Welch DUOSEAL 1399B-01, Руководство пользователя

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2.226 Other Forms of contamination control
The application of the gas ballast is a moderate and very successful method for the removal of condensable
vapors. For very heavily laden systems, other means of removal such as oil separators may be required.
For mild cases of contamination the simple expedient of a cold trap or a change of oil serve the purpose.
2.23 System Leaks - Impact & Detection
2.231 Large Leaks
The importance of eliminating all leaks in a vacuum system is obvious when it is realized that a leak into the
system, at atmospheric pressure, expands in volume by a factor of 750,000 to 10,000,000 or more. The pump
must remove this added volume to maintain the desired vacuum. Fortunately a number of effective techniques
for leak detection have been developed. Large leaks can be located by pressurizing the system and painting the
suspected area with a thick soap solution. Escaping air will produce soap bubbles.
2.232 Small Leaks
Small leaks may also be detected by spraying a suspected area with acetone or gases rich in hydrogen, and
observing a sudden change in pressure on an electrical gauge. The difference in calibration of these gauges, for
air and other gases, will produce a distinct change in the pressure reading. To use this method of detection, the
system must be under vacuum and the gauge sensing tube must be located between the pump and the area to be
probed. Use extreme caution, as these materials are highly flammable!
2.233 Fine Leaks
Locating very fine leaks requires a helium-sensitive, mass-spectrometer leak detector.
This instrument will locate leaks which cannot be detected by any other method.
Numerous fine leaks can have the total effect of a large leak.
2.30 Shutdown Procedures
2.301 DuoSeal Shutdown
A few simple precautions are all that is necessary when shutdown is in order. If a gauge is connected to the
system, first isolate the gauge, then turn off the power and open the system to atmosphere. If the pump is
removed from the system, cover the intake port with a rubber stopper or suitable cover to protect the pump
against contamination and loose particles. If the pump has been contaminated in service and is going to be
shelved for a prolonged period it is best to drain the oil and refill with a fresh charge.