http://www.engineeringnews.co.za
  SEARCH
Login
R/€ = 14.09Change: 0.08
R/$ = 10.50Change: 0.03
Au 1305.70 $/ozChange: 6.82
Pt 1484.50 $/ozChange: 11.00
 
 
Note: Search is limited to the most recent 250 articles. Set date range to access earlier articles.
Where? With... When?








Start
 
End
 
 
And must exclude these words...
Close Main Search
Close Main Login
My Profile News Alerts Newsletters Logout Close Main Profile
 
Agriculture   Automotive   Chemicals   Competition Policy   Construction   Defence   Economy   Electricity   Energy   Environment   ICT   Metals   Mining   Science and Technology   Services   Trade   Transport & Logistics   Water  
What's On Press Office Suppliers Directory Research Jobs Announcements Contact Us
 
 
 
RSS Feed
Article   Comments   Other News   Research   Magazine  
 
 
Jul 06, 2012

SF6 gas should be bad news for those who believe in global warming

Back
Gas|Switchgear|YouTube|Gas-insulated Electrical Gear|Gas-insulated Switch|Miracle Gas|Oil|Oil-filled Circuit Breakers|Products|Dielectric
Gas|Switchgear||Products|
gas-company|switchgear|youtube|gas-insulated-electrical-gear|gas-insulated-switch|miracle-gas|oil|oil-filled-circuit-breakers|products|dielectric
More Insight
© Reuse this



There is a gas called sulphur hexafluoride, or SF6, for short. Most housewives are fully knowledgeable about SF6 and buy it with the groceries. Or not really.

Okay, no housewives, then. But, listen to the tale. It so happens that if you take a domestic circuit breaker (or trip switch) of the type you find in a domestic switchboard, its purpose is to open to interrupt current when there is an overload.

When the overload occurs, the contact of the circuit breaker opens and there is a small arc. The arc goes out after a while, since it cools down. This all happens very quickly. In an 11 000 V circuit breaker, the contacts that open under an overload will also have an arc. However, if that arc was in air, it would not go out, owing to what is called the ‘plasma effect’. So, as a result, the contacts of an 11 000 V circuit breaker are immersed in a tank in insulating oil, which cools the arc down in an overload condition.

The downside of this is that you have to change the oil every two years or so – more often if the circuit breaker is used regularly. These so-called oil circuit breakers, or OCBs, have a very long life. If they are looked after properly, they will last 60-plus years. And changing the oil is no big deal.

But enter stage left, SF6, the miracle gas. An extract from Wikipedia: “SF6 is used in the electrical industry as a gaseous dielectric medium for high-voltage circuit breakers, switchgear . . . often replacing oil-filled circuit breakers that can contain harmful PCBs.” (Oops, that’s a lie; PCB’s vanished years ago.)

Wikipedia goes on: “SF6 gas, under pressure, is used as an insulator in gas-insulated switch- gear (GIS) because it has a much higher dielec- tric strength than air or dry nitrogen. This prop- erty makes it possible to significantly reduce the size of electrical gear. This makes GIS more suitable for certain purposes, such as indoor placement, as opposed to air-insulated electrical gear, which takes up considerably more room. Gas-insulated electrical gear is also more resistant to the effects of pollution and climate, as well as being more reliable in long-term operation because of its controlled operating environment . . .”

Oh, wow, ain’t it wonderful? It is for all these wonderful reasons that SF6 very largely displaced oil in 11 000 V circuit breakers and, in GIS switchgear, it continues to do so. There are even YouTube videos of people having fun with SF6 which, since it is six times heavier than air, makes your voice go very deep when you breathe it in. There is a minor downside – when it is exposed to sustained or intense electrical arcs, SF6 gas decomposes to form sulphur fluoride gases and toxic metal fluorides.

If moisture is present, the decomposition by-products can include hydrofluoric and sulphuric acids. Wait a minute . . . hydrofluoric and sulphuric acids? You use the first to etch glass and the second to dissolve rust. Right. Useful stuff.

But there is also a major downside. You may want to dispose of this gas or the gas may find its way into the atmosphere for some reason. Should we worry? Waaaal . . . according to the Intergovernmental Panel on Climate Change, SF6 is the most potent greenhouse gas that it has evaluated, with a global warming potential 22 800 times that of carbon dioxide (CO2) over a 100-year period.

Average global SF6 concentrations increased by about 7% each year during the 1980s and 1990s. But, comfortingly (again from Wikipedia) “given the low amounts of SF6 released, compared with CO2, its overall contribution to global warming is estimated to be less than 0.2%”.

So that would mean it is still in use, right? Is it 0.2 % a year or what? And being indestructible (unlike CO2), it is not going to go away. So, in 50 years, 10% of global warming will be by an indestructible gas? But there is a financial imperative by switchgear manu- factures to keep on with the stuff. Well, if you believe in global warming, it makes no sense. Fortunately, I don’t . . . but using the stuff really makes no sense.

