10 Factors to Consider When Choosing Butterfly Valves

A butterfly quarter is a quarter-turn valve, allowing for a quick shut off making it cost-efficient. The “butterfly” is a metal disc positioned in the center of the pipe with a rod passing through the disc to an actuator on the outside of the valve. It is in the shape of a gear, which is usually referred to as a gearbox, while the handwheel is connected to the stem. Rotating the actuator turns the disc either parallel or perpendicular to the flow.  The valve is fully opened or closed when the disc is rotated a quarter turn, to stop, regulate, or start the flow. They are suited for handling large flows of liquid and gas at low pressures.

Read on for more information on how to choose a butterfly valve.

 

Pressure Drop

Energy costs go up with excessive pressure drop. The valve or valves are but one factor in a piping system that contributes to pressure drop. Of equal concern are these factors:

 

• The flow area of piping.

• Friction loss against pipe walls.

• Change of flow direction via fittings

• Butterfly valves have flow characteristics three times better than globe valves and approximately 75% of an equivalent size gate valve.

 

Operating Life

Butterfly valves can provide many maintenance-free cycles and still accommodate "bubble tight" shut-off.

 

Weight

Installation dollars saved with lightweight butterfly valves as compared to heavyweight cast iron valves; i.e. a 10" butterfly may weight 55 pounds, whereas a 10" iron gate may weigh 490 pounds. This can be an important saving when it is calculated over an entire system. The heavier the system, the stronger the pipe hangers, and the more expensive they become. So, by considering the weight of a valve one can also reduce piping system costs.

 

Versatility

Butterfly valves can be used for on/off service and throttling/balancing. They are superior in "versatility" as compared to a gate or globe valve. Butterfly valves have a wider range of chemical resistance due to the trim options and choice of elastomeric liners.

 

Bubble Tight Shut-Off

Gate and globe (metal to metal) seats cannot provide bubble-tight shut-off. Resilient seated butterfly valves are bubble-tight by design.

 

Physical Size

Butterfly valves take up approximately 1/6 the space of a gate valve. Every cubic foot of a building costs money.

I.E.: 10" butterfly is about 21" high and a 10" iron gate is about 43" high.

 

Cost

A butterfly valve is generally 40% the cost of an iron gate valve, not only in low initial costs but in low installation costs as well.

 

Maintenance

Properly installed butterfly valves are virtually self cleaning and are less susceptible to failure due to trash material in the line.

 

Ease of Operation

Butterfly valves offer 1/4" turn (90 degrees) open to close. Gates and globes require multiple turns to open and close. Ease of opening or closing means that butterfly valves can employ less expensive operators.

 

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Bronze VS Brass Valves-Which is Your Best Choice?

While a valve's intended application often determines its composition, as one media or another may be more compatible, it's not always clear as to why this is true. Choices of materials, however, are limited to man's metallurgical prowess. Two of the most common materials used to produce valves are bronze and brass. This preference came about because both metals are extremely malleable. Both are man-made combinations of natural metallurgical elements: brass is an alloy made from copper and zinc, while bronze--one of the oldest alloys--is made primarily from copper and tin.  Valves produced from either metal provide numerous and various advantages, though which one is correct for your application--and which one is better--may be debatable.

 

Bronze Valves

The Romans were probably the first to fashion flow control valves--very similar to those of today--out of bronze as early as the 1st Century B.C. Piping was manufactured out of the lead, as were the welds connecting systems together. Much like modern bronze valves of today, the Romans used copper, tin, and lead to make the metal malleable, though today's bronze sometimes includes manganese or aluminum as additives, as well as nickel. One drawback of bronze is that valves can only be produced by casting, or by machining cast ingots. The rough exterior of bronze--which is known for porosity and shrinkage cavities--is a direct result of casting (though bronze alloys containing nickel, lead, and bismuth will hold a polish).  On the upside, bronze is fairly inexpensive, extremely ductile, and is great for resisting corrosion, particularly from any corrosives similar to seawater.

