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#1 - Pumpdown
Curves as a Diagnostic Tool
Pumpdown curves can be a useful tool for diagnosing vacuum system problems. The
collection, use, and interpretation of pumpdown curves are discussed and
explained.
Pumpdown Curves as a Diagnostic Tool (.pdf file)
#2 -
Rate-of-Rise Curves as a Diagnostic Tool
Rate-of-rise curves can be a powerful surveillance and diagnostic tool for
vacuum problems. When used either alone or in consort with pumpdown curves, they
can provide early warning of incipient vacuum problems and can help diagnose
those problems. Interpretation and collection of the curves are discussed and
explained. [top of list]
Rate-of-Rise Curves
as a Diagnostic Tool (.pdf file)
#3 - Gas Loads
from Elastomer and Metal Seals
Elastomer and metal gaskets are both in common use today. Each has its benefits
and uses. An analysis of the mechanisms for gas loads from elastomer seals in
terms of outgassing and atmospheric permeation is presented. Practical
considerations and comparisons are provided to help make the elastomer vs. metal
decision. [top of list]
Gas Loads from
Elastomer and Metal Seals (.pdf file)
#4 - Sorting
Out the Turbo, Drag, and Turbo/Drag Pump Family
Turbomolecular, molecular drag, and turbo/drag pumps can be classified as a
family. Although each type, within the family, is different, it is not always
clear which is which when looking at manufacturers' literature. The difference
is discussed and explained in terms of pumping mechanism, application, and
roughing/backing requirements.
[top of list]
Sorting
Out the Turbo, Drag, and Turbo/Drag Pump Family (.pdf file)
#5 - Knowing
Your Effective Pumping Speed
The effective speed of a
vacuum pump is the actual speed at the chamber. The importance of pumping speed
in meeting gas loads is discussed. The effects of pumping speed losses through
connecting tubulation in terms of conductance is shown. Simple methods for
calculating both conductance and effective pumping speed are presented.
[top of list]
Knowing
Your Effective Pumping Speed (.pdf file)
#6 - Dry Gas
Techniques for Reducing Water Vapor in Vacuum Systems
The desorption of water
vapor in vacuum systems is a constant and troublesome problem. The effects of
desorption, evidenced by long pumpdown times, can be partially overcome by using
various techniques involving dry gas in the chamber. The techniques and effects
are explained and discussed.
[top of list]
Dry Gas Techniques
for Reducing Water Vapor in Vacuum Systems (.pdf file)
#7 - The
Difference Between Volume and Mass Flow
A certain amount of
confusion exists in vacuum technology that can be traced to misunderstandings
regarding the difference between volume and mass flow. The differences and their
relative importance to the Q=SP relationship are discussed and explained.
[top of list]
The Difference Between Volume and Mass Flow (.pdf file)
#8 -
Understanding Virtual Leaks
The presence of virtual
leaks can be a major problem in the performance of vacuum systems. Understanding
what virtual leaks are and how they result in detrimental effects is discussed
and presented. The practical techniques of eliminating them or minimizing their
effects are given for both new designs and in existing systems.
[top of list]
Understanding Virtual Leaks (.pdf file)
#9 - Oil-Sealed
Pumps and Backstreaming
Although there is a
continuing trend toward replacing oil-sealed mechanical pumps with oil-free
pumps, replacement is not always necessary. In order to make a decision, it's
necessary to understand the source(s) and mechanisms of oil backstreaming from
oil-sealed pumps. The sources and types of oil contamination are explained and
discussed along with techniques to eliminate or reduce backstreaming.
[top of list]
Oil-Sealed Pumps
and Backstreaming (.pdf file)
#10 -
Backstreaming Traps for Oil-Sealed Pumps
The use of traps to deal
with the oil backstreaming from oil-sealed mechanical pumps can be dan
acceptable solution or a potential disaster. In order to make the go/no go
decision on their use, it is necessary to understand their trapping mechanisms
along with what can go wrong if they are misunderstood or misused. Application
advantages and penalties are discussed.
