Heraeus HS 12, Руководство по обслуживанию, Страница: 86 / 282

Service Instructions HERAsafe HS/12/18
Valid: 05.2001 / 50060091 / A
• 57 •
B12 Pressure sensor
Purpose of the adjustment:
Setting of alarm values. The pressure sensor is ad-
justed so that a visible and an audible alarm are trig-
gered when the downflow velocity exceeds a
maximum value or falls below a minimum value.
Apparatus
:
Voltmeter.
Calibration of the apparatus:
The voltmeter must be calibrated in accordance with
the manufacturer’s instructions.
Test area:
Positions of the lowest and of the highest values as
measured during the downflow velocity test (see sec-
tion B6).
Test conditions:
There must be no objects in the safety cabinets work
chamber. The doors and the windows of the room
where the cabinet is located must be closed (no draft).
Perform the adjustment
Lower alarm position:
1. Turn on the unit. The lead-time for the first meas-
urement is 20 minutes.
2. Measure the blower voltage at the control box
terminal strip (see Annex C) and record the value.
3. Install the measuring head at measuring point X
with the lowest value (see section B6).
4. Measure the downflow velocity.
5. Adjust the blower voltage at potentiometer P2 of
the speed controller (see Fig. 3) so that the down-
flow velocity at measuring point
X in zone 1 is
0.24 m/s (47 fpm).
6. Rotate the adjustment wheel until the lower pres-
sure sensor responds and triggers the alarm (with
the hood closed, the lower pressure sensor is at
the lower position in the control box).
B Field tests
Upper alarm position:
6. Install the measuring head at measuring point Y
with the highest value (see section B6).
7. Measure the downflow velocity.
8. Adjust the blower voltage at potentiometer P2 of
the speed controller (see Fig. 3) so that the down-
flow velocity at measuring point
Y in zone 4 is
0.60 m/s (118 fpm).
9. Rotate the adjustment wheel until the upper pres-
sure sensor responds and triggers the alarm (with
the hood closed, the upper pressure sensor is at
the highest position in the control box).
10. Adjust the blower voltage at potentiometer P2 of
the speed controller to the original value.
NOTE - Unit commissioning:
Prior to the commissioning of the unit:
 Perform test run!
 Check safety devices for proper opera-
tion!