A Guide to Ball Valves
This guide has been designed to provide a comprehensive overview of the Stainless Steel Ball Valves available, the associated spare parts as well as their uses. Its Purpose is to provide the necessary information required in order to select the correct ball valve for a particular application.
A Ball valve is a type of shut-off valve that is used to control flow where a simple ‘on’ or ‘off’ flow is required. They are easy to operate and can "shut off" or "open" flow with a simple 90 degree turn of the handle. The name is derived from the spherical internal ball that has a hole bored-through it, which rotates to open and close the flow. They are versatile able to transfer liquids and gasses in a wide pressure and temperature range. They are reliable, capable of repeating the same function of sealing well after many cycles, even after extended periods of disuse. They are durable and have a long and predictable service life.
They Utilize a hollow ball that rotates allowing a flow through it when aligned and stops the flow when it is in a closed position. A quick 90 Degree turn of the handle is all that is needed to fully open or close the valve flow. When the handle is parallel and in-line with the pipe, then the valve is open. When the handle is perpendicular and at right angles to the pipe, then the valve is closed. It is this 90° turn either clock wise or anti-clockwise to open or shut the flow of the valve ,that led them to also be known as quarter-turn valves. The valve has an internal rotary ball with a hollow bore running through the center. This Inner ball is connected to the handle via a stem. So by turning the handle the ball rotates and when the hollow bore is aligned with the pipe and the in same direction as the flow, then the flow is open, and when the bore is perpendicular to the flow, then flow is shut off.
Although there are numerous parts making up the valve the basic components are made up of the following:
Also referred to as the valve housing or shell, it contains all the inner components of the valve. Usually composed of a rigid metal, in this case Stainless Steel, it protects all the internal components and keeps them in the correct position and aligned for proper functioning. It also facilitated access for the external handle to connect with and rotate the internal ball, via the stem. The valve body comes in three assembly options: one-piece, two piece and three-piece designs.
This is the part that gave the valve its name. It is a ball that has "flow path" known as a bore, through the center that allows the medium to flow through it. The ball is rotated by the stem, which either opens the flow when the bore is in-line with the pipe or closes the flow when the bore is perpendicular to the flow. There are two types of bore design: Full port and Reduced port.
Also referred to as the shaft, it connects the external handle that rotates the inner ball. The Stem has washers and packing rings to ensure a tight seal and to prevent any leaks. The stem is rotated as the handle is turned, which in turn rotates the ball, opening and closing the flow.
The Seat sits between the ball and the valve body and ensures a water tight seal. There are two seats that sit on either side of the ball and are usually composed of Teflon (PTFE).
The handle is also often called the lever. it a standard ball valve it is the manual way used to turn the ball valve to the open or closed position.
They open and close quickly using minumal force with a simple 90 degree (quarter-turn) of the handle a
There are two main types of bore profiles: Full Port and Reduced Port. The bore refers to the size of the hole that is drilled or bored into the ball. This bore or hole through the ball is also referred to as a port. A full bore is also called a full port and a reduced bore is also called a reduced port.
A full bore has a internal diameter that is the same as the pipe it is connected to. This allows the flow rate to remain constant through the length of the line, this means a full port valve has a very low flow resistance. Since the flow resistance is so low, there is minimal friction loss during the flow of the fluid, and as a result the pressure drop is negligible. This low Pressure drop in the application makes pumping the process fluid much easier.
Since the internal diameter of the port is the same as the pipe size, a full port valve is made with a larger ball which necessitates a larger valve body. This results in a slightly larger and more expensive valve than that of a reduced port valve.
Full port vales are suitable for transporting fluids with mixed solids, where any restriction in flow could result in particle build up that could in the long term cause separation of the mixtures flowing through it.
Full port valves are also easier to clean as opposed to the reduced port. In a process called "pigging" pipes are inspected and cleaned. This process involves using projectile devices called "pigs", which are used to flow in the pipes and remove particle build up. This process can only be performed on full bore valves that have the same internal diameter as the process piping they are connected to, and is not suitable for reduced bore valves or butterfly valves.
A reduced bore has a internal diameter that is one pipe size smaller than the pipe size it is connected to. So a 1" Reduced port ball valve with have a 3/4" Internal Diameter. Since the piping internal diameter becomes smaller at the valve, this reduces the flow area and causes flow resistance, which in turn results in a pressure drop. Since the amount of flow stays the same, the flow rate increases as the flow area decreases due to the narrower pipe diameter of the reduced bore.
Since the ball is smaller in a reduced port valve it requires a smaller valve body. This results in a smaller and less expensive valve. They are ideal for applications where flow rate is not a concern and the build up of particles is not likley to occur.
The most common types of manual ball valves are the 1-Piece, 2-Piece and 3-Piece. Another relatively common type is the 3-way ball valve, these 4 types account for the vast majority of the most often used valves.
A One-Piece has valve body cast out of a single piece of material. This means that there no joints in the body which eliminates the risk of leaks. The one-piece has a smaller body than the other valves making it the most cost effective. This also results in a smaller ball which means one-piece valves always have a reduced port. This means the internal diameter of the pipe decreases by one size at the point where the valve is installed. they are generally used where cleaning is not a concern and where the possibility of particle build up is low.
