Chapter 7 - System Description
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MNL000301.doc
Revision 2
01/04/2019
SourceSystem TE11
© Versum Materials, Inc. as of the revision and date shown. All rights reserved.
Confidential and Proprietary Data
Page
7
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5
7.3
Auto Switchover System
For automatic switchover to occur, both cylinders must be placed into a "PROCESS GAS FLOW"
mode. Whichever cylinder is started first will begin flow, the other cylinder will wait in a "standby"
state until the cylinder flowing gas is stopped by a “VERY LOW DELIVERY PRESSURE”, “VERY
LOW CYLINDER PRESSURE”, or “VERY LOW CYLINDER WEIGHT” alarm. If a global related
shutdown alarm arises, both cylinders will return to the "IDLE" mode and all pneumatic valves will
close.
Minimum hardware requirements for the automatic switchover system is one dual GASGUARD®
TE11 controller, and two process gas panels sharing the process out piping. Chapter 7 Section 2 on
page 7-4 depicts a two cylinder low pressure auto switchover system. Process gas switchover between
right and left cylinders is initiated by a very low delivery pressure, a very low process gas cylinder
pressure or weight (on liquid cylinders). This switchover set point is set and entered by the customer.
After an automatic switchover has occurred, the low process cylinder can be purged for a cylinder
change while the other cylinder is flowing gas. This cycle is called "PRE-PURGE". When the
automated pre-purge cycles are completed, the "CHANGE CYLINDER" mode must be selected. The
cylinder can physically be removed and replaced during this time. During a cylinder change-out
procedure, sufficient Personal Protective Equipment (PPE) must be worn assuming hazardous process
gas is still present in the pigtail line. See Chapter 1 Section 9 for details on PPE.
With a new cylinder in place, the next step would be "POST-PURGE". Any air which may have
entered the pigtail and valve connection during change out is removed during these purging cycles.
When post-purge is complete, the cylinder can be put into the "PROCESS GAS FLOW" mode again,
which will now place it into standby until the other cylinder is stopped.