Configuration Options

   V2 Vacuum Isolation Valve, 2-Stage, Soft Start, Bellows-sealed


  • Type
    Two-stage Soft Start Bellows-sealed Isolation Valves
  • Vacuum Range
    Atmosphere to 1.0 x 10-9 Torr
  • Body Configuration
    Angle, Inline
  • Port Size
    NW25, NW40, NW50, NW80, NW100
  • Helium Leak Rate
    1.0 x 10-9 std cc/sec
  • Cylinder Volume
    0.25 in3 (4.1 cm3)
  • Limit Switch Rating
    5A - 250 VAC
  • Single Pole, Single Throw
    5A - 30 VDC
  • Blow-By Pressure
    Main: 30 - 60 psia, depending on configuration
    Bypass: 45 psia
  • Maximum Internal Spring Closing Pressure
    Main: 30 - 60 psia, depending on configuration
    Bypass: 40 psia
  • Maximum Bakeout Temperature
  • Suggested Nominal Pressure Supply
    65 psig
  • Bypass Orifice
    0.225, 0.063, 0.125, 0.187 inches and custom configurations available


Two-stage Valve Design

The Two-Stage Valve is specifically to accommodate space constraints and soft start the system in two steps. In the first stage, the bypass valve allows slow pumping from atmospheric pressure to a userspecified vacuum pressure. In the second stage, the main valve opens, allowing use of full pumping speed. The Two-Stage Valve features a removable small orifice within the bypass valve to vary slow pump speeds. A normally closed, pneumatically actuated valve at both stages, the TwoStage Valve is offered with an optional thumbscrew or micrometer head for the bypass valve. This allows for flow adjustment by limiting the stroke.

Valve Body Design

The body is made of high grade, corrosion resistant, 304 stainless steel using clean, tungsten inert gas (TIG) welding for significantly fewer entrapment areas, resulting in less contaminant build-up. A formed 321 stainless steel bellows, not edge-welded, prevents outgassing, virtual leaks, and particle entrapment between bellows convolutions and extends the valve’s cycle life. The bellows stroke length is optimized to ensure a longer cycle life while maintaining a high conductance. Elastomer seal choices include Viton® and Chemraz®, which has a higher chemical resistance. Vacuum exposed parts are clean and free of lubricants.


To achieve a soft pumpdown and isolate your vacuum system, MKS recommends its Two-Stage Valve. It integrates a small bypass valve into an isolation valve, significantly simplifying system setup and reducing costs.

The Two-Stage Valve is best suited for high vacuum applications, specifically semiconductor or optical processing for which a cleaner environment is necessary. With the integrated slow pumpdown feature, turbulent flow is diminished preventing contamination buildup and damage to your product.

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