Coal mining accidents caused by gas and coal dust explosions account for the most fatal mining disasters around the world. However, dangerous Methane gas is present at most underground mines as well and not only in coal mines.
This was, once again, confirmed when a fatal methane gas explosion occurred underground at the ZAPOLYARNY Nickle Mine in Northern Russia on 7 July 2017, claiming 4 lives when a build-up of methane gas ignited.
The most recent was a coal mine in Kashmir that collapsed on 7 August 2017 after a gas explosion took place at the Seri Darra village near Muzaffarabad killing five miners. The site has been shut down until further notice and six officials of the mining company were arrested for failing to observe safety standards.
A photo of an underground mining tunnel that collapsed due to a gas explosionIn June 2017 13 miners that died at coal mine in the Cucunuba district of Colombia in a methane gas explosion and the 35 miners were killed in a similar way at the EMESTSNYURT Coal Mine in Iran on 4 May 2017.
During the past four months 57 miners were killed in underground gas explosions.
At the PIKE RIVER Coal Mine in the West Coast Region of New Zealand’s South Island a methane explosion occurred underground 1 500 meters from the mine’ s entrance and killing 29 miners on 19 November 2010.
At the PIKE RIVER Coal Mine the ventilation shaft had been totally blown away. Coal dust, if not sufficiently suppressed, could contribute to fatal explosions and all equipment installed must duly comply with the IEC 60079-1 flameproof requirements. At some opencast mines, the view is taken that no precautions need to be taken to prevent the build-up of methane gas as sufficient ventilation should exist to prevent explosions.
The possibility, however, exists that pockets of methane gas and coal dust is present which could ignite and cause explosions such as in 2004 at the Blair Athol Coal (BAC) located in Central Queensland, Australia when coal dust and gasses exploded. The extend of the severe damage caused to draglines as well as nearby trucks when gas and coal dust exploded in an open mine operation.
The worst coal mine disaster ever occurred on 26 April 1942 at the Benxihu colliery, in the Homelike coal mine, China causing the loss of 1,549 lives. The fatal underground explosion was caused by a mixture of gas and coal dust setting alight and this underground fire exploded out of the mine shaft entrance which is situated above ground level.
The ventilation system was shut off and the pit head was sealed by the mine operator to deprive the underground of oxygen to prevent the fire from further damage which could cause a total collapse of the mine. Carbon monoxide poisoning due to the closure of the ventilation system was reported to have caused most of the deaths. The impact of a gas and coal dust explosion is clearly shown where it the reaches the shaft entrance above ground.
Excess ground water plays a major role in the safety of the mines and it has as a major effect on production underground should the pumping system be inadequate and flooding would occur. In most underground applications, the submersible pump will be totally submerged and operate in the presence of methane gas.
In South Africa, the areas that have been mined out are referred to as “madala sites” and submersible pumps are mainly used to pump away the sludge and water from these areas and here often there is also methane gas present.
Coal Mine water is usually contaminated with acid and the pumps required for these applications need to be manufactured from specialised materials such as Duplex Stainless Steels which are able to handle the erosion and corrosion as a result of the acidic liquids, containing solids, being pumped.
To minimize the damage when an electrical flash occurs inside an electrical enclosure it is essential that these enclosures comply with IEC 60079-1, this applies to all submersible pumps as well. It should be ensured that there is sufficient protection to ensure that failure of the mechanical seals of the pump is detected before the liquid comes into contact with the electrical winding of the pump.
The surface temperature of the electrical winding is normally around 120oC and should a seal failure occur the colder liquid being pumped will come into contact with the winding and this would subject the winding to a thermal shock – causing an electrical short circuit down to earth, in an occurrence like this it is possible that there will be an electrical flash.
In instances where the submersible pump does is not flameproof the electrical flash will ignite the methane gas with fatal results. Most submersible pumps rely on the liquid being pumped for the cooling of the electrical winding and should there be no liquid available to be pumped the electrical winding will overheat and burn out. Should the submersible pump not be flameproof and methane gas be present this would result in an explosion.
The electrical windings should be fitted with thermistors measuring the temperature of the electrical windings and should the windings overheat the electrical supply to the pump will be cut off to prevent an electrical short circuit as well as any possible subsequent explosions. To protect flameproof submersible pumps, it is also essential to have a flameproof electrical control panel installed as close as possible to the pump.
The control panel needs to firstly have overload protection, secondly a sensing device to measure when the mechanical seals have failed and thirdly a relay suited to the thermistors to prevent the electrical winding overheating.
