Bluefield was recently engaged by a global coal mining company to produce a Scope of Work for their very large mobile equipment assets. The fleet required upgrading due to aging components.
During a review with stakeholders regarding the replacement of all high voltage switch boards, I drew their attention to the fact that their existing switchboards equipment and, in fact, most of their electrical infrastructure, utilised SF6 gas type circuit breakers. This is currently common across the global market.
SF6 gas is a toxic synthetic gas which is damaging to the environment and extremely hazardous to employees.
I advised the stakeholders that the European Union had declared that the use of SF6 gas type equipment utilised in the electrical transmission industry was to be phased out by 2025 as it is the greenhouse gas with the largest global warming potential.
Bluefield was consequently commissioned to investigate further, find an alternative, and alter the SOW accordingly to align with the Miner’s continual evaluation of operations, equipment and processes, respond to environmental concerns faced by climate change, and mitigate any hazards where employees were exposed.
My investigation found the following:
Mitigating Climate Change.
- SF6 Gas Circuit Breakers has been a critical technology under review for some time. Sulphur-hexafluoride (SF6) is used in the HV electrical transmission industry because it is an excellent gaseous dielectric medium.
- SF6 is also the greenhouse gas with the largest global warming potential (GWP) 22,800 times more than CO2.
- With a GWP of around 22,800 over a 100-year time horizon, SF6 is the most potent greenhouse gas regulated under the Kyoto Protocol (Rigby et al, 2010: 10305). Its GWP of 22,800 means that it is 22,800 times more effective at trapping infrared radiation (i.e., creating the greenhouse effect) than an equivalent amount of carbon dioxide over a 100-year period (Blackburn, 2015: 5).
- SF6 is widely believed to have an atmospheric lifetime of 3,200 years (Diggelmann et al, 2016: 70)
- The potential for global warming reduction is further underscored when you look at the sheer quantity of SF6 installed worldwide. Specifically, studies indicate 10,000 tons of SF6 are installed each year, with 80% concentrated in the transmission industry alone.
- This creates further costs and a myriad of bureaucratic compliance legislation for companies, that must be adhered to. For example, when SF6-filled equipment is near the end of its life or has technical problems, special care must be taken in its recycling process and maintenance. Only licensed or authorized hazardous waste managers are permitted to handle, transport and recycle the gas according to national or regional regulations and standards (Deux, 2013: 4). These lifecycle management costs will continue to rise as the global demand for electricity, and, thus, switchgear, increases.
Mitigation of exposure
- During its working cycle, SF6 decomposes under electrical stress, forming toxic by-products that are a health threat for working personnel in the event of exposure. (ICF Consulting, 2002: 1)
- These by-products include, among other things, disulfuric decafluoride (S2 F10) which is a highly toxic gas (Blackburn 2015:) It has been referred to by the US Environmental Protection Agency (EPA) as “the by-product of greatest concern due to its relatively high toxicity.” (ICF Consulting, 2002: 2)
- S2 F10’s toxicity is on a par with phosgene, the infamous chemical warfare pulmonary agent used during the First World War (Blackburn, 2015: 2).
The installation of Vacuum Circuit breakers or G3 (a relatively new technology 2012) gas type circuit breakers is a viable alternative to mitigate the GWP and the ongoing costs associated with maintenance and disposal of SF6 circuit breakers and the mitigation of exposure to employees.
Bluefield, in collaboration with the switchboard manufacturer and suppliers of switchgear, found the best possible solution was to change to vacuum type circuit breakers as the G3 gas type would not be available in the immediate to short term. As a direct result of Bluefield’s report, the client reviewed all future works regarding their electrical transmission and the subsequent switchgear types being utilised. The SOW was changed accordingly, and a remote switching unit was also added to protect employees and further mitigate any arc flash hazard.
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