Comparing Vacuum Capability of Pump Models WELCH 1375 & PFEIFFER DUO65

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Discussion Overview

The discussion revolves around comparing the vacuum capabilities of two pump models, WELCH 1375 and PFEIFFER DUO65, focusing on their ultimate pressures and implications for performance in practical applications.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions whether the lower ultimate pressure of the PFEIFFER DUO65 (2 x 10^-3 Torr) indicates it is inferior to the WELCH 1375 (1 x 10^-4 Torr), given both have the same speed of 35 CFM.
  • Another participant suggests that while there is a significant difference in vacuum quality, other factors such as price, size, power consumption, noise, and durability may also influence the decision on which pump to choose.
  • A participant inquires about the significance of the Speed vs. Ultimate Pressure curve, specifically asking if a machine with a lower CFM (20 CFM) but a similar ultimate pressure (1 x 10^-4 Torr) would be acceptable.
  • It is noted that a higher CFM pump will evacuate a volume faster than a lower CFM pump, but the latter may still be effective if time is not a constraint.
  • Participants discuss the practical implications of pumpdown times in setups requiring frequent access to elements operating under vacuum conditions.

Areas of Agreement / Disagreement

Participants express differing views on the importance of ultimate pressure versus other operational factors, indicating that the discussion remains unresolved regarding the best choice of pump based solely on ultimate pressure.

Contextual Notes

There are assumptions regarding the operational context and specific requirements for vacuum applications that are not fully articulated, which may affect the evaluation of the pumps.

Who May Find This Useful

This discussion may be useful for individuals considering the purchase of vacuum pumps for applications where ultimate pressure and operational efficiency are critical factors.

vultac
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Dear All,

Appreciate if you can guide me on understanding the ultimate pressure of vacuum pump.

I have two models for review.

One has ultimate pressure of 1 x 10^-4Torr the other has 2 x 10^-3Torr.

From this can it be said that the vacuum capability of the first pump (1 x 10^-4) larger range? is better than the second pump?

Both has speed 35CFM.

Model 1 Pump WELCH 1375
Model 2 Pump PFEIFFER DUO65

Thanks for your help.
 
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These specs indicate coarse vacuum pumps, where the quality of the ultimate vacuum is not that critical.
My guess is other parameters, such as price, size, power use, noise or durability are also factors in the purchase decision.
If those don't matter in your case, then yes there is a factor of 20 difference in the vacuum quality produced by the two pumps.
 
Hi, thanks for replying.

What is the signifance of the curve for the Speed vs the Ultimate Pressure. What does the curve implies?

ie if i found a machine that is running at 20CFM (15 less) but having 1 x 10^-4torr. is that ok?
 
The pump will not exhaust the volume to the ultimate pressure immediately,
A higher CFM rating unit will pump down a volume faster than the lower rated pump, but if you can afford the time, the lower CFM rated pump will serve equally well.
Do note that if you have any sort of a setup where you need to repeatedly access some element that is operating when in vacuum, it can be a real pain to wait for the pumpdown each time you adjust something.
What drives the need for a vacuum?
 

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