Effective Check Valve Selection and Placement for ...

PRINCIPLES OF PIPING DESIGN

In general, optimal piping system designs follow three basic principles:

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1. There must be a 5-10x nominal pipe size (NPS) of straight pipe on either side of the valve, i.e., both the upstream and the downstream sides of the valve.
2. The minimum pressure to open a check valve is referred to as the cracking pressure. However, to fully operate a valve, the system requires twice the differential pressure.
3. While many styles of check valves will work in horizontal piping, only axial flow (&#;silent&#;) check valves are suitable for use in vertical piping. Whenever possible, a horizontal line is preferred since it rules out gravity, but vertical piping must be considered for flows that require up or down transport.

COMMON PIPING DESIGN MISTAKES

Following the above principles facilitates the proper configuration of check valves in a piping system with minimal need for maintenance and maximum reliability. However, many industry professionals may find it challenging to navigate the nuances of pipeline design. Some of the most common mistakes made when designing a pipeline involve:

Valve Location

As mentioned in Principle #1, valves should have enough clearance&#;i.e., straight pipe&#;on either side from other pipeline components, such as pumps, elbows, expansion joints, and other valves, to function properly. When positioned upstream, these components can cause turbulence, which affects the performance of the check valve and can cause increased wear and, consequently, failure. The same can be said of other types of valves, such as ball valves and control valves; they perform best when the media flow is laminar, not turbulent.

Axial flow check valves can be installed close to the inlet of an isolating value if it is full port and fully open.

Flow Conditions

As outlined in Principle #2, there must be enough pressure to keep the valve fully open under minimum, normal, and maximum flow conditions. It is not enough to match the valve size to the pipe; it is necessary to do the sizing calculations to pick the right sized valve for the given flow conditions.

Vertical Pipe Runs

Avoid using swing check valves in vertical pipes. The downward flow keeps the valve open, and the upward flow leads to water hammer from the disc slamming against the seating. As specified by Principle #3, use only axial flow check valves in vertical pipes. The strong spring of the axial flow check valve avoids water hammer by ensuring that the valve closes before the reverse flow happens.

CHOOSING THE BEST CHECK VALVE FOR YOUR APPLICATION

There are several factors to keep in mind when choosing a valve for a piping system. These selection considerations include:

Valve Location

As required by Principles 1 & 3 above, the location of a valve is important; horizontal piping is preferred for all valves except axial flow check valves, and there must be sufficient straight piping on either side of the valve.

Valve Size

Check valves remain open only when there is sufficient pressure in the line. Therefore, the pressure available with minimum flow must be considered along with maximum and normal flow conditions while selecting the valve. This is the requirement per Principle #2 above.

For more Ductile Iron Ball Check Valveinformation, please contact us. We will provide professional answers.

Additional reading:
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Valve Material

When choosing a valve material, the focus is on choosing one that is compatible with the characteristics of the piping and requirements of the application (i.e., temperature, pressure, corrosion resistance, etc.). This generally results in the body material of the valve matching the flange material of the pipe. For example, a carbon steel line typically features a carbon steel valve body. Carbon steel is the most commonly employed valve material, with cast iron and stainless steel following close behind.

TYPES OF VALVES USED IN INDUSTRIAL PIPING

Valves find use in a variety of industrial piping system applications. Typical applications include:

• Preventing reverse flow (check valves)
• Managing the flow of process fluids, including concentrated acids and bases
• Redirecting flow from one line to another
• Restricting flow for system balancing purposes
• Controlling cooling rates to regulate temperature
• Stopping flow during a system failure

Industry professionals employ a wide range of valves to fulfill the above functions, depending on the requirements and restrictions of their unique application. Some of the most common valve types used are:

• Check valves have a disc, stem, or a similar moving part that closes if the flow reverses or stops.
• Ball valves are the most common type of valve and feature a ball with a round hole in the center. When aligned with the pipe, the valve is ON. When turned 90°, it is OFF.
• Diaphragm valves are used for precise flow control, especially when the media contains solids.
• Flanged valves use bolts to secure the connection and a gasket to seal the joint.
• Gate valves turn flow ON and OFF with a vertical disc that moves up and down.
• Globe valves regulate flow with a disk that moves relative to a stationary ring seat.
• Needle valves are similar to a globe valve, but they use a tapered plug for finer flow control.
• Relief valves are safety valves that prevent excessive pressure buildup in the system.
• Wafer valves in general have a smaller footprint in the system.

