Stokes Microvac -Rotary Piston

The Stokes Microvac rotary piston pump has set the standard for performance, efficiency, reliability and repairability in the industry for over 80 years, improved and upgraded to the latest J version.

Pumping Speeds
212, 412, 612 m3/h

Final Pressure
Up to 0.033 mbar

Reduced Noise
Latest valve design and controlled balancing reduces booth noise and vibration.

Auto lubrication
provides proper flow of oil to bearings and sealing surfaces and prevents backflow into system

Space-saving design which saves up to 50% of valuable floor space.

Simple mechanism for high reliability and ease of rebuild and on-site maintenance.

Over 80 years of time tested, proven performance.

Value for investment
Low rotational speed enables longer pump life cycle.

Technical Data Summary


Pumping Speed

Ultimate vacuum (total pressure)

Ultimate vacuum (with gas ballast)

Motor power

Noise at ultimate










< 0.033

< 0.26






< 0.033







< 0.033




Features & Benefits

Reliability and Dependability

The Stokes Microvac rotary piston pump has set the standard for performance, efficiency, reliability and repairability in the industry for over 80 years. The Stokes Microvac J series rotary piston pump has been improved, upgraded, and fine-tuned to deliver even better dependability and productivity combined with minimal maintenance and process downtime.

Built-in protection systems

The integral oil distribution system eliminates external piping and delivers leak-free operation in a stylised design. A stiffer motor mounting platform cuts flexibility to minimise motor belt wear. A stylised oil reservoir cover and side cover ‘O’ rings improve sealing to eliminate oil leakage. An integral gas ballast valve built into the side cover allows quick adaptation to automatic gas ballast. A wide range of versatile accessories are available along with the ability to integrate with a range of mechanical boosters making the Stokes Microvac easily adaptable to suit your application and pumping requirements.


Up to date technology, continued investment in design and technology improvements.

No unplanned downtime, worry free pumping backed by full warranty and after sales support.

ESI series

The Stokes Microvac ESI series (Extended Service Interval) sets the standard for reduced maintenance and extended service intervals in arduous applications. The ESI series incorporates all the time proven design features of the Stokes Microvac 412J while integrating key accessories and features for improved performance in the most demanding applications. The ESI series can be retrofitted with any Microvac and or mechanical booster combination to suit your special application and pumping requirements.

Condensable Vapours

Vapours condensing in pump oil leads to poor lubrication, increased wear of moving parts and loss of vacuum performance.

The EM is designed to run hot and has a two open position gas ballast valve to allow the highest gas ballast flowrates of any similar sized pump. The EM pump has great flexibility to operate on applications as a high-vacuum mode or as a high-throughput mode.

All two-stage pumps have to "compromise" the oil lubrication system to achieve good ultimate vacuum, but if the pump is operated at high inlet pressure or with high vapour loads, the high vacuum stage will suffer from oil starvation and high rates of condensation of vapours in the oil. Edwards unique "Mode Selector Switch", in combination with gas ballast position GB2, allows the pump to handle the highest vapour loads of any pump in its class without any wear or loss of lubrication.


Performance Curve

1. without gas ballast            2. with gas ballast

1. without gas ballast            2. with gas ballast