(continued from page 1)
Deeper vacuums can complete air removal with fewer sequences. When dealing
with a vacuum-resistant product, one vacuum from atmospheric (14.7 psia) to 2.0
psia, followed by a nitrogen backfill to 14.7 psia, will quickly reduce the %volair
to 13.6% (Table I). Products that can withstand this rate and depth of vacuum
will usually tolerate an equally rapid nitrogen injection. Fast ramp rates for
nitrogen backfilling also minimize product-level moisture loss.
| Process Phase |
Cycle Segment |
Set Point (in. HgA) |
Set Point (psia) |
Ramp Rate (psi/min) |
Segment Time (min) |
Cumulative Cycle Time (min) |
| Cycle start | 29.9 | 14.7 | N/A | N/A | 0.0 | |
| Air removal | Evacuation 1 | 4.1 | 2.0 | 1.00 | 12.7 | 12.7 |
| Nitrogen purge 1 | 29.9 | 14.7 | 1.00 | 12.7 | 25.4 | |
| Evacuation 2 | 4.1 | 2.0 | 1.00 | 12.7 | 38.1 | |
| Humidification | Steam injection | 6.3 | 3.1 | 0.02 | 55.0 | 93.1 |
| EtO inject | EtO injection | 17.9 | 8.8 | 0.20 | 28.5 | 121.6 |
| Nitrogen overlay | 29.5 | 14.5 | 0.20 | 28.5 | 150.1 | |
| Gas contact | 29.5 | 14.5 | 0.00 | 480.0 | 630.1 | |
| EtO removal | Postevacuation #1 | 4.1 | 2.0 | 1.00 | 12.5 | 642.6 |
| Nitrogen flush #1 | 29.9 | 14.7 | 1.00 | 12.7 | 655.3 | |
| Postevacuation #2 | 4.1 | 2.0 | 1.00 | 12.7 | 668.0 | |
| Nitrogen flush #2 | 29.9 | 14.7 | 1.00 | 12.7 | 680.7 | |
| Postevacuation #3 | 4.1 | 2.0 | 1.00 | 12.7 | 693.4 | |
| Final air inbleed | 29.9 | 14.7 | 1.00 | 12.7 | 706.1 | |
| Total cycle time (min) | 706.1 | 706.1 |
| Process Phase |
Cycle Segment |
Partial Pressure Air (psi) |
Partial Pressure Inerts (psi) (nitrogen and steam) |
Partial Pressure EtO (psi) |
Total Partial Pressures (psia) |
| Cycle start | 14.70 | 0.00 | 0.00 | 14.70 | |
| Air removal | Evacuation 1 | 2.00 | 0.00 | 0.00 | 2.00 |
| Nitrogen purge 1 | 2.00 | 12.70 | 0.00 | 14.70 | |
| Evacuation 2 | 0.27 | 1.73 | 0.00 | 2.00 | |
| Humidification | Steam injection | 0.27 | 2.83 | 0.00 | 3.10 |
| EtO inject | EtO injection | 0.27 | 2.83 | 5.70 | 8.80 |
| Nitrogen overlay | 0.27 | 8.53 | 5.70 | 14.50 | |
| Gas contact | 0.27 | 8.53 | 5.70 | 14.50 | |
| EtO removal | Postevacuation #1 | 0.04 | 1.18 | 0.79 | 2.00 |
| Nitrogen flush #1 | 0.04 | 13.88 | 0.79 | 14.70 | |
| Postevacuation #2 | 0.01 | 1.89 | 0.11 | 2.00 | |
| Nitrogen flush #2 | 0.01 | 14.59 | 0.11 | 14.70 | |
| Postevacuation #3 | 0.00 | 1.98 | 0.01 | 2.00 | |
| Final air inbleed | 12.70 | 1.98 | 0.01 | 14.70 | |
| Total cycle time (min) |
| Process Phase |
Cycle Segment |
%Volume Air |
%Volume Inerts (nitrogen and steam) |
%Volume EtO |
%Volume Total |
| Cycle start | 100.00 | 0.00 | 0.00 | 100.00 | |
| Air removal | Evacuation 1 | 100.00 | 0.00 | 0.00 | 100.00 |
| Nitrogen purge 1 | 13.61 | 86.39 | 0.00 | 100.00 | |
| Evacuation 2 | 13.61 | 86.39 | 0.00 | 100.00 | |
| Humidification | Steam injection | 8.78 | 91.22 | 0.00 | 100.00 |
| EtO inject | EtO injection | 3.09 | 32.14 | 64.77 | 100.00 |
| Nitrogen overlay | 1.88 | 58.81 | 39.31 | 100.00 | |
| Gas contact | 1.88 | 58.81 | 39.31 | 100.00 | |
| EtO removal | Postevacuation #1 | 1.88 | 58.81 | 39.31 | 100.00 |
| Nitrogen flush #1 | 0.26 | 94.40 | 5.35 | 100.00 | |
| Postevacuation #2 | 0.26 | 94.40 | 5.35 | 100.00 | |
| Nitrogen flush #2 | 0.03 | 99.24 | 0.73 | 100.00 | |
| Postevacuation #3 | 0.03 | 99.24 | 0.73 | 100.00 | |
| Final air inbleed | 86.40 | 13.50 | 0.10 | 100.00 | |
| Total cycle time (min) |
In the case of a vacuum-sensitive product, such as a kit containing multiple
devices, the air-removal phase could require multiple slow vacuums—down to 7.0
psia, for example. The first vacuum/nitrogen sequence will only bring the %volair
from 100% down to 47.62% (Table II). In this case, the process engineer must
consider that the desiccating effect inherent in this process is further
amplified. Multiple vacuum/nitrogen injections coupled with slow ramp rates mean
that there is more time for moisture to be driven out of the load by the induced
pressure gradient. Water becomes more volatile as temperature is increased and
pressure is decreased. In these circumstances, one must begin the
steam-injection phase as soon as possible in order to replace some of the
moisture lost during the multiple slow-vacuum phases.
