Chapter 2: prerequisites – Labconco XPert Weigh Boxes 5220331 User Manual
Page 8
Chapter 2: Prerequisites
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4
Labconco does not recommend hard duct connections to remote blowers
without a thimble due to the air volume balance requirements with such
systems. Hard duct connections should only be used when the glove box
impeller is disconnected and only a single roof-mounted blower is used.
Note that reliance on an external exhaust blower does not provide
airflow control at the glove box.
If a positive internal pressure clean air ISO Class 3 condition (ISO 14644-1)
is desired, the motorized impeller can be rotated to work in positive pressure
mode (see Figure 3-3). See Chapter 7 for the Positive Pressure Conversion
Kit. See the following Negative and Positive Pressure Particle Test data in
the charts below. Both charts show the dilution rates of the glove boxes.
XPert Weigh Box Particle Testing under Negative Pressure
0
24
14
13
11
12
11
11
9
6
4
0
0
60
1
1
1
1
0
0
0
0
0
0
0
0
50
100
150
200
250
300
350
400
450
500
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Time (Minutes)
Nu
mb
er of
Pa
rti
cles
(Per C
u
b
ic M
e
te
r Per M
in
u
te)
> 0.3 Micron
> 0.5 Micron
Airflow Testing Performed at 50 Dial Setting (61 CFM)
with Glove Box Under Negative Pressure.
NOTE: Ambient Air Baseline Particle Count at 1 Minute
294132 Particles measuring 0.3 Micron detected within 1 Minute.
33296 Particles measuring 0.5 Micron detected within 1 Minute.