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By D. Harrington

At the time of mine accidents one frequently hears the expression "there will be accidents as long as there are mines", or it may be varied to state that the accident in question was unavoidable, or something similar indicating inability to prevent accidents. However, it is the opinion of the writer, after over twenty-one years experience in both coal and metal mining, seven years being spent wholly in safety work, that by far the greater number of all accidents is due to carelessness or negligence. This carelessness or negligence may be on part of the victim of the accident or of one of his companions, or on part of his employer or possibly even of the inspector or safety man, and in some cases all of these agencies are involved. It manifests itself in various guises, one of the most serious being violation of state mining laws or regulations or of mine rules, and frequently the rules of ordinary common-sense. The cause very frequently is that trait in human nature to "take a chance" and it has been the writer's observation that the worst offender is the old-time miner who has come safely through many years experience, who was mining when the "safety man was a baby", and who clings to old-time ideas and practices and has "no use" for "newfangled" present-day "notions". Unquestionably, there are accidents, wholly unavoidable and many are caused by ignorance and by the new-comer in mining, yet as previously indicated, the writer's observation is that the old-timer is by far the worst offender, bringing grief to himself, companions and employer. Of the numerous manifestations of carelessness and negligence in connection with mine accidents, which have come to the notice of the writer, only one will be treated in this paper, viz: Violation of State Mining Law, and mention will be made only of explosions and major accidents in coal' mines with which the writer came in personal contact as investigator. In most cases, in addition to mine inspection after the accident, the writer heard the evidence given at Coroner's inquest and thus was enabled to for¬mulate fairly definite impressions as to events and conditions leading up to the occurrence.

Jan 1, 1922

A great many questions were asked Mr. Bright, and Mr. Bright's opinion was given on a number of subjects. He spoke at length on spring suspension of locomotives, bringing out the necessity for better spring suspension due to heavier weights and higher speeds now developed. The subject of dynamic braking was brought up, and the opinion of the engineers present was that dynamic braking was not a desirable feature except where heavy, long, adverse grade is encountered. Mr. Goddard and Mr. Bright had a spirited discussion regarding ball bearings, bringing out the opinion of the meeting that ball bearings in motors are preferable to sleeve bearings, and the few failures so far encountered are due to improper application or insufficient size of bearing. Mr. Shubart brought up the question of locomotive speed, mentioning some high speed work on main haulage, also an interesting experiment in a large Eastern mine where very slow speed, 3 1/2 miles per hour, gathering locomotives were substituted for the high speed gathering locomotives with an increase in cars gathered and a material decrease in derailment and accident. Mr. Bright mentioned the improvement in gathering reels, and Mr. Shubart mentioned the safety in the use of the concentric cable in direct current, using the outer wire as the ground wire, so that in case of accident to the cable, the ground wire acted as a protector to the live wire, materially decreasing the danger of sparking. Mr. H. I. Smith of the Bureau of Mines brought up the question of explosion proof construction, and Mr.. Bright and. Mr. Shubart explained the construction adopted by two of the larger manufacturers. Experiment has shown that the force of explosion in motors due to gas does not exceed 150 pounds per square inch. All forms of screen or baffles have proven an actual source of danger, due to the collection of dust, usually soaked in oil, forming an active means of propagating flame, together with the fact that all these appendages are frequently left off when the motors are repaired. Modern construction eliminates all openings, screens, devices for stopping or extinguishing flame. The motor is made entirely enclosed, practically air tight, all joints are ground and all openings necessary for access and attention are closed by bolted plates. The case is made stout enough to withstand any interior explosions, and ample ribbing is provided for heat dissipation. Mr. Bright was asked regarding the use of contactor control. He replied that his company is now recommending contactor controls for series and parallel starting on all locomotives of 13 tons and over, and particularly on the tandem units that are now becoming popular in coal mining work. The question of dynamic braking and reversing was brought up and Mr. Bright explained that this made a very complicated contactor installation but they had

Jan 1, 1922

By Scott Dupont

Due to the scarcity of miners, and the necessity of decreasing the cost of mining, the Phelps-Dodge Corporation, Stag Canon Branch, at Dawson, [ ] New Mexico, decided to try, by various methods of mining, to increase the tonnage of coal mined per man, per day. With this in view, they first tried mining on a 250-foot face, maintaining the track at the face and using six to eight men shovel- [ ] ling. These men were able to aver age from ten to twelve tons each per, day when they were loading, but with