Edited by: Martin Zhuwakinyu
© Reuse this Comment Guidelines
 
 
 
 
 
 
 
 
Other Terry Mackenzie-Hoy News
In the book The Wind in the Willows, Kenneth Grahame writes: “There’s nothing – absolutely nothing – half so much worth doing as messing about in boats . . ." If you have not read The Wind in the Willows, buy it and read it to your children (that is, if you...
Stonehenge is a prehistoric monument in Wiltshire, England. One of the most famous sites in the world, Stonehenge is the remains of a ring of standing stones set within earthworks. Go on, look it up on the internet. People have devoted their entire lives to the study...
If you have never heard of the TV series House of Cards then skip some paragraphs. The following is an extract from the online edition of the UK newspaper, The Guardian: “Why are all the House of Cards journalists so bad at journalism? Zoe and the gang can’t...
More
 
 
Latest News
Updated 20 minutes ago Unregistered motorists in Gauteng owe the SA National Roads Agency Limited (Sanral) over R1-billion in unpaid e-toll accounts, Transport Minister Dipuo Peters said. As of May 31, the unaudited amount owed for more than 90 days was R156 623 567 while R995 362 885 was...
The head of economics and trade at the Delegation of the European Union (EU) in Pretoria has acknowledged South Africa’s trade negotiators won important concessions in the long-running Economic Partnership Agreement (EPA) trade talks. But he says it was South...
Responding in writing to a recent Parliamentary question by the Democratic Alliance, Transport Minister Dipuo Peters has provided an update for each of the country’s 13 bus-rapid transport (BRT) systems, noting that each network is at a different stage of...
More
 
 
Recent Research Reports
Real Economy Year Book 2014 (PDF Report)
This edition drills down into the performance and outlook for a variety of sectors, including automotive, construction, electricity, transport, steel, water, coal, gold, iron-ore and platinum.
Real Economy Insight: Automotive 2014 (PDF Report)
This four-page brief covers key developments in the automotive industry over the past 12 months, including an overview of South Africa’s automotive market, trade figures, production and the policies influencing the sector.
Real Economy Insight: Construction 2014 (PDF Report)
This five-page brief covers key developments in the construction industry over the past 12 months. It provides an overview of the sector and includes details of employment in the sector, infrastructure and municipal spending, as well as insight into companies’...
Real Economy Insight: Electricity 2014 (PDF Report)
This five-page brief covers key developments in the electricity industry over the past 12 months, including details of State-owned power utility Eskom’s generation activities, funding and tariffs, independent power producers and prospects for the sector.
Real Economy Insight: Road and Rail 2014 (PDF Report)
This six-page brief covers key developments in the road and rail industries over the past 12 months, including details of South Africa’s road and rail network and prospects for both sectors.
Real Economy Insight: Steel 2014 (PDF Report)
This four-page brief covers key developments in the steel industry over the past 12 months. It provides an overview of the global and South African steel and stainless steel markets, South Africa’s major steel producers and events that have shaped these markets.
 
 
 
 
 
This Week's Magazine
Multinational semiconductor chipmaker corporation Intel announced its national campaign to further acquire partners to drive its She Will Connect programme, an initiative that aims to expand digital literacy skills to young women in developing countries, further into...
South Africa's MeerKAT radio telescope array programme should get back on schedule within a few months. This assurance has been given by SKA South Africa (SKA SA) associate director: science and technology Prof Justin Jonas. Early last month, Science and Technology...
The Passenger Rail Agency of South Africa’s (PRASA’s) Metrorail service will remain a subsidised service following its current multibillion-rand rolling stock, station, depot and signalling upgrade programme. PRASA group CEO Lucky Montana has allayed fears that...
GARYN RAPSON Contaminated Land Provisions in the National Environmental Management: Waste Act No 59 of 2008 will open the door for court battles to determine who will be held liable for the remediation
The uncertainties around the remediation of affected areas as addressed in the Contaminated Land Provisions in the National Environmental Management: Waste Act No 59 of 2008 will possibly spark litigation and disputes between landowners and businesses, contractors...
South Africa is currently the largest component of the African Development Bank’s (AfDB’s) active portfolio in Southern Africa, comprising 62.5% of the bank’s $7.9-billion exposure to the 12-country region – the second largest beneficiary is Mauritius, which...
 
 
 
 
 
 
 
 
 
Alert Close
Embed Code Close
content
Research Reports Close
Research Reports are a product of the
Research Channel Africa. Reports can be bought individually or you can gain full access to all reports as part of a Research Channel Africa subscription.
Find Out More Buy Report
 
 
Close
Engineering News
Completely Re-Engineered
Experience it now. Click here
*website to launch in a few weeks