ENMET ISA-44-RAL-OD - Manual (Page 12)

ENMET Corporation ISA-44RAL-OD / ISA-44RAH-OD
8
3.3 Sample Head Assembly
The sample head connects to a compressed air line. This unit continuously monitors the respiratory lines for carbon
monoxide and oxygen. Figure 4 illustrates this unit. Assembly parts are listed and defined below:
P RESSURE R EGULATOR : Reduces the pressure of sample air from the compressed air line before passing over
the sensor. It includes a meter to measure the pressure in pounds per square inch (psi)
at the regulator exit.
Q UICK R ELEASE P NEUMATIC F ITTING : For quick connect/disconnect; fits into the port of an air line or filter unit and an
ENMET calibration gas fixture. Air inlet fitting is a Milton 727, which is compatible
with Hansen 1000 series. This fitting also connects with the exit fitting of the high
pressure regulator on an ISA-44RAH-OD. If you substitute other fittings, the
calibration fixture must also be changed.
H UMIDIFIER : This adds moisture to the air sample that passes over the sensor, which is a
requirement for correct sensor operation.
M ETALLIC O XIDE S ENSOR
(MOS Sensor):
Solid-state gas sensing element, contained in the sensor housing. When the amount
of CO in the air passing over the sensor increases to a preset level, the equipment
alarms and relays activate.
M ETERING O RIFICE : This replaceable assembly has a tiny orifice (hole) to ensure constant flow of air
between the humidifier and pressure regulator.
E LECTROCHEMICAL S ENSOR : Oxygen sensing element, contained in the sensor housing.
Hydrocarbon Filter To enhance low level calibrations by removal of hydrocarbon vapors from the air
sample.
Figure 4: Sample Head Assembly, Typical Hook-up
Locate the Sample
Point after Purification
Regulator Panel.
Oxygen Cell
and
MOS Sensor
Hydrocarbon
Filter
Pressure
Regulator
Quick Release
Fittings
Humidifier
(keep filled to
Water Level mark)
Metering
Orifice
Top Mount to
Avoid Water Trap
Locate near compressor
holding tank so sample air
reaches the sensor before
the same respiratory air
reaches the workers.
Plant Air
50 – 250 PSIG
Cut-Off Valve
(optional)
Cable to
enclosure