Type 77 Vacuum Pressure Regulator

Brand: Marsh Bellofram Group of Companies

The Type 77 Vacuum Pressure Regulator from Bellofram PCD incorporates a fixed negative 15 psig bias spring to maintain vacuum outputs up to 29″ Hg.

An adjustable opposing range spring increases controlled pressure outputs up to 150 psig.

Output pressure droop under varying downstream flow conditions is minimized by use of an aspirator tube which adjusts the air supply valve opening in accordance with flow velocity. A balanced supply valve, utilizing a reinforced rolling diaphragm, keeps regulator output virtually immune to changes in supply pressure. Stack-up construction makes the Type 77 easily serviceable, without removing it from the air line.

The Type 77 provides precise control in sub atmospheric pressure applications. Specific uses include sample collecting systems, air quality monitoring, parts coating operations, and other industrial functions requiring controlled system pressure from 29″ Hg vacuum to 150 psig.

The regulator may be installed either upstream or downstream from the vacuum pump. Upstream installation is preferred when rapid evacuation of a vessel or system is required, because the exhaust capacity of the pump is normally greater than that of the regulator.

In all other applications, the regulator can be located between the pump and the vessel.
  • Single-unit control of pressures from 29″ Hg vacuum to 150 psi. 
  • Flow capacity up to 40 SCFM. 
  • Dampening action of aspirator tube maintains stable output pressure. 
  • Output virtually unaffected by changes in supply pressure. 
  • Can be disassembled and serviced without removing from line.



  • 1/2” (1.3 cm) Water Column

Flow Capacity

  • 40 scfm (1,130 L/M) @ 100 psig (6.9 bar) Supply, 20 psig (1.4 bar) output
  • 2.5 scfm (71 L/M) @ 29” Hg (740 mmHg) Vacuum

Effect of Supply Pressure Variation (25 psig / 1.7 bar) on Outlet Pressure

  • Less than 0.1 psig (0.01 bar)

Exhaust Capacity at 5 psig (0.34 bar) Above Set Point

  • 4 scfm (1,13 LPM)

Maximum Supply Pressure

  • 250 psig (17.2 bar)

Ambient Temperature Limits

  • -40° to 200° F (-40° to 93° C)

Output Pressure Ranges

  • Vacuum to 150 psig (10.3 bar)
  • Vacuum to 100 psig (6.9 bar)
  • Vacuum to 30 psig (2.1 bar)
  • Vacuum to 10 psig (0.7 bar)
  • Vacuum to 2 psig (0.1 bar)

Total Air Consumption at Maximum Output

  • 6 SCFH (2.8 LPM)

Port Size

  • 1/4” BSPT, 3/8” BSPT
  • 1/4” NPT, 3/8” NPT

Materials of Construction

  • Spring: Music wire
  • Knob: Phenolic Plastic
  • Diaphragm: Buna-N with Polyester Fabric
  • Trim: Stainless Steel, Brass,-Plated Steel, Acetal and Buna-N
  • Body: Die Cast Aluminum with Vinyl Paint

Mounting Options

  • Pipe
  • Panel
  • Bracket


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