In addition to the valves listed above, there are many other types available, each of which is suitable for varying industrial applications.

Jeff Kane is director of sales and marketing for DFT Inc., located in Exton, PA. He is a long-time member of VMA&#;s Education & Training Committee.  

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Not all valves are built the same and there&#;s good reason for that. Knowing a few basic facts about the different materials will ultimately have long-term effects on your application&#;s capabilities. Cast iron, ductile iron, bronze and stainless steel are all similar metals but what stands each of these apart? We&#;ll assist you in choosing the best metal solution for your everyday valve application needs.

Cast Iron

Cast iron &#; a metal made from mostly iron with small amounts of carbon and silicone &#; is known for its tolerance to extreme temperatures. It can handle temperatures over 2,100 degrees Fahrenheit. It is a very strong metal and can usually go undamaged through situations of intense vibration; however, cast iron is extremely rigid and has a low resistance to bending. Almost any bending will cause the material to fracture or break completely. A big advantage to cast iron is the cost. It is a relatively inexpensive metal and a very economical and useful option for most situations.

Ductile Iron

Ductile iron, as its very name suggests, is more flexible than cast iron. It is an iron alloy made with nodule-shaped graphite crating a metal that has a little more room to bend without breaking or cracking. With the ability to flex, however, comes a lower overall temperature tolerance than cast iron and a slightly higher cost.

Valves built from ductile iron have excellent corrosion resistance and superb strength, making it a great choice for applications in which a tougher material is needed and in conditions where weathering is likely. Here at Flomatic all of our ductile iron valves are epoxy coated to protect the valves from long term erosion and corrosion in many different fields of application.

Bronze

The use of bronze in plumbing systems dates back to the Roman Empire. Made primarily from copper and tin, this metal is both strong and malleable. It does not crack as easily as iron as it has high ductility. Bronze is also known for its high resistance to corrosion even against harsher fluids and those similar to seawater. However, the nature of the alloy causes it to have a somewhat rough and porous surface which can leave the material susceptible to pitting and degradation over time if not properly maintained.

It is important to note that consumers should seek out valves with the lowest lead content. Make sure if you&#;re picking out a bronze valve for potable water, you&#;re choosing a valve that is ANSI/NSF 372 & ANSI/NSF 61 certified. These certifications mean it meets the minimum lead requirements for safe and healthy drinking water.

Stainless Steel

Stainless steel has become a very popular valve material for many reasons. Valves made from this metal have exceptionally high oxidation and corrosion resistance and extreme durability, making a product that lasts a long time. Stainless steel valves do not rust, even if placed in areas of high moisture or directly in water. This property makes them a great choice for coastal regions where saltwater corrosion may be a concern.

The smooth metal is easily cleaned, and a popular choice for food and beverage applications. Stainless steel has good heat resistance; however, it is not ideal for extreme high-temperature applications. A potential downside of stainless-steel valves is that they&#;re very expensive. However, with price, comes high-quality.

What do these terms all mean?

Using the information provided above, think about your scenario and the conditions in which the valve will be used. Will it be outdoors? In severe temperature? Will this metal be susceptible to movement and vibration? Once you determine the extremes, you&#;re easily able to choose the appropriate metal for your application.

And of course, never be afraid to ask the experts. With over 85 years of industrial experience in the valve market, Flomatic knows valves inside and out and we are happy to guide you to the right product for the right application.

If you want to learn more, please visit our website DI Dismantling Joints Manufacturer.