Compression fittings are one of the most popular ways to connect two pieces of ductwork or pipework in plumbing or fluid control application. Compression fittings really shine in environments that require two pipes of different materials to be joined together. In this case, the compression fitting will be manufactured from one of the connecting materials. Read on to find out more about compression fittings, how they work, and the applications they suit.
What is a compression fitting?
Put simply, compression fittings compress a component of one fitting into another to create an absolutely airtight seal between these two different lines. In this case, a compression fitting will consist of a sleeve, a nut, and the body of the fitting itself. The sleeve works to act as a seal when the nut compresses into the fitted body.
Compression fittings are often used in hydraulic, gas, and water systems. They enable the connection of a tube, such as copper or steel, to a threaded component such as a valve. Due to their nature, compression fittings are used in a variety of applications, most commonly in applications that are tight on space and therefore make it hard to solder two parts together without creating an unnecessary fire hazard.
How do compression fittings work?
The working mechanism of a compression fitting varies based on the size of the compression fitting itself.
In applications requiring a small compression fitting, the compression fitting is composed of an outer compression nut and an inner compression ring, which is also referred to as a ferrule. This ferrule is typically made of brass, copper, or steel and can vary in shape, however, they are most commonly made in the shape of a ring with beveled edges.
When the nut of the compression fitting is tightened, the ferrule is compressed between the nut and receiving fitting. This then causes both ends of the ferrule to be clamped around the pipe, whilst the middle of the ferrule bows away from the pipe to allow for free flow. The result of tightening the compression fitting is that the ferrule seals the space between the pipe, nut, and receiving fitting, which creates a water and airtight seal.
Compression fittings that are larger in size often do not have a single nut to compress the ferrule, but instead, they often have a flange with a ring of bolts. The bolts must be tightened evenly to ensure that the seal is air and watertight.
The most important thing to remember with a compression fitting is that the entire integrity of the fitting is determined by the ferrule. If the ferrule is over-tightened and therefore damaged, the compression fitting will no longer operate properly and will be prone to leaks. Therefore, care must be taken when applying a compression fitting to the pipework.
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Why use a compression fitting?
One of the biggest advantages of compression fittings is that they do not require any soldering. This means that they are ideal for use in dangerous environments, such as where soldering may cause flammable media to ignite.
This also makes them much easier and quicker to assemble and disassemble as required. This makes maintenance really straightforward and simple, as these fittings can easily be separated and re-attached without any damage to the connection.
Another benefit of compression fittings is that they can be fit quickly and easily with no need for special tools or skills to operate these fittings. This can also make them a perfect solution for reactive work to create sealing solutions.
What are the disadvantages of compression fittings?
Unfortunately, compression fittings are by nature not as robust as soldered fittings, which is why they are typically used in applications that require the fitting to not be disturbed or subject to any movement, bending, or flexing.
Another disadvantage of using compression fittings is that they are often significantly more bulky than a soldered connection and therefore can take up more space in a confined area.
Compression fittings also generally tend to work best when they have been tightened once and are not disturbed, however, this really does depend on the fitting type. It is best to discuss this with your compression fitting supplier to understand exactly which type is best suited to your application.
Which applications suit a compression fitting?
Compression fittings are perfect for use in areas that are either difficult to access, or in which it would be difficult to solder two connecting components together safely. Additionally, compression fittings are well suited to temporary connections, as well as in areas that handle hazardous material and need to be maintained frequently, thus requiring an easy replacement. These applications include, but are not limited to:
- Hydraulic applications
- Nuclear applications
- Oil and gas applications
- Pipeline applications
- Pneumatic applications
- Subsea applications
What are the most common compression fitting types?
Some of the most common types of compression fitting are brass and stainless steel options. Brass compression fittings are often used in a range of pneumatic and hydraulic applications due to being compatible with industrial fluids. Brass is resistant to corrosive fluids due to its nature, which enables it to be stronger in corrosive applications, whilst the high-tensile strength of brass makes it more resistant to high pressure.
However, stainless steel fittings are designed with high pressures, vacuums, and consistent vibration in mind, operating to deliver a completely leak-proof joint. This makes stainless steel fittings suitable for almost any environment, with a particular focus being on water hammer and vibration applications due to the strength and corrosion-resistant properties of stainless steel.
Each of these two types of compression fitting is well suited to very different environments and applications. For example, for petrochemical applications or for applications that use highly acidic liquid, it will be best to use stainless steel compression fittings. Whereas, brass compression fittings are perfect for use in high-temperature environments due to the thermal and electrical conductivity properties. It is important to consider these factors when considering which fitting type to use.
How to choose the correct compression fitting for your application
There are several key things to consider when choosing a compression fitting for your application. These include:
- The size of the compression fitting
- The systems operating pressure
- The type of media the compression fitting will be handling
- The environment the compression fitting will be housed in.
Consider all of these vitally important factors when selecting a compression fitting for your application and it is unlikely that you will select the wrong choice!
