Bob Gallagher explores leak detection and repair strategies to track down fugitive emissions.
Fugitive emissions – unintended leaks of gases or vapours from pressurised industrial equipment – can be extremely hazardous to workers, the community, and the environment. Faulty pieces of equipment – commonly valves and connectors – are typically to blame, and even small discharges can add up to dangerous levels of volatile air pollutants. This has led to the tightening of regulations globally, with many governments now requiring industries to implement leak detection and repair programs to monitor, analyse and reduce the volume of hazardous gases escaping into the environment.
Meeting industrial regulations
Fugitive emissions can be caused by a number of different factors, from simple expansion and contraction of components or gasket failures to improper maintenance practices. Accumulation of volatile organic compounds (VOCs), even from small leaks, can cause workers to be exposed to dangerous concentrations of the chemicals, and can also contribute to smog and air pollution with links to asthma, cancer, infertility and birth defects. Owing to these health concerns, many governments and health agencies place strict requirements on companies to monitor and manage emissions. European Standard EN 15446:2008 applies across the European Union and requires the measurement of fugitive emissions of VOCs from process equipment. If a leak is detected, it mandates the measurement of gas concentration at the interface of a leak, using a portable instrument to calculate a mass emission rate.
In the US, the industry is overseen by a host of regulatory bodies – such as the Environmental Protection Agency (EPA) and the Federal Energy Regulatory Commission – which are enforcing increasingly stringent fugitive emission guidelines. The EPA first introduced its Clean Air Act in 1970 to protect the public and the environment from VOCs and, in 1983, it mandated compulsory leak detection and repair (LDAR) programmes throughout the industry. These regulations have been continuously updated since, with the agency introducing the New Source Performance Standards, the National Emission Standards for Hazardous Air Pollutants, and the Resource Conservation and Recovery Act, all of which involve the application of LDAR to monitor and reduce hazardous gas emissions. There are 25 federal standards that require facilities to implement LDAR programmes using the monitoring procedure known as Method 21.
What are LDAR programmes?
An LDAR programme is designed to identify and overhaul leaking equipment, allowing a facility to control and reduce fugitive emissions. Any component subject to LDAR requirements must be monitored at specified, regular intervals to determine whether it is leaking and, if found faulty, it must be repaired or replaced within a specified time frame. A best practice programme will follow at least five phases, which occur on an on-going basis:
The first 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 define potential leaks. Method 21 requires VOC emissions from regulated components to be measured in parts per million (ppm). A leak is defined whenever the measured concentration exceeds the threshold standard (also known as the ‘leak definition’) for the applicable regulation. Leak definitions vary by regulation, component type, service, and monitoring interval. If there are multiple regulations or components, use the lowest leak definition 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 first 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 final 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 refinery can typically contain hundreds of thousands – if not millions – of potential leak sources, it can often be beneficial 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 flame 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 Scientific TVA2020 toxic vapour analyser, can be configured 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 defined 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 flanges, for example – while observing the readout. If an emission is detected that breaches the specified leak definition value, then the results must be reported, and the faulty feature repaired or replaced.
Benefitting from LDAR
An effective LDAR programme, using advanced technology, offers significant benefits to stakeholders in industrial settings. Importantly, it is often mandated by government, state or local regulations, and must be addressed to avoid significant fines 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 benefits 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.
