What are Diaphragm Valves?

Diaphragm valves are bi-directional on-off throttle valves. They control the flow and speed of fluids through an area. Diaphragm valves regulate the area through which fluids enter or exit the system. The name diaphragm comes from a thin and flexible membrane that moves up and down within the valve’s body, causing it to open and close. Diaphragm valves can be made from plastics, single-use materials, and stainless steel. Stainless steel Diaphragm valves are easy to maintain, and they are clean and leak-proof.

How Do Diaphragm Valves Work?

Diaphragm valves are pretty similar to pinch valves in the way they work. The valve has a linear compressor that pushes the thin diaphragm into contact with the valve’s body. When the user decides to shut the valve, the actuator is pressed or turned, pushing the membrane to the edge of the valve, thus closing the valve.

Criteria for Selecting a Diaphragm Valve

You may encounter some problems specifying the correct valve size to use as there are no industry standard diaphragm valves. Below are some parameters you can consider when purchasing a diaphragm valve, so you can make the right choice.

● Valve size: The size of the valve is important since they have different throttling applications. As such, the size of the valve has a way of affecting the control of the fluids. To get the right valve size to use, ensure that the volume of the process fluid moving through the system is known. Hence, it’s important to know the state of the liquid, how it flows, as well as the viscosity and specific gravity of the fluid. Endure to also know the inlet and outlet pressures and temperatures.

● Deciding the Type of Actuator to Use: The actuator type will determine the size of the diaphragm valve you should select. Actuation types include electric motor, thermal, pneumatic, hydraulic, etc. This factor determines how the valve is opened or closed. The type of actuator you use depends on the force of the fluid flow through the system.

Advantages of Using a Diaphragm Valve

1. It serves as an on-off and throttling service valves
2. There is no case of stem leakage when using the diaphragm valve
3. The diaphragm valve provides tight bubble service
4. There are no pockets that trap impurities, slurries, and other solids.
5. Diaphragm valves have suitable linings that are resistant to chemical attacks.

Disadvantages of the Diaphragm Valve

1. Diaphragm valves are not suitable for use where the temperature is below -60 or more than 450 degrees Fahrenheit.
2. It is also not suitable for use in a flow system, where the flow pressure is more than 300psi.
3. Diaphragm valves are not ideal for use in multi-turn operations

Application of Diaphragm Valves

Diaphragm valves are used in different industries because they are cheap, very effective, and made in different sizes and forms. Below are some common places where the diaphragm valve is of importance:
1. Power industry
2. Vacuum services
3. Breweries
4. Corrosive applications
5. Water treatment facilities, and
6. Pharmaceutical manufacturing systems

What Are Butterfly Valves?

A butterfly valve controls fluid flow using a rotating circular plate or two hinged semicircular plates attached to a transverse spindle and mounted on a pipe to prevent or control flow. Butterfly valves are used mainly in places with limited space. They are very easy to operate and they open fast, with just a 90-degree rotation of the handle that will cause the valve’s complete opening or closure.

Advantages of Using Butterfly Valves

1. They are relatively light in weight
2. Butterfly valves work well in small spaces since they have a compact design
3. Have low-pressure drop and high-pressure recovery
4. They are used to provide bubble-tight service

Disadvantages of the Butterfly Valve

1. The butterfly valve leaves residual materials in the pipeline.
2. The flow turbulence affects the movement of the disc.
3. Sometimes, the thickness of the valve may restrict the fluid flow.
4. Thick liquids can sometimes prevent the disc from moving freely.

Application of Butterfly Valve

Some common applications where the butterfly valve offers effective control includes:
1. Vacuum service
2. Slurry and similar services
3. High pressure and high-temperature water and steam services
4. Compressed air or gas applications
5. Cooling water, air, games, and fire protection.

The most significant difference between the butterfly and diaphragm valves is their valve elements. The diaphragm valve uses a thin, flexible membrane, whereas a butterfly valve uses a circular plate that controls fluid flow by closing and opening.
Are you in search of top-quality valves for your system? Visit Adamant valves to get high-quality sanitary valves, including stainless steel diaphragm valves, butterfly valves, pneumatic valves, and electric valves for different flow systems. Feel free to call us today at (949) 407 8897 to reach our experts and get the perfect valve for your system.

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Therefore, the control mechanism is completely separated from the media channel, making the diaphragm valve applicable not only to the food industry and medical and health industry but also to some difficult transmission mediums and dangerous mediums.

