Explanations of sanitary butterfly valves and their benefits with a list of manufacturers
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Sanitary butterfly valves are butterfly valves made of stainless steel and designed for environmental conditions that are hygienic, clean, and antiseptic. They are highly durable, exceptionally strong, and corrosion resistant and are preferred for high pressure and high temperature applications.
The function of sanitary butterfly valves is the same as other forms of butterfly valves, which is to control fluid flow by rotating a disk placed in a pipe. The essential difference between sanitary butterfly valves and all the other forms is the use of stainless steel to form the components of the valve, which enhances the valve’s performance, makes it sanitary, and gives it more endurance.
Stainless steel has been a staple of industrial applications for many years due to its many benefits. Its use in the manufacture of sanitary butterfly valves has made it the first choice for hygienic and sterile applications. The use of stainless steel is built on stainless steel's ability to withstand extremes in temperatures where there is liquid and gas flow. Clean in place (CIP) and sterilize in place (SIP) systems, used in food processing, rely on stainless steel butterfly valves to be compatible with the systems and be able to endure the effects of cleaning chemicals.
The introduction of stainless steel took place several years ago, even though it is claimed to have been introduced at the beginning of the twentieth century. The many names of stainless steel include inox or inoxidable from French, nichtrostende Stähle from German, and rustless steel. It is an iron-based alloy that contains a percentage of chromium, molybdenum, carbon, nickel, and nitrogen, which vary in accordance with the grade of stainless steel.
One of the steps in the manufacture of butterfly valves is the selection of the metal or material used to form the body and disc of the valve. Although stainless steel is the best form of metal for the manufacture of butterfly valves, the term stainless steel covers a long list of alloyed metals that are named stainless steel. In fact, there are over 150 grades of stainless steel that vary in accordance with how they are alloyed.
The many grades of stainless steel fall into five categories, which are engineered for various industrial applications. It is essential to understand the different types of stainless steel in order to select the proper type and grade for a sanitary butterfly valve. The five categories of stainless steel are differentiated by their crystalline structure and their alloying metals. The categories of stainless steel are austenitic, ferritic, martensitic, duplex, and precipitation hardened.
Stainless steel butterfly valves have become an essential part of a wide variety of industrial applications. Austenitic grades 304 and 306 are the most commonly used due to their superior corrosion resistance, durability, and ability to withstand high pressure. The structure of butterfly valves includes the body, disc, and valve shaft.
Stainless steel 304 is a T300 series stainless steel. It is composed of iron, 18% chromium, and 8% nickel and is often referred to as the 18/8 stainless steel in reference to the percentages of chromium and nickel. The use of stainless steel grade 304 in the manufacture of butterfly valves is due to its deep drawing capabilities, which makes it easy to bend, shape, cut, and form.
Like stainless steel 316, stainless steel 304 is part of the austenitic group of stainless steels. Its high melting point, which is between 1398.9°C to 1451.4°C (2550°F to 2650°F), makes it ideal for the construction of butterfly valves. The nickel content gives it a unique crystalline structure and resistance to pitting. Stainless steel 304’s resistance to corrosion and rust is due to its chromium content that forms an oxide film layer when exposed to air. It is a self-healing layer that shields and protects the underlying layer of metal.
The main difference between stainless steel 304 and 316 is the addition of a small portion of molybdenum, which adds to the metal’s resistance to corrosion. There are different versions of stainless steel 316 that vary in regard to the amount of carbon each version contains. Grade 316L has a low carbon content while 316H has a high carbon content. The strength of each is determined by their carbon content, with 316H being stronger than 316L. As can be deduced, the higher carbon content of 316H makes it harder and gives it its increased strength.
The molybdenum content of stainless steel 316 is what separates it from other types of stainless steel. The molybdenum alloy enables stainless steel 316 to resist chemicals that contain chlorides and other forms of chemicals. Although stainless steel 304 is the most used stainless steel, grade 316 is second in line due to its exceptional performance in marine, pharmaceutical, food processing, and chemical manufacturing environments. The alloys contained in stainless steel 316 gives it one of its names, which is Cr-Ni-Mo, with Mo representing the metal’s 2% to 3% molybdenum content.
