ADVERTISEMENT FEATURE COVER STORY C
onventional gas warning systems can only detect a gas leak if the gas comes in to
contact with the detection device. As a result, external influences such as wind can delay the gas cloud or prevent it from reaching the sensor altogether. Dräger have developed a new gas warning device that is not affected by these environmental factors and detects a high-pressure gas leak as soon as gas escapes.
FUNDAMENTALS OF ULTRASONIC GAS LEAK DETECTION Gas molecules that escape a pressurised system produces a mixture of audible and ultrasonic noise, known as broadband noise. Ultrasonic Gas Leak Detectors filter out the
audible range – responding to sound in frequencies between 20 kHz and 80 kHz - far higher than frequencies human ear can detect The ultrasonic sound amplitude (pressure) is
proportional to the leak rate – the bigger the leak rate the higher the sound volume.
WHY ULTRASONIC GAS LEAK DETECTION (UGLD)?
Approximately 36 per cent of major gas
releases and 69 per cent of significant gas releases are undetected by gas detectors1
“Field trials have indicated that gas plumes
in well ventilated areas may not be detected by fixed point or open path detectors. The analysis of hydrocarbon release incidents
shows that conventional gas detectors have 65 per cent detection efficiency. The potential therefore exists for gas from undetected leaks to disperse to adjacent
areas, accumulate in ventilation dead spots in the modules, or for the release to continue undetected for some time...”2
Multiple studies have shown that: over one per cent of the global supply of gases are lost due to leaks. Besides the financial
losses, this also brings with it a reduction in safety for people and facilities.
The Dräger Polytron 8900 UGLD transmitter is
an early warning area monitor for detecting high- pressure gas leaks in outdoor industrial process environments. Thanks to an ultrasonic acoustic sensor, it responds earlier than conventional gas detectors because it registers the sound of leaking gas instead of measuring the concentration of accumulated gas clouds. As gas escapes, leaks are immediately detected in the surrounding area, regardless of the wind direction.
EASY-TO-UNDERSTAND DISPLAY FOR TEST RESULTS In the event of a potentially hazardous situation, the measured sound pressure is displayed in an easy-to-understand test value range of zero to 100 per cent. This value is easy to interpret, giving you complete transparency over the task at hand.
8 WINTER 2020 | INDUSTRIAL COMPLIANCE
ACOUSTIC GAS LEAK DETECTION WITH
DRÄGER POLYTRON 8900 UGLD The Polytron 8900 UGLD triggers the gas
leak alarm whenever the ultrasonic sound caused by the gas leak exceeds background noise by 11 per cent for a pre-adjustable period of up to 30 seconds.
A PERFECT COMPLEMENT TO YOUR GAS DETECTION SYSTEM The Dräger Polytron 8900 extends the Polytron 8000 series family with acoustic gas leak detection. All transmitters in this series have the same design and an identical user interface. A common user interface ensures that little training or maintenance is required for existing users. The Polytron 8900 UGLD perfectly complements existing flame and gas detection systems with reliable early gas leak warnings.
DELIVERS RESULTS THAT ARE EASY TO UNDERSTAND For an easy interpretation of results, the measured values on the display of the Polytron 8900 UGLD are shown from zero to 100 per cent of the full-scale decibel sensitivity range. The ultrasound level is immediately displayed and transmitted and allows for an easy interpretation. Alarms are configured at a specific level above a predetermined background noise level. Additionally, a time delay of up to 30 seconds can be set in the control system.
CAN EVEN DETECT GAS LEAKS IN LOUD INDUSTRIAL ENVIRONMENTS Loud process areas generate noise which is mostly in the audible spectrum. Gas leaks from pressurised vessels above 10 bar generate both audible sound and inaudible ultrasound. Since Polytron 8900 is tuned to measure in the ultrasound spectrum, it can easily identify gas leaks with a leak rate of 100 g/sec in a 20m radius circle.
ROBUST DESIGN AND FULLY- SEALED SENSOR The Polytron 8900 UGLD is an explosion-proof transmitter with a sensor housed in a galvanically-isolated, intrinsically-safe enclosure. The sensor is an ultrasonic microphone that is completely sealed in PVCC, making it impervious to water and dirt. It provides reliable readings without the need for an additional environmental protection baffle. Regular calibration is not necessary, but unlike some other UGLDs on the market, calibration is possible and easy with the offered calibration kits. The expected lifespan of the ultrasonic sensor is more than 10 years.
Tel: 01670 352 891 Email: Marketing.uk
1. Health and Safety Executive (HSE) Offshore Hydrocarbons Release database (2001-2008) – (McGillivray and Hare, 2008) 2. Health and Safety Executive in the UK Operational Guidance: www.hse.gov.uk/foi/internalops/hid_circs/technical_osd/spc_tech_osd_05.htm
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