Published in the May 2009 Coal USA Magazine

As the needs of mines change, suppliers and original equipment manufacturers have been working to remain a step ahead. Responding primarily to customer feedback and the trends it has noted over time, the West Virginia company took to the drawing board and emerged with a new product, a new 35-inch, 800-ton yield MRS.

While promoting the new product, JH Fletcher has also sought to remind an industry seeing a resurgence of interest in methane gas collection and horizontal exploration that the LHD remains a multifunctional and vital underground staple.

Mobile Roof Support

“As the need for productive mining alternatives increases, the number of mining operations using Mobile Roof Supports for retreat mining is growing,” according to Fletcher officials.

“The mining industry is seeing that, when properly used, Mobile Roof Supports can allow the economic recovery of reserves with a higher degree of safety and improved productivity.”

As US mine faces advance into much deeper, thinner and anomalous seams than ever before, Fletcher evaluated its 600t MRS initially introduced to the product line in 1988 and gave it a significant makeover, releasing the most recent version last year.

The original unit had a yield of 600t and workable spread of 32-63in. As many operators are encountering the need for higher-capacity equipment under much heavier overburden, Fletcher upped the capacity yield to 800t in the newest model to its lineup and extended the range to 35-66in.

The new release model has many of the same features as the 600t-yield unit, including an alloy steel design and sloped edges to minimize lateral stress and allow the support to clearly tram through loose roof. Both also have a side-to-side roof assembly with a 15-degree range to help more closely match the roof horizon underground and a front-to-rear operator-controlled support plate tilt with a 25-degree range for safety.

Additionally, both the 600t and 800t models are controlled remotely via a lightweight radio remote transmitter. Powered by just a 9-volt battery, the fire suppression system can also be activated with this remote.

What’s new for the 800t unit, however, is a newly-developed and digitally-enhanced load monitoring system that keeps an operator abreast of the unit’s status at all times. Officials said significant engineering upgrade work was also done on the recently-released model.

Unfortunately, those mines seeking to retrofit their 600t machines with the new capacity and collapsible height are out of luck. The company noted that conversions simply were not possible due to the unit’s intricate design. However, the company said interest in the piece had increased and it was recommending it for all new MRS orders.

LHD horizontal drill

It was introduced in 1978 – a boom time for coal, but also an era of mining which had vastly different goals than those of today’s mines. All along, though, Fletcher’s LHD horizontal drill has remained key to the needs of operations.

Primarily used for coalbed degasification to drain methane ahead of longwall panels, the company said the LHD has been in contact with coal seams across all of the nation’s coalfields.

While initially capable of achieving a horizontal long hole of 2000ft, some of its recently-reported holes have extended more than a mile.

The unit has always featured robust details, including rotational torques up to 2500ft/lb, hollow shaft drill chucks for EW, NQ and BQ rods, and both in-hole motor and straight rotary drill systems. It can be customized with skid mounts, dolly tows, rubber tires or crawler drive undercarriages for the specific needs of a mine.

Additionally, it is permissible for use in 480 or 575 VAC electrical systems, and a load-sense hydraulic system keeps operators on top of the unit’s status at any time.

As the mining industry has seen a large resurgence of interest in pre-development exploration for cost-efficiency and safety, the LHD is a pocket ace for a company traditionally considered one of the nation’s most extensive strata control suppliers. Renewed interest in methane capture, particularly during recent years amid innovative coal liquefaction efforts in the US, has also brought this unit back to the forefront.

Fletcher officials said the drill had been a flexible solution for other situations as well, including the dewatering of coal and rock, mapping old workings, and the draining of oil beds in Wyoming.

No matter the use, the company noted that it was a steerable drilling system and could achieve quite accurate drillhole placement when used with new survey and guide systems that have entered the industry spotlight in recent years.

Available in thrust capacities of up to 100,000lb with rotational torques of up to 5000ft/lb, officials note that the most common range for coal remains in the area of 50,000lb for thrust and 3000ft/lb RT.