Vacuum/positive pressure regulator
Type 77
Marsh Bellofram
Featuring an aluminum die-cast construction with weather-resistant vinyl paint finish, the Type 77 incorporates a fixed negative 15 psig bias spring to maintain vacuum outputs and controlled system pressure from 29" Hg, with flow capacity to 40 SCFM. An adjustable opposing range spring increases controlled pressure outputs. Output pressure droop under varying downstream flow conditions is minimized by the incorporation of an aspirator tube, which adjusts the air supply valve opening in accordance with flow velocity. The dampening action of the aspirator tube maintains continuous and stable output pressure.
Units are available with 1/4 NPT, 3/8 NPT, 1/4 BSPT or 3/8 BSPT port size. A balanced supply valve, utilizing a reinforced rolling diaphragm, keeps regulator output virtually unaffected by changes in supply pressure. Stack-up construction allows for disassembly and repair without disconnecting the unit from the air line.
The Type 77 is particularly effective in providing precise vacuum pressure control within sub-atmospheric monitoring applications. The regulator may be installed either upstream or downstream from the vacuum pump. Units may be either pipe-, panel- or bracket-mounted. For more information about the Type 77, visit www.marshbellofram.com.
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