40
41
1158 Flushing Stage
An exposure assessment should be conducted to determine appropriate Flushing and Aeration parameter set points The Flushing stage and Aeration stage are typically necessary for removing
ethylene oxide (EO) from the chamber, packaging, and load materials
Removal of EO from the chamber and the load depends on multiple factors, including but not limited to: material composition of the load, the size of the load, the temperature and time, and the
parameters set in the Flushing stage and Aeration stage
The preprogrammed cycle parameters for the Flushing stage are the set points that populate the 3M™ Cycle Programmer when creating a new cycle
Note:
Use of preprogrammed cycle set points for the Flushing stage also requires assessment on each custom cycle for validating that facility procedures meet national, state, and local
requirements for short term exposure limits (STELs) and long term exposure limits (LTELs)
•
Number of flushing cycles
is the number of fresh air purges and complete vacuums performed for the Flushing stage
•
Vent rate
is the rate that filtered air is allowed into the chamber raising the pressure while proceeding to the flushing
Hold time: Top
set point (see Figure 48) Four (4) vent rates are
available; 100%, 75%, 50% and 25% The
vent rate
programmed will apply for all programmed flushing cycles Vent rate is controlled by the percentage of time the vent valve is energized
and opened to the chamber
• A
Vent rate
set point of 100% is the fastest pressure rise rate The vent valve is open to chamber 100% of the time until the programmed flushing hold time: top is satisfied The
preprogrammed cycle vent rate is 100%
• A
Vent rate
set point of 25% is the slowest rate in which the vent valve is open to chamber 25% of the time until the programmed flushing hold time: top is satisfied
•
Hold time: Top
is the amount of time the vent will remain open while the vacuum draws air through the chamber The Hold time: Top timer starts after Hold time: Bottom is complete A set
point of one minute will produce a sharp transition to the next programmed flushing cycle (Figure 48) A longer Hold time: Top set point will produce a gradual transition to equilibrium of air
flowing thorough the chamber, several mBar (kPa) below atmosphere, until the Hold time: Top duration is satisfied and the cycle proceeds to the next programmed flushing cycle (Figure 48)
•
Vacuum level
is the target chamber pressure for each flushing cycle
•
Hold time: Bottom
is the duration the chamber will hold parameters constant after the vacuum level is attained (Figure 48)
•
Locked aeration time
is the amount of aeration the cycle will perform prior to allowing Operator or Supervisor access to the chamber
•
No exhaust hood aeration time
is the minimum amount of aeration the cycle will perform, prior to allowing an Operator or Supervisor access to the chamber, if the exhaust hood option is
not enabled or if the required air flow is not adequate through the exhaust hood
8. Flushing
5
2
99
Maximum
Set Point
Minimum
Parameter
Number of flushing cycles
Units
25
Vent rate
100
%
Hold time: Top
4
300
0
90
180
1
99
min
mbar
Vacuum level
100
100
300
Hold time: Bottom
0
99
min
Locked aeration time
0
999
min
No exhaust hood aeration time
0
999
min
25
Vacuum rate
100
%
100
Figure 47
Flushing Stage
