American Dental Tech Blog

Monthly Archives: March 2009

  • Tech Tips #8: Vacuum Valves- HVE or SE?

    HVE or SE?

    The HVE is the larger sized suction on the unit and will have a standardized 7/16” opening at the end. This is an industry standard and almost no units will have HVE’s of any other size. Likewise, any attachments for an HVE will be 7/16” in diameter. Also standardized in size is the tubing to which a HVE will attach. HVE’s fit on ½” inside diameter tubing. The tubing can be corrugated (ridged inside and out), or come in a variety of asepsis (easy-to-clean) designs. Some of the newer smooth HVE tubing is closer to 7/16” inside diameter as it is softer and more flexible and needs to be smaller to stay securely attached to your valve.

    The SE is the smaller suction and will often have a rubber tip, SE’s attach to standard 7/32” inside diameter tubing. This tubing is generally very soft and flexible. NOTE: The difference between a HVE and a SE is the diameter, not the length, HVE’s can be short or long.

    Installation

    All vacuum valves have a barbed fitting at the base which is simply inserted into your tubing. Unlike the barbs on your air and water supply lines, no sleeves or similar components are required to secure the tubing to the barb. The pliant nature of vacuum tubing and greater size of vacuum valve barbs allows for a secure fit without using sleeve clamps.

    To install a new vacuum valve, simply cut the old valve off of your tubing and insert the barb from the new valve into your tubing. It may be necessary to dip the tubing in hot water (about the same temperature as a cup of coffee) to soften the tubing which will make it easier to insert the barb.

    Troubleshooting

    A common complaint with vacuum valves is an inability to turn them off or on.

    Most valves will either have a lever to push or a knob to turn, to turn the vacuum on or off. The lever or knob rotates a cylinder inside the valve which is what actually opens and closes. The cylinder will normally have o’rings to seal it.

    These o’rings can dry and wear from contact with the various fluids (including vacuum line cleaner) and should be lubricated at least once a week. To expose the o’rings on a lever style valve, gently pry the lever apart and pull it off the valve. The cylinder can then be pushed out from one side to expose the o’rings. On a valve with a knob (rotary style) the cylinder can be pushed straight out from the bottom (side opposite the knob) to expose the o’rings. Clean the cylinder with a mild detergent and soft brush, and lubricate the o’rings with a silicone based lubricant. If the o’rings show signs of excessive wear (nicks, cuts, or distortion) they should be replaced.

    A handy trick to snapping the lever back onto your valve, is to push the lever on from the end using the contours of the valve itself to spread the lever out until it is seated onto the cylinder.

    Some valves will have a plastic cylinder without o’rings. These are more commonly used on valves which are not designed to withstand autoclaving but will be soaked in disinfectant. It is quite common for these valves to swell from absorbing the disinfectant which will lead to a cylinder which is now too big for the valve. Simply allowing the valve to dry out for a day will return it to proper size and function. If you soak your valves, you may need to rotate valves in and out of use to allow for an adequate drying time. You can also try lubricating the plastic cylinder with silicone lubricant.

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