 

Choosing Brass Valves

Even more malleable than bronze, brass is also more versatile, as different combinations of copper and zinc create a wide range of brasses with varying properties.  Brass also lends itself well to manufacturing, as it can be cast, forged, heat extruded, or cold drawn in its creation. It is very machinable, and its smooth surface helps keep finishing costs down. Brass is highly corrosion-resistant, though high levels of chlorine can break down zinc content. Otherwise, brass is perfect for a variety of media, including natural gas. And, for potable water, brass is a natural choice over bronze, as it typically contains much lower levels of lead than bronze.

Of course, by today's standards, these contrasts and comparisons are rudimentary. Modern metallurgy is far more advanced than what even the Romans may have dreamed of. Today's foundries cast superior bronze alloys which are utilized for countless applications, though use for potable water is slowly being phased out. Likewise, modern brass alloys that resist dezincification--a problem associated with standard extruded brass (because of the zinc content)--are being produced via hi-tech fabricating techniques using chemicals and heat. These breakthroughs in metallurgy help to negate a need for lead in the mix, and increase the longevity of piping and valves, ensuring the continued use of brass for years to come. But, while brass enjoys several advantages over bronze, don't count it out just yet. Lead Free Bronze valves (bronze valves meeting or exceeding Clean Water Act lead restrictions) are readily available, and are generally the first choice for water pipes with diameters under 3" when keeping costs down is a must. Coincidentally, it's no mystery that both bronze and brass are favored as valve material by numerous industries utilizing piping systems, as both alloys have excellent solderability characteristics.

 

Applications of Bronze Valves vs Brass Valves

 

Because of their specific properties, bronze valves are best suited for the following applications and industries:

• Petrochemical

• Marine

• Safety relief

• Flow direction control

• Flow shut-off

• Flow Control

 

Brass valves are uniquely suited to these applications:

• Air and liquid shut-off

• Natural gas shut-off

• Flow direction control

• Potable water

• Flow Control

 

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The Differences Between Ball Valves And Butterfly Valves

When it comes to finding the right valve for your marine or industrial job, ball valves and butterfly valves often take center stage.

Contents:

• Understanding The Butterfly Valve

• Understanding The Ball Valve

• Ball Valves VS Butterfly Valves

• Selection Criteria

• Find The Right Valve for The Right Project

Understanding The Butterfly Valve

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Butterfly Valve

A butterfly valve has a disc (E) driven by a lever or handwheel (A). When closed, the disc is perpendicular to the pipe flow direction. A seal (F) which seats within the valve body (D) ensures a tight closure with the valve disc. A butterfly valves valve characteristics are close to a linear relationship between the flow rate and the stem (C) position. The butterfly valve can be controlled manually, electrically, or pneumatically.

At larger diameters, butterfly valves are generally regarded as cheaper than ball valves. They have the least amount of parts and are relatively lightweight, requiring less support. The weight advantage of butterfly valves to ball valves can be significant at larger pipe diameters. There is a higher probability of leakage at high-pressure differences between the sides of a butterfly valve disc and the seal compared to a ball valve. Also, in applications with large pipe diameters, this high-pressure difference makes it difficult to open the valve, thereby requiring a bypass valve to balance both side’s pressure before the valve can be opened.

There is a pressure drop across the butterfly valve as the disc remains inside the flow even when fully open. This hinders using butterfly valves in process streams that need to be pigged, such as in the oil and gas industry. Butterfly valves are typically ON/OFF valves and are not suitable for precise fluid flow control.

Understanding The Ball Valve

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Ball Valve

A ball valve has a hollow spherical ball (F) that is pivoted at one or both ends. The top end of the ball is attached to a shaft (C), which is rotated by a handle (A) to change the valve position to open or close. When fully open, the hole in the ball lies parallel with the pipe flow direction. The ball rests on a seat (E) inside the valve body (G). The ball valve can be controlled manually, electrically, and pneumatically.

Ball valves can also have three-way or four-way flow directions in a T or L shaped bore. A ball valve’s flow characteristics can be read in our technical article on controlling fluid flow with ball valves.

The bore in a ball valve can vary from a size smaller than the pipe diameter (reduced port or reduced bore), a size equal to the pipe diameter (full port), or a V-port design. The design of the ball does affect flow characteristics. A ball valve can have a pressure drop across the valve in a reduced port ball valve or almost zero pressure drop in a full port ball valve, while a V-port design is ideal for stable flow control.

