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December 22, 2008
Barbed fittings are used on the plastic tubing inside a dental unit. Most of the hoses are held on with barbs and sleeve clamps. A barb is simply a serrated hollow projection over which the tubing is placed. The barbs grip the tubing and a sleeve clamp is then pushed over the tubing forcing it onto the barb:
Image of a Double Ended Barb (ADAI part #14-11)
Note, the sleeve clamp will be slightly beveled at one end. The beveled end should go on towards the barb. Given the rigidity of metal barbs, it makes it easier to slide the sleeve clamp down. Some barb fittings are plastic and will have more “give” so you will need to slide the sleeve clamp over a plastic barb with the unbeveled end first to increase the pressure on the tubing.
Image of Barb Tee (ADAI part #14-05)
Keep in mind:
Compression fittings are similar to barbs in that you have a small hollow tube the tubing will slide over, and a plastic sleeve to hold the tubing in place. However, unlike a barb, on a compression fitting the internal tube is smooth (not serrated) and a threaded nut screws down over the sleeve squeezing (compressing) it onto the tubing. On a compression fitting, the sleeve is tapered on the outside causing it to compress further as the nut is tightened over it.
Compression fittings are normally used for larger lines (1/4” or 3/8” outside diameter) and are more commonly encountered in your junction box- where the air and water enter the room.
Compression fittings are also sometimes used on brass or copper pipes. You will normally only encounter these on the manual shut-offs in your junction box. These shut-off valves will have a large handle and look like the valve you’ll see under your sink. The sleeve on this fitting will be brass.
Pipe threads are relatively coarse and, as the name implies, will be used to join something to a pipe (including another pipe). Pipe thread size is determined by measuring the inside diameter of the pipe (NOT the thread). Male threads are on the outside of the pipe or fitting, and female threads are on the inside. For ease in identifying, we have pipe thread profiles shown at actual size in our print catalog (wherein we have more control over sizing than in an e-mail).
Machine threads are more fine and tend to be used with barb fittings, screws, bolts and nuts. It is not practical to measure a machine thread, but if you need to match a machine thread nut or bolt, just bring it to your local hardware store for a match.
American Dental Accessories, Inc.
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