Stainless steel 321 is a titanium stainless steel that is known for its strength and resistance to thermal stress. It can handle high pressure applications, which makes it reliable in demanding environments and conditions. Stainless steel 321 has the same corrosive resistance as other stainless steels but is able to endure aggressive media in situations where there is potential oxidation.
SS321 is weldable by fusion and resistance welding using 347 filler rods or electrodes. It can withstand temperatures of 700°C (1290°F) for two hours before needing to cool. The stress properties of stainless steel 321 are better than stainless steel 304 due to its titanium content. It has exceptional stress fracture and creep resistance at high temperatures.
The many positive properties of stainless steel are the main reason that it is chosen for the manufacture of sanitary butterfly valves. Other metals, such as carbon steel, are less expensive and have more strength but are susceptible to degradation from the elements, factors that do not affect stainless steel. In addition, carbon steel is not sanitary or hygienic enough to be used in food processing and pharmaceutical applications. In the midst of the long list of the benefits of stainless steel butterfly valves, it is important to understand that stainless steel butterfly valves are more expensive than carbon steel, plastic, and other forms of butterfly valves but are the only ones that meet FDA standards for hygienic processes. The aspect that makes their choice more tenable is their very long life and antiseptic reslience.
Sanitary butterfly valves vary in how they are configured. Regardless of their dissimilarities, all sanitary butterfly valves perform the same function of controlling the flow of liquids and gases. The name, butterfly valves, is derived from the disc that rotates to allow and stop flow. Regardless of the simplicity of their function, butterfly valves are required to be strong, durable, long lasting, and operate smoothly, which is the reason that stainless steel is used as the main material for their bodies.
All butterfly valves consist of a body or housing, disc, stem, actuator, seat, and bolts. All of these work together to control flow. How they are shaped, aligned, and configured differentiates the various types of butterfly valves. Of the list of components, the one that is not made of stainless steel is the seat, which is made of a material to form a tight, secure seat and is hygienically clean.
The body design for sanitary butterfly valves is configured to fit between pipe flanges with the most common end connections being flanged, double lug, and wafer. Sanitary butterfly valves have to be slim enough to fit in the pipe but robust enough to control flow. The wafer type of body is the most economical and is secured to a pipe with bolt holes. It is easy to install and prevents backflow.
Lug style stainless steel butterfly valves are more expensive and are connected to the pipe by lug holes on the outside of the butterfly valve. The lug style helps carry the weight of the piping and allows for dead end serving on one side of the piping. The inserts are threaded on both ends, which make it possible to install the lug butterfly valves using bolts and no nuts.
A type of sanitary butterfly valve that is unlike lug and wafer is a flange or double flange type that has two flanges with one on each side of the valve. The flanges are bolted to the pipe for a secure, tight connection. The use of double flanged stainless steel butterfly valves is to ensure stability and a strong structure, especially in applications that have high pressure.
The disc is the gate that opens and closes to control fluid flow. The process is completed as the disc rotates around the stem that is bored through the disc. Although the function of all butterfly valve discs is the same, they vary in their design and orientation to improve flow, seal, and torque. The disc, also spelled disk, can be concentric or eccentric, with concentric being the most common.
With concentric discs, the stem passes through the centerline of the disk with an equal portion of the disc on either side of the stem. It is the simplest form of disc. Concentric discs have their axis aligned with a pipe’s centerline. With concentric discs, the upper and lower ends of the disc are smooth and flat surfaces to create a tight closed seat. During closure, the disc compresses when it rotates causing the seat ring to deform elastically.
Eccentric discs have stems that do not pass through the centerline but are located behind the centerline in the opposite direction of the flow. They are designed to prevent contact of the disc and seal before the disc is fully closed, which prolongs the life of the valve. With eccentric disc butterfly valves, the offset location of the stem provides a tighter seal with the valve seat.
Sanitary butterfly valve stems, also known as the shaft, are the component that connects the disc to the actuation mechanism and sends torque. The names of stems are wetted or non-wetted, which refers to the amount of protection the material of a stem provides. All forms of stainless steel stems are non-wetted due to their ability to protect against corrosive and erosive materials.
As with the disc, the positioning of the stem varies in regard to whether the disc is concentric or eccentric. Stems can be non-offset or offset, which includes single, double, and triple offset. All forms of offsets have the stem positioned in an eccentric position behind the disc. Each form has the disc contact the seat at a different angle.
