Mine Safety     

Drilling for  life – SA’s latest rescue drill put through its paces

(Published in Mining magazine June 2014 )

By Stef Terblanche

It may sound wasteful or even cynical for anyone to spend R69-million on state-of-the-art new equipment and then express the hope of never having to use it.

However, the reason is simple, if tragic… Coalbrook Colliery in 1960, where 435 miners lost their lives after underground workings collapsed. The equipment in question being a rescue drill and ancillary equipment…which rescuers did not have back then.

But should disaster strike again today – and that is what nobody hopes for – the local coal mining industry is fully prepared. After Coalbrook the South African Chamber of Mines purchased its first rescue drill and ancillary equipment for underground rescue operations and updated these over the years.

After its most recent purchase, one of the best mine rescue services equipped with the best and latest  rescue technology available, is on hand to deal with any emergency.

After an extensive collaborative effort by the SA Chamber of Mines, its Collieries Committee and coal mining members, a specially established Task Team, the Colliery Training College (CTC) and the Mines Rescue Service (MRS), the local coal industry’s brand new rescue capability was unveiled to the public on February 18 this year.

Under the full glare of the public spotlight, the CTC using the newly acquired Schramm T130XD and Schramm T685WS drills, and the MRS using the winders, rescue capsule and ancillary equipment, showed what they were capable of in a successful simulated rescue operation.

Mr Dick Kruger, Deputy Head of Techno Economics at the Chamber of Mines explains that the new drills represent brand new technology, with those operating them acquiring new knowledge with each hole drilled. As a result test or practice holes have already been drilled, but the new equipment has yet to be used in a real emergency.

Kruger recalls that after the Coalbrook disaster the coal producing members of the Chamber of Mines decided to purchase the first rescue drill for South Africa, a Wirth L10, together with ancillary equipment in 1967 at a cost of R600,000.

“But it proved unsatisfactory when, during test drilling trials a penetration rate of only 200mm per hour could be attained in the dolerite rock which overlays the greater part of South Africa’s coal fields,” says Kruger.

During 1975 the Chamber learnt of drilling equipment manufactured by Ingersoll-Rand which was suitable for rescue work and, importantly,  could drill through dolerite at an acceptable rate. 

This led to the purchase of an Ingersoll-Rand T4 Drillmaster drill for probe holes and an Ingersoll-Rand T5 Drillmaster drill for the rescue holes, together with the necessary ancillary equipment. Both drills were mounted on self propelled road going vehicles.

The T5 was modified to enable rotary drilling at 250mm diameter or down-the-hole hammer drilling at 760mm diameter to a depth of 250m.  It would have been able to reach the workings of at least 80% of the collieries operating at the time. So the Wirth L10 drill was retained to deepen holes to 500m to reach the workings of those collieries that were deeper.

Over the years this equipment was thoroughly put to the test with the drilling of many holes, some of them in real emergencies.

The first emergency was in November 1984 following a large methane explosion at Usutu Colliery near Ermelo.  The next emergency occurred in June 1991 when the T5 was used successfully to evacuate 26 trapped coal miners after a roof collapse in the Emaswati Colliery in Swaziland.

In 1994 16 miners trapped underground by a fire at the Gloria Colliery were rescued, but 17 miners in a rescue bay could not be reached in time. In 2003 the T5 was used to allow divers to recover the body of a drowned miner at the Matla Colliery. And in 1981 the T4 was also used to drill holes to assist with fire fighting on a coal mine in the Utrecht area.

After a major underground colliery fire in 2005 and the realisation that the MRS lacked adequate inertisation capacity, it was decided to purchase a mobile inertisation system at a cost of R22-million.

The mobile fire inertisation system consists of a mobile generator, trailers,  and gas chromatography equipment. It can produce 0.5 cubic metres of nitrogen per second or 1,800 cubic metres of nitrogen per hour at a pressure of 9 bar and a purity of 97%. It was decided the T4 probe drill would be used to drill holes into burning workings through which the inert gas would be injected.

By 2009 the continued use of the existing rescue drill and other equipment, now more than 40 years old, was causing some concern. Despite still being in fairly good condition, shortcomings were identified that placed the reliability of the drill for rescue operations in doubt.

A Task Team appointed on the recommendation of the Collieries Committee of the Chamber investigated a number of options for replacing the current equipment, finally opting for the  the Schramm T130XD drill to replace the T5 rescue drill, and the Schramm T685WS to replace the T4 pilot drill, each with its own suite of ancillary equipment.

 In November 2011 the two new drills plus ancillary equipment were bought at a cost of R65,675,000. In addition a new rescue winder and rescue capsule, a new probe hole camera and an additional gas chromatograph were also purchased at a cost of R3,372,000. The old mobile rescue winder was converted into a supply winder.

The new equipment arrived in September 2012 and after tests and some modifications for local requirements  the drills were released to the Rescue Drilling Unit in July 2013. A vertical test rescue hole was drilled to a depth of 56m at Goedehoop Colliery and, after some initial problems had been overcome, the hole was declared suitable for rescue training. A second, inclined hole was drilled in November 2013.

