The Stokes Model 412H-11 is a large 300 CFM oil-sealed rotary piston vacuum pump that is the standard for industrial roughing vacuum applications. The Stokes Pennwalt 412H-11 can rough from atmosphere to it’s 2.5x10-2 Torr ultimate pressure and have a 10 horse power motor. The Stokes Microvac pumps are self-contained, oil-sealed rotary piston type units. The piston is driven eccentrically around the pump shaft and guides through two floating hinge bars that are free to oscillate in the pump housing. The exhaust valves are of the corrosion-resistant, heavy duty, poppet type. When the pump is in operation, lubrication of the internal parts is completely automatic. Oil is forced by atmospheric pressure from the reservoir through the oil lines to the shaft bearings. The oil is then fed into the pump to provide the necessary piston-to-cylinder oil seal. Finally, the oil is forced out through the exhaust valve with the air and returns to the reservoir. A solenoid valve automatically prevents oil from flooding the pump in the event of a power failure, or when the pump is shutdown without vacuum being broken. These Stokes 412H-11 oil-sealed rotary piston vacuum pumps require 12 gallons of Edward's Stokes V-Lube grade F vacuum pump oil, have a 4 inch ASA inlet flange, a combination 3 inch ASA / ANSI and 3 inch female NPT exhaust discharge port, are water cooled with 1/2 inch female NPT water cooling connections, and operate on 3-Phase 208-230 VAC or 440-480 VAC at 60 Hz. The pump intake is 4 inch ASA ANSI without o-ring groove, therefore, the intake adapter fitting need to include an o-ring groove and some options are listed in the optional accessories section below. The Pennwalt Stokes 412H-11 user's instruction and parts manuals are available in PDF format below.

The pump is provided with a manually operated gas ballast valve to overcome the adverse affect on vacuum resulting from oil contamination. Contamination occurs when water vapor or other gaseous components enter the pump and condense within the pump mixing with the oil as emulsified droplets. The condensate will mix with the oil and "flash" into vapor again as the oil circulates into high vacuum in the pump cylinder limiting the vacuum to the vapor pressure of the condensed water. Gas Ballast is a controlled bleed of air from the atmosphere. This air caries the water vapor through the compression cycle without it condensing to liquid and mixing with oil. Thus, the water vapors are exhausted without contaminating the pump oil. Other contaminates are also removed by ballasting except those that dissolve in the oil.

The priced listed above is for a rebuilt Stokes Pennwalt model 412H-11 Microvac oil-sealed rotary piston vacuum pump. We also repair these same models in our Albuquerque NM Facility. Please call (505) 872-0037 for more information.