In many cases, sanitary butterfly valves are installed straight up and vertical, a design that can last many years. The longest lasting position is horizontal and parallel to the pipe. In general, the orientation of the stem is chosen in regard to the specifics of an application. Although the one-piece design of the stem is quite common, there are split stems that come in two pieces.
Of the many components of a sanitary butterfly valve, the stem is the most resilient and must be protected from the media. The offset position of the eccentric stem design is long lasting due to the positioning of the stem in this regard. The strength, durability, and toughness of stainless steel is the reason that it is so widely used for the manufacture of sanitary butterfly valves and, in particular, butterfly valve stems.
The seat of a stainless steel butterfly valve is where the disc rests when the valve is closed. It provides a tight seal regardless of thermal, friction, or impact stress from a process. The various forms of butterfly seats take different forms and are made of different hygienic and sanitary materials.
One of the variations between the types of seats is in regard to their ability to endure temperatures, such as ethylene propylene diene monomer (EPDM) being able to endure temperatures between -34.44°C and 121.11°C (-30°F and 250°F) while fluoroelastomer (FKM) has a temperature range of -17.78°C up to 148.89°C (0°F up to 300°F). Sanitary butterfly valve manufacturers select seats in accordance with the pressure and temperature of a specific application.
The actuator for a sanitary butterfly valve can take different forms, which can be manual or automatic. The selection of the actuator method is dependent on the application for which the butterfly valve is being used. Actuators are mechanical devices that control the mechanism of a butterfly valve and rotate the stem to activate the disc. Although manual power is common, automated actuators are more convenient and are powered by air, electricity, or liquids.
Electric sanitary butterfly valve actuators have a bi-directional motor that provides remote control of the valve. The system includes a gearbox that lowers the motor's speed and increases torque. The use of electric actuators is due to their simple installation and maintenance free structure. They are used in non-critical and light duty applications. Electric actuators operate quietly and use little energy. In some cases, electric actuators have limit switches that turn the power off when the valve is fully closed.
Pneumatic or air powered actuators have multiple ports of the entry and removal of compressed air. The entrance of air causes rotary motion to a plunger or piston that increases torque on the stem and rotates the disc to open or close. In some cases, a pneumatic actuator may have solenoids that respond to electrical signals that control the position of the actuator. The wide use of pneumatic actuators is due to their compact and lightweight design that makes them less expensive. The quick action of pneumatic actuators makes them ideal for mixing and blending applications that require repeated activation of a sanitary butterfly valve.
Heavy duty butterfly valves require greater torque to rotate a butterfly valve’s disc. Such instances require the power and force of a hydraulic actuator that uses fluid pressure to open and close the valve. As pressure builds up on the valve, the force of the fluid pushes a piston that opens the valve. When the pressure dissipates, the piston closes the valve. Hydraulic actuators provide an economical method for automatically opening and closing large butterfly valves.
The oldest, best known, and most reliable actuator is a manual actuator that uses a handwheel, crank, and lever to rotate the disc to open or close the valve. It is the simplest form of actuator and the easiest to operate. The handle is connected to the stem, which allows an operator to turn the handle to open or close the valve. Of the various varieties, the lever type is the simplest and most cost-effective flow controlling method. In the case of all forms of manually operated sanitary butterfly valves, the stem and disc are made of stainless steel due stainless steel’s durability and its resistance to rust and corrosion.
Although the operation of manual actuated butterfly valves is rather simple, there is a certain amount of complexity as they get larger. In the case of handwheel operated manual sanitary butterfly valves, gears may be included in the actuator to lower the necessary force to supply the torque to rotate the stem and disc. Manually operated sanitary butterfly valves are used for special conditions that do not require frequent activation of the valve.
The configuration of a hygienic system is one of the determining factors regarding the selection of a sanitary butterfly valve and its actuator. As would be expected, the stem of a sanitary butterfly valve must be able to couple with an actuator, which is determined during the selection and design phase of a sanitary butterfly valve. Other considerations include cycling times, the speed of an actuator, and its cost and maintenance. In essence, an actuator should simplify the smooth, timely, and optimum performance of a sanitary butterfly valve.
