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Compression fitting
A compression fitting is a fitting used in plumbing and electrical conduit systems to join two tubes or thin-walled pipes together. In instances where two pipes made of dissimilar materials are to be joined (most commonly PVC and copper), the fittings will be made of one or more compatible materials appropriate for the connection. Compression fittings for attaching tubing (piping) commonly have compression rings, called ferrules (American English) or olives (British English), in them, and are sometimes referred to as flareless fittings. There are also flare fittings that do not require ferrules/olives.
Compression fittings are used extensively in hydraulic, gas, and water systems to enable the connection of tubing to threaded components like valves and tools. Compression fittings are suited to a variety of applications, such as plumbing systems in confined spaces where copper pipe would be difficult to solder without creating a fire hazard, and extensively in hydraulic industrial applications. A major benefit is that the fittings allow easy disconnection and reconnection. There are now open source 3-D printable easy fittings that can be customized to connect pipes of any size up to 4.5MPa.
In small sizes, the compression fitting is composed of an outer compression nut and an inner compression ring (ferrule) that is typically made of brass, copper, or steel. Ferrules vary in shape and material but are commonly ring-shaped with beveled edges. To work properly, the ferrule must be oriented correctly. Copper ferrules are normally barrel-shaped which means they cannot be fitted incorrectly. In other cases, particularly in hydraulic and high pressure applications, the ferrule must be fitted so that the longest sloping face of the ferrule faces away from the nut. Hydraulic-style ferrules have one end which is larger with a 45 degree chamfer which tapers away (from installation contact with the nut), and a small end with two internal biting edges.
When the nut is tightened, the ferrule is compressed between the nut and the receiving fitting, causing both ends of the ferrule to be clamped around the pipe. The result is that the ferrule seals the space between the pipe, nut, and receiving fitting, forming a tight joint. The clamping support of the pipe help prevent movement of the pipe in the fitting, but it is only the taper at the receiving fitting itself that needs to seal completely. If it does seal (to both the pipe and the compression fitting), then no fluid can get to the nut threads or the taper to leak. As a result, some similar fittings can be made using a ferrules with only one taper where the seal prevents fluid from reaching the nut.
Larger sizes of compression fitting do not have a single nut to compress the ferrule but a flange with a ring of bolts that performs this task. The bolts must be tightened evenly.
Thread sealants such as joint compound (pipe dope or thread seal tape such as PTFE tape) are unnecessary on compression fitting threads, as it is not the thread that seals the joint but rather the compression of the ferrule between the nut and pipe. However, a small amount of plumber's grease or light oil applied to the threads will provide lubrication to help ensure a smooth, consistent tightening of the compression nut.
It is critical to avoid over-tightening the nut or else the integrity of the compression fitting will be compromised by the excessive force. If the nut is overtightened the ferrule will deform improperly causing the joint to fail. Indeed, overtightening is the most common cause of leaks in compression fittings. A good rule of thumb is to tighten the nut first by hand until it is too difficult to continue and then tighten the nut one half-turn more with the aid of a wrench; the actual amount varies with the size of the fitting, as a larger one requires less tightening. The fitting is then tested: if slight weeping is observed, the fitting is gradually tightened until the weeping stops.
The integrity of the compression fitting is determined by the ferrule, which is easily prone to damage. Thus care should be taken when handling and tightening the fitting, although if the ferrule is damaged it is easily replaced.
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Compression fitting AI simulator
(@Compression fitting_simulator)
Compression fitting
A compression fitting is a fitting used in plumbing and electrical conduit systems to join two tubes or thin-walled pipes together. In instances where two pipes made of dissimilar materials are to be joined (most commonly PVC and copper), the fittings will be made of one or more compatible materials appropriate for the connection. Compression fittings for attaching tubing (piping) commonly have compression rings, called ferrules (American English) or olives (British English), in them, and are sometimes referred to as flareless fittings. There are also flare fittings that do not require ferrules/olives.
Compression fittings are used extensively in hydraulic, gas, and water systems to enable the connection of tubing to threaded components like valves and tools. Compression fittings are suited to a variety of applications, such as plumbing systems in confined spaces where copper pipe would be difficult to solder without creating a fire hazard, and extensively in hydraulic industrial applications. A major benefit is that the fittings allow easy disconnection and reconnection. There are now open source 3-D printable easy fittings that can be customized to connect pipes of any size up to 4.5MPa.
In small sizes, the compression fitting is composed of an outer compression nut and an inner compression ring (ferrule) that is typically made of brass, copper, or steel. Ferrules vary in shape and material but are commonly ring-shaped with beveled edges. To work properly, the ferrule must be oriented correctly. Copper ferrules are normally barrel-shaped which means they cannot be fitted incorrectly. In other cases, particularly in hydraulic and high pressure applications, the ferrule must be fitted so that the longest sloping face of the ferrule faces away from the nut. Hydraulic-style ferrules have one end which is larger with a 45 degree chamfer which tapers away (from installation contact with the nut), and a small end with two internal biting edges.
When the nut is tightened, the ferrule is compressed between the nut and the receiving fitting, causing both ends of the ferrule to be clamped around the pipe. The result is that the ferrule seals the space between the pipe, nut, and receiving fitting, forming a tight joint. The clamping support of the pipe help prevent movement of the pipe in the fitting, but it is only the taper at the receiving fitting itself that needs to seal completely. If it does seal (to both the pipe and the compression fitting), then no fluid can get to the nut threads or the taper to leak. As a result, some similar fittings can be made using a ferrules with only one taper where the seal prevents fluid from reaching the nut.
Larger sizes of compression fitting do not have a single nut to compress the ferrule but a flange with a ring of bolts that performs this task. The bolts must be tightened evenly.
Thread sealants such as joint compound (pipe dope or thread seal tape such as PTFE tape) are unnecessary on compression fitting threads, as it is not the thread that seals the joint but rather the compression of the ferrule between the nut and pipe. However, a small amount of plumber's grease or light oil applied to the threads will provide lubrication to help ensure a smooth, consistent tightening of the compression nut.
It is critical to avoid over-tightening the nut or else the integrity of the compression fitting will be compromised by the excessive force. If the nut is overtightened the ferrule will deform improperly causing the joint to fail. Indeed, overtightening is the most common cause of leaks in compression fittings. A good rule of thumb is to tighten the nut first by hand until it is too difficult to continue and then tighten the nut one half-turn more with the aid of a wrench; the actual amount varies with the size of the fitting, as a larger one requires less tightening. The fitting is then tested: if slight weeping is observed, the fitting is gradually tightened until the weeping stops.
The integrity of the compression fitting is determined by the ferrule, which is easily prone to damage. Thus care should be taken when handling and tightening the fitting, although if the ferrule is damaged it is easily replaced.