HIPPO Flameproof Submersible Pump range control panel The HIPPO Flameproof Submersible Electrical Control Panel showing the control relays
HAZLETON PUMPS manufactured its first flameproof pumps in 1993 and the company continually researches ways to improve the safety features of the HIPPO Flameproof Submersible Slurry Pump range.
In order to move the HIPPO Flameproof Submersible Slurry pump effectively around underground a Flameproof Submersible Pump System was developed. This system consists of a HIPPO Flameproof Submersible Slurry pump mounted on a skip that can be moved around with a tractor to reach the various places where nuisance liquid is present that needs be removed.
The skid mounted HIPPO Flameproof Submersible Slurry Pump System
In areas where a tractor cannot be utilised to move the skid mounted HIPPO Flameproof Submersible Slurry pump system a trolley mounted Flameproof Submersible Slurry pump system could be provided which can be moved around by hand.
The trolley mounted HIPPO Flameproof Submersible Slurry Pump System
The skid mounted HIPPO Flameproof Submersible Slurry Pump System in underground operation in a typical coal mine
Due to the major increase in volume of liquids that have to be pumped from underground in coal mines directly to surface HAZLETON PUMPS has successfully designed and manufactured the world’s first High-Volume; High-Head; Medium/High Voltage Flameproof Submersible Slurry Pump. This pump has specialized protective features to ensure that the stator winding would never burn out due to overheating or the failure of the mechanical seals.
The HIPPO High Volume; High Head; Medium/High Voltage Flameproof Submersible Slurry Pump
To ensure the elimination of an electrical flash inside the pump enclosure when using Medium/High Voltage equipment such as submersible pumps in areas where flammable gasses might be present, HAZLETON PUMPS developed the essential additional protection required.
The pump enclosure will be under vacuum pressure and this pressure could also be monitored by means of a pressure transmitter. In the event of the enclosure leaking, the vacuum created will be lost and the pressure transmitter will cause an indicator light to be activated to confirm the loss of vacuum. The enclosure could then be isolated, resealed, re-vacuumed and returned to operation. This invention has been patented as well as trademarked.
This device can be fitted to all enclosures and equipment such as transformers and similar equipment. When such equipment should fail it could have an impact on the safety – in particular where it is installed in an explosive environment such as underground in coal mines where methane gas is present.
By preventing the electric flash from igniting the atmosphere in the enclosure the damage that could be caused will be contained and no major explosion will occur. An example of the danger when a transformer explodes was illustrated when two employees at the TENKE copper mine in
Democratic Republic of Congo suffered injuries in an electrical fire at the weekend of 15 – 16 July 2017 when the mine experienced an electrical short in a single transformer that supplies the SAG Mill at the Kwatebala plant, resulting in a localised fire.
HAZLETON PUMPS has won several awards for the HIPPO Flameproof Submersible Slurry Pump range:
2006 Winner of an award from Design Institute of South Africa (DISA) for the HIPPO Flameproof Submersible Slurry Pump Range.
2011 Winner TT 100 Award for Excellence in Management of Research for the HIPPO Flameproof Submersible Slurry Pump Range.
2015 Engineering Federation of South Africa (SEIFSA) Awarded the Company of the Year and winner in the Customer Service Company of the Year award for development of the HIPPO High-Volume, High-Head, Medium/High Voltage Flameproof Submersible Slurry Pump range as well as the repair and refurbishment of the HIPPO Submersible Slurry Pump range
2015 HAZLETON PUMPS won the prestigious South African Premier Business Awards’ (SAPBA) Manufacturer of the Year award for the design, development and manufacture of a Medium/High Voltage Slurry Submersible Pump while also winning of the SMME Company of the Year.
2016 The Southern African Development Corporation (SADC) Quality Awards bestowed the honour of the winner of the Southern African SMME Company of the Year on the Company, and Product of the Year for the High-Volume, High-Head, Medium/High Voltage Flameproof Submersible Slurry Pump range.
2016 South African Flameproof Association (SAFA) for the HIPPO Flameproof High Voltage Submersible Slurry Pump which was awarded as the Most Innovative Product or Engineering Solution of the Year and is the only product of its type in the world
2017 Engineering Federation of South Africa (SEIFSA) Awarded the Company of the Year and winner in the Customer Service Company of the Year award for design, development and manufacture of the HIPPO Submersible Slurry Pump range as well as the repair and refurbishment of this Submersible Slurry Pump range.