There are many different choices for end connections, with wafer, lug, double flanged, clamp, and end weld being some of the common types. The selection of end connection is based on ease of maintenance, dead end service, weight, and cost. The end connection of a sanitary butterfly valve is the interface between the butterfly valve and the pipe and impacts how the valve will be installed. It determines the operation and performance of a butterfly valve and its efficiency.
Flange end connections are one of the most common forms of end connection. This type of connection is used for medium and large diameter pipes due its ability to provide a tight and secure seal. Flange end connections are easy to install and can withstand high and low pressure and are used for low pressure water pipes and medium pressure steam pipes. It is used for alkali and acid pipes due to the ability to be disassembled and inspected. The major flaw with flange connections is the amount of space they require and the need for sufficient clearance for the flange and bolts.
Wafer end connections are secured by clamping the valve body ends together with pipe flanges. This type of end connection is lightweight and capable of enduring medium and low-pressure applications. Wafer end connections have a thin body without any flanges and use flanges on the pipe to bolt them together. Although wafer end connections are lightweight, easy to install, and save on materials, they necessitate high flange parallelism to ensure a secure and tight seal.
Welded end connections are available in socket welds for small diameter pipes with high pressure and butt welds for large diameter pipes with high pressure and temperatures. The use of weld end connections for sanitary butterfly valves has to be carefully considered due to the permanence and inaccessibility of the valve. The outstanding characteristic of welded end connections is their tight seal, which makes them ideal for applications with high pressure and temperatures that handle corrosive media. The welding process eliminates potential gaps and ensures a tight seal, which can be a positive factor of hygienic applications.
Although welded end connections are difficult to maintain, they are ideal for applications that have excessive pressure and temperatures. As can be assumed, once a sanitary butterfly valve is welded, it is nearly impossible to remove. Welded end connections are designed for use over long periods of time without replacement.
Threaded end connections are designed for small diameter, low pressure applications. Sanitary butterfly valves screw into threaded pipes, which makes installation simple and easy. The threads of the valve are located externally or internally on both ends and are screwed into the pipe like connecting a faucet. In many cases, threaded end connections are placed before or after a water meter. Threaded butterfly valves are used due to stainless steel’s resistance to corrosion due to other materials deteriorating over time, which makes them ideal for hygienic applications. They are used for low pressure, normal temperature, fresh water pipes.
The common use of clamp on end connections is for quick installs for low pressure pipes, such as fire protection and temporary municipal pipes. Sanitary butterfly valves with a clamp end connection have a ferrule at both ends and are secured by a clamp. They are widely used due to their ability to be quickly connected and disconnected for pipe cleaning, maintenance, and inspection, which makes them ideal for food processing and pharmaceuticals. Clamp end connections cannot hold high pressure, and their strength is limited with a pressure rating below 1.6 MPa.
There are three factors that help determine the type of connection for a sanitary butterfly valve. The first of the factors is whether an application requires quick assembly and disassembly of butterfly valves, which determines the end type and the abilities of a sanitary butterfly valve. Other common factors that apply to all forms of butterfly valves are pressure and the diameter of the pipe.
The most common type of end connection is flanged, due its ability to withstand high pressure and be configured for any pipe diameter. The use of welded end connections has to be carefully considered due to its permanence. Clamp end connections are used for their ease of installation and flexibility. They are available to fit any diameter sized pipe but are limited to specific applications. It is imperative to match the end connection to the application to ensure the best performance of a sanitary butterfly valve.
Butterfly valves are a critical component in the food and beverage industry. Regardless of the actuator and end connection, they are used for their simple design and ease of operation. Sanitary butterfly valves are normally installed between sections of processing pipes to give operators control over product flow. They are chosen for their ability to provide a tight, safe, and secure seal to prevent contamination of the product.
The main use of sanitary butterfly valves is in food processing and pharmaceuticals, where high standards of hygiene, efficiency, and cleanliness are crucial and a necessity. Sanitary butterfly valves are a critical and essential part of maintaining uncontaminated conditions. They control flow, ensure clean conditions, and operate smoothly and swiftly. Sanitary butterfly valves are designed specifically for applications that require the highest levels of cleanliness and sterilization. They are designed to be easily cleaned and disinfected during maintenance, which makes them the preferred choice for hygienic applications.