Unlike butterfly valves, ball valves have zero leakage when fully closed. The fluid pressure upstream of the valve pushes the ball against the seal, ensuring a positive shutoff position. Ball valves will easily open at a high-pressure difference on both sides of the valve and therefore do not require a pressure-balancing bypass.

Ball Valves VS Butterfly Valves

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Several common features

ㆍThey are both quarter-turn rotary valves, which require a 90-degree rotation from opening to closing.

ㆍThese two materials are usually composed of cast iron, stainless steel, and brass.

ㆍEach valve effectively regulates the flow of most types of gases and liquids in a wide temperature range.

ㆍThey are relatively cheap, durable, and reliable.

ㆍBoth ball valves and butterfly valves are easily available through valve distributors.

These similarities do not mean the valves are interchangeable in all process functions. Instead, it suggests and corroborates why we need to take a closer look at the valves characteristics and what applications to use each valve. Let's take a look at the difference between ball valves and butterfly valves, and how they affect their use:

Differences

Design

Generally speaking, the ball valve is a ball with a hole. A butterfly valve usually consists of a disc mounted on a rotating shaft.

Features

When using a ball valve, turn the valve handle to block or partially block the hole on the ball or open the flow of gas or liquid through the valve. When using a butterfly valve, turning the valve handle turns the disk 90 degrees, to either fully open or fully block the flow of gas or liquid through the valve.

Pressure

One advantage of the ball valve is that it almost always rotates, no matter how much pressure is applied on the supply side. Once opened, the pressure hardly drops because the hole in the ball allows 100 percent of the gas or liquid to flow. The structure of the butterfly valve makes a part of the valve disc always interfere with the flow of liquid or gas. This means that when using a butterfly valve, there will always be a pressure drop. This also means that the butterfly valve may be difficult to open, and a bypass valve may be needed to create balance in the lines before the large butterfly valve can work properly.

Uses

Ball valves are more effective in sealing than butterfly valves, so ball valves are generally more suitable for projects involving the flow of gas. The cost of construction and maintenance of butterfly valves is usually low, so they are often used in large municipal water supply and sewer projects. They are also common in projects that control the flow of river or stream water.

Selection Criteria

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The following criteria can be considered before selecting between a butterfly valve and a ball valve:

ㆍApplication: Butterfly valves are commonly used in water-based processes such as sewages, beer and soda production, etc. They are popular in chemical, agricultural, waste treatment plants, and food industries, partly because they are easy to clean. Ball valves can handle both liquid and gases with some solid particles (slurry). They are common in process plants, power plants, petroleum refining, oil, and gas exploration as they can be pigged for cleaning.

Flow capacity: Butterfly valves can provide a larger flow capacity as they are readily available at a larger pipe diameter than a ball valve.

ㆍSealing: Ball valves provide a tight seal in process applications that require zero leakages when shutoff.

ㆍOperating condition: Ball valves can operate up to 1,000 bar and 400 degrees Celsius. Butterfly valves typically operate at a lower pressure (less than 50 bar) and temperature (less than 250 degrees Celsius).

ㆍFlow regulation: Both valve types can be used for on/off control and proportional control, but ball valves are typically used for proportional due to better flow regulation.

ㆍPorts: A butterfly valve can only have two ports, while a ball valve can have more than two ports.

Find The Right Valve for The Right Project

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Ball valves and butterfly valves are universal, relatively cheap, and can stand the test of time. Which one is suitable for which project depends on the size and scope of the task. If you need help determining whether a project requires ball valves, butterfly valves, or other types of valves, please contact a qualified valve distributor today. 

What Is The Wafer Type Butterfly Valve?

The butterfly plate of the wafer type butterfly valve is set up in the diameter instructions of the pipeline. In the round channel of the butterfly valve body, the disc-shaped butterfly plate turns around the axis and the turning angle is between 0 ° and 90 °, which can play the duty of flow policy.

 

What are the efficiency advantages?

The wafer type butterfly valve is normally installed flat. Wafer type butterfly valve performance benefits are that its disc is mounted in the diameter instructions of the pipe. The wafer type butterfly valve is made up of only a few components and is defined by a basic framework, tiny dimension, and lightweight. Furthermore, it can be quickly opened up and closed by revolving 90 °, and the operation is straightforward. In the round passage of the butterfly valve body, the disc revolves around the axis, and the turning angle is between 0 ° and 90 °. When the turning is 90 °, the valve is completely open. In the meantime, the valve has great liquid control characteristics.