A Two-Piece has a valve body cast out of two pieces that thread together. The two-piece has a larger body which allows for a larger ball which means a full port is possible. This means the internal diameter of pipe the remains constant throughout the pipe, once the valve is installed. They are the most commonly used among all the ball valve types and are good for mixtures and applications where an optimal flow rate is preferred. The Valve body can be dismantled for cleaning and to service the seals, however the valve will have to be removed from the pipe, unlike the three piece.
A Three-Piece has valve body cast out of three pieces that are held together by bolt connections fitted to each of the two ends. The three-piece also has a larger body which allows for a larger ball with a full port. They are ideal for applications where regular maintenance and cleaning is required. By loosening the bolt connections the valve separates into three parts and the internal ball and seats can be accessed without removing the two ends connected to the pipe. This makes them ideal for food & beverage applications and in pharmaceutical industries where sanitation and regular cleaning is required.
These mulit-port valves are used in mixing or splitting flow (T-Port) and also for diverting (L-Port) multiple streams of fluid. This is achieved by means of a L-shaped or T-shaped bore in the ball. On top of this they also open and close the flow to multiple fluid streams. There are two types of 3-way ball valves L-Port and T-Port:
For general industrial purposed ball valves are most commonly manufactured out of Brass, Stainless Steel and Polypropylene.
Brass is a metal alloy composed of copper and zinc that ranges in color from yellow to red, depending on the concentration of zinc. Traditionally brass was the most common material used for manufacturing ball valves. This trend appears to be changing due to the increasingly better price of stainless steel. Brass is resistant to most Acids and Alkalis with the exception of solutions with high chlorine levels which can cause dezincification. They are particularly resistant to salt water. Brass valves are often used in oil and gas processing and are also used for water applications.
Stainless steel is a metal alloy composed characteristically of higher levels of iron, chromium and sometimes, nickel. It is the Chromium content in particular that allows this steel alloy to acquire its exceptional corrosion resistance. Strong, corrosion-resistant and able to handle extreme temperatures, they are the most diverse of the commonly used valves. They are well suited to handle chlorinated water which is why they are often used in applications connected to swimming pools. they are also suited to extreme industrial conditions like petroleum refineries and desalination plants since they offer good corrosive resistance to chemicals even under high pressure and high temperature conditions. Widely used in wineries and breweries, stainless steel is well suited to handle hot wort, made during the mashing process to produce beer.
Iron is an abundant low cost metal that is prone to rust. They can withstand a large range of temperature and pressure. Iron is generally made into Cast Iron and Ductile Iron ball valves. Ductile iron is more robust and offers better resistance to fatigue and to impact. Iron valves are most often used in water, oil, steam, and gas pipeline applications.
Polypropylene is a thermoplastic polymer made by combining propylene monomers. It has good resistance to many acids and bases but when it comes to organic solvents it offers only selective compatibility. As temperature increases its pressure rating and chemical resistance decreases. Widely used in the manufacturing industry for fertilizers, chemicals, paper and suger etc.
PVC is an acronym for polyvinyl chloride. PVC is resistant to most acids, bases, salt solutions, and organic solvents. It is not suitable for chlorinated and aromatic hydrocarbons, and it is also not suitable for temperatures above 140 °F. PVC ball valves have a lower pressure rating since they are not as strong as metal ball valves. They are widely used in water supply & drainage, irrigation and also for corrosive media.
Material
Advantages
Disadvantages
Stainless steel
Inert, Abrasive & Corrosion Resistant
Higher Price (Constantly Decreasing Relative to Brass)
Brass
Durable
Prone to Dezincification
Polypropylene
Cost-Effective, Corrosion Resistant
Shorter Service Time, Limited Pressure & Temperature
There are numersous parts of contruction that make aup a ball valve. however are far as replace ments part go it is usually only the seats that may require servicing over time and occasionally the handles. For a full like of parts that make up a 2-Piece Ball valve see the diagram below.
The handle is used to turn the valve from the open to the closed position. It does this by turning 90 degrees. It is connected to the stem which in turn connects to the ball. The valve is in the open position when the handle is in-line or parallel to the pipe and it is in the closed position when the handle is at right angles to the pipe. In this way the handle position let the user know if the valve is open or if it is closed. Handles can be replaced and handle covers can be specially branded.
Generally Valve Seats are made out of Teflon (PTFE). PTFE Is an abbreviation of Polytetrafluorethylene. PTFE is chemical and corrosion resistant and is very good at handling temperature extremes. On top of that the coefficient of friction is small which means the handles is relatively easy to turn.
They can be used with a full range of media, which include liquids, gases, water, chemicals, fuels and food & beverage, as long as the material selection for the valve is compatible with the media being transferred. Due to their relative low cost, ease of use and versatility ball valves are used in almost any industry that uses liquid or gas. These include fuel, oil & gas, chemical, pharmaceutical, food & beverage processing, HVAC and sanitary applications. They are also widely used in many manufacturing processes and in residential applications. Their versatility also enables them to be used corrosive applications and cryogenics.
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