[top of list]
Backstreaming Traps for Oil-Sealed Pumps (.pdf file)
#11 - Recent
Advances in Vacuum Sealing Techniques
Advances in vacuum
technology often proceed in an irregular fashion. Sealing techniques have been
relatively static for some years, but new advances have recently been introduced
to overcome the problems found with oil-rings. One is a metal seal that directly
replaces ISO-KF/MF O-ring seals. Another is a totally gasketless sealing system.
Their application is discussed.
[top of list]
Recent Advances in Vacuum Sealing Techniques (.pdf file)
#12 - The
Vacuum Chamber: Volume or Surface Area?
Vacuum chambers are often
configured during the design stage to keep the volume as low as possible. This
consideration is usually applied under the assumption that this will reduce the
gas load and result in faster
pumpdown. In fact, the surface area is the most
important consideration. The source(s) of both surface and volume gas loads are
discussed and explained. [top
of list]
The
Vacuum Chamber: Volume or Surface Area? (.pdf file)
#13 - Crossover
Pressure and Cryopumping
The crossover pressure from
roughing pump to cryopump is often assumed to be as low a roughing pressure as
possible in order to reduce the amount of gas condensed within the cryopump in
the belief that this will extend the time between required regenerations. In
fact, the maximum crossover pressure listed in the manufacturers' data sheets is
actually the most ideal pressure. This concept is discussed and explained.
[top of list]
Crossover Pressure and Cryopumping (.pdf file)
#14 - Gas Loads
and O-Rings
Careful consideration and
understanding of gas loads from O-rings are important in understanding the
behavior of vacuum systems.
[top of list]
Gas
Loads and O-Rings (.pdf file)
#15 - Sources
of Water Vapor in Vacuum Systems
Water vapor is a major
problem in vacuum technology, but understanding its sources is a key to
improving system performance.
[top of list]
Sources
of Water Vapor in Vacuum Systems (.pdf file)
#16 - How To
Assess Gas Loads in Vacuum System Design
A practical technique for
assessing quantitative values for
gas loads. [top of list]
How
To Assess Gas Loads in Vacuum System Desing (.pdf file)
#17 - How To
Choose a Diaphragm Pump
Understanding how diaphragm
pumps work can help apply
them properly. [top of list]
How To Choose a
Diaphragm Pump (.pdf file)
#18 - How To
Match Pumping Speed to Gas Load
Determining and
understanding a vacuum system's gas loads and pumping speed will provide the key
to designing or understanding the performance of any vacuum system.
[top of list]
How
To Match Pumping Speed to Gas Load (.pdf file)
#19 - Gas Loads
in Vacuum Systems
Using "gas load thinking"
when considering vacuum problems streamlines the trouble-shooting process.
[top of list]
Gas Loads in Vacuum Systems (.pdf file)
#20 - Creating
a Vacuum
What really happens within
a vacuum chamber as it's pumped down to create a vacuum environment.
[top of list]
Creating a
Vacuum (.pdf file)
#21 - Why
Create a Vacuum?
Creating a vacuum in terms
of the physical and chemical properties of a device or process.
[top of list]
Why Create
a Vacuum? (.pdf file)
#22 - Desorbing
Water in Vacuum System: Bakeout or UV?
Shorter pumpdown times or lower pressures can be achieved
by using either bakout or UV energy to desorb water vapor. Here's how to make
the choice.
[top of list]
Desorbing Water in
Vacuum System: Bakeout or UV? (.pdf file)
#23 - How To
Use Getters and Getter Pumps
Getter pumping can be an
important addition to many vacuum processes if properly understood and applied.
[top of list]
How To Use Getters and
Getter Pumps (.pdf file)
#24 - How To
Use the Q=SP Fundamental Vacuum Relationship
Using and understanding
vacuum technology's fundamental relationship
can be a vital and practical tool
in applying vacuum technology to your process.
