Hose clamp

A hose clamp is a device used to attach and seal a hose onto a fitting such as a barb or nib.

Types

Many types are available, including:

Screw/band clamps

Screw clamps, known in many places as Jubilee Clips, consist of a band (usually stainless steel) into which a screw thread pattern has been cut. One end of the band contains a captive screw. The clamp is put around the hose or tube to be connected, with the loose end being fed into a narrow space between the band and the captive screw. When the screw is turned, it pulls the threads of the band, causing the band to tighten around the hose. Screw clamps are normally used for hoses 1/2 in diameter and up, with other clamps used for smaller hoses.

Pairs of screw clamps on a short rubber unit form a "no-hub band," often used for attaching sections of domestic wastewater piping, or used for other pipes as a flexible coupler (to fix alignment difficulties or to prevent pipe breakage due to relative movement of sections) or an emergency repair.

Spring clamps

Spring clamps are typically made from a strip of spring steel , cut so that one side has a narrow protrusion centered on the end, and the other side a pair of narrow protrusions on either side. The ends of these protrusions are then bent outwards, and the strip rolled to form a ring, with the protruding tabs intermeshing. To use the clamp, the exposed tabs are pressed towards each other (typically using pliers), increasing the diameter of the ring, and the clamp is slid onto the hose, past the portion that will go onto the barb. The hose is then fit onto the barb, the clamp expanded again, slid onto the portion of the hose over the barb, then released, compressing the hose onto the barb. Clamps of this design are rarely used for high pressures or large hoses, as they would require unwieldy amounts of steel to generate enough clamping force, and be impossible to work with using just hand tools. They are typically used on small hoses (3/4 in diameter and under), although they are occasionally seen on larger hoses used for vacuum lines, where their primary purpose is to keep the hoses from being accidentally removed rather than to provide a seal.

Another type of spring clamp, typically only used on vacuum hoses, is just a piece of spring steel wire bent into a loop, with the ends curled to provide handles.  These are used similar to standard spring clamps, but are just pinched by hand, and provide very little clamping force.  Rather than attempting to seal a hose into a barb, they just place a slight pressure on the hose, helping to keep it from sliding off the barb.

Wire clamps

Wire clamps consist of a piece of heavy wire, typically steel, first bent into a tight U, then formed into a ring shape with one end overlapping the other, and finally the ends bent outwards and cut. A captive nut is attached to one end, and a captive screw to the other. When the screw is tightened, the overlapped ends of the wire are pushed apart, tightening the wire loop around the hose. For an explanation of why this seemingly awkward design is used, see the section on sealing the connection.

Other methods

Many other methods can be used to attach hoses or tubing, such as compression fittings (where a nylon or soft metal ferrule is compressed onto the hose by the tightening of the fitting), push-fit fittings (where the hose is inserted inside of a compression sleeve, designed such that force against the hose causes the sleeve to tighten), swage fittings/crimp fittings (where a stiff collar is compressed onto the hose), clamp fittings (where two blocks are tightened onto the sides of the hose, often found on garden hoses ), and a multitude of others. However, these devices are not typically referred to as hose clamps.

Uses and applications

Hose clamps are typically limited to moderate pressures, such as those found in automotive and home applications. At high pressures, especially with large hose sizes, the clamp would have to be unwieldy to be able to withstand the forces expanding it without allowing the hose to slide off the barb or a leak to form. For these high pressure applications, compression fittings, thick crimp fittings, or other designs are normally used.

Hose clamps are frequently used for things other than their intended use, and are often used as a more permanent version of duct tape wherever a tightening band around something would be useful. The screw band type in particular is very strong, and is used for non-plumbing purposes far more than the other types. These clamps can be found doing everything from mounting signs to holding together emergency (or otherwise) home repairs.

Some things seen assembled with hose clamps include the tail boom on a GMP Cricket model helicopter, a homemade gas scooter, makeshift pipe hangers, mounts for rooftop TV and shortwave antennas, and virtually every imaginable automobile body component.

Sealing and mechanical strength

One of the fundamental goals of most hose clamps is to ensure a tight seal between the hose and the barb, preventing the working fluid from escaping. To this goal, they are designed to provide even pressure on all sides, with no gaps. An example of this would be wire clamps. An obvious design would seem to be simply having a wire around the hose, one end attached to a nut, and the other end to the screw, and when tightened, pulling the ends of the wire towards each other. However, this will leave a gap where no pressure is applied (underneath the screw), and cause a leak. To combat this, the more complicated and weaker design of having the ends overlap and then be pushed apart from each other is used, as this ensures pressure around the entire circumference of the hose.

To ensure a good seal, the barb must be smooth and free of nicks, scratches, or contamination. Stuck hoses should never be removed by slitting them, as this can leave a scratch on the barb which will cause a leak.

The other goal of a hose clamp is to provide mechanical attachment, to keep the hose from coming off the barb. To do this, they are typically placed behind a raised part of the barb, such that if the clamp does not slide on the hose, the clamp would have to expand to fit over the raised part, thus preventing the hose from being removed.