Detcon IR-700 - Manual (Page 10)

Model IR-700
IR-700 Instruction Manual Rev. 3.1 Page 6 of 40
2.2 Sensor Placement
Selection of sensor location is critical to the overall safe performance of the product. Five factors play an
important role in selection of sensor locations:
(1) Density of the gas to be detected
(2) Most probable leak sources within the industrial process
(3) Ventilation or prevailing wind conditions
(4) Personnel exposure.
(5) Maintenance access.
Density
Placement of sensors relative to the density of the target gas is such that sensors for the detection of heavier
than air gases should be located within 4 feet of grade as these heavy gases will tend to settle in low lying
areas. For gases lighter than air, sensor placement should be 4-8 feet above grade in open areas or in pitched
areas of enclosed spaces.
NOTE: Methane is lighter than air. Most other combustible hydrocarbon gases are heavier
than air. Compare the molecular weight, density, or specific gravity of the target gas(es) with
that of air to determine appropriate placement.
Leak Sources
The most probable leak sources within an industrial process include flanges, valves, and tubing connections of
the sealed type where seals may either fail or wear.
Other leak sources are best determined by facility
engineers with experience in similar processes.
Ventilation
Normal ventilation or prevailing wind conditions can dictate efficient location of gas sensors in a manner
where the migration of gas clouds is quickly detected.
Personnel Exposure
The undetected migration of gas clouds should not be allowed to approach concentrated personnel areas such
as control rooms, maintenance or warehouse buildings.
A more general and applicable thought toward
selecting sensor location is combining leak source and perimeter protection in the best possible configuration.
Maintenance Access
Consideration should be given to providing easy access for maintenance personnel. Consideration should also
be given to the consequences of close proximity to contaminants that may foul the sensor prematurely.
NOTE: In all installations the gas sensor should point straight down. Refer to Figure 10.
Improper sensor orientation may result in false readings and permanent sensor damage.
Additional Placement Considerations
The sensor should not be positioned where it may be sprayed or coated with surface contaminating substances.
Painting sensor assemblies is prohibited.