Published in the August 2007 American Longwall Magazine

There is a large gap between automation levels at US longwall mines. According to Norwest Corporation's longwall automation survey, conducted this year with 70% of US longwall faces represented, there is a big difference with the haves and the have-nots on an automation level. As a rule, relatively new mines are using higher degrees of automation is no big surprise. However, what is surprising is that the average typical longwall is about half as automated as the most automated face in the US.

So what is longwall automation? Definitions can vary wildly. In the Norwest survey the meaning was left up to the operator. Depending on who you talk with, some define automation as no workers on the face, while others think workers may still be on the face as the "eyes and ears" in the event of problems.

The largest contradiction that the survey revealed was the productivity gains recognized in using automation, but the reluctance to install because of start-up costs. All operators responding to this question reported that automation on their longwall faces had improved productivity levels. Productivity increases, against using manual controls, of 10-20% were estimated by operators for approximately half the faces. One operator reported that automation has gained 1.5 to two passes per shift.

So if large productivity gains can be made, why is it 60% of participants consider the cost of automation as a disadvantage? Survey coordinator Kirk Nobis offered up some rationalizations: "Sometimes certain features may be hard to justify at the time of purchase. Some mines may not have a market for the extra production gained and therefore spending dollars is a concern."

The negatives operators raised about automation included the worker skill level required, the cost involved, and work force integration.

Operators for four out of five faces report equipment operator and maintenance skill levels must be higher when using automation on the longwall faces. Manufacturer training and support was cited as being very important to successful automation. One operator reported that "[automation] does make us better mechanics and electricians. We have to do this".

Work force integration of automation features was reported a disadvantage by the operators for relatively few faces. "Operators reported that a factor of the workforce acceptance of automation is concern about the possible loss of jobs. One operator reassigned any redundant face workers to other longwall-associated tasks such as outby support and other utility work," Nobis said in his report.

While disadvantages to automation were raised, a lot of advantages also came to the fore. The most commonly reported benefits were centered on overall cost implications with associated increased productivity levels and reduced work force requirements. Health and safety benefits were cited by all operators, as well as increased system availability.

Operators, for approximately one-third of the faces, reported improved coal quality in conjunction with reduced Out of Seam Dilution (OSD). One operator believed that reduced OSD by itself justified the cost of the automation features.

The benefits of longwall automation were reported for the following percentages of faces:

• Cost implications - 100%
• Health and safety benefits - 100%
• Increased productivity levels - 100%
• Overall system availability - 94%
• Reduced work force - 87%
• Improved coal quality - 32%
• Reduced OSD production - 29%

If the benefits are fairly obvious for automation, what is holding many mines back? Nobis offered up a couple of suggestions:

• "What we are doing now works for us" - meaning there is no incentive to change.
• Geologic conditions - automation may not be able to adapt to changing conditions such as varying seam thickness.
• Just making the change required management priority and committing the time and resources to do so is a large hindrance.
• Some safety concerns on remote operations.

Looking at the different facets of automation, almost one-third of faces reported using some sort of automated cutting - such as face cutting sequences, wedge cuts and gate end turns. The most commonly automated cutting used was programmable or "memory cuts" along the longwall face when wedge cuts or gate end turns were not required. Memory cutting cycles were reported used from 50% to 70% of the face operating time and as high as 98% of the time. Only three faces were reported using automated cutting for gate end turns.

Five faces were reported to be using automated cutting for wedge cuts. One face was reported to be using remote "off the face" operation of the cutting machine cycle. Safety issues were cited as a reason by several operators for not using remote shearer operation.

Almost half the faces utilized automation either to directly control the shearer cutting speed or to provide feedback from the cutter motors. Horizon control was in use at four faces. Approximately four out of five faces transmitted data from the shearer to the surface.

Approximately 75% of the faces reported using automatic machine shutdown in the event of abnormal maintenance conditions. About one in five faces reported using collision prevention features to control shearer movement.

Almost all of the operators reported using the shearer to initiate shield movement, with infrared signal the most commonly reported method for activating the shield movement. The majority of faces practice multi-shield activation and the use of reed rod sensing to aid in face alignment was reported on about half the faces.

More than 70% of the longwalls reported automatically collecting data from the face equipment for maintenance monitoring, while 83% of the faces monitored the shield leg pressures.

The survey found numerous AFC functions to be automatically controlled including:

• Chain tensioning - 93%
• Start/stop - 92%
• Ram push - 73%
• Alignment - 57%
• Load sensing - 42%

Almost half of the crusher and stage loader systems are automatically controlled for start and stop operation, but only 13% are monitored for maintenance issues.

Approximately 85% of the faces transmitted data to the surface for display.

Operators reported linking key equipment set points and alarms into the mine's leaky feeder radio system. Automatically enunciated voice messages would be broadcast to crew member radios about equipment conditions such as overloads and stoppages.

The survey also dealt with an operation's "wish list" of automation features. Those mentioned included:

• Fixed or improved horizon control
• Optimum shearer cutting rate in conjunction with other equipment
• Face alignment
• Increased real-time machine condition monitoring
• Better video cameras
• Remote operation via video links
• Warning system for face stress areas
• Automated air curtain to isolate fresh air from dust
• Complete face cutting
• Improved memory cut repeatability

Interestingly, most of these "wish" features are actually currently available and in use at some longwall faces. Which begs the question - why are they on a wish list? Nobis suggested that some mines might have the automation capability but don't realize the capacity is there; the older equipment possibly did not have automation features when new, and the mine has continued with the status quo; and the typical mine manager may have so many day-to-day issues that they simply have not looked at automation.

So do operators think that the day of the fully automated, remotely operated face is near? Only about 30% thought that an automated face was possible - whether at their mine or elsewhere. Five of the nine mines with a high automation rating stated full face automation was possible or probable at their mine or another mine in the future.

Operators reported buying equipment compatible for full automation, but stated numerous issues must be addressed and answered before full automation would happen.