http://www.engineeringnews.co.za
  SEARCH
Login
R/€ = 14.87Change: 0.01
R/$ = 13.30Change: 0.00
Au 1133.54 $/ozChange: -1.31
Pt 1018.00 $/ozChange: -2.00
 
 
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 Tenders Suppliers Directory Research Jobs Announcements Letters 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|Gas|Switchgear|YouTube|Gas-insulated Electrical Gear|Gas-insulated Switch|Miracle Gas|Oil|Oil-filled Circuit Breakers|Products|Dielectric
Environment|Gas|Switchgear||Products|
environment|gas|switchgear|youtube|gas-insulated-electrical-gear|gas-insulated-switch|miracle-gas|oil|oil-filled-circuit-breakers|products|dielectric
© 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
Creamer Media Senior Deputy Editor
© Reuse this Comment Guidelines (150 word limit)
 
 
 
 
 
 
 
 
Other Terry Mackenzie-Hoy News
Back in 1994, your servant (myself) was given the opportunity to buy a cellphone. The phone is an American design that flips open when you want to speak. I buy it with the thought that, if it does not bring me any new work, I will throw it away. The phone battery...
Some lessons take time to learn. I think we all know that the platinum miners' strike from January to June 2014 resulted in the miners getting what they were demanding: a minimum wage of R12 000 a month and additional benefits. Further, the wage increase was...
More often than not on projects, the efforts of my practice and my staff are directed by people who are not engineers. Generally, we are appointed to a project some months after it has begun and the very first thing we are told is that all the information they need...
More
 
 
Latest News
A preliminary investigation by the Railway Safety Regulator (RSR) into the derailment of a Shosholoza Meyl train in Kimberley earlier this month, found that Transnet Freight Rail (TFR) had failed to communicate with the Passenger Rail Agency of South Africa (PRASA)...
Three of home improvement company Illiad’s major shareholders – Sanlam, Visio and Coronation, which held 69.25% – have agreed to vote in favour of a takeover by Steinhoff, with the company’s remaining shareholders to vote on the deal on September 29. Seventy-five per...
Government should face the fact that South Africa’s full-blown jobs crisis is a matter of urgent public importance, the Democratic Alliance (DA) said on Friday. MP James Vos, the DA shadow minister of tourism, was responding to a letter by Baleka Mbete, the Speaker...
More
 
 
Recent Research Reports
Defence 2015: A review of South Africa's defence sector (PDF Report)
Creamer Media’s Coal 2015 report examines South Africa’s coal industry with regards to the business environment, the key participants in the sector, local demand, export sales and coal logistics, projects being undertaken by the large and smaller participants in the...
Real Economy Year Book 2015 (PDF Report)
There are very few beacons of hope on South Africa’s economic horizon. Economic growth is weak, unemployment is rising, electricity supply is insufficient to meet demand and/or spur growth, with poor prospects for many of the commodities mined and exported. However,...
Real Economy Insight: Automotive 2015 (PDF Report)
Creamer Media’s Real Economy Year Book comprises separate reports under the banner Real Economy Insight and investigates key developments in the automotive, construction, electricity, road and rail, steel, water, gold, iron-ore and platinum sectors.
Real Economy Insight: Water 2015 (PDF Report)
Creamer Media’s Real Economy Year Book has been divided into individual reports under the banner Real Economy Insight and investigates key developments in the automotive, construction, electricity, road and rail, steel, water, coal, gold, iron-ore and platinum sectors.
Real Economy Insight: Construction 2015 (PDF Report)
Creamer Media’s Real Economy Year Book has been divided into individual reports under the banner Real Economy Insight and investigates key developments in the automotive, construction, electricity, road and rail, steel, water, coal, gold, iron-ore and platinum sectors.
Real Economy Insight: Electricity 2015 (PDF Report)
Creamer Media’s Real Economy Year Book has been divided into individual reports under the banner Real Economy Insight and investigates key developments in the automotive, construction, electricity, road and rail, steel, water, coal, gold, iron-ore and platinum sectors.
 
 
 
 
 
This Week's Magazine
Training company The Intelligence Transfer Centre will host the fourth yearly Environmental Crimes Conference at the Indaba Hotel, in Fourways, Johannesburg between September 9 and 10. Confirmed key regulatory bodies that will attend the event include the Department...
The government of Egypt has said it is ready to provide technical assistance to Malawi in the development of the Shire–Zambezi waterway, which is designed to link landlocked Malawi to the Indian Ocean by opening the two rivers for navigation. Egyptian ambassador to...
Kenya is finally set to start building a new multipurpose petroleum pipeline, after securing a $350-loan from a consortium of banks, including South Africa's Rand Merchant Bank. The other banks in the consortium are the Cooperative Bank of Kenya, Citibank's Kenya...
MARAIS VAN HEERDEN The owner/operator should be able to view the overall project design and progress made at any time
Three-dimensional (3D) engineering design models can now be viewed on tablets, which enable stakeholders to view the design without having to buy the design software used to create it, says engineering design firm 3DDraughting executive Marais van Heerden. The...
Ford’s newest offering in a long list of newcomers to the local market in the last two years is the B-Max multi-activity vehicle (MAV). The B-Max will play in the so called B-MAV segment, or the small MAV segment, currently dominated by Toyota’s Avanza, which sells...
 
 
 
 
 
 
 
 
 
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
Subscribe Now for $96 Close
Subscribe Now for $96