On February 18 the drills were unveiled to the public and the rescue winder and rescue capsule were successfully tested in the vertical hole at Goedehoop Colliery.

“At present we have the best and the most modern rescue equipment available in the world,” enthuses Christo de Klerk, general manager of MRS who will be in charge of using much of the equipment in a real emergency.

In the rescue demonstration it was shown how miners trapped underground by a major collapse or fire alert the MRS. The rescue team will then drill a 165mm probe hole to where the trapped miners are. Next a sample tube of the gas chromatograph is lowered down the probe hole to determine whether any inflammable gasses are present.

Then a borehole camera is lowered to locate the number and location of the trapped miners. Using the supply mobile winder, food, liquids, medication and communication equipment are lowered to the miners through the probe hole.

The trapped miners are then informed that a larger rescue hole is to be drilled and are asked to stand clear of the point where the drill will break through. Once the rescue hole has been drilled, the mobile rescue winder is used to lower a member of the rescue team in a rescue capsule down the hole. The trapped miners are then raised to the surface in the rescue capsule one by one, with the member of the rescue team being the last to leave.

In the event of an underground fire, a probe hole will be drilled into the fire area while rescue teams will install seals underground to contain the fire in the smallest possible area. The mobile inertisation unit will then pump nitrogen into the fire area, putting out the fire.

“The drills are owned by MRS but are held at CTC in Witbank because it is centrally located for the coal mines and because they have the technical or engineering experts to operate them. At MRS in Evander we are in charge of the mobile rescue winders, the camera and the gas chromatographs,” says De Kerk.

All members of the proto rescue team are volunteers who are fulltime underground employees on the mines and who have undergone special, rigorous training.

The equipment was bought specifically with South Africa’s sub-surface coal mines in mind, allowing for the drilling of rescue holes to a maximum depth of 300m. That is the same depth as the deepest coal seams in South Africa, says De Klerk.

In emergency situations the rescue drill is used only once the normal underground access and exit routes become blocked. In such a case, drilling a hole presents the fastest rescue route.

De Klerk says by drilling at least four rescue holes a year on different coal mines the rescue teams gain training and experience and the mines are prepared for emergencies in advance.

De Klerk says the new equipment should have a “good service” lifespan of at least twenty years. But whether it will ever need to be used, is another matter as De Klerk says South Africa’s coal mines are among the safest in the world with the best track record.

Nonetheless, if anyone still doubts the need for this expensive equipment, the near tragedy in 2010 when 33 miners were trapped underground for two months in the San Jose Mine, Copiapo, Chile in 2010 should dispel it.

Millions of people around the globe watched on television as the miners were hoisted to safety, one by one, in a small bullet-shaped capsule. As the last person brought to the surface stepped out of that capsule, the entire world applauded, dramatically bringing home the value of such rescue capability.

Schramm T685WS  Truck Mounted Drill

The probe hole drill

–   Replaces the old Ingersoll-Rand T4 Drillmaster.

–   Standard Applications: Water well; Environmental; Geothermal; Exploration; Blast Hole & Mining; and Shallow Oil.

–   A world proven, heavy duty, heavy hoist, truck mounted drill rig.

–   Separate drill rig sub frame design permits stable mounting on standard trucks, the Schramm tracked drill carrier, trailers and other special purpose vehicles.

–   High capacity single reduction top head drive rotation and efficient pipe handling systems make it  ideal for the toughest drilling projects.

–   Uses down-the-hole hammer, air rotary, mud rotary and dual tube techniques.

–   Up to 93,700 lb (43,502 kg) pullup.

–   28 inch (711 mm) table opening.

–   760 hp (567 kw) deck engine.

–   On-board air compressor to 1350 cfm @ 350 psi & 1150 @ 500 psi (38 cu m/min @ 24.1 bar & 32.6 cu m/min @ 35.5 bar).

–   Hydraulic mud pumps.

Schramm T130XD Carrier Mounted Rig

The large diameter access and rescue hole

–   Replaces the old Ingersoll-Rand T5 Drillmaster machine.

–   Standard Applications: Water Well; Environmental; Geothermal; Exploration.

–   A heavy duty, heavy hoist, carrier mounted drill rig. 

–   Utilises the latest concepts in mast design and technology. 

–   Telescoping construction permits long head travel and working height to allow use of Range III casing, yet short overall length in the transport position. 

–   Front overhang of less than 6 feet allows site access on roads requiring a compact machine. 

–   Heavy pullback capacity it perfect for shallow oil and gas, coal bed methane drainage and deep water well applications.

–   130,000 lbs. (59,090 kg) actual pull-up.

–   28 inch (711 mm) table opening.

–   760 hp deck engine.

–   1350/350 – 1150/500 variable volume compressor.

–   (38 cu. m/min @ 24.1 bar & 32.6 cu m/min @ 35.5 bar).

–   50 feet (15.25 m) of clear head travel.

–   Range III casing.