 

What type of sealing does it come from?

The butterfly valve has 2 sealing types: an elastomeric seal and a metal seal. For the previous, the sealing ring can be mounted on the valve body or connected to the perimeter of the disc. The wafer butterfly valves with steel seals generally have a much longer life than elastomeric seal valves, however, it's hard for total seal. Metal seals can suit greater running temperatures, while elastomeric seals have temperature-limited defects.

 

Wafer type butterfly valves VS flange kind butterfly valves

Usual butterfly valves include wafer type butterfly valves and flange kind butterfly valves. The wafer butterfly valve is linked between the flanges of the two pipes by the stud screws. The flange type butterfly valve represents a valve with the flange, and the flange on both ends of the valve is connected to the pipe flange by bolts.

 

Where can it be used?

If a butterfly valve is needed for flow control, the major problems are the appropriate dimension and type of valve. The structural principle of the butterfly valve is especially appropriate for making huge diameter valves. Butterfly valves are extensively made use of not just in general markets such as oil, gas, chemical, and water treatment, but likewise in the cooling water system for thermal nuclear power plants. This type of valve ought to usually be set up flat in the pipe.

 

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Installation And Maintenance of Ball Valves

The valve is a control component in the fluid-conveying system. It has the functions of cut-off, regulation, diversion, prevention of reverse flow, stabilization, diversion, and adjustment of medium flow balance.

The valve is also one of the most typical pieces of equipment in the thermal system. The quality of the valve and whether the valve is selected reasonably according to the characteristics of the valve will play a decisive role in the heating quality.

Since the valves are all laid in-ground wells, they are not easy to be detected because they run, leak, drip, and leak. Generally, they can only be discovered when the user complains, the inspection is found, or the equipment is damaged.

The ball valve came out in the 1950s. It is a valve that has been used more and more in thermal systems in recent years. Its superior performance is unattainable by other valves. It has no fluid resistance, is lightweight, has sealing performance, zero leakage, and opens and closes. The advantages of fast switching, free from medium erosion and long service life, have gradually gained the favor of enterprise valve selection. However, how to perform routine maintenance and repair of valves in daily operation has also become a work that cannot be ignored by heating companies.

By understanding the working principle of the valve and the characteristics of the product, as well as the operation method and troubleshooting, the relevant production operation system can be formulated in the company's normal production to ensure the safe operation of the valve equipment.

The correct use, installation, and maintenance of ball valves are very important, and it is also content that heating companies must refer to when formulating operating procedures. Scientific management and maintenance of ball valves during the construction period can not only ensure safety but also reduce construction and operation management. 

Pay attention to the following aspects:

1)Use the correct method to load and unload the valve to avoid mechanical damage to the valve. When lifting the valve, the lifting strap cannot be tied to the valve stem or actuator for lifting. If the valve is operated in violation of regulations, it will cause the valve stem to bend, the valve stem seal failure and the turbine box to be destroyed.

2)Before the valve leaves the factory, blind plates or caps should be sealed at both ends of the valve to prevent water, sand, and other impurities from entering the valve cavity during transportation and on the construction site, causing damage and corrosion to the seal.

3)At the construction site, the valves should be placed neatly and should not be placed randomly, which will cause breakage and damage to the valve drain valve or grease injection valve.

4)Before the welding construction of the fully welded ball valve, confirm that the valve is welded in the fully open position to avoid the welding spatter from causing damage to the ball and scratching the sealing surface. The welding temperature between the valve seat is controlled at 140 degrees.

5)After completing the water pressure test, the water in the valve cavity should be drained to prevent corrosion and freezing.

Valve Installation

• Ball valves can be installed in any orientation. However in bigger sizes to reduce the load on the valve caused by the actuator or gearbox trying to pull away it may be necessary to install the drive shaft vertically. Electric actuators usually require vertical installation.

• Verify the material of the ball valve body, seat, and ball before installation. Ensure that there are no defects caused by storage or transportation.

