technology is perceived and used. For good reasons, refinery operators are cautious and will generally want to observe new systems in parallel to existing techniques before trusting them 100%. But in the future, it is likely that critical alarms and process trips will also be triggered by these wireless devices in the same way that their hard-wired cousins are doing today”.
Beyond process safety: long term health and environmental benefits
Gas detection systems also sniff for toxic VOC gases such as Benzene, Toluene, Ethylbenzene and Xylene (BTEX) to minimise health risks to the plant operators. Increasingly, gas detection systems are being used for environmental monitoring of VOC emissions from valves, flanges, pumps, compressors and pressure relief devices.
Fixed detectors can continuously monitor for leaks 24 hours a day and are replacing hand-held portable systems that require operators to walk the site sniffing for leaks. This results in labour cost-savings and demonstrates to the environmental regulators that improvements in monitoring are being made. Furthermore, through maintenance for leak reduction, the monitored results can also demonstrate a long-term reduction in VOC emissions. The result is better for the environment and better for the process economics: leaks represent waste. This is a compelling reason to augment existing fixed gas detection systems with wireless devices.
To ensure that these emissions are measured in a harmonised way, the US EPA has published Method 21 – ‘determination of volatile organic compound leaks’. It prescribes suitable distances between the potential leak point and the gas detector and makes proposals for suitable gas detection technologies such as photoionisation, infrared absorption or catalytic oxidation.
Method 21 also specifies the frequency of calibration of gas detection systems and the nature of the zero and calibration gas mixture cylinders that should be used. It confirms that the Zero Gas should be: ‘Air, less than 10 parts per million by volume (ppmv) VOC’. For calibration gas mixtures it is equally clear.
‘If
cylinder calibration gas mixtures are used, they must be analysed and certified by the manufacturer to be within 2 percent accuracy, and a shelf life must be specified’.
So, where can gas-detection system users source a product with this specification in the Asia Pacific Region? Alan Watkins, Executive General Manager at Coregas in Australia has the answer:
Hamburg refinery Toxic gas storage area
Author Contact Details Stephen B. Harrison - Principal, Germany at Nexant • Kranzlstraße 21, 82538 Geretsried, Germany • Tel: +49 (0)8171 24 64 954 • E-mail:
sbharrison@nexant.com • Web:
www.nexant.com
“at our Specialty Gases laboratory in Yennora, close to Sydney we can prepare highly sophisticated calibration gas mixtures for gas detection. BTEX mixtures with concentrations as low as 1ppm can be supplied with a Coregas QC certificate with an accuracy within 2 percent which complies with the Method 21 requirement.
“When it comes to the Zero Gas, clearly it should contain minimal amounts of the target chemical species to be detected. The Coregas ‘Zero Air’ product specification is less than 1 ppm of total hydrocarbons, which is one order of magnitude less than the Method 21 requirement, so our product comfortably exceeds that specification”.
What next for digitalisation?
Up to now, it is estimated that the penetration of wireless gas detectors within the chemical sensor type fixed systems is approximately 5%. In the next five years, it is possible that the penetration of wireless solutions within this segment will double. This will be driven by new adopters and increased usage by the early adopters because the wireless system is so naturally scalable.
As digitalisation gains hold in industrial automation, virtually every analogue device will be digitalised as the preventative maintenance is replaced by proactive maintenance driven by inexpensive data aggregation and intelligent analysis. The first step has already begun as electromechanical switches are increasingly replaced by electronic counterparts. In this regard, United Electric Controls also offers the ‘One Series’ HART enabled electronic switch. Its unique feature is the combination of a local solid-state relay which allows the device to execute a process control intervention (eg closing a
UEC One Series gauge kg-cm valve) while transmitting data via the HART protocol.
The HART enabled One Series is packed with intelligent self- diagnostics which report minor faults before they escalate to major safety issues and will work seamlessly with control systems in refineries deploying the up-and-coming Field Device Integration (FDI) technology. At present, the electronics are quite power intensive, and a battery-operated WirelessHART model does not yet exist. However, with a bit of creative electrical engineering this technology may soon follow in the footsteps of WirelessHART gas detection.
www.envirotech-online.com AET October / November 2019
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