Hygiene is the first consideration for sanitary butterfly valves. They are capable of maintaining exceptionally high cleanliness standards while providing efficient service. As with all forms of sanitary butterfly valves, these valves are made of high quality stainless steel due to its resistance to corrosion and contamination. In addition, stainless steel is used due to its inability to react to the chemicals and products the valves control.
From the stem and disc to the body of the valve, all sanitary butterfly valves are designed to operate efficiently and quickly, under all conditions. They make it easy to control flow while assisting with processing. This aspect of sanitary butterfly valves makes them very beneficial for industry use.
It is essential that sanitary butterfly valves be able to be easily cleaned. This is one of the reasons that stainless steel is so popular as a base metal. Other metals and plastics have the potential of interacting with the substances that pass through the valve. Stainless steel, with its oxide film, is non-reactive and perfect for sanitary conditions.
The design and many configurations of sanitary butterfly valves that manufacturers offer makes it easy to find a valve that easily fits efficiently into a system. Manufacturers work closely with their clients to find the right valve for an application. Information and options are offered for all forms of conditions from pressure and temperature needs to end connections.
The selection of materials is one of the initial steps in the construction of sanitary butterfly valves. The metal that all forms of sanitary butterfly valves are made of is stainless steel, which makes up the body, stem, and disc. Although hard seals are a possible choice, they are seldom used for sanitary butterfly valves due to their poor seal.
The material used to form the seal of a sanitary butterfly valve is food grade rubber, which includes silicone, natural rubber, nitrile, neoprene, and polyurethane. Food grade rubber has been certified and approved by the Food and Drug Administration (FDA) for use in the preparation of food, sanitary manufacturing, and packaging.
The original butterfly valves were used for low pressure applications that required limited functionality. Over the years, as butterfly valves improved, they have become a major part of a wide range of industrial applications. Their increased use is due to innovations in design and the addition of various features that improved their adaptability to a wide range of industrial functions.
One of the interesting aspects of sanitary butterfly valves is the number of industries that rely on them to provide optimum service. The basic structure and function of sanitary butterfly valves is rather simple, which belies how essential they are for the protection of equipment and processes. Although the food and pharmaceutical industries are the main users of sanitary butterfly valves, several other industries rely on their hygienic properties.
Sanitary butterfly valves are preferred over gate valves for water treatment due to sanitary butterfly valve’s lightweight, ease of manipulation, and low pressure drop. The most common form of sanitary butterfly valve used by water treatment are double eccentric butterfly valves due to their ability to provide a tight and secure shut off.
The food and beverage industry relies on the accuracy, strength, endurance, and precision control offered by sanitary butterfly valves. As any chef will tell you, control of the distribution of ingredients is an essential part of producing a good product. The ease of manipulating makes sanitary butterfly valves the perfect tool for ensuring high quality products. The smooth even surface provided by stainless steel makes sanitary butterfly valves easy to clean and maintain. Regulating flow, preventing backflow, and isolation are essential and crucial features required for food and beverage processing. The long list of products that require a hygienic environment rely on sanitary butterfly valves and their clean sanitary surfaces.
Powder sanitary butterfly valves covers special aspects of the food industry, which includes products like organic infant formulas, organic follow on milk, organic milk, organic cereals, allergenic formulas, milk free infant formulas, dietetic baby food, probiotics, and polyunsaturated fatty acids. These particular food products require exceptional accuracy in production and packaging. Industries that produce these products place themselves between the dairy industry and pharmaceutical products. They pay special attention to the selection of components that meet the highest sanitary standards.
During production, ingredients are blended with water. The mixture is then pumped to a heat exchanger to be pasteurized. The resulting liquid is homogenized, which is followed by being evaporated or spray dried. As the product dries, powder droplets fall to the bottom of the dryer where they are discharged through a sanitary butterfly valve. The nature of powder products demands the highest standards of cleanliness due to the surrounding conditions being conducive to bacterial growth.
As with the food and beverage industry, sanitary butterfly valves for the pharmaceutical industry are used to regulate flow, prevent backflow, and isolation. For the pharmaceutical industry, sanitary butterfly valves are popular due to their low maintenance requirements and exceptionally tight shut off. The smooth stainless steel surface makes them easy to clean and ensure a sterile environment. The main use of sanitary butterfly valves is for the production of vaccines and other forms of medicines.
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