• Verify the pressure rating of the valve vs the application requirement.

• Verify the temperature rating of the valve vs the application requirement.

• Verify the valve thread (BSP, NPT, socket weld ANSI), flange (ANSI 150, ANSI 300, etc), or solvent weld (BLP schedule 40) vs the application requirement.

• Complete all welding works before valve installation and be sure the flange has cooled to ambient temperature before installing the ball valve.

• Make sure there is no welding residue, waste, rust, or other debris in the pipe before installation. Wash with water or a mild detergent if needed.

• Clean the surface of the flange or pipe thread that will come in contact with the ball valve to ensure it is free of dust and debris. Wash with water or a mild detergent if needed.

• Make sure there is no warpage of the flange or misalignment of the ball valve in relation to the flange.

• Support for the valve was necessary to reduce the load on the piping (important on the bigger valve and actuator assemblies).

• For 2-way and 3way threaded valves (BVS, BVF8, BLS3) it will be necessary for metal pipework to allow for removal of the valve for maintenance by having a pipe union installed. 3 piece threaded and 2-piece flanged ball valves can be removed for maintenance without disturbing the pipework.

• Tighten the bolts on a flanged valve one at a time doing it in stages so even pressure is applied and a seal is formed between the valve and flanges.

• Once the installation is complete, operate the valve several times to ensure it is free from impingement and rotates through its full 90-degree operation.

Daily maintenance and maintenance of ball valves

1)For ball valves, formulate periodic inspections of the valve's sealing performance and check through the drain valve. If there is internal leakage, follow the procedure.

2)According to the frequency of valve movement, inject a certain amount of grease into the valve seat. Generally, an appropriate amount of grease should be injected after the valve is moved once, and the amount of each injection is 1/8 of the sealing system, so as to avoid impurities in the pipeline to the greatest extent. The back cavity of the valve seat affects the movement of the valve seat, thereby causing seal failure, while ensuring that the sealing surface is always in a lubricated state, prolonging the service life.

3)For valves with little movement, open and close operations should be carried out once a year, and a certain amount of grease and cleaning fluid should be injected to avoid dry grinding when the ball is moving and reduce the valve operating torque.

4)Before the winter, the ball valve should be maintained. The key point is to drain the water in the valve cavity and the water in the actuator to avoid freezing and freezing in winter, which will affect the function of use.

5)Add wear-resistant grease to the valve worm gear head actuator every year, regularly check the valve stem seal, remove rust, and do external protection.

In order to improve the reliability of the valve and prolong its service life of the valve, it is very important to do early maintenance and supervision work. Many problems can be avoided by early detection and timely treatment.

Therefore, in the management and maintenance of the ball valve, not only must professional training be strengthened to ensure that the maintenance is scientific, standardized, and safe, but also the concept must be changed, preventive maintenance management, and the safety of the heating system must be ensured to ensure the heating quality.

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Butterfly Valve Introduction Guide

The invention of the butterfly valve has improved the processes and applications of various industries.

What is a butterfly valve?

The butterfly valve is a mechanism that regulates the flow of materials in a large pipe diameter through a quarter-turn rotation of the disc.

A rod passes through the center of the disc, and this rod is connected to a drive that controls the movement of the disc. The position of the disc is parallel or perpendicular to the flow of the medium. The butterfly valve is different from other valves because the butterfly plate is always in the fluid, resulting in pressure changes at any position of the valve.

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Why is it called a butterfly valve?

Some valves are named after their shapes, such as ball valves, globe valves, needle valves, etc. Other valves are named after their movement and function: gate valve, plug valve, pinch valve, life valve, slide valve, etc. The butterfly control valve is also named for its movement.

The butterfly valve gets its name because its movement is similar to that of wings in flight. The rod is similar to the body of a butterfly, and the disc moves like a butterfly's wings. The movement of a butterfly valve is similar to that when a butterfly descends, its wings move up and down in a 90-degree motion.

What is the purpose of the butterfly valve?

The butterfly valve regulates the flow by starting, decelerating, or stopping the medium. The disc opens and closes with a low torque of 90 degrees, which is suitable for any compatible application. Because of their low cost and lightweight, butterfly valves are generally more popular than other types of valves.

