Barton Model 291B has an explosion-proof case that is certified for Class I, Division 1, Groups B, C & D service. The large cover lens allows maximum readability of the indicating pointer.
The Barton weatherproof Model 289A and the explosion-proof Model 291B are differential pressure indicating switches. The 289A has a NEMA-4 watertight die-cast aluminum case (finished with a weather-resistant black epoxy resin paint). The cover lens is secured in the bezel with an elastomer ring to reduce the possibility of accidental breakage. This ring also acts as a seal between the bezel and the case to ensure a moisture, fume and dust-free atmosphere for the indicator and switch mechanism.
Switches and all adjustments are readily accessible when the cover is removed. The built-in switches energize either single or dual alarm circuits when the measured differential pressures exceed predetermined limits. These limits may be either maximum, minimum, or both.