Topical Glossary

This glossary of clamp, coupling and assembly terms is loosely arranged by topic, with one concept leading into the next.

If you're looking for a specific term, try our alphabetically arranged Stainless Steel Hose Clamp Glossary.

T-Bolt: A cold-headed bolt with a "T" shaped head. Comes in a variety of lengths, materials, and thread configurations. The width of the T-head can be augmented with the addition of a wrapper when necessary. T-bolts may be made of stainless steel, plated alloy steel, or other special materials.

Trunnion: A "T" shaped bushing or bearing element through which the T-bolt passes. It provides a bearing surface for the nut and the other end pushes the trunnion loop end of the clamp. For maximum strength and corrosion resistance it should be constructed of a stainless steel body and stainless steel cap. The two piece trunnion is superior in strength to the one piece trunnion for the same construction thickness. The trunnion is used in many T-bolt latch styles including the standard T-bolt latch.

Wrapper: An additional piece of metal, usually stainless steel formed around the head of a T-bolt to give extra bearing surface.

Over-Center Handle: A hinged fastener component, used with a wrapped T-bolt, which can be opened and closed without tools after the initial installation. Light, medium and heavy-duty stainless steel styles are available.

Quick-Release Latch: A hinged stainless steel latch component that allows for quick disassembly or change-out of the wrapped T-bolt. This latch needs a wrapped T-bolt to mate with it, and allows the clamp to be removed without taking the nut all the way off the end of the T-bolt. A quick-release latch is held in place by the looped end of the clamp, where the latch can pivot, where the T-bolt would normally be captured.

Saddle Quick-Release Latch: A fixed stainless steel component that allows for quick disassembly or replacement of the T-bolt. This latch does not use a wrapped T-bolt to mate with it, and allows the clamp to be removed without taking the nut all the way off the end of the T-bolt. A saddle quick-release latchis welded in place on the clamp band.

Self-Locking Nut: A nut that locks in to place as it is tightened (torqued) on the bolt. Up to a certain limit of length of run up and/or run down on the bolt, it will not loosen under vibration. If vibration is not present in the application, cost can be saved by using non-self locking nuts.

T-Handle: A metal T-shaped handle used in place of a nut to allow for hand tightening and easy removal. May be stainless steel or plated steel.

Knob: A plastic piece with a metal threaded insert used in place of a metal nut to allow for hand tightening and easy removal.

Tongue: An extra piece of stainless steel, rolled to the diameter of the clamp and welded in place to cover the open gap under the latch. Used to create a "perfect circle" of sealing and/or to prevent pinching of hose when the clamp is tightened on plastic or rubber hose. May be made flat or with sides.

Channel Tongue: A tongue with sides. The sides provide extra rigidity and is thus used where a flat tongue is not sufficient to prevent pinching of the hose, especially soft or silicone hose. It is welded in place.

Floating Bridge: A style of tongue with sides that is loosely crimped to the clamp. Thus it as allowed to "float" in place as the band loops, that are being tightened (by the T-bolt, trunnion, and nut), can independently slide over the ends of the floating bridge. This component is also used to prevent pinching of the hose, especially soft or silicone hose, during installation of the clamp.

Band Loops: Each end of the band is bent back on itself forming loops at each end of the clamp. One loop captures the T-head of the T-bolt and the other loop captures the T-shaped part of the trunnion, in a standard latch configuration. Thus there is a T-bolt loop and a trunnion loop. In the case of a clamp having a saddle latch, the looped shape of the saddle latch replaces the T-bolt loop. For a quick release clamp, the T-bolt loop captures the round rivet of the quick release latch, instead of the head of the T-bolt.

T-Bolt Band Clamp: A clamp made from stainless steel, with looped ends, that is tightened with a T-bolt, trunnion, and nut for the basic latch style. Other latch styles are available. Many variations are possible with band width, band thickness, band material, and types, sizes, and materials of components. Popular configurations and sizes are always in stock and available.

V-Band Coupling Coupling (clamp): Stainless steel clamp with V-shaped retainers welded inside. Used to connect flanged pipe, tubing, or vessel mating pieces, that are all appropriately designed to mate with the proper "V" shaped retainer.

Air Gap (or Radial Gap): This only applies to V-Band clamps, and it is the distance between the I.D. of the V-Band clamp and the O.D. of the flange. The I.D. of the V-Band clamp equals the flange O.D. plus two times the air gap. A properly sized V-Band clamp will always be bigger than the O.D. of the flanges. A very common sizing mistake is to order a V-Band clamp that is the same diameter as the flanges. This air gap is achieved by deliberately designing the total flange apex (width) to be larger than the retainer apex (width) by a design criteria. (See Clampco V-Retainer cross section designs that show how proper air gaps are achieved with different retainer and flange designs.) In general for commercial applications this air gap is either 1/16 of an inch or 3/64 of an inch for a few low profile designs. For aircraft/aerospace applications, sometimes 1/32 of an inch is the designed air gap, but this requires smaller retainer and flange tolerances and usually results in higher costs. When there is no air gap, no amount of torqueing will cause the flanges to wedge together any better. When the air gap is too large, higher stresses are put on the retainers, thus reducing performance, and perhaps causing installation difficulty (the real problem is often misdiagnosed as a bolt that is not long enough to get the nut started).

