virtual leak

virtual leak

[′vər·chə·wəl ′lēk]
(engineering)
The semblance of the vacuum system leak caused by a gradual desorptive release of gas at a rate which cannot be accurately predicted.
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References in periodicals archive ?
The IR radiation will heat the internal surfaces and desorb the adsorbed contaminants, especially water vapor, and provide enough heat to drive contaminants out of the surface oxide layer, pores, cracks, and virtual leak traps.
Returning a chamber to full: 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
For example, a blind-tapped-hole virtual leak can be relieved by providing a drilled-through hole along the screw's longitudinal axis.
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
The ball valve has never been considered a good choice because of inherent virtual leak possibilities, stem leaks, and gas entrapment.
How to Choose a Valve
2] filling virtual leak voids and barring water diffusion into those voids due to the small [N.
Fight Humidity in Your Vacuum System
2] instead of air is more a function of pre-filling the virtual leak voids with water-free gas.
Reduce Water Vapor in Vacuum Systems
In this situation, a leaking front seat could create a virtual leak.
Ball Valves Are Durable And Easy to Maintain
A virtual leak is caused by entrapped air within the vacuum system, commonly between two mating metal surfaces that are not welded or brazed.
Design away those tough vacuum system riddles
Thermal effects create virtual leaks that must be compensated for by test methods to achieve the failsafe leak test standard.
Five steps to leak-proof testing success
O-ring grooves often provide dead volumes that can trap gases and become virtual leaks.
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
Pockets of gas trapped within the confines of the vacuum chamber are usually referred to as virtual leaks, but this term is used only because they can easily be mistaken for real leaks.
Vacuum Envelope Penetration
Internal virtual leaks also provide a useful example in that pockets of active gas can result in gas-process reactions that are never detected by the gauges.
Molecular Flux Provides Process Understanding
Although this problem is avoided with UV energy, which will flood the whole chamber, the UV energy will not penetrate into the trapped volume of virtual leaks or reach the surfaces of O-rings recessed between flanges.
Desorbing Water in Vacuum Systems: Bakeout or UV?

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