Generally, sanitary diaphragm valves are recommended for use under conditions of service or for media requiring strict sealing performance, mud medium, abrasion, lightweight construction, low-pressure cut-off (small pressure difference), small leakage to the atmosphere, and abrasion; Besides, diaphragm valves can also be used on the occasion of double adjustment, throttling, channel constriction, low noise, cavitation and vaporization, and small operating torque; Under the conditions of high-temperature medium, high-pressure medium, high-pressure cut-off (large pressure difference), quick opening and closing and short structure length, diaphragm valve is not selected, except for metal diaphragm valve.

Due to the structural design of the diaphragm valve itself, it is particularly suitable for ultra-pure media or highly polluting, highly viscous liquids, gases, corrosive or inert media. When combined with control equipment, a diaphragm valve can replace other traditional control systems, especially for solid and non-polluting inert media. The sanitary diaphragm valve operating mechanism in the pipeline is not exposed to the transport fluid, so it is not polluting and does not require packing, and the stem packing part is not likely to leak. Therefore, diaphragm valves are specially designed for transporting corrosive, viscous fluids, such as mud, food, medicine, and woven adhesives.

The metal sanitary diaphragm valve is constructed by clamping a thin, semispherical sheet of metal into the body as a barrier between the stem and the fluid. The valve closing is achieved by pressing the disc onto the seat through the stem head and metal film, while the valve is opened by an internal spring and the disc rises when the stem rises and disengages in contact with the membrane. There is no direct contact between the stem and the disc, and the disc does not pass through the stem leaving the seat, so this valve is used in a differential one-way flow and is usually “under the seat”.However, a large amount of backflow should be avoided in use, so as not to affect valve closure.

Generally speaking, it is economical and effective to select a metal diaphragm valve under high temperature and high pressure. This valve can also be used at low temperature and low pressure when a synthetic rubber diaphragm valve is not desired.

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The diaphragm valve that appeared in the 1920s is a special form of cut-off valve. Its opening and closing parts are a piece of the diaphragm made of soft material to separate the body cavity, cover cavity, and drive parts, so it is called a diaphragm valve.

The most prominent feature of the diaphragm valve is the diaphragm to the lower body cavity and the upper cover cavity separated so that the upper part of the diaphragm stem, disc, and other parts are not subject to medium corrosion, which saves the packing seal structure, and there will be no leakage of the medium.

Stainless steel sanitary diaphragm valve

Stainless steel sanitary diaphragm valve uses the stem to tighten elastomer film on the seat to block the air path. Rotating the handwheel can drive the stem up and down so that the diaphragm from the seat to open the valve or the diaphragm tight pressure on the seat to close the valve. If the nitrile butadiene rubber diaphragm is used, the valves are suitable for the front-end and drainage pipeline and the noncorrosive gas transport within the temperature of 25 ~ 80 ℃; If the fluorine rubber diaphragm is used, the valve can be used to the high vacuum system with a temperature range of – 30 ~ 150 ℃.

Although the stainless steel sanitary diaphragm valve has a variety of unique performances, each kind of valve body in use has a service life and maintenance cycle. Only the sanitary diaphragm valve maintenance works well, the valve body can better play its performance and have a longer service life. Attention must be paid to the maintenance of the sanitary diaphragm valve in the process of use, and there are detailed descriptions of the maintenance requirements in the operation manual.

Diaphragm Valve Maintenance Requirements

There are certain requirements for the maintenance of the stainless steel sanitary diaphragm valve. Due to the existence of a diaphragm in this valve body structure, there are strict requirements in daily storage. The valve body must be placed in a dry and ventilated indoor, prevent the aging of the diaphragm caused by the damage of the valve body.

In addition to the maintenance of a sanitary diaphragm valve, the diaphragm is also an important maintenance part in the process of use. According to different media, the maintenance cycle for the diaphragm is not the same, and it needed to be replaced according to the different cycles so that the valve body can be better used. The metal surface of the valve body must be kept clean without oil stains and appropriate application of rust remover, so as to prevent the valve body from serious oxidation corrosion.

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* The spool shape and structure are mainly considered according to the selected flow characteristics and unbalanced forces.

* When the fluid medium is suspension containing the high concentration of wear particles, the valve core, and the valve seat joint surface will be serious friction every time it is closed. Therefore, the flow path of the valve should be smooth and the internal material of the valve should be hard.

* Due to the corrosive medium, the valve with simple structure should be selected as far as possible if the regulating function can be satisfied.

* When the temperature and pressure of the medium are high and the change is significant, valves in which the material of the spool and seat is less subject to temperature and pressure changes need to be selected.

