B7 Airflow Pattern Test - Heraeus HS 9 Service Manual

B Field tests
B7 Airflow pattern test
Purpose of the test:
This test is performed to check the displacement air-
flow and to check the cabinet and the front window for
possible leaks. You will check to ensure that the dis-
placement airflow passes along the entire work area,
if the vertical passage is correct, and no air escapes
through joints and seals of the housing and of the
front window.
Testing apparatus:
Smoke tubes.
NOTE – Airflow set points:
The individual test sections for airflow pat-
terns can only be performed when the inflow and the
downflow velocities are at set point.
A. Airflow direction test:
1. Test method, Fig. B5: Set the work opening to a
height of 20 cm (8 in). Scan the work chamber
from one end to the other along the centerline of
the work area. Hold the smoke tube so that its tip
is approximately 15 cm (6 in) above the edge of
the window.
2. Acceptance according to NSF, Annex A: The
smoke shows smooth downward flow with no
dead spots or reflux. No smoke escapes from the
cabinet.
B. Front window retention test:
1. Test method, Fig. B6: Scan the work chamber
from one end to the other 2.5 cm (1 in) behind the
front window by using a smoke tube. Hold the
smoke tube so that its tip is approximately 15 cm
(6 in) above the work opening.
2. Acceptance according to NSF, Annex A: The
smoke shows smooth downward flow with no
dead spots or reflux. No smoke escapes from the
cabinet.
Figure B5 / B6
Fig. B5, Airflow direction test
8 in
Fig. B6, Front window retention test
6 in
• 50 •
Service Instructions HERAsafe HS/12/18
6 in
1 in
Valid: 05.2001 / 50060091 / A