Anderson Greenwood Marvac Model 920 Pilot Operated Pressure and Vacuum Relief Valve

Description

The Anderson Greenwood Marvac Model 920 is a pilot-operated pressure and vacuum relief valve designed to provide precise relief while directing discharges to a closed header system. This valve is engineered to protect storage tanks from damage or deformation due to excessive internal pressure or vacuum, ensuring process safety and compliance with environmental regulations.

The pilot operation enables the valve to open accurately at the set pressure, ensuring minimal emissions and loss of product due to evaporation. It features a modular design, allowing for quick in-situ maintenance without removing the valve from service. The soft seating provides a leak-tight seal, ensuring a leakage rate of 0.5 SCFH (0.015 Nm³/hr) or less at 90% of the setpoint.

For harsh weather applications, an optional all-weather coating prevents condensate from freezing and sticking to critical components, ensuring reliable operation even in extreme conditions.

Key Features

• Accurate Pressure and Vacuum Relief: Pilot operation ensures precise opening and closing.

• Fully Opens at 10% Overpressure: Allows settings close to MAWP (Maximum Allowable Working Pressure) or MAWV (Maximum Allowable Working Vacuum) while minimizing emissions.

• Leak-Tight Design: Achieves a leakage rate of 0.5 SCFH or less at 90% of the setpoint.

• Modular Construction: All components can be removed and replaced in-situ, enabling easy maintenance.

• Material Flexibility: Available in aluminum, carbon steel, stainless steel, and high-grade alloys to suit various industrial applications.

• All-Weather Performance: Optional ice-resistant coating prevents frozen condensate buildup and sticking of key components.

Technical Specifications

1. Materials & Construction

• Available Materials:

  • Aluminum with aluminum or stainless steel trim

  • Carbon steel with stainless steel trim

  • Low-temperature carbon steel with stainless steel trim

  • Stainless steel with stainless steel trim

  • Special alloys available upon request
    

2. Valve Sizes & Connections

• Available Sizes:

  • 2” x 3” to 12” x 16” (DN 50 x 80 to DN 300 x 400)

• Flanged Connections:

  • Aluminum Body: ANSI Class 150 flat-face, DIN 2633 (PN 16) flat-face

  • Carbon Steel & Stainless Steel Body: ANSI Class 150 (raised or flat-face), DIN 2633 (PN 16) raised or flat-face
    

3. Operating Parameters

• Pressure Relief Setpoints: 4.8 to 415 inches w.c. (12 to 1034 mbarg)

• Vacuum Relief Setpoints: Configurable based on application

• Leakage Rate: 0.5 SCFH (0.015 Nm³/hr) or less at 90% of the setpoint
  

4. Environmental & Service Options

• Optional Features:

  • Backflow preventer

  • Field test connection

  • Supply filter

  • Integral sensing

  • Cryogenic valve configurations

• Temperature Considerations: Special measures are required for condensable gases such as n-Butane, Isobutane, or Butadiene, where the operating fluid's saturation temperature falls within ambient temperature extremes.
  

5. Industry Compliance & Approvals

• Certified to API Standard 2000

• ATEX Directive 2014/34/EU Approved

• Each valve is factory-tested for:

  • Proper pressure and vacuum settings

  • Leak tightness at 75% of the setpoint

Applications

• Storage Tank Protection in oil & gas, chemical, and pharmaceutical industries

• Vapor Recovery Systems to reduce product losses

• Minimizing Emissions & Compliance with Environmental Regulations

• Preventing Tank Deformation Due to Overpressure or Vacuum Conditions