* In the actual production process, flash evaporation and cavitation not only affect the calculation of flow coefficient but also form vibration and noise, making the service life of the valve shorter. Therefore, the valve should be selected to prevent flash evaporation and the cavitation valve.

* No matter what type of valve, its output force is used to overcome the effectiveness of the load (mainly refers to the unbalanced force and unbalanced torque plus friction, sealing force, gravity and other related forces).Therefore, in order to make the diaphragm valve work normally, the matching actuator to be able to produce enough output force to overcome all kinds of resistance, ensure the high seal and valve open. For double-acting pneumatic, hydraulic, electric actuators, there is generally no reset spring, and the magnitude of the force is independent of its direction. Therefore, the key to select the actuator is to find out the maximum output force and motor torque. For single-acting pneumatic actuators, the output force is related to the opening of the valve, the force on the diaphragm valve will also affect the motion characteristics, so it is required to establish a force balance in the opening range of the entire diaphragm valve.

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The Sanitary diaphragm valve adopts the clamp type. It has the advantages of simple structure, beautiful appearance, quick assembly and disassembly, quick switch, flexible operation, small fluid resistance, safe and reliable use.

Sanitary diaphragm valves use a flexible diaphragm connected to a compressor by a stud which is molded into the diaphragm. Instead of pinching the liner closed to provide shut-off, the diaphragm is pushed into contact with the bottom of the valve body to provide shut-off.

What is the use of a sanitary diaphragm valve?

Its steel parts are made of acid-proof stainless steel, and the sealing parts are made of food silicone rubber or polytetrafluoroethylene material, which conforms to food safety standards. It’s widely used in food, wine, beverages, dairy products, fine chemicals, pharmaceutical, and biological engineering, and many other industries.

Sanitary diaphragm valves are more informally known as clean valves thanks to their simple yet efficient working principle. A handwheel / An actuator is used to control the shaft that connects to the diaphragm membrane, which in turn controls the flow rate for the process media.

What is a sanitary pneumatic diaphragm valve?

The sanitary pneumatic diaphragm valve consists of sanitary diaphragm valve and a pneumatic actuator. It uses compressed air as the driving force to regulate the flow of fluid medium in the pipeline.

Since valve body that has a corrosion-resistant lining and diaphragm that is corrosion-resistant are used in the structure, and there’s no stuffing structure, the throttle element is the elastic diaphragm, the flow channel of the valve body is smooth, pneumatic diaphragm valve has the advantages of small resistance, large flow, no leakage, convenience and reliability, fire-and explosion-proof. It’s widely used for flow regulation in industrial automation systems that contain strong acid, strong alkali, strong corrosion, high viscosity, glumes, fiber, and toxic media.

Conclusion

In simple terms, the main purpose of a sanitary diaphragm valve is to control the flow of liquids and gases. Sanitary diaphragm valves have a rubber diaphragm that moves up and down within the body of the valve, causing opening and closing against a hard seat.

Adamant Valves is a global sanitary valves manufacturer and valves supplier. It has grown to become one of the leading valves manufacturers for high precision stainless steel sanitary valves, pumps, and pipe fittings.

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Principle of operation

Diaphragm valves are normally closed with the diaphragm close to the inner chamber of the valve body and closing the pipeline flow path. When the diaphragm valve needs to perform cleaning or opening tasks, it is necessary to manually rotate the hand wheel or drive the pneumatic control actuator to drive the stem upward movement of the spherical diaphragm will be followed by upward bending, so as to make the valve into a conduction state.

The diaphragm separates the inner cavity of the lower valve body from the inner cavity of the upper cover so that the stem, spool and other parts located in the upper part of the diaphragm are not subject to the corrosion of the medium. This not only saves the packing seal structure and will not produce the medium leakage, and the optimized valve body design will also make the cleaning fluid completely excreted and will not cause the retention.

Mounting Angle of the valve body

The sealing edge of the sanitary diaphragm valve must be separated from the media, which is challenging for the horizontal pipe installation system. For this reason, the diaphragm valve needs to rotate axially (emptying Angle) until the point furthest from the center of the seal edge is aligned with the lowest point of the pipe connection. In this way, the medium can pass through the valve unimpeded under low-pressure drop and valve open state.

