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Reference Manual
00809-0100-3003, Rev AA
Section 2: General operation
The GDU-Incus is omni-directional and is recommended to be mounted between 10 to 16 ft. (3 to 5 m)
above the area of interest to eliminate ground absorption and reflections.
It is recommended that the area where the GDU-Incus is to be situated is ultrasonically mapped prior to
installation or at commissioning while all processes are running to establish a background noise level
for alarm purposes. The alarm level should be set above the background noise level. Please contact an
Emerson representative to request a mapping survey or mapping tools.
The GDU-Incus responds instantaneously to pressurized gas leaks or other sources of ultrasonic noise
between 25 kHz and 100 kHz. It is, therefore, recommended that a delay time is built in to the control
system or alternatively, programmed in the GDU-Incus when using it in standalone mode to prevent
spurious alarms. The delay time is recommended to be set at a minimum of fifteen (15) seconds but
this should be increased in response to the process located near to the detector as shown in the graph
in section 4.1.2.
The maximum area which can be monitored by a single GDU-Incus is affected by several factors such as
background (ambient) ultrasound level, gas pressure, leak size, temperature of the gas, and
environmental conditions. Emerson has formulated a series of calculations that take all of these
external factors into account and are able to determine accurate coverage information for most
installations. Please contact an Emerson representative to advise on appropriate coverage for each
installation.
The GDU-Incus detection coverage can be verified at installation or as part of a maintenance schedule
using the GDU-PTV Performance Target Verification Kit to simulate an actual gas release of known size
and pressure at the perimeter of the GDU-Incus detection radius. See section
parts and accessories or contact an Emerson representative for further details.
Compared to other Ultrasonic and traditional forms of detection, the GDU-Incus has the following
advantages:
•
Gas does not need to reach the sensor for detection to occur.
•
Unaffected by weather conditions.
•
Sensors are unaffected by temperature, pressure, moisture, and contaminant build-up.
•
Multiple sensor redundancy in each unit.
•
Continuous self-test function.
•
No calibration required results in cost saving over detector lifecycle.
•
Can be remotely tested from up to 26.25 ft. (8 m) distance saving on maintenance scaffold costs.
•
4-20 mA Current Loop with HART communication as standard, plus relay outputs for 'Fault' and
'Alarm' conditions.
•
Can operate standalone or as part of an interfaced control system.
May 2019
6.5
for a listing of spare
3
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