Jan 1, 1926

[Participating Scholarship Colleges and Universities 144 Andalex Resources, Inc 91 Behre Dolbear & Company, Inc 93 Canyon Fuel Company, LLC 92 Big Sky Coal Company 114 Commercial Testing & Engineering Company 96 Continental Conveyor & Equipment Co 97 Copper Mountain Resort 108 Cove Shoe Co., Inc 110, 111]

Jan 1, 1999

Jan 1, 1985

Jan 1, 1926

By Stanley C. Suboleski

Overview ? Ten minutes or ?the hook? ? Focus on Appalachia, productivity and production ? Message: ? Appalachian mining scene has fundamentally changed

Jan 1, 2007

Jan 1, 1927

MR. GERALD ALLEY (C 11 i e f Draftsman, C. F. & I. Co.) : This invention is primarily intended to correct anything that goes wrong with the fan and any conditions in your air current underground which do not produce a change in your fan water gauge

Jan 1, 1925

MR. HARRINGTON: I would like to ask Mr. Bottomley if they fire their shots while the men are in the mine? MR. BOTTOMLEY: No sir; the shot-firing law in our State requires the shots to be fired after the men are out of the mine. We fire more shots than we did under the hand method of loading. Where formerly four holes were drilled, now we drill eight, using the same amount of powder as we did formerly, perhaps a little more, but we use a slower grade of powder. CHAIRMAN LITTLEJOHN: Any further discussion, gentlemen? MR. GIBSON: Mr. Chairman, I would like to ask Mr. Bottomley, if, in his shot-firing system, as I understand it, he has a very high coal and is working something like eleven feet? MR. BOTTOMLEY: Something like that. MR. GIBSON: I read the article that you referred to. Did you use both the first and the second delay explo¬ders in shooting the coal? MR. BOTTOMLEY: We use the ordinary fuse. MR. GIBSON: That is what I wanted to find out; whether you use the delay exploders and the detonators. In Utah, we are getting away from the fuse altogether, because we do not think it is accomplishing anything to use the electric light on the cap, and' at the same time shooting with fuse. We are defeating the object we might gain in using the electric safety lamp. That is a point that might be discussed a little further. MR. E. H. JOHNSON, The Coloder Company: I would like-since it is a general opinion that mechanical loading breaks up the coal, to ask Mr. Bottomley, if he finds a larger percentage of small coal, or how much, through the use of the mechanical loaders? MR. BOTTOMLEY: We do not find any great difference. In fact, we have succeeded in improving our lump coal percentage, and that is important, because it is largely domestic. At first, when the machines were installed, the boys shot the coal too hard, and we fell down a little, about two or three per cent, the first month, in our lump percentage, and we tightened up a little and changed our methods in shooting and got on to the stunt of drilling more holes and getting a slower grade of powder. We could not load as much coal in one day as we could before, but we did succeed in in. creasing our lump coal percentage four and a half per cent over the hand method, and that is quite a factor-quite an important factor and since our domestic trade is over with, we loosened up on the shooting and we are running about the same as we did with the hand loading, maybe a half per cent more, or one per cent, but pretty much the same. MR. SHUBART: Your coal is very high? MR. BOTTOMLEY: Yes. MR. SHUBART: Have you tried sunbbing the coal before shooting? MR. BOTTOMLEY: No, we have not tried that. It is very hard coal to shoot; we have no defined cleavage in our coal. It is the worst coal I ever saw to shoot. We do not try to snub it. Formerly, as I said, the miners drilled four holes, pretty well up near the top, and then four holes down, within about three feet of the bottom. It is the same thing as a snub shot, and that we find is the best method for shooting the coal. We have not tried any mechanical device for snubbing as yet. SECRETARY SHUBART: At one mine I saw snubbing tried with a Jeffrey undercutter with a seven-foot Jeffrey bar. This mine, by the way, is very similar to Mr. Bottomley's condition. They have very high coal, so the snub cut is a small percentage. They cut a seven foot undercut and raise the machine on an eight inch tie and undercut five feet to give the effect of a snub cut, 14 inches at the front of the cut, and then six inches at the back of the cut. They made a very marked increase in lump. (The bug dust would be a small percentage of the total coal), and they increased the percentage of the slack at the same time. They found a decrease by reason of the easier shooting of about 15 per cent in their slack. In other words their nut and lump coal ran considerably higher and their slack decreased 5 per cent with the snubbing cut. Mr. Bottomley, I believe, understands those conditions.