Fields of application

Sanitary diaphragm valve adopts reinforced silicone rubber, the valve body of which through high-speed finishing polishing and the smoothness reaches Ra0.2μm, so it is widely used in biological, pharmaceutical, food, electronic systems with high requirements for aseptic. Actually, the sanitary diaphragm valve is the most reliable product in the field of biological pharmacy. All kinds of mediums are made according to special requirements, and they are smooth and free from contact, dead Angle, absolute high cleanliness and complete quality assurance system. Therefore, it is widely used in the field of biological pharmacy and the system with high aseptic requirements such as water for injection, which is specially designed for GMP requirements.

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Sanitary diaphragm valves use a flexible diaphragm made of soft materials that separate the valve body cavity from the valve cover cavity. Diaphragm valves provide on/off throttling and bi-directional flow. They control flow rates by reducing or increasing the area that fluid can pass through. Performing various pressure testing methods for diaphragm valves before installing them is critical to the health and longevity of any fluid or gas system.

A diaphragm valve is actually nothing more than a “clamp” valve — an elastic diaphragm that is connected to the compression component by screws. The valve stem drives the compression component to move up and down. When the compression component moves up, the diaphragm rises, leading to an open channel. When the compression component moves down, the diaphragm is pressed against the valve body weir (assuming it is a weir valve) or pressed to the bottom of the structure (assuming it is a straight-through valve).

Diaphragm valves offer a distinct advantage — their main functional component is housed separately from the fluid passing through it. This helps ensure the purity of the fluid by diminishing contamination from corroded parts. It also makes the valve more dependable, as high-pressure fluids cannot damage the diaphragm, a problem seen in some other, more traditional valve types.

Pressure Testing Method for Diaphragm Valve

The strength test for diaphragm valves is very similar to the pressure testing methods for butterfly valves. First, introduce the medium from one end, open the valve flap, and keep the other end closed. Second, raise the test pressure to the specified value and then check for any leakage around the valve body and valve cover. If there are no leaks, then it’s considered qualified. Finally, depressurize the system to the sealing test pressure, close the valve disc, and open the other end for inspection. If there’s no leakage, then it’s considered qualified.

Pressure Testing Method for Diaphragm Valve

The diaphragm isolates the medium from the upper cavity of the valve stem, so even if there is no stuffing medium, there won’t be leakage. However, due to the limitations of the diaphragm and lining materials, the pressure resistance and temperature resistance are relatively poor. It is usually only suitable for occasions where the nominal pressure is 1.6MPa and the temperature is below 150 degrees Celsius.

How Do Diaphragm Valves Work?

What is a Diaphragm Valve Used for?

Diaphragm valves have a simple structure and low fluid resistance, making them suitable for switching and throttling. They offer a larger flow capacity compared with other valves of the same specifications. Their leak-free performance makes them perfect for the regulation of medium and high viscosity fluids and fluids with suspended solids.

Conclusion

The diaphragm valve is a relatively new and highly specialized type of block valve. Its opening and the closing diaphragm are made of softer materials, and separates the valve body cavity from the valve cover cavity and drive components. This diaphragm structure makes it a unique design with myriad applications and potential for more in the future. This helpful equipment is widely used in various fields, with the most commonly used diaphragm valves being rubber-lined diaphragm valves, fluorine-lined diaphragm valves, unlined diaphragm valves, and plastic diaphragm valves.

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In production, the sanitary diaphragm valve is mainly used to control water, gas, oil, and other media, which is applicable to different industries such as petroleum, metallurgy, medicine, brewing, beverage, and dairy products.

Superior Performance

* Scientific design

The sanitary diaphragm valve is a flexible diaphragm or composite diaphragm in the body and bonnet, and the closing member is a compression device connected to the diaphragm. Its seat can be weir or straight through the pipe wall. The advantage of the sanitary diaphragm valve is that its control mechanism is separated from the medium path, which not only ensures the purity of the working medium but also prevents the possibility of the medium in the pipeline hitting the working part of the control mechanism.

* Flexible operation

In addition, there is no need for any form of separate sealing at the stem unless used as a safety device in controlling hazardous media. In the diaphragm valve, the working medium only comes into contact with the diaphragm and the body, both of which can be made of a variety of different materials, so the valve is ideal for controlling a variety of working media, especially those with chemically aggressive or suspended particles. The working temperature of the sanitary diaphragm valve is usually limited by the diaphragm and body lining material used, its working temperature range is about – 50 ~ 175 ℃.

* Simple structure

The diaphragm valve can be controlled freely in different media. Water, liquid, gas, all kinds of stamp products can be used to cut off and connect, and there will be no leakage. The actuator for the diaphragm valve is simple and can be operated remotely or manually, and different media can be controlled by pressing the rubber film directly onto the seat using the stem. Moreover, it has many connection modes and is very flexible in operation, which includes quick-release flange connection, welding connection, and movable flange connection.

