SYSTEM TECHNICAL PRINCIPLES OF OPERATION - continued.
Filter Access. A filter access port with a removable cover is provided on the side of the tank When the tank is
emptied. this port is used to service the internal filter elements.
Water Removal. The water sump at the bottom of the tank collects the water separated from the fuel stream.
Piping connects the sump to a drain port for water removal. The drain piping contains a manually operated valve
to open and shut off the water drain.
Freeze Protection The bottom of the filter-separator tank, water sump, and water drain piping are covered by a
defrost (heating) shroud. The defrost shroud directs hot exhaust gas from the system pump assembly around the
parts of the filter-separator which can contain water. Heating is needed whenever the filter-separator is operated
at temperatures below the freezing point of water (32°F). A manually adjustable door is located on the end of the
shroud. This door provides adjustable flow of hot exhaust gas through the shroud.
DP (Differential Pressure) Monitoring. When the filter-separator is in operation, a drop in pressure occurs from
the inlet side to the outlet side of the tank. This is due mainly to the flow resistance of the filter stages. As solids
are collected by the filter elements, the drop in pressure increases. Eventually, when the pressure drop reaches
a certain value, the filter elements need to be replaced. Tubing outside the tank connects the high pressure
(inlet) side and the low pressure (outlet) side of the tank to a DP gage mounted on the tank wall. The gage
shows the tank pressure difference directly on a color-zoned dial for monitoring filter element condition. The dial
green zone, 0-20 psid (pound-force per square inch difference). is the normal operating range. The 20-35 psid
range is colored yellow to warn of the approaching end of serviceable filter life. The first stage filter elements
should be changed when DP indication reaches this zone. If the gage needle reaches the red zone, 35-50 psid,
the elements could be damaged by continuing operation.
The water detector kit adapter assembly is used to obtain a sample of flowing fuel that is tested for water content
to determine the effectiveness of the filter-separator. The adapter assembly is installed in the fuel supply line
onto the fuel outlet coupling of the filter-separator. A sample is obtained by attaching the water adapter
assembly detector kit to the adapter's coupling sample.