Flanges form a pivotal part of a number of industrial processes, which is why they can be found in abundance, alongside gaskets, from any valve supplier in the market.
They connect pipes, valves and other components of a piping system in place of welding them, allowing for improved versatility, safety and ease of maintenance.
There are a number of ways in which they do this, but since this depends on the type, use and material of the industrial flange, we will go into more detail on this later.
A flange can be internal or external and forms a disc-shaped rim when joined to objects. This allows them to be attached to pipes and valves with relative ease, as opposed to having the joints of such systems welded.
This essentially enables the pipework system to be worked on and moved with more ease, since their joints are not welded, but can rather be disconnected from the flange.
In doing this, flanges create a pressurised seal for the system, which is essential not only for its correct functioning but also so that it can be used safely.
Of course, this is a rather broad definition of the word flange. There are, however, many different types of them, they are used differently depending on their application, and they are also made from varying materials depending on what they are being used for, and what type of environment they are being applied to.
So let’s explore industrial flanges in a little more detail by considering what they are used for, what they are made up of, and the different types of flanges available for industrial applications.
What is Industrial Flanges Used For?
As we have mentioned in the section above, flanges are typically used to join joints and valves in piping systems so that they can be worked on, replaced, maintained or manipulated with greater ease.
To do this, flanges will either be welded or screwed on to the joints, depending on which type you are using and what for. These are then bolted with a gasket to provide the system with a pressurised seal.
There are, however, quite a few different types of flanges, and even within those categories, they can be made up of different materials to give them particular properties.
For this reason, it is not easy to talk about what they do, without first looking at their composition and their different types.
Materials Commonly Used in Industrial Flanges
For the most part, flanges will be manufactured from one type of material throughout and will match the materials that make up the piping network so as to reduce the risk of galvanic corrosion.
This isn’t always the case, however, as is the case with lined flanges, where their internal parts do not match the materials used to make up the flange itself.
So, let’s take a closer look at these materials, and what unique properties they offer the flange once it has been manufactured:
Stainless steel is sturdy and reliable, but above all it is resistant to galvanic corrosion. This makes it ideal for areas where flanges are required to offer additional strength and durability, especially where there is the presence of water or other fluids.
This makes stainless steel ideal for lined flanges, which were mentioned above as having different materials in its makeup.
This is because when to different alloys come into contact in the presence of electrolytes, they tend to result in galvanic corrosion on one of them. Stainless steel stops this from happening.
Cast iron is notoriously resistant to damage, even under some of the toughest conditions.
It is remarkably tough and is also an excellent material for absorbing energy and can be shaped without damage thanks to its ductility.
Because of these properties, cast iron is exceptionally resistant to wear, making it ideal for a number of industrial applications.
It also offers these properties at a lower cost when compared to other alloys, but is prone to rust, takes a long time to cool, and offers poor impact resistance. Making it a particularly brittle material for industrial flanges.
Aluminium has a number of advantageous and unique properties that make it ideal for a range of uses for flanges.
Firstly, it is very lightweight, making it simple to work with. It, like stainless steel, is highly resistant to corrosion, while offering exceptional thermal conductivity.
It is also quite ductile which makes manufacturing flanges out of aluminium relatively easy.
It does, however, start to lose strength at higher temperatures, which makes it unsuited to pipe-systems that carry steam.
Brass is very malleable when compared to other alloy compounds, making it easy to forge into flanges.
It also offers reduced friction, but has a low melting point, and so may not be ideal for use in flanges on high-temperature systems. However, where temperatures are controlled, brass is ideal for heat flow since it is an excellent thermal conductor.
It is also corrosion-resistant and can also be recycled quite effectively since it is easier to separate from other metals.
Bronze offers a relatively high melting point and density.
It is also an excellent heat conductor, making it well suited to thermal transfer systems. It isn’t very well suited to chemical systems, however, since it is highly reactive to a number of chemicals.
Chlorine, for instance, when put into contact with brass, results in the formation of copper chloride which will corrode through the bronze.
Plastic is extremely cost-effective, although it doesn’t offer the strength, durability or conductivity of alloys; which still renders it highly useful for flanges in a range of applications.
Additionally, it is excellent when it comes to impact resistance, is completely immune to corrosion as well as wear from chemicals and water.
