Despatch LCC1-51-3 - Manual (Page 37)

28
HEPA Filter / Magnehelic Pressure Gauge
The LCC Series oven is equipped with a Magnehelic pressure gauge which measures
the pressure in front of the HEPA filter. As the filter becomes dirty, the pressure will
increase. Despatch recommends changing the filter when the pressure is 1” w.c.
greater than when the filter was first installed.
Since the pressure can be affected by many factors involved in the installation, it is
important to record the pressure of a new filter, so that the pressure readings can be
periodically checked against this baseline. The table below is provided for recording
this information.
For a nitrogen atmosphere oven, the pressure reading also gives an indication of the
integrity of the seals. If the pressure recorded in Columns D or E decrease in time, the
oven seals should be inspected.
HEPA Filter Preventative Maintenance Table
A B C D E F
Date Comments Pressure
(inches of
water) *1 Pressure
with:
150 SCFH
(LCC1-16)
200 SCFH
(LCC1-51)
nitrogen
purge *2 Pressure
with:
75 SCFH
(LCC1-16)
150 SCFH
(LCC1-51)
nitrogen
maintain *2 Oven
Temperature
Typical Values 2-3” 1.5-2”
above
value in
column C 0.5-1” above
value in
column C 60°C
Filter first installed.
*1 With Purge and Maintain valves off for a nitrogen atmosphere oven. Cooling fan off for an air
atmosphere oven.
*2 For a nitrogen atmosphere oven only.