Detcon FP-700 - Manual (Page 11)

Model FP-700
FP-700 Instruction Manual Rev. 3.0 Page 7 of 40
When possible in an area void of high wind, accumulating dust, rain or splashing from hose spray, direct steam
releases, and continuous vibration. If the sensor cannot be mounted away from these conditions then make
sure the Detcon Harsh Environment Splashguard accessory is used.
Do not mount in locations where temperatures will exceed the operating temperature limits of the sensor.
Where direct sunlight leads to exceeding the high temperature-operating limit, use a sunshade to help reduce
temperature.
2.3 Sensor Contaminants and Interference
Detcon 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-700 sensor assembly is designed to be threaded into a ¾” Female NPT fitting of a standard cast metal,
Explosion-Proof Enclosure or Junction Box. There are two wrench flats on the upper section of the sensor that
should be used to thread the sensor into the ¾” female NPT receiving connection. Thread the sensor up until
tight (5 turns is typically expected) and until the display is pointed in the direction that sensor will normally be
viewed and accessed.
The FP-700 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. Detcon provides a standard
selection of junction boxes available as sensor accessories (See Figure 4 below), but any appropriately rated
enclosure with a downward facing ¾” NPT female connection will suffice.
When mounting on a wall, it is recommended to use a 0.25”-0.5” spacer underneath the mounting ears of the
Detcon standard J-Box to offset the sensor assembly from the wall and create open access around the sensor
assembly. Spacing requirements for other junction boxes may vary.
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 J-box accessories are available separately.)