It also has excellent thermal and electrical insulation properties, making it well suited to pipe systems that are used to transfer heat or to heat structures.
Forged Carbon Steel
Forged carbon steel offers excellent material when manufacturing flanges since it offers incredible strength and an extended lifespan in the face of other alloys.
Still, forged carbon steel comes in four different grades, each providing different properties depending on their concentrations of carbon. The higher the concentrations of carbon, the more brittle the alloy seems to get.
Types of Industrial Flanges
Now that we have explored the wide range of unique materials that can be used to manufacture industrial flanges, let’s take a closer look at their different types, and how they are used.
There are many different types of flanges, including blind flanges; slip-on flanges; socket-weld flanges; threaded pipe flanges; weld neck flanges; lap joint flanges and ring-type flanges.
Blind flanges are most commonly used to seal pipelines, pumps and valves.
They offer the property of reversibility for expansion.
Thanks to the absence of a centre bore which makes them solid, blind flanges need not be supplied with hubs, and are well suited for application where the pressure on gas or fluid lines needs to be tested.
Where other types of flanges are used to connect pipes in a system, blind flanges are used to seal them off when they are not intended to be used.
Slip on flanges are often considered to be the most affordable option out of the different available types. They are also fitted with the most ease, as the name would suggest.
Their outer diameter must be slightly wider than the pipe they will be fitted to, and as such, they come in all shapes and sizes.
Once they have been fitted to the pipe, fillet-welding is necessary to ensure that they are properly insulated to prevent leaks or losses in pressure on the system.
Socket-weld flanges are ideal for steam pipes since they are best suited to applications that work with high levels of pressure running through smaller pipes.
Installation is also fairly simple.
The pipe is simply inserted into the socket of the flange and is then fillet welded to the flange’s top or hub, allowing for enough space for fluid to move through it.
Threaded Pipe Flanges
Thanks to the inclusion of an outer thread, these types of flanges have the added advantage of not requiring any welding when they are fitted to pipe systems.
While the threading gives them enough strength to not require welding, it also means that these types of industrial flanges are unsuitable for use on systems that are characterised by high levels of pressure.
They are also not well suited to applications that require no thermal cycles, which may, when present, cause the threads to loosen and become ineffective.
The threads on these types of flanges are generally tapered, which allows them to create an effective seal between the flange and the pipe it is fitted to.
While it isn’t common, there are a few applications where a threaded flange will be combined with a seal weld to better withstand pressures and offer improved insulation.
Weld Neck Flanges
Weld neck flanges are particularly well used in industrial applications where extremely high pressure and stress is a concern for the pipe system. Because of this, they need to be robust, reliable and highly resistant to impact, friction and stress.
They are welded to the inside of a pipe at the same diameter. This, in turn, reduces the amount of friction they need to withstand, as well as erosion and turbulence.
Because they are welded at the same diameter as the pipe, they have the appearance of a smooth weld when compared to other types of flanges. They are made up of a circular fitting that is placed within a pipe. A protruding rim will then come out around its circumference at the same diameter as the outside of the pipe.
Lap Joint Flanges
Lap joint flanges are best used in applications where low pressures are present and there is a consistent need for disassembly on the system; since they make this process much more convenient than other types of industrial flanges.
They are fitted in conjunction with a sub end. In doing so, a lap-joint ring is placed over the stub which is then butt-welded to the pipe it is being used on.
Since the stub end is welded to the pipe and not the lap-joint, the flange can still be rotated after it has been fitted.
This allows for manoeuvrability and ease of disassembly when it is required.
Ring-type flanges are generally used in conjunction with other types of flanges, particularly blind flanges, slip-on flanges and weld neck flanges.
Their primary function is to eliminate the chance of leakages in pipe systems.
They do this thanks to their grooves which can be compressed to fit into the flange types mentioned above.
Because of the way its hexagonal groove compresses when fitted to another flange and pipe, ring-type flanges are excellent for applications where more tolerance to heat and high pressures is needed.
These industrial flanges are typically not welded to piping systems but are rather sealed when bolts on its rim are tightened to compress the gasket into the groove; which essentially results in a metal-to-metal seal.
Contact D&D Valve and Engineering Supplies for Details
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