South Africa is one of the ten largest coal producers and the fourth largest coal exporting country in the world. As the coal seams here are buried too deep beneath the ground for opencast mining, they are mined using a room-and-pillar technique. Minesites are divided into a series of rooms, which are cut into the coal bed using continuous miners. These machines extract the coal while digging a hole at the same time and can mine coal at a rate of 5 t/min. Once the coal is removed, the ceiling is shored up with pillars to prevent it from collapse.
Downtime on these continuous miners could cost coal mines up to US$10,000/hr in lost production – a cost so high that some mines measure this downtime in minutes. There are many factors that can cause downtime, but the majority of cases are due to hydraulic hose assembly failure.
Ensuring uptime for continuous miners operating in these highly abrasive environments is therefore a top priority. Eaton Hydraulic’s Aeroquip X-FLEX hose has been performing to expectations and helping manufacturers servicing continuous miners meet their contracted coal extraction rate terms by increasing uptime and decreasing maintenance and service times.
“Eaton’s route to market for South Africa’s mining industry is through a distribution network for which we supply hydraulic assemblies, fittings and accessories,” explained Jorge De Lima, team lead sales for Southern Africa for Eaton’s Hydraulics business. “Many of these companies are contracted by the mine to ensure that the continuous miners meet or exceed a certain rate per tonne of coal extracted, which is why avoiding downtime is of the utmost importance.”
The area on a continuous miner where most breakdowns occur is on shear cylinders, which move the cutting bobbin. Upon daily servicing, these areas are cleared of coal debris and the assembly is checked for any cuts, signs of abrasion or visible leaks from the threaded connection. In disciplined sites, the preferred hose used on these machines is Eaton’s GH506, which offers excellent performance when cleaned and serviced regularly. The hose end fitting features a special wire trap design that requires the hose to be both externally and internally skived to help ensure hose and fitting integrity under impulse conditions.
“At one particular minesite, which operated several continuous miners, the total annual downtime caused by the failure of hydraulic hose assemblies was 9000 min. – this equates to approximately US$1.5 million in lost production,” recounted De Lima. “Here, the servicing regime had gradually relaxed over time and the hose assembly was failing.”
While the supplier was contracted to ensure that the continuous miners met or exceeded the set rate per tonne of coal extracted, it could not influence the rigour of the daily service regime. To overcome this challenge, the supplier replaced the original GH506 hose assembly with Eaton’s higher specification Aeroquip® X-FLEX hose.
X-FLEX features a rugged, abrasion resistant DURA-TUFF cover, which provides longer life in this abrasive environment compared with the original high-pressure hose. In addition, it provides a 46% reduction in force-to-bend ratio, which made it easier for the supplier to handle in the shop, and less time consuming to fit on the equipment.
When used in conjunction with one-piece Aeroquip global spiral TTC crimp fittings, the X-FLEX hose assembly is also easier to build, since skiving is not required.
“On replacement of this original hose assembly with Eaton’s Aeroquip X-FLEX very high pressure spiral hose, duty time increased considerably and downtime for the mine was reduced by 2000 min.,” said De Lima.
Squeezing lost production costs by US$333,000, by simply replacing a hose, is very attractive for the mine and indeed the supplier. With supply and service of these minesites in the region of US$50,000/month, the mine has effectively saved and recovered its spend.
Written by Eaton Hydraulics. Edited by Sam Dodson
Read the article online at: https://www.worldcoal.com/mining/22122014/reducing-continuous-miner-downtime-1702/