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 CASE M11 - Selection of Filters - Breathing Air System, R. Johnston
Problem: Incorrect piping of Pall Trinity particulate filters in breathing
air systems.
Symptoms:
Excessive pressure drop; premature failure of filter elements.
Collection of Facts: Pall Trinity produces both coalescing type moisture
Separator (reverse Ultipor) and particulate filter (Epocel) elements. The
housing for these elements is identical, but the direction of flow is opposite
for each.
Solution:
Correct piping configuration is as follows:
Reverse Ultipor - top inlet/side outlet
Epocel - side inlet/top outlet
CASE M12 - Freeze-up of Dome Pressure Regulators, R. Johnston
Freeze-up of dome loaded pressure regulators at several facilities.
Problem:
Icing up of regulators; little or no air flow to low pressure side.
Symptoms:
Collection of Facts: At least 2 installations have experienced freeze-up
problems. In each case, moisture content of the air was high but within
acceptable limits.
Solution:
Install 2 regulators in series to "step down" pressure in
a.
two stages, or replace regulator with one having higher
flow capacity.
If possible, replace orifice with one of larger diameter.
b.
As a last resort, add a refrigerated air dryer to system.
c.
CASE M13 - Manned Chambers-Pressure Problem (Door), R. Johnston
Problem: The inner doors of some chambers are equipped with dogs. This
permits the outer lock to be pressurized higher than the inner lock.
Symptoms:
If door dogs fail, inner door may swing open violently.
Collection of Facts: Chamber doors were designed only to withstand pressure
from the inside. If subject to a greater outside pressure, i.e. from the
outer lock, the dogs could fail causing the door to swing open. This could
present a serious personnel hazard.
Solution: Remove dogs from inner lock; in the interim, post sign on chamber
to warn against pressurizing outer lock greater than inner lock.
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