| Process Phase |
Cycle Segment |
Set Point (in.HgA) |
Set Point (psia) |
Ramp Rate (psi/min) |
Segment Time (min) |
Cumulative Cycle Time (min) |
| Cycle start | 29.9 | 14.7 | N/A | N/A | 0.0 | |
| Air removal | Evacuation 1 | 14.3 | 7.0 | 0.25 | 30.8 | 30.8 |
| Nitrogen purge 1 | 29.9 | 14.7 | 0.25 | 30.8 | 61.6 | |
| Evacuation 2 | 14.3 | 7.0 | 0.25 | 30.8 | 92.4 | |
| Nitrogen purge 2 | 29.9 | 14.7 | 0.25 | 30.8 | 123.2 | |
| Evacuation 3 | 14.3 | 7.0 | 0.25 | 30.8 | 154.0 | |
| Nitrogen purge 3 | 29.9 | 14.7 | 0.25 | 30.8 | 184.8 | |
| Evacuation 4 | 14.3 | 7.0 | 0.25 | 30.8 | 215.6 | |
| Nitrogen purge 4 | 29.9 | 14.7 | 0.25 | 30.8 | 246.4 | |
| Evacuation 5 | 14.3 | 7.0 | 0.25 | 30.8 | 277.2 | |
| Humidification | Steam injection | 16.5 | 8.1 | 0.02 | 55.0 | 332.2 |
| EtO inject | EtO injection | 28.1 | 13.8 | 0.20 | 28.5 | 360.7 |
| Nitrogen overlay | 29.5 | 14.5 | 0.20 | 3.5 | 364.2 | |
| Gas contact | 29.5 | 14.5 | 0.00 | 480.0 | 844.2 | |
| EtO removal | Postevacuation #1 | 14.3 | 7.0 | 0.25 | 30.0 | 874.2 |
| Nitrogen flush #1 | 29.9 | 14.7 | 0.25 | 30.8 | 905.0 | |
| Postevacuation #2 | 14.3 | 7.0 | 0.25 | 30.8 | 935.8 | |
| Nitrogen flush #2 | 29.9 | 14.7 | 0.25 | 30.8 | 966.6 | |
| Postevacuation #3 | 14.3 | 7.0 | 0.25 | 30.8 | 997.4 | |
| Nitrogen flush #3 | 29.9 | 14.7 | 0.25 | 30.8 | 1028.2 | |
| Postevacuation #4 | 14.3 | 7.0 | 0.25 | 30.8 | 1059.0 | |
| Nitrogen flush #4 | 29.9 | 14.7 | 0.25 | 30.8 | 1089.8 | |
| Postevacuation #5 | 14.3 | 7.0 | 0.30 | 30.8 | 1120.6 | |
| Final air inbleed | 29.9 | 14.7 | 0.25 | 30.8 | 1151.4 | |
| Total cycle time (min) | 1151.4 | 1151.4 |
| Process Phase |
Cycle Segment |
Partial Pressure Air (psi) |
Partial Pressure Inerts (psi) (nitrogen and steam) |
Partial Pressure EtO (psi) |
Total Partial Pressures (psia) |
| Cycle start | 14.70 | 0.00 | 0.00 | 14.70 | |
| Air removal | Evacuation 1 | 7.00 | 0.00 | 0.00 | 7.00 |
| Nitrogen purge 1 | 7.70 | 0.00 | 14.70 | 47.62 | |
| Evacuation 2 | 3.33 | 3.67 | 0.00 | 7.00 | |
| Nitrogen purge 2 | 3.33 | 11.37 | 0.00 | 14.70 | |
| Evacuation 3 | 1.59 | 5.41 | 0.00 | 7.00 | |
| Nitrogen purge 3 | 1.59 | 13.11 | 0.00 | 14.70 | |
| Evacuation 4 | 0.76 | 6.24 | 0.00 | 7.00 | |
| Nitrogen purge 4 | 0.76 | 13.94 | 0.00 | 14.70 | |
| Evacuation 5 | 0.36 | 6.64 | 0.00 | 7.00 | |
| Humidification | Steam injection | 0.36 | 7.74 | 0.00 | 8.10 |
| EtO inject | EtO injection | 0.36 | 7.74 | 5.70 | 13.80 |
