PRODUCTION • PROCESSING • HANDLING
at specifi ed, regular intervals to determine whether it is leaking and, if found faulty, it must be repaired or replaced within a specifi ed time frame. A best practice programme will follow at least fi ve phases, which occur on an on-going basis: The fi rst phase is to identify
components. Tag each regulated component with a unique ID and label on a piping and instrumentation diagram, site plan, and equipment log. Keep records up to date when new components are added, or old components are replaced or retired. Next is to defi ne potential leaks. Method 21 requires VOC emissions from regulated components to be measured in parts per million (ppm). A leak is defi ned whenever the measured concentration exceeds the threshold standard (also known as the ‘leak defi nition’) for the applicable regulation. Leak defi nitions vary by regulation, component type, service, and monitoring interval. If there are multiple regulations or components, use the lowest leak defi nition to simplify monitoring and reduce the chances of confusion. This provides a safety margin for workers closest to the potential leaks and reduces the chances of leaks being missed. The third phase is to monitor
components. Follow best practice guidelines for monitoring components. An electronic, automatic data logger saves time and improves accuracy. Ensure Method 21 procedures are being properly followed, and that the necessary records are maintained. Repair components comes next.
Develop a protocol and timetable for repairing components, with a fi rst attempt at repair occurring as soon as possible after detection. Ideally, recently repaired components should then be monitored more frequently, to verify that the repair was successful. The fi nal phase is to keep consistent records. Schedule internal and third
part audits of LDAR records on a regular basis. How the data is handled is entirely up to the company but, since a refi nery can typically contain hundreds of thousands – if not millions – of potential leak sources, it can often be benefi cial to use dedicated LDAR software packages to track and report results. This treasure trove of data can also be used to predict potential leaks before they occur, and automatically schedule preventative maintenance activities.
TECHNOLOGIES TO SUPPORT LDAR The industry standard practice for detecting fugitive methane emissions is to use fl ame ionisation detectors (FID). These use the ions formed during the combustion of a sample gas stream to determine the concentration of organic species and allow a wide dynamic and linear range to produce stable and repeatable responses. Some analysers, such as the Thermo Scientifi c TVA2020 toxic vapour analyser, can be confi gured with both FID and photo ionisation detection (PID), allowing a more rapid reading of both organic and inorganic compounds. PID measures ionised compounds that are excited by photons of UV energy in the device to identify a wider range of compounds than FID, including some inorganic compounds. The measurement process – as defi ned in the EPA’s Method 21 guidelines – requires the detector to be slowly moved around the periphery of the component in question – the interface between two fl anges, for example – while observing
Portable gas detectors, such as the TVA2020 toxic vapor analyser, quickly detect fugitive emissions of organic and inorganic compounds for Method 21 compliant LDAR applications
the readout. If an emission is detected that breaches the specifi ed leak defi nition value, then the results must be reported, and the faulty feature repaired or replaced.
An LDAR programme
is designed to identify and overhaul leaking equipment 28
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BENEFITTING FROM LDAR An eff ective LDAR programme, using advanced technology, off ers signifi cant benefi ts to stakeholders in industrial settings. Importantly, it is often mandated by government, state or local regulations, and must be addressed to avoid signifi cant fi nes or enforcement action. LDAR also safeguards the health of workers, by keeping tissue-damaging VOC emissions down to a minimum in enclosed areas, as well as contributing to cleaner air with health and environmental benefi ts for the wider community. Reducing product loss through leaks also protects the revenues and reputation of a company, ultimately improving the bottom line.
Bob Gallagher is with Thermo Fisher Scientific.
www.thermofisher.com
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