Butterfly Valve

For some processes, extreme temperatures and corrosion are factors that can easily damage the valve seal. Butterfly valves can withstand extreme cold or extreme heat. This means that the integrity of the sealing device is critical for high-risk applications such as energy production and oil processing (because a leak may threaten public safety or the environment).

Where is the butterfly valve located?

There are some standard guidelines for the positioning of butterfly valve components. The butterfly valve needs to have a certain distance from other parts, such as pumps, elbows, and another valves-6 pipe diameter separation is ideal.

Generally, the valve stem of a butterfly valve is installed vertically with the actuator directly above it, but in some cases, the valve stem is installed horizontally. When connected to a pump or check valve, the disc must have a gap to avoid interference with other nearby components.

3 Main Butterfly Valve Types 

While these valves all do essentially the same function, there are variations of butterfly valve design to suit different operations. Below are the three main butterfly valve types.

• Zero-offset Butterfly Valve

  “Concentric” or “rubber seated” are other names for the zero-offset design. Zero-offset means there is no offset by the stem of the valve. The valve seals via interference along the disc edge at the stem between the disc and the rubber seat. The rubber seated valve has the lowest pressure rating (up to 250 PSI) and withstands heat up to 400°F. Its rubber seat encases the body to prevent contact with the material which maintains the purity of the media.

• High-Performance Double Offset Butterfly Valve

  This butterfly valve is referred to as a double offset because the offset is in two places: at the line of the disc seat /body seal, and at the bore. Off-center positioning increases durability for the seal. High-performance valves tolerate pressure up to 1440 PSI and temps up to 1200°F. A cam-action occurs from the stem being behind the disc as it rubs against the during rotation at 90° for the first 10 degrees of opening, but also for the 10 degrees of closing.

• Triple Offset Butterfly Valve

  The best type of butterfly valve for high-pressure systems is the triple offset butterfly valve. Of the three types, the triple offset is the most advanced with lower emissions and is designed to work with various environments. Its heat tolerance is 1200°F as it can withstand 1,480 PSI of pressure. Like the double offset valve, the triple offset valve consists of two offsets situated in the center, but with a third offset having cam action with right-angled conical sealing. It is frictionless and long-wearing by the metal seal components not making contact until their final point.

Common Butterfly Valve Applications

Cast steel Butterfly valve

Some processes need more tolerant and wear-resistant valves with special features. Below are some common applications that rely on the unique mechanisms of a butterfly control valve.

• Food Processing

  Simple design, high durability, and low maintenance are the features needed to regulate fluid flow in any piping system. Certified Food Grade Seat is best for the Food Processing sector, so a White seat is preferred. 

  While standard resilient seated valves are not 3A approved, there are many on the market that maintain sanitary connections inside and outside. The body material for the valve can range from Epoxy coated iron to Nylon 11 coated iron to Bronze, 304SS, and 316SS.

• Refineries

  The butterfly valve is commonly found in refineries. These would typically use the more “high end” High-Performance valve with Steel Bodies, or the Triple Offset design that is “Fire Safe” and bubble tight. Many applications involving water use the resiliently seated version.

• Shut Off Valves

  A butterfly valve is often the best choice as a general shut-off valve above 1.5”-148”. Their simple design allows them to take up less space and less weight than other types of valves. These valves provide a tighter seal than a gate of globe valve and are usually bubble tight. This is most useful when trying to stop the fluid flow as it prevents any fluid from passing through the pipe when closed.

• Ship Building

  Because of their high durability in saltwater, butterfly valves are commonly used in ships where ABS-approved materials are selected. This type of valve effectively creates a water-tight shutoff in the piping system of a ship to prevent any flow in the pipe. Their small size also allows them to be used in those tight spaces that are common aboard the ship.

  They can be used for “jack up” rigs, ballast systems, ship side, and many other applications. Fire Safe approved valves are also necessary for many applications. Additional capabilities are automation and pneumatic function (“closed-loop” pneumatic underwater, electric, and hydraulic).

  Be sure to use valves with an ISO-5211 mounting pad and stem. This way it’s easier to get a drop-in replacement at any port. Also, be wary of valves that just have an ISO-5211 mounting pad as the stems are often manufacturer’s “special.”

  
  

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