[top of list]
How To Use the Q=SP
Fundamental Vacuum Relationship (.pdf file)
#25 - How To
Choose a Roughing/Backing Pump for the Turbo and Drag Family
Choosing the right
roughing/backing pump is as important as choosing the right high vacuum pump.
The simple process of working through the pump's operating parameters will
assure a successful installation.
[top of list]
How To Choose a
Roughing/Backing Pump for the Turbo and Drag Family (.pdf file)
#26 -
Contamination in Vacuum Systems: Sources and Remedies
Contamination can be
scourge of any vacuum process. Learning how to detect and avoid contamination
can lead to cleaner and more productive vacuum processes.
[top of list]
Contamination in Vacuum
Systems: Sources and Remedies (.pdf file)
#27 - The
Effects of Humidity on Vacuum System Performance
Humidity is the source of
most of the water vapor problems encountered
in vacuum technology. You can't
fight a war unless you know your
enemy. [top of list]
The Effects of Humidity
on Vacuum System Performance (.pdf file)
#28 - Making
the Oil-Sealed vs. Oil-Free Decision
Oil-free pumps can be a
solution to oil contamination problems, but the decision to use them or not is
complex. Working through the decision process requires a simple analysis of the
options available. [top of
list]
Making the Oil-Sealed
vs. Oil-Free Decision (.pdf file)
#29 - Molecular
Flux Provides Process Understanding
Many process problems can
be hidden when pressure is the only parameter monitored, but considering and
understanding the flux of gas molecules through a process chamber can reveal
effects that can make or break a process.
[top of list]
Molecular Flux Provides
Process Understanding (.pdf file)
#30 - Vacuum
Envelope Penetration
All vacuum systems are
subject to penetration by atmospheric gases
due to leaks or permeation of the
materials of construction. It is
important to understand the differences between
these two different problems.
[top of list]
Vacuum Envelope
Penetration (.pdf file)
#31 - Matching
Vacuum Pump to Process
Choosing the best pump for
a vacuum process can be a daunting
experience, but a systematic review of the
process requirements and the performance parameters of the available pumps can
help make the best choice. [top
of list]
Matching Vacuum Pump to
Process (.pdf file)
#32 -
Diagnosing Vacuum Problems with Pumpdown and Rate-of-Rise Curves
Pumpdown and rate-of-rise
curves can provide simple tools to monitor and diagnose a system's performance
and problems. [top of list]
Diagnosing Vacuum
Problems with Pumpdown and Rate-of-Rise Curves (.pdf file)
#33 - Pumping
Water Vapor
Water vapor pumping presents problems to all vacuum
processes, and pumping it requires careful understanding in order to achieve
full pumpdown efficiency and performance.
[top of list]
Pumping Water Vapor
(.pdf file)
#34 - Vacuum
Requirements for Cryogenic Vessels
Applying vacuum technology
to cryogenic dewars and transfer
lines. [top of list]
Vacuum Requirements for
Cryogenic Vessels (.pdf file)
#35 -
Understanding Pressure and Measurement
Pressure is an
important component of the Q=SP fundamental vacuum relationship, but it means
much more in practice and application. [top of list]
Understanding Pressure and
Measurement (.pdf file)
#36 -
Choosing the Right Vacuum Materials
An in-depth
review of each and every material exposed to the vacuum system is absolutely
essential to ensure a successful system design. [top of list]
Choosing the Right Vacuum
Materials (.pdf file)
#37 - Will
RGAs Replace Ion Gauges?
