Diaphragm flexes, as the pressure keeps on increasing the Diaphragm keeps on flexing more.If backpressure occurs (or it is a normally closed diaphragm check valve) the diaphragm will be forced against the opening and seal it to prevent any backflow

What are the applications of the diaphragm non-return valve?

• • Vacuum systems
  • Food industry
  • Solar industries

Butterfly non-return valve

A butterfly check valve is also known as a dual, folding disk, double disk, or splits check valve. The halves of the disk open toward the centerline, as seen in the diagram, during the forward flow of the fluid. With reverse flow, the halves open and seal the pipe. The short distance that the halves have to travel lessens the slamming effect on the disks.

What are the applications of the butterfly non-return valves?

• • Ventilating systems
  • Heating systems
  • Air conditioning system

Dual non-return valves

Dual non-return valves are also known as double check valves. As the name suggests in one mechanism they consist of two non-return valves.  In Which both of them work independently. The main benefit is if one stops working. The other one acts as a backup to perform the function. They are also used in a situation wherein there is dealing with high pressure, this helps in distribution of high pressure in both the valves equally and work more efficiently.

What are the applications of dual non-return valves?

• • Combi boiler system
  • Fire sprinkler
  • Lawn irrigation facilities

 Swing non-return valves

They consist of the disc or a trunnion that swings open with an inlet pressure. If In a situation there is the backflow of pressure or the inlet pressure decreases this will result in shutting off the discs and create a sealing effect. The body of the swing check valve is available in a Y-pattern or straight body design. The straight body design has the disc hinged at the top so that it seals against the seat, which is integral to the body. A single-disc swing check valve is designed with the closure element attached to the top of the cap.

What are the applications of swing non-return valve?

• • • Sewage treatment
    • Wastewater management plant
    • Household items

Name	Advantages	disadvantages
Ball non-return valve	Can be used with all types of fluids such as liquid or in the gaseous state. Can be installed for vertical flow too.	Not suitable for high pressures.
Spring-loaded in line	Wide range of uses Safeguards pipes from the hammering effect.	They could not be opened up for repairing
Spring-loaded y type	Safeguards pipes from the hammering effect They could be opened up for maintenance and repair	They are heavier and acquire a huge space
Diaphragm non-return valves	They have a very flexible disc. Good sealing effect	Not economical for maintenance.
Butterfly non-return valves	Has faster functioning Wide range of uses	They are not suitable for very high pressure.
Dual non-return valves	Helps in the distribution of pressure Acts as backup if one check valve stops functioning	They are very costly and acquire huge space.
Swing non-return valve	They have replaceable seat rings Low turbulence and pressure drop Easy openings at a lower pressure.	The continual flapping would harm the seating elements

What are the various types of non-return valves based on the material used?

Brass

Brass material is very versatile it could be used for liquid, solid, and even for gaseous materials. They are not recommended for seawater as they would get corroded easily. They are usually used for pressure and low-temperature applications. They are cost-effective.

PVC(polyvinyl chloride)

PVC is a very common material that is used for low-temperature applications wherein the temperature does not exist 60 degrees Celsius. They are anti-corrosive and could be used in seawater and humid atmosphere. They are very cost-friendly.

Stainless steel

They are one of the strongest and durable materials. They are used in high temperature and high pressure for heavy applications. They have the most superior corrosion resistive properties. They are expensive compared to the PVC and brass-type non-return valves.

 

What are the advantages of non-return valves?

• They prevent the backflow of fluid
• Self-actuated as well as automated actuated
• They are available in wide ranges as per the requirements of the customer
• Fewer moving parts
• They play a major role in preventing backflow
• They require minimal power to operate
• Fast functioning
• They perform in high as well as low pressure

 

What are the disadvantages of a non-return valve?

• Internal parts could not be checked for repairing or maintenance
• Noise caused by slamming of discs

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