Last week I visited a facility in which a brand-new spraybooth had been installed. The facility manager asked me to review the contractor's installation before signing off on the booth. After checking out several items we could not find a manometer or Magnehelic differential pressure gauge to measure the pressure differential across the dry filters.Mounted on one of the walls of the sheet metal structure we found a new, clean, and colorful control panel in which a Magnehelic differential pressure gauge had been installed. Obviously, we assumed that the gauge was there to measure the pressure differential across the filters.As you may be aware, a Magnehelic gauge, or even a simple manometer, has two connecting points so that one can measure the differential across a barrier such as the filters. Upon further examination we found that one plastic tube lead inside the working area of the booth, as to be expected. The second tube, which should have been connected to the exhaust section of the spraybooth, was missing. Moreover, when the spraybooth blower was turned on the needle on the Magnehelic gauge read well below the zero point. Why was no tube connected to the second connecting point? Clearly, the contractor had made a silly mistake.
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