Feature Description; Intended Use; Gas Leaks - Dräger Polytron 8900 UGLD Instrucciones De Uso

A 6 Port for sensor
B Sensor replacement
C Calibration set-up
3.2

Feature description

Polytron 8000 instruments are housed in a rugged stainless
steel enclosure for indoor and outdoor applications.
The flameproof / explosion proof enclosure provides three ¾"
NPT openings, which can be used for field wiring or direct
attachment of a sensor.
Polytron 8900 UGLD consists of an ultrasonic sensor (remote
or integrated) and the transmitter. The ultrasonic sensor
detects the ultrasonic sound level of the surrounding areas.
The detected ultrasound is then indicated as percentage of
full scale measuring range on the display and the analog
interface.
Signal conversion table
% 0 20
dB < 55 66
Level of ultrasound, status messages, and menu choices are
displayed on a backlit graphic LC-display and 3 colored LEDs.
Navigation through the menu is done by taping a magnetic
wand on the glass at the appropriate indicator. The instrument
can be configured, calibrated and maintained non-intrusively
without declassifying the area.
The instrument can be operated as current source or sink.
With the optional remote sensing head, the ultrasonic sensor
can be mounted at a distance of up to 30 m from the
transmitter.
3.3

Intended use

Polytron 8900 UGLD is an explosion proof instrument for
continuous ultrasonic gas leak detection (Ultrasonic Gas Leak
Detection = UGLD).
The instrument can be connected through a sealed conduit or
approved cable gland to a Dräger monitoring system or a
Programmable Logic Controller (PLC).
For a safe operation, the connection to a central controller is
necessary.
The instrument is designed to be installed in permanent
locations and is approved for use in hazardous, classified
areas.
A mapping survey of the installation site should be conducted
to determine environmental conditions. With the obtained data
the instrument is commissioned.
3.4 Ultrasonic gas leak detection (UGLD)
Pressurized gas leaks (minimum pressure 2 bar / 29 psi)
generate both acoustic and ultrasound. Airborne ultrasound
has a frequency range of approx. 16 kHz to >100 kHz.
Instructions for use |
Dräger Polytron
40 60 80 100
77 88 99 110
®
8900 UGLD
There are three primary factors that influence the intensity of
the ultrasound signal:
– Physical size of the leak (mass flow)
– Pressure drop between the pressurized vessel or pipeline
and the surrounding atmosphere.
– Gas properties
Gases with lower molecular mass (or higher speed of
sound) appear louder.
Ultrasound travels at the speed of sound and is only slightly
influenced by wind or strong air currents. Thus, the instrument
detects pressurized gas leaks that point detectors could miss
due to environmental conditions. The position of the gas leak
relative to the instrument does not significantly affect the
ability of the system to detect leaks.
Size and ultrasound distribution of a leak
Wind
UGLD

3.4.1 Gas leaks

Point detectors detect gas concentrations (e.g. ppm, %LEL).
UGLD transmitters indicate a change in a known
environment. This could be the onset of a hazard caused by a
leak on the basis of measured ultrasound.
Ultrasound emitted by gas leaks is proportional to the leak
rate. Leak rate is also called mass flow rate and describes the
amount of gas released over time [kg/s].
3.4.2 Background noise
Background noise is recurrent noise from running machinery
or other sound sources that emit ultrasound.
3.4.3 Alarm settings
The instrument displays the ultrasonic sound level in
percentage of the full scale measuring range [%].
The lowest value of the measuring range showing 0 % is
equivalent to < 55 dB.
The highest value represented by 100 % measuring range is
equivalent to approx. 110 dB.
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Description en
10 % LEL
50 % LEL
100 % LEL
Gas leak
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