* Widespread use    

The actuator of the diaphragm valve consists of three types, one is air type, one is normally closed and the other is normally open. All three of the standard valves are aesthetically pleasing and simple in construction. Sanitary diaphragm valves are used in many industries to control fluid, solid, gas, and other media, and their control function is to make cutoff and connection flexibly. It is applicable to water heating, food, medicine, and other industries, as well as petroleum and metallurgy, and other highly corrosive industries.

Maintaining Methods

The biopharmaceutical industry relies on sanitary diaphragm valves for its demanding process applications due to a unique need for cleaning and drainage, and pressure with temperature capabilities. Over the past 40 years, the basic design of these valves has remained the same: body, diaphragm, top works, and four fasteners. Proper installation and maintenance of these valves require experienced personnel and rigorous service practices to ensure consistent and reliable valve performance.

Sanitary diaphragm valve act both as a gasket and dynamic seal. They are often exposed to harsh chemicals, high temperatures, and high pressures, resulting in significant wear and an increased need for routine maintenance. Proper valve maintenance requires several steps on the part of the maintenance team to ensure that the valve will operate at its full potential.

* Valve/installation assembly

One of the most important elements of maintenance is a good fitting when replacing the diaphragm. Failure to assemble the valve properly may result in batch contamination, poor valve performance, and a short life cycle. Proper installation of the diaphragm according to the manufacturer’s instructions is essential. If the installation is incorrect, excessive force during operation may damage the diaphragm. The fluids can then pass through the closed valve or, in the worst case, cause a catastrophic failure that results in fluid contamination and leakage. Tightening and retightening are also important steps in the assembly process that can often lead to seal failure, either by making the seal too tight or too loose for proper performance.

* Replacing the diaphragm

Another aspect of valve maintenance is knowing when a replacement diaphragm is needed. To ensure that the valves do not fail, some companies regularly change the diaphragm (eg every six months), whether necessary or not. Facilities that use diaphragms with shorter life expectancy, such as rubber diaphragms, may be more likely to require more regular changes. However, constant replacement of diaphragms without any sign of failure can cost factories unnecessary time and money. Knowing the signs of valve failure is also essential to maintaining the valves of an installation. Physical signs that a valve or diaphragm needs to be replaced are excessive wear, corrosion, or fluid leakage.

Application Fields

A sanitary diaphragm valve is considered a highly hygienic valve due to its mode of operation. This technique is called “input from above.” The upper inlet facilitates the welding and extraction of the clamps during the maintenance of the valve. Sanitary diaphragm valves are the preferred choice of valves used in the pharmaceutical industry. This is due to its well-known characteristic of being very clean. They are ideal for applications where strangulation, unobstructed flow, and positive shutdown are required for sensitive and ultrapure media. These means are found in the pharmaceutical industry. Sanitary diaphragm valves are the only truly hygienic flow valves for applications in the pharmaceutical industry. The rest of the appropriate valves have 90-degree settings.

The sanitary diaphragm valve works by isolating the treatment medium from its surroundings and from all the moving parts of the valve. In this way, it successfully protects the contamination from media, thus guaranteeing the continuous operation of the valve without interruption.

Sanitary diaphragm valves have the following advantageous qualities: vapor resistance, high durability, flexibility for maintenance, as well as being quite clean and hygienic. They also have some other features. The sanitary diaphragm valve can be electronically polished to achieve a beautiful and better surface finish.

When mounted in line with a two-degree tilt angle, the valve is automatically vented. The body of the sanitary diaphragm valve has no trapping zones. They have their body mainly of forged 316L stainless steel. The main difference between the molding materials and the forged pieces is that the molded materials are more porous than the forged materials. Since the valves are made of forged materials, the porosity of the materials allows the valves to be polished to finish up to 10 Ra.

As “top-entry” valves, sanitary diaphragm valves can be welded to the desired location and their seals can be easily removed from the system. In fact, the diaphragms and covers of these diaphragm valves can be worked during maintenance without having to remove the valve body from the treatment lines. The sanitary diaphragm valve body has a unique design called a unique weir design. This simple but important design allows the valves to be configured and configured in addition to a single block valve. Individual blocks can be customized for specific or specific applications.

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A sanitary diaphragm valve is considered a highly hygienic valve due to its mode of operation. This technique is called “input from above.” The upper inlet facilitates the welding and extraction of the clamps during the maintenance of the valve.

