http://www.engineeringnews.co.za
  SEARCH
Login
R/€ = 14.21Change: 0.10
R/$ = 11.24Change: 0.03
Au 1216.55 $/ozChange: 7.86
Pt 1281.50 $/ozChange: -20.50
 
 
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 Tenders 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
Environment|Switchgear|YouTube|Gas-insulated Electrical Gear|Gas-insulated Switch|Miracle Gas|Oil|Oil-filled Circuit Breakers|Products|Dielectric
Environment|Switchgear||Products|
environment|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 (150 word limit)
 
 
 
 
 
 
 
 
Other Terry Mackenzie-Hoy News
I have been surprised to find that many people know the Lonmin, Impala Platinum and Anglo American Platinum strike is over but few know the terms of settlement. Besides other terms, workers whose basic wages were less than R12 500 a month receive a yearly wage...
There is a place down the road which sells tea and coffee, as in beans and leaves.  It has many types of tea and coffee and they are all in bins and stuff. Surrounding the bins are shelves, and every single spot on the shelves is crammed with glass tea cups, tea...
Four years ago, I went to Zambia, to the Zambezi river, to fish for tiger fish. The fishing camp was exquisite, the food great and the fishing good (the fellow fishermen were the usual bunch of  no-hopers who do not get out enough and behave like schoolboys when they...
Article contains comments
More
 
 
Latest News
Updated 14 minutes ago The shortlist of innovations in the Africa Prize for Engineering Innovation was announced on Wednesday, comprising 12 new innovations from seven African countries. The shortlist announced by the UK’s Royal Academy of Engineering (RAEng) included innovations in...
Updated 18 minutes ago As Reunert finalises its exit from the telecommunications market, the group has moved to limit the impact on the employees of its ill-fated subsidiary Nashua Mobile. The Competition Tribunal this week approved the sale of Nashua’s subscriber base to mobile operators...
Updated 35 minutes ago Cement production at Sephaku Holdings subsidiary Sephaku Cement’s (SepCem’s) Aganang integrated plant, in the North West, was scheduled to start this month, following the successful start of clinker production in August, the company announced on Wednesday. Further,...
More
 
 
Recent Research Reports
Road and Rail 2014: A review of South Africa's road and rail infrastructure (PDF report)
Creamer Media’s Road and Rail 2014 report examines South Africa’s road and rail transport system, with particular focus on the size and state of the country’s road and rail network, the funding and maintenance of these respective networks, and the push to move road...
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.
 
 
 
 
 
This Week's Magazine
Updated 5 hours ago The latest TransUnion Vehicle Pricing Index (VPI) contains a number of small, but significant indications that the tide may at last be turning for the beleaguered used car industry. For the third successive quarter, used car inflation has increased on a year-on-year...
The South African new vehicle market is likely to reach around 630 000 units in 2014, down from the 650 000 units recorded in 2013, says Toyota South Africa Motors (TSAM) president and CEO Dr Johan van Zyl. Van Zyl is also president of the National Association of...
Efforts by the Kenya government to increase energy generation by 5 000 MW over the next three years received a major boost following the award of a $2-billion contract to build a coal power plant in Lamu.  Despite allegations of irregular tendering process, the...
Using crafty wordplay on a well-known Internet meme, brilliant South African-born US entrepreneur and businessperson Elon Musk announced that Tesla Motors would not initiate patent lawsuits against anyone who, in good faith, wanted to use its technology. Instead,...
August new vehicle sales declined by 1.4%, to 55 722 units, compared with the same month last year. Assisted by the car rental market, the South African new passenger car market, at 37 953 units, contracted by 1 047 units, or 2.7%, compared with August last year.
 
 
 
 
 
 
 
 
 
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