Detcon FP-624D-HT - Manual (Page 12)

Model FP-624D-HT
FP-624D-HT Instruction Manual Rev. 1.1 Page 8 of 44
Detcon High Temperature combustible gas sensors may be adversely affected by exposure to certain airborne
substances.
Loss of sensitivity or corrosion may be gradual if such materials are present in sufficient
concentrations.
The performance of the detector elements may be temporarily impaired during operation in the presence of
substances described as inhibitors. Inhibitors are usually volatile substances containing halogen compounds.
Inhibitors include halide compounds such as Cl
2
, ClO
2
, F
2
, HF, HCl, Br
2
, vinyl chloride, and methyl chloride.
Inhibition is typically a temporary effect and the detectors generally recover after short periods of operation
back in clean air.
Some background gases may act as poisoning agents and have a more damaging effect on the sensor.
Although the sensor is designed to be poison resistant, it does have physical limits. Poisoning gases deactivate
the active detector’s catalytic ability and cause a permanent reduction in the span sensitivity. Examples of
typical poisons are: silicone oils and greases, siloxanes (HMDS), H
2
S, anti-knock petrol additives, and
phosphate esters. Activated carbon filters can be used to provide additional protection from poisoning in most
cases.
The presence of such inhibitors and poisons in an area does not preclude the use of this sensor technology,
although it is likely that the sensor lifetime will be shorter as a result. Use of this sensor in these environments
may require more frequent calibration checks to ensure safe system performance.
2.4 Mounting Installation
The FP-624D-HT should be vertically oriented so that the sensor points straight downward. The explosion-
proof enclosure or junction box would then typically be mounted on a wall or pole (See Figure 8). Detcon
provides a selection of standard junction boxes in both Aluminum and Stainless Steel.
NOTE: Do not use Teflon Tape or any other type of Pipe Thread material on the ¾” threads
unless the unit is mounted in a severe or harsh environment. Metal-on-metal contact must be
maintained to provide a solid electrical ground path. If Teflon Tape is used the Sensor must be
externally grounded using a ground strap.
When mounting on a pole, secure the Junction Box to a suitable mounting plate and attach the mounting plate
to the pole using U-Bolts. (Pole-Mounting brackets for Detcon Junction Box’s are available separately.)