Pressure
measurement in high vacuum can be important, but is an ion gauge good enough, or
do you need a residual gas analyzer? [top of list]
Will RGAs Replace Ion
Gauges? (.pdf file)
#38 -
Solving Process Problems at the Molecular Flux Level
Working from
pressure readings alone can mislead and misdirect a search for process problems,
but reaching down a layer further into the molecular flux level can provide real
solutions. [top of list]
Solving Process Problems at
the Molecular Flux Level (.pdf file)
#39 -
Matching Cryopumping Techniques to Application
Cryopumps and
cryopumping have become fairly ubiquitous in vacuum technology. There are many
variations within the category, and it is necessary to understand the variations
in order to achieve the best practical results. [top of list]
Matching Cryopumping
Techniques to Application (.pdf file)
#40 -
Pumping Speed in the Drydown Zone
The extended
pumpdown time through the water vapor-dominated drydown zone is a complex
process that can be dissected to show that it is only partially dependent upon
pumping speed. [top of list]
Pumping Speed in the
Drydown Zone (.pdf file)
#41 -
Bending the Rules: When the Vacuum Rules Get in the Way, Careful Analysis Allows
Rule Bending
Vacuum technology has
many fixed rules, but when the application requires the rules to be bent,
careful analysis of the rules and application will often allow the rules to be
worked around. [top of list]
Bending the Rules (.pdf
file)
#42 -
The Use and Misuse of O-Rings
Elastomer
O-ring seals are commonly used to provide demountable vacuum seals. The proper
choice of material, installation, and handling are key to a successful vacuum
design. [top of list]
The Use and Misuse of
O-Rings (.pdf file)
#43 -
Anatomy of a Pumpdown
Dividing a pumpdown
curve into zones that reflect the actual gases being pumped within the zones is
a useful technique for sorting out problems and solutions. [top of list]
Anatomy of a Pumpdown (.pdf
file)
#44 -
Sealing Materials Require a Careful Choice
Elastomer and metal
seals each have thier attendant advantages and disadvantages, but it is not
always necessary to use either one exclusively. If the application is carefully
considered, a mixed installation can be the best decision. [top of list]
Sealing Materials Require a
Careful Choice (.pdf file)
#45 -
Thermal Conductivity Gauges
Thermal conductivity
pressure gauges are extremely common in vacuum technology, but an understanding
of their principles of measurement and operation can help in their proper
application. [top of list]
Thermal Conductivity Gauges
(.pdf file)
#46 -
Nitpicking Your Vacuum System
Detailed system
analysis is a painful process that can make all the difference between a
successful design or a total failure. It's all a question of mindset. [top of list]
Nitpicking Your Vacuum
System (.pdf file)
#47 – UV
Conquers the Drydown Zone
All vacuum systems
encounter the drydown zone where the slow desorption of water vapor
controls the system’s pumpdown performance. Powered desorption by UV radiation
can shorten the pumpdown time substantially. [top of list]
UV Conquers the Drydown
Zone(.pdf file)
#48
–Understanding the Effects of Air Exposure
All vacuum systems
are subject to the buildup of water vapor on surfaces during air exposure. It’s
now possible to quantify and compare the amount of water buildup under varying
conditions of exposure. [top of list]
Understanding the Effects
of Air Exposure(.pdf file)
#49 –
Pumpdown Effects of Water Vapor Buildup
The pumpdown
performance in traversing the drydown zone can be quantified by calculating the
monolayers of adsorbed water molecules and determining the subsequent desorption
rate graphically. [top of list]
Pumpdown Effects of Water
Vapor Buildup(.pdf file)
#50 –
Gas Purge Solutions to Oil and Water Contamination Problems
Contamination
problems can be solved or avoided by special gas purging of the system and/or
pumping lines during operation. [top of list]
Gas Purge Solutions to Oil
and Water Contamination Problems(.pdf file)
#51 –
Pumping Specific Gases in High Vacuum
There’s more to
planning and designing a vacuum process pumping system than just maximizing
pumping speed. Matching the pumping performance of each discrete gas species
encountered will ensure maximum pumping performance. [top of list]
Pumping Specific Gases in
High Vacuum(.pdf file)
#52 –
Conditioning Vacuum Chambers
Confronting a high
gas load from a new or newly cleaned vacuum chamber can be daunting, but there
are some simple techniques for bringing it into normal condition. [top of list]
Conditioning Vacuum
Chambers(.pdf file)
