B6 Downflow Velocity Test - Heraeus HS 9 Service Manual

B Field tests
B6 Downflow velocity test
Purpose of the test:
This test is performed to check the values of the
downflow velocities (displacement airflow) in the work
area of the safety cabinet.
Apparatus:
Thermal anemometer
Calibration of the apparatus:
The thermal anemometer must be calibrated in accor-
dance with the manufacturer's instructions or IES-RP-
CC-013-86T (Institute of Environmental Sciences, Mt.
Prospect, Illinois).
Accuracy of the apparatus:
Accuracy of ± 0.01 m/s (± 2.00 fpm) or a maximum of
3 % of the indicated velocity.
Test conditions:
There must be no objects in the safety cabinets work
chamber. The doors and windows of the room where
the cabinet is located must be closed (no draft).
Test grid in the work area, Fig. B7:
The cabinet is operated with non-uniform (zoned)
displacement airflow. Therefore, the deviation of the
measured individual values must not exceed 20% of
the average for each zone. The test area consists of a
rectangle that encloses the entire work area and is di-
vided into a grid with a distance B of 11.2 cm (4.4 in).
Minimum size of the grid: 4 rows with 7 measuring
points per row (HS 12) and 11 measuring points per
row (HS18).
The grid should be located at a distance A of 15.2 cm
(6 in) to the two sides C of the cabinet and the back-
panel D of the cabinet.
The test area must be aligned with the front window in
the horizontal and vertical planes.
The anemometer probe must be tightly fixed at the
measuring point to ensure accurate measurements.
Ensure that the distance between the measuring
points is correct; the grid must not be distorted.
Figure B3
Fig. B3, Test area for downflow velocity test
HS 12
HS 18
• 48 •
Service Instructions HERAsafe HS/12/18
6 in 4,4 in 6 in
4,4 in
15.2 cm
11.2 cm 11.2 cm 15.2 cm
B
A B
A
C
Valid: 05.2001 / 50060091 / A
A
D
A