V-retainer: A V-shaped stainless steel component welded on the inside of a V-band clamp (coupling). V-retainers are used to wedge on to and hold together flanges on the ends of pipe, tubing, or vessel mating pieces (like a filter body and lid).

Apex: The flat area at the bottom (closed) shape of the V-retainer cross section or the total flange width (including any gasket). This apex, the angle of the sides of the "V", and the depth of the "V" are critical dimensions for the proper fit and seal of any V-band coupling (clamp) to flange application. The flanges must also be designed and manufactured properly to mate well with the V-band coupling. Poorly designed flanges cause many problems that are at first blamed on the V-band coupling. There should always be a difference in these two apexes (widths) and the total flange apex should be bigger than the retainer apex according to specific design specifications. Both retainer and flange apexes are calculated to be at the theoretical intersection points of lines drawn from the sides and apexes of the retainer and flange profiles. See Clampco retainer series 31 for an example of how retainers and flanges should be designed to mate with each other.

O.D.: Outside diameter; critical measurement of hose or flanges required to properly size the diameter of the clamp.

I.D.: Inside diameter of hose or flange. This is NOT the correct diameter for sizing a clamp.

Nominal diameter: The engineered, "ideal" or "normal" diameter of a given clamp when it has been properly sized for the intended OD and properly installed. Because of certain limitations, there is a limit (or minimum nominal diameter) that can be ordered for each T-bolt clamp design series.

Up-Adjustment: The largest adjustment possible up or added to the nominal diameter of a given clamp. When added to the nominal diameter this gives the maximum diameter that the clamp may be installed over a hose. This can sometimes be maximized by use of a longer bolt. For very small diameters there really is no practical up adjustment, because physical interference problems prevent any up adjustment. For these applications a longer bolt achieves nothing. Up Adjustment only applies to band clamps -- not V-band clamps.

Down-Adjustment: The largest adjustment possible down, or subtracted from the nominal diameter of a given clamp. When subtracted from the nominal diameter this gives the minimum or smallest diameter the clamp may be installed on a hose and still create a good seal. Down Adjustment only apples to band clamps -- not V-band clamps.

Diametrical Adjustment: This is the total diametrical adjustment a band clamp will have. It is determined by adding the Up-adjustment and the Down-adjustment together (it is also the difference between the maximum diameter and the minimum diameter). The only way to achieve more adjustment is to use a longer bolt, however this is not possible with very small diameter clamps. The length of the bolt and the loop to loop gap must be configured together properly depending on what the application needs. Diametrical Adjustment only applies to band clamps -- not V-band clamps.

Loop-to-Loop Gap: The measured distance from one loop of a clamp to the opposite loop, or component, when the clamp has been installed and tightened properly. This dimension is engineered to achieve the desired combination of Up and Down Adjustment for band clamps. For V-band couplings (clamps) this is the proper gap to allow ease of assembly of the T-bolt during installation, but yet avoid having no gap after installation. A distance that is either too small or too large indicates a mis-sized T-bolt clamp, and this may result in a poor seal or not getting the proper diametrical adjustment to accommodate the normal tolerances of hose outside diameters. For a V-band a gap that is too large will cause installation difficulty. If a V-band gap is too small it may cause sealing problems where flange tolerances allow the gap to go to zero. No loop-to-loop gap is an extremely poor "design" condition that is to be avoided, because no amount of torquing will seal any better when this gap is zero.

Torque: The amount of force times distance (in either inch-pounds or Newton-meters) that is used to tighten the nut on a clamp. There is no one value that works for all installations, but there is a maximum value of torque that each combination of tightening components will withstand, that should not be exceeded. The proper torque is unique for each application and must be developed by the customer.

Band Tension: This is the force that is generated in the clamp band as the Band Loops are made to come closer to each other during the installation torque up. In a standard T-bolt, trunnion, nut combination, the T-bolt loop is pulled by the T-head of the bolt. The other loop, the trunnion loop, is pushed by the T-shape of the trunnion, as the nut bears down on the other end of the trunnion as the nut is torqued on the bolt that moves through the clearance hole in the trunnion. It is a rather amazing yet elegantly simple design that is highly efficient. It is normally at least twice as efficient as worm gear (or worm screw) clamps in generating band tension for the same amount of torque. This is simply a result of better mechanical design.

Galling: A condition created by like-metal surfaces rubbing together. In clamping situations, this causes the nut to bind up on the bolt, and sometimes actually weld together, so that the clamp cannot seal properly and/or properly be torqued. This can be avoided by properly lubricating the surfaces of either the bolt or nut or both. Galling occurs more frequently between like metals, especially same or similar stainless steels, and is a condition to be avoided.

Silver-Plating: A shiny finish achieved by depositing a silver coating on metal through electrolysis. Used to produce a fine protective finish and/or to prevent galling. It is widely used on nuts, especially stainless steel locknuts, to prevent galling. It liquefies at high temperatures and flows, thus acting as an extremely efficient lubricant between like stainless steel materials.

Black Oxide: A dull black protective finish achieved through a chemical process.

Electropolish: An electrical process to create a clean, bright, shiny surface by removing surface scratches, discolorations, oxidation, etc.

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