Sanitary diaphragm valves in the pharmaceutical industry

Sanitary diaphragm valves are the preferred choice of valves used in the pharmaceutical industry. This is due to its well-known characteristic of being very clean. They are ideal for applications where strangulation, unobstructed flow, and positive shutdown are required for sensitive and ultrapure media. These means are found in the pharmaceutical industry. Sanitary diaphragm valves are the only truly hygienic flow valves for applications in the pharmaceutical industry. The rest of the appropriate valves have 90-degree settings.

How Does the sanitary diaphragm valve work for medicine?

The sanitary diaphragm valve works by isolating the treatment medium from its surroundings and from all the moving parts of the valve. In this way, it successfully protects the contamination from media, thus guaranteeing the continuous operation of the valve without interruption.

Sanitary diaphragm valves have the following advantageous qualities: vapor resistance, high durability, flexibility for maintenance, as well as being quite clean and hygienic. They also have some other features. The sanitary diaphragm valve can be electronically polished to achieve a beautiful and better surface finish.

When mounted in line with a two-degree tilt angle, the valve is automatically vented. The body of the sanitary diaphragm valve has no trapping zones. They have their body mainly of forged 316L stainless steel. The main difference between the molding materials and the forged pieces is that the molded materials are more porous than the forged materials. Since the valves are made of forged materials, the porosity of the materials allows the valves to be polished to finishes up to 10 Ra.

As “top-entry” valves, sanitary diaphragm valves can be welded to the desired location and their seals can be easily removed from the system. In fact, the diaphragms and covers of these diaphragm valves can be worked during maintenance without having to remove the valve body from the treatment lines. The sanitary diaphragm valve body has a unique design called a unique weir design. This simple but important design allows the valves to be configured and configured in addition to a single block valve. Individual blocks can be customized for specific or specific applications.

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Sanitary diaphragm valve has the advantages of simple structure, beautiful shape, quick disassembly and assembly, flexible operation, small fluid resistance, and safe and reliable use, so it is suitable for chemical, petroleum, metallurgy, water heating, food, medicine, and other industries of water, gas, oil and corrosive medium control.

The pneumatic sanitary diaphragm valve is a special form of the cut-off valve, that appeared in the 1920s. Its opening and closing parts are made of a piece of the soft material diaphragm, the valve body cavity, and cover cavity and drive parts separated, so it is called a pneumatic health diaphragm valve.

The most prominent feature of the pneumatic health diaphragm valve is the diaphragm to the lower body cavity and the upper cover cavity are separated, so that the valve stem, disc, and other parts located above the diaphragm are not subject to medium corrosion, eliminating the packing seal structure, and will not produce medium leakage.

Selection principles of the pneumatic sanitary diaphragm valve

The pneumatic sanitary diaphragm valve is a clamping class valve and is mainly used for opening and closing the pipeline. It has two main advantages: one is that the valve does not require a separate stem packing seal structure, while the diaphragm plays a role in stem sealing while cutting off the medium; the second is the flexibility of the diaphragm has a reliable closing performance, and it can even do a good cut off sewage.

Therefore, the operating mechanism and the media channel are completely separated, so that the pneumatic diaphragm valve can not only apply to the food industry and medical and health industry, but also be applicable to some difficult-to-transport mediums and the greater risk of the medium.

Usually, the selection of a diaphragm valve will be recommended in the requirements of strict sealing performance, mud medium, wear, light structure, and low-pressure cut-off (pressure difference is small) to the atmosphere a small amount of leakage, and abrasion of the medium.

Pneumatic sanitary diaphragm valves are characterized by a thin, hemispherical metal film clamped to the body as a barrier between stem and fluid, and the valve closure is achieved by pressing the disc against the seat through the stem head and metal film. The valve is opened by an internal spring that lifts the disc when the stem rises and disengages from contact with the film.

As the valve travel is equal to the film travel, so the valve features a much smaller lift than the general valve. To overcome resistance losses due to low lift, the seats and flow area are larger than normal valves to achieve greater flow.

Since the valve seat is large, the force is much greater than the normal valve to obtain sufficient sealing force on the disc because there is no direct contact between the stem and the disc. The disc does not move the stem away from the seat, so the valve is suitable for differential pressure unidirectional flow, and the medium is usually “under the seat”.However, large amounts of backflow should be avoided in service to avoid affecting valve closure. Generally speaking, the choice of the metal diaphragm valve is economical and effective in high-temperature and high-pressure environments.

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