ROOTS™ RAM™-DVJ WHISPAIR™ dry exhausters have an exclusive discharge jet plenum design which allows cool, atmospheric air to flow into the cylinder. This unique design permits continuous operation at vacuum levels to blank-off with a single stage unit. Standard dry vacuum exhausters are limited to approx. 16" Hg vacuum because operation at higher vacuum levels can cause extreme discharge temperatures resulting in casing and impeller distortion and possible failure. The RAM™ vacuum exhauster's integral cooling design eliminates the problems caused by high discharge temperatures at vacuum levels beyond 16" Hg. The basic model is designed using integral-shaft ductile iron impellers with an involute profile. the casing and headplates are grey iron, while the drive end cover and gear cover are aluminum. Carburized and ground alloy steel spur timing gears are taper mounted on the shafts, secured with a locknut. Cylindrical roller bearings are splash lubricated at both the gear end and the drive end.Piston rings reduce air leakage through the head-plate bores and lip-type oil seals prevent lubricants from entering the air chamber. Units can be equipped with mechanical seals for gas applications. All units are designed with rugged steel mounting feet which permit in-field adaptability to either vertical or horizontal installation requirements. ROOTS™ DVJ WHISPAIR™ exhausters can be arranged to operate in two and three stage systems to achieve vacuum levels down to 1 Torr.