AFC Development

    In 1996, a new American longwall mining equipment company was founded by a group of respected conveyor system professionals and Longwall Associates, Inc., the international designer and manufacturer of longwall face conveyor and stageloader systems was born. With substantial investments in the United States and Australia, Longwall Associates, Inc. has become the only international designer and manufacturer specializing in longwall face conveyor and stageloader systems. The company produces face conveyors, stageloaders, shearer haulage systems, crushers, crawler mounted belt tailpieces and shearer cutting drums.
    Longwall Associates face conveyor drive frames are custom built for each application and the company also undertakes rebuilds of their own equipment and other manufacturer’s systems. According to Ken Dunn, Sales Manager, “Drive frame designs have not changed a lot through the years but what we have found, strangely enough, is that some of the other peoples’ designs are losing basic components, that is basic design features that were there years ago have been eroded and we are having to address issues that we would consider as a basic fundamental design.”
    Longwall Associates have invested a great deal of research and development in developing a new range of gearboxes. “We have a gearbox designer who is part of our team and we have taken a clean sheet of paper and designed a new range of gearboxes. We are hoping that the performance of these will outshine everything, so we are very excited about that development,” said Dunn.
    Kevin Howden, Engineering Manager, elaborated, “The range of gearboxes are sized by the torque. We have 20-series, 40-series, 50-series, and a 70-series under development, that is 700,000 newton-meters three second torque. Horsepower wise, they range from the 20 series, which is a stageloader gearbox and about 400 horsepower up to the biggest size depending on the ratio of about 1500 horsepower. We got everyone concerned involved from the ground level including service technicians who assemble the gearboxes, the engineering team and many of the senior people within the company. We were all invited to have an input, and we feel like we have got a pretty good product.”
    One of the critical items of a face conveyor is the chain tensioner. This can be difficult to control as there are always occasions where large lumps pass under the shearer causing sudden slack chain. Longwall Associates is doing work on the control side of chain tensioning, for even greater effectiveness.
    On sprocket designs, the company is constantly evaluating new material to provide longer life. Howden explains, “The trend is for wider faces and longer panels, so customers don’t want to change the sprocket in the panel. We are constantly being asked to go from two to three to four and beyond million ton panels without changing sprockets, so that is what we are striving for. We believe we have a product among the best and we are developing different materials to go beyond that.” Longwall Associates has developed a new patented non-driven return end that is the same design regardless of the width of the stageloader and uses the theory of skidding flight bars to eliminate the usual stresses.

    Today panlines are getting bigger and chain speeds faster. “I think the ultimate width of conveyor today on the face is 1.2 meters,” said Dunn. “I guess that will go up in a few years time but that is the widest at the moment. Chain sizes are operating up to 52 millimeters but I don’t see them going further than that for the next few years.” Stageloaders are also getting bigger and faster. “We have found that fitting 30-millimeter chain on stageloaders is out of the window,” said Dunn. “We suggest larger chain sizes for more reliability such as 38 millimeters.” 
    The subject of automatic chain tensioning on face conveyors was given greater attention beginning about a decade ago as larger chain sizes were used and face conveyor auto tensioning taildrives have become more popular. “Basically the old method of using twin cylinder push on a tensionable tail drive has now been replaced by a single cylinder on the gob side which is easier to use with less hydraulics,” said Howden. “Also you don’t have to worry about protecting the cylinder on the face side from the ranging arm. There is now more sophistication with regard to the monitoring of the drive itself to position and sense the pressure within the system so it can react accordingly.
    Not all face conveyors are fitted with an auto tensionable tail drive and Longwall Associates feels that further explanations need to be given to some customers to demonstrate the advantages of the system and the very great importance of chain tensioning.
    In face conveyor applications, there is a considerable amount of custom design work to suit the customers’ mining plan. “To get the chain races to last through a long panel is sometimes a work of art,” said Dunn. “We have got special designs on the table that allows us to do that with extra heavy duty races. This gives customers the opportunity to work not a panel, but multiple panels, and that’s a real big feature for most operators these days.”
    A range of stageloaders is also designed and produced by Longwall Associates to match their face conveyors. With bigger chains in use and seam heights getting lower, face conveyor speeds have become much faster. “Face conveyor speeds over the last decade and a half have increased typically to between 300 and 350 FPM,” said Dunn. “It’s commonplace to have stageloaders today running at 400 to 500 FPM and the bigger chains are used to achieve that without any in panel maintenance.”
    As seams have got lower, the problem of volumetric capacity becomes increasingly important. “There are some things that we have done to the stageloader drive itself to use a different type of race which allows us to gain a few inches there,” Howden said. “Currently we are able to manufacture some of the lowest height belt tail pieces for a given application including side shifting capabilities. In these couple of areas, we can really gain as much as four to six inches in height.” 
    Stageloader widths are now up to 1.5 meters wide and Ken Dunn feels that there is no need to go much wider than that in the next few years but that volumetric capacity is a really critical matter. “This is one that we address very very well and we have been successful gaining business by our approach to that. We’ve got floating coverplates, which are controlled by the material flow itself, not hydraulics. This simplicity has gone down very well. I also think that side shifting facilities now are almost essential with belt lifting devices incorporated as well. Things have become very sophisticated and we’ve got a good range, probably the biggest in the industry from the largest out at Sufco to the smallest unit at Dugout Mine when they first went into production.”
    Longwall Associates has also developed a new range of crushers. The largest one manufactured to date is for JWR No. 4 Mine in Alabama. The conditions there are very arduous due to the amount of rock. That machine is fitted with a 500 HP motor, is belt driven and has a kinetic energy of over two million foot pounds including the motor. The machine allows Jim Walter to twin seam mine for the first time since the late 70’s when they started mining.
    Over the years, Longwall Associates has developed partnerships with its customers. “They are starting to share their mining plans with us and discuss what we want to achieve,” said Dunn. “We’ve got the flexibility of design to be able to produce equipment that will suit the mine plan and get the expected life from the equipment.” This allows effective planning years ahead and equipment to be properly custom designed for the job.
    Coal Leader asked Ken Dunn for his thoughts on the occasion of the Longwall Associates open house. “We are very pleased with the way things have gone in the last few years from a small company starting out in competition with other companies established for many years. We have found a niche where we want to be and customers are starting to recognize our capabilities and our general approach. If you look at the experience that our staff has we’ve got more experience than anybody else and we are the only specialists at face conveyors in the industry. We pay attention to detail and we have got a fully American made product. We are all proud of it.”
    The engineering challenges for the company are substantial. “We are always being pushed to the limit to make it faster and stronger and smaller, so that is my challenge and thankfully we have some good tools,” said Howden. “We use the latest technology with the 3D design and we are kept on our toes as always. We are in a good position to take advantage of the market.”
    Longwall Associates currently has 100 employees and are running well within their capability. They have seen a steady increase in business in the last couple of years and have got further room to grow. Both Dunn and Howden have over 70 years between them in longwall face conveyor experience and find it to be a pretty exciting time.
    “I have a final comment on quality,” added Dunn. “I’ve been in the industry now for 35 years and have never seen such an organization that’s in complete control of the quality of equipment that goes out the door. This says a lot for the capabilities of the guys in the shop. Also, with the price of downtime being enormous the increased reliability for our customers is vital. This is certainly one of the things I’m very proud to be associated with,” he said.     cl

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