| Nitrogen overlay | 0.36 | 8.44 | 5.70 | 14.50 | |
| Gas contact | 0.36 | 8.44 | 5.70 | 14.50 | |
| EtO removal | Postevacuation #1 | 0.17 | 4.07 | 2.75 | 7.00 |
| Nitrogen flush #1 | 0.17 | 11.77 | 2.75 | 14.70 | |
| Postevacuation #2 | 0.08 | 5.61 | 1.31 | 7.00 | |
| Nitrogen flush #2 | 0.08 | 13.31 | 1.31 | 14.70 | |
| Postevacuation #3 | 0.04 | 6.34 | 0.62 | 7.00 | |
| Nitrogen flush #3 | 0.04 | 14.04 | 0.62 | 14.70 | |
| Postevacuation #4 | 0.02 | 6.68 | 0.30 | 7.00 | |
| Nitrogen flush #4 | 0.02 | 14.38 | 0.30 | 14.70 | |
| Postevacuation #5 | 0.01 | 6.85 | 0.14 | 7.00 | |
| Final air inbleed | 7.71 | 6.85 | 0.14 | 14.70 | |
| Total cycle time (min) |
| Process Phase |
Cycle Segment |
%Volume Air |
%Volume Inerts (nitrogen and steam) |
%Volume EtO |
%Volume Total |
| Cycle start | 100.00 | 0.00 | 0.00 | 100.00 | |
| Air removal | Evacuation 1 | 100.00 | 0.00 | 0.00 | 100.00 |
| Nitrogen purge 1 | 52.38 | 0.00 | 100.00 | 7.00 | |
| Evacuation 2 | 47.62 | 52.38 | 0.00 | 100.00 | |
| Nitrogen purge 2 | 22.68 | 77.32 | 0.00 | 100.00 | |
| Evacuation 3 | 22.68 | 77.32 | 0.00 | 100.00 | |
| Nitrogen purge 3 | 10.80 | 89.20 | 0.00 | 100.00 | |
| Evacuation 4 | 10.80 | 89.20 | 0.00 | 100.00 | |
| Nitrogen purge 4 | 5.14 | 94.86 | 0.00 | 100.00 | |
| Evacuation 5 | 5.14 | 94.86 | 0.00 | 100.00 | |
| Humidification | Steam injection | 4.44 | 95.56 | 0.00 | 100.00 |
| EtO inject | EtO injection | 2.61 | 56.09 | 41.30 | 100.00 |
| Nitrogen overlay | 2.48 | 58.21 | 39.31 | 100.00 | |
| Gas contact | 2.48 | 58.21 | 39.31 | 100.00 | |
| EtO removal | Postevacuation #1 | 2.48 | 58.21 | 39.31 | 100.00 |
| Nitrogen flush #1 | 1.18 | 80.10 | 18.72 | 100.00 | |
| Postevacuation #2 | 1.18 | 80.10 | 18.72 | 100.00 | |
| Nitrogen flush #2 | 0.56 | 90.52 | 8.91 | 100.00 | |
| Postevacuation #3 | 0.56 | 90.52 | 8.91 | 100.00 | |
| Nitrogen flush #3 | 0.27 | 95.49 | 4.24 | 100.00 | |
| Postevacuation #4 | 0.27 | 95.49 | 4.24 | 100.00 | |
| Nitrogen flush #4 | 0.13 | 97.85 | 2.02 | 100.00 | |
| Postevacuation #5 | 0.13 | 97.85 | 2.02 | 100.00 | |
| Final air inbleed | 52.44 | 46.60 | 0.96 | 100.00 | |
| Total cycle time (min) |
A comparison of the two cycles illustrated in Tables I and II shows that the deep-vacuum cycle completes the air-elimination phase and arrives at the start of steam injection in 38.1 minutes, whereas the shallow-vacuum cycle requires 277.2 minutes.
Click Here to Proceed to Page 3, Steam Injection and Conditioning Dwell