SPOTLIGHT REPORT ON HIGH VACUUM PUMPS

CAD/CAM DesignOur engineers use the latest technology

CAD/CAM Systems to design our high

vacuum pumps. They are checked and

then re-checked. These details are then

downloaded to our MAZAK machining

centers that precisely manufacture all

the parts, which are then submitted to

stringent quality testing, using custom-

designed gauging equipment.

SPOTLIGHT REPORT ON HIGH VACUUM PUMPS

When it comes to specifying a high vacu-

um pump, you want to know as much as

possible about the design and construction

details. We put together this spotlight

report so you can compare the details of

MHV pumps with others and make an

informed decision.


We set the standards and provide the lowest long-term cost of ownership.

Metallurgical High Vacuum Others

FEATURE BENEFIT

100% American Made (9) High quality standards ??

Oil sealed Rotary Piston Design Excellent reliability in adverse operating conditions

Rotary vane pumps, drypumps, diaphragm pumps

All pump bearings are spherical roller type

Withstands acidic environments better than ball bearings

Ball bearings

Full pressurized lubrication with oil filtration (4, 13)

Longer pump life. ?? Most use vacuumto circulate oil

Dual spin-on oil filters (5) Longer pump life, easier maintenance

None ??

Available acid filter neutralizes hydrochloric and hydrofluoric acids for longer life

??

“Filter Fink” Oil Filter Condition gauge (2)

Easier maintenance, shows when to change filters

??

On-board run hour meter (3) Helps with maintenance logging ??

Oil pressure and oil temperature gauges (4,10)

Simplifies pump monitoring ??

Premium efficiency Reliance "XEX" totally enclosed, fan cooled motor (1)

High efficiency, withstands rough environments

Standard efficiency, open drip proof motor

Rugged, ventilated sheet metal guard (11)

Operator safety, longer belt life Non-ventilated, plastic belt guard

Premium mechanical shaft seal with ceramic coating

Longer life ??

Inconel valve springs are standard

Crack-free operation in corrosive environments

??

Water temperature modulating

valve standard

Reduces water usage and assures proper pump temperature

regardless of pump gas load

??

Direct bolt-in replacement Easy interchangeability ??

Construction: Class 40 Grey Cast Iron Body & Pistons

Withstands rough conditions ??

Moving Parts: 4150 Heat Treated Steel Less wear, longer life ??


Manufacturing and Quality ControlAfter assembly by our skilled technicians, all pumps are subjected to a run-inperiod and a stringent test for performance, including a helium leak check andbase pressure measurement. During the run-in period (hot test), a glycol - watersolution is used to cool the pump. This prevents cracking of the water jackets ifthe pump is later subjected to sub-freezing temperatures. We supervise andaudit each pump test right here on our factory floor. We then produce a signedtest report showing the pump’s performance.

Burn-in test on MHV pump


Long Life Design FeaturesMHV pumps incorporate our experience gained since 1981 in the high vacuum field. We’ve seen how pumps fail. We’ve also seen why they fail in demanding thermal process applications. That is reflected in our approach to making better pumps that withstand tough conditions.

Bearings used in MHVWe use spherical roller bearings in our pumps, and these last longer than ball bearings even under acid oil conditions. The original Stokes 412 pump main shaft used a double row ball bearing on each end and a spherical roller bearing in the center.


Bearings used in MHV pumps save the dayIn order to operate, a ball bearing must have a ball radius less than the racecurvature. This results in a point contact of the ball to the race which“spreads out” to a small “oval” area under load due to elastic deformation.

By replacing the duplex ball bearings with spherical roller bearings, the ball torace contact is changed from a point to a line which allows considerable moreload capacity in a smaller overall package. The line contact (which changes to a small rectangular area of contact due to elastic deformation of the rollersand races) also allows longer life in acid oil environments.

In acid oil environments, the ball bear-ings can fail rapidly - internal clearancecan increase from a few thousandthswhen new to well over 30 thousandthsin a few weeks! As the bearing clear-ances increase, the mechanical sealbegins leaking and base pressure onthe pump increases. Unfortunately, anew seal will quickly fail until theunderlying bearing problem is rectified.

The exact failure mode in the failure of the ball bearing is not known but itappears the acid in the oil attacks theballs and races, reducing the ball diame-ter while at the same time increasingthe outer race diameter. Excess bearingclearance quickly results. There is nospalling or gross pitting corrosion of the races or balls, they appear smooth.Races and balls have a tight brown coating all over and we suspect an oxidation mechanism is occurring. An identical failure mechanism is occur-ring in the spherical roller bearing butthe fact that it has line contact and canbetter support the load “saves the day”.


Pressure Oil System A standard gear-type oil pump (6) provides positive lubrication of bearings and all other moving parts such as pistons, hinge bars, eccentrics and piston slides. Oil is injected into the critical tang / hinge bar interface to prevent dry start-up galling.

Maintenance MonitorsOil temperature (10) and pressure (4) gauges and an hour meter (3) are standard in our pumps to help with maintenance logging.

Contamination & Oil Filtration - Not just one, but two spin-on filters (5) are used on MHV pumps, because we’ve seen premature pump failures caused by oil contamination.We have included two places to monitor your oil condition—and oil level gage (8) and oil flow sight gage (7). We’ve also seen excess maintenance, with filters changed early,which is why we’ve also included a oil filter condition gage (2) that signals when it’s time to change filters.

Note: Numbers in ( ) refer to photograph below.


Higher Pumping SpeedMHV’s 430 cfm model (HS430) will pump 33% faster than 300 cfm Stokes modelsand gets to working vacuum levels in less time, as shown in the chart below.

SPOTLIGHT REPORT ON HIGH VACUUM PUMPS

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