Table 2. hepa filter pressure reading worksheet – Despatch Stackable LCC/LCD-4 User Manual

Page 20

HEORY OF

PERATION

Stackable LCC/LCD Oven

Owner’s Manual

Version 1.1

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retrieval systems without the written permission of Despatch Industries, unless for purchaser's personal use.

recommends changing the filter when the pressure is 1” w.c. greater than when the filter was first
installed (Refer to section 4.3 for filter replacement).

Since pressure can be affected by many factors involved in the
installation, it is important to record the pressure of a new filter as
a baseline. Recorded pressure readings allow for new readings to
be periodically checked against this baseline. Use Table 2 for
recording this information (See Section 8.1 for a blank
worksheet).

For a nitrogen atmosphere oven, pressure readings also give an
indication of the integrity of the seals. If the pressure recorded in
Columns D or E decrease over time, inspect the oven seals.

Table 2. HEPA Filter Pressure Reading Worksheet.

Date

Comments

Pressure
(inches of
water)

Pressure with:
150 SCFH (LCC1-
16); 200 SCFH
(LCC1-51) nitrogen
purge

Pressure with:
75 SCFH (LCC1-
16); 150 SCFH
(LCC1-51) nitrogen
maintain

Oven
Temperature

Typical
Values

3”

1.5-

2” above value

in Column C

0.5-

1” above value

in Column C

60°C

Filter first
installed

With Purge and Maintain valves off for a nitrogen atmosphere oven. Cooling fan off for an air

atmosphere oven.

For a nitrogen atmosphere oven only.

Figure 4. Magnehelic Pressure
Gauge Measures Pressure in front of
the HEPA filter.