Operating Instructions – Labmaster
©
130 and MB20G Systems
Instruction Manual
Chapter 3: Principles of Operation
© MBraun, Inc. Edition 1/2007 Page 3-2
3.3 Purging the System
Purging the glovebox replaces the ambient air inside the box with the working gas by providing
a constant flow of working gas into and out of the box. The purge function can be performed
either manually by the user or automatically by the system. The automatic or “quick purge”
function is not included with all systems but is an available option that can be purchased at any
time after the glovebox has been installed and/or running for any period of time.
As a general guideline a system should be purged when the oxygen level inside the box
exceeds 100ppm. Possible reasons for an elevated oxygen level are:
• Initial commissioning of the system;
• Recent service or repair made to the system;
• Room atmosphere entering the box due to improper use;
• Leaks in the system or other damage (e.g. torn gloves, etc.).
The purging process can be performed three (3) different ways:
Reverse Purge
Performed on systems with no manual purge valve or automatic purge
function. This can also be performed on systems with either of the
mentioned options if the user chooses to do so.
The Reverse Purge method purges the working gas directly into the
user’s room environment, use caution when working in the vicinity of
a glovebox undergoing reverse purge.
Manual Purge
Performed on systems with a manual purge valve located on the top of
the glovebox system. This valve should be vented to a fume hood or
facility exhaust system.
Automatic Purge
Performed on systems with this function incorporated into the PLC
program via the VSA valve. This valve should be vented to a fume hood
or facility exhaust system.
Both reverse purge and manual purge procedures require the user to enter box pressure
setpoints in the PLC prior to beginning operation. The automatic purge function does not require
any parameters to be set prior to beginning the operation.
Purge time and gas consumption varies and is based on glovebox volume and the level of purity
required in the glovebox.
Figure 1 - Purge Gas Consumption
Figure 1 above shows that a desired box atmosphere purity of 10ppm requires approximately
14.50m³ of purge gas per cubic meter of box volume (refer to the Box Volume Table below):
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