Since the inception of the National Environmental Management: Air Quality Act (39 of 2004), the focus on emission management strategies implemented has been on point sources (emission limits for stacks/vents/chimneys of Listed Activities and Controlled Emitters). Fugitive Emissions remain largely uncontrolled and unaccounted for due to the emissions being quantified and the challenge in managing the sources of emissions. The aim of a Fugitive Emissions Management Plan will identify sources and potential sources of fugitive emissions, will consider the risk to sensitive receptors and has been produced with the intention to reduce fugitive emissions causing activities.
DEFINITION OF A FUGITIVE EMISSION
It is important to distinguish between leaks, spills, venting and fugitive emissions because the consequences of each may be very different, furthermore each requires a different response strategy and different measures are required to prevent their occurrence.
Fugitive emissions can be defined as,
“small leaks or releases of gases or vapours from pressurized equipment and components (either unintentionally or by design) that do not lead to an immediate emergency situation (risk of harm to personnel, public or risk of fire or explosion), integrity risk or process or facility shutdown” – Enbridge, 2017
Therefore, fugitive emissions may continue to emit for periods of time if not identified and addressed.
Leaks or unintentional releases of gases or process fluid that lead to an immediate safety risk, emergency or facility shutdown are defined as gas leaks or spills.
Some components are designed to emit controlled quantities of gas as part of normal operation. Emissions from such components are categorised as fugitive emissions but do not require a repair decision or remedial action provided, they are operating normally and within design limits.
Process venting including facility blowdowns (i.e. removal of water from a cooling tower sump) is not a fugitive emission. Vented gas is accounted for under reporting procedures as vented emissions
COMMON SOURCES OF FUGITIVE EMISSIONS
Fugitive emissions come from two sources: standard equipment components and abnormal processes. Surveyors should be aware of both types of fugitive emissions.
Standard Equipment Components
Fugitive emissions from standard equipment components are the result of components wearing out or failing over time, being improperly installed, or loosening due to vibration. These fugitive emissions can often be easily detected during a fugitive emissions survey or screening, and the component can often be immediately refitted, repaired, or replaced.
The following components are common sources of fugitive emissions:
• connections (especially threaded connections) and fittings
• instruments and valves (e.g., pressure-relief valves and control valves)
• seals and housings (e.g., pneumatic controller case seals and tank thief hatch seals)
Fugitive emissions from abnormal processes typically result from equipment malfunctioning or becoming inoperative, or from processes functioning abnormally. These types of emissions may be more difficult to detect because they can be more intermittent and may require a detailed investigation before the source can be identified and repaired.
The following abnormal processes are common sources of fugitive emissions:
• unlit flares (ignitors and pilots)
• malfunctioning pneumatic instruments
• conservation units (e.g., vapour recovery units) that have unexpectedly quit operating
• equipment components emitting vent gas upstream of equipment actively controlling vent gas-Hydrocarbon storage tanks can also be sources of fugitive emissions from abnormal processes when
• thief hatches are open outside the time required for pressure relief,
• leaking process gas or volatile product moves past the seats of drains or blowdown valves,
• gas and liquids are separated inefficiently allowing gas to carry through,
• piping changes result in high vapour carry through, and
• pigging operations displace large volumes of gas to the tank.
KCM prepares a Fugitive Emissions Management as per the following:
- An assessment of the risk of fugitive emission problems, from normal and abnormal situations, including worst case scenarios, for example of weather, temperature or breakdowns and accidents.
- The appropriate controls (both physical and management) needed to manage those risks.
- Suitable monitoring.
- Regular review of the effectiveness of fugitive emissions control measures.
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