Jan 1, 1926

The 65th Regular Meeting of the Rocky Mountain Coal Mining Institute convened at the Stanley Hotel, Estes Park, Colorado, and was in session at 10:00 a.m. The first session was called to order by Past President Joe T. Taylor, Kaiser Steel Corporation, Palo Alto, California. Manager of the Stanley Hotel, who welcomed the guests to the Stanley. After a few remarks, he introduced Bob Dean, for- mer Manager of the Stanley Hotel and again associated with the Stanley, who also made a welcoming talk as Mr. Dean has hosted the Institute at the Colorado Hotel in Glenwood Springs and in Estes Park. Mr. Taylor introduced President Stanley C. Shubart, Secretary-Treasurer, Schloss & Shubart, Inc., Denver, Colorado. Stan was raised in the machinery end of the coal industry following the footsteps of his Dad who was one of the founders of the RMCMI in 1912. And following his Dad's years of service to the Institute, 12 of them as Secretary, Stan has been active as Chairman of the Hotel & Registration Committee for 16 years, and, prior to his election as President, was General Chair- man for two years He is a graduate of the University of Colorado with a degree in mechanical engineering. He served our country in World War II and retired as a Colonel, Army Ordnance, after 43 years in the Reserve. He is a Trustee of National Jewish Hospital and was their President for 3 years. He has been active in many Military and professional societies, and in civic projects. I give you our President, Stan Shubart, for his remarks.

Jan 1, 1969

By C. E. Drennan

Your Chairman and the Program Committee have limited the time allotted to me, and so, with your permission, I will omit the preliminaries, and wade right into my subject. I believe I am safe in taking for granted that you are all agreed that electricity is the most feasible means of transmitting the power used in coal mining. If you are not, then the papers read before the Association in previous years have failed of their object. If you are so convinced, the only question is as to the choice between alternating and direct current, and the voltage. Fundamentally, this is primarily a matter of dollars and cents. With the sole exception of your trolley locomotives, there is no part of your equipment that cannot be operated as well on alternating as on direct current. With your pay rolls at their present high level and the efficiency of the labor you employ at the stage it now occupies, I believe you will agree, first, that everything possible must be done to increase the tons of coal produced per man employed; and, second, that ample power at all times must be available at every machine so that every one of your men can really get out a day's work without any avoidable delay. Speaking Electrically, all this means is a machine instead of a man wherever it is possible for a machine to do a man's work, and full voltage at the machine always, so that there can be no excuse for the work not being done promptly and efficiently-and dependably. The real reason for the selection of one kind of current or the other can best be understood by considering the formula which determines the size of wire required for transmitting electrical energy. The size of the copper required, and, consequently; its weight and cost, depends upon four factors: 1. The amount of energy or power to be transmitted. 2. The distance to be covered. 3. The percentage of loss allowed. 4. The voltage at the receiving end of the line. These factors enter into the problem to different extents, and, briefly, the size of wire depends directly upon the amount of power and the distance transmitted, and inversely upon the percentage of loss allowed and the square of the voltage. From this it will be seen that, with the amount of power and the distance fixed, if the loss is to be cut in two, the wire must be doubled with a given voltage, while if the loss remains constant and the voltage is doubled, the wire may be cut in four; that is, reduced 75 per cent in weight and cost. Now, standard motors are designed and recommended by their builders to run within a range of 10 per cent under voltage to 10 per cent above voltage - 440-volt motor, then, should preferably not be operated on less than 400 volts

Jan 1, 1923

PRESIDENT LITTLEJOHN: The paper of Mr. Emrick will now be open for discussion for about twenty minutes. The meeting is now open for discussion. MR. EMRICK: There is some question that may have occurred to you at different times, that is how are you going to tell when the bits are properly made? A fairly good rule to go by is when the used bits come out of the mine, if half of them are bent and half of them are broken, the average is pretty good MR. GEO. B. PRYDE (Union Pacific Coal Company): I would like to ask Mr. Emrick if he has any figures as to the saving of Dower with the different styles of its. MR. EMRICK: I suppose you mean chisel point bits and pick point bits? MR. PRYDE: Yes. MR. EMRICK: So far as I have been able to learn, the only reason why chisel point bits are used is to prevent coring that might be done by the cutter chain. The pick point bit, of course, is the proper thing to use. It can be used when the position of the cutter links in the cutter chain is right. I do not know of any figures which give power consumption ratings on the use of pick point and chisel point bits, but there are tests and ratings, etc., which have been taken- which have been tested as against different bits, which have been given proper clearances against bits not having been given proper clearances, and they will run,-in their saving in power, they will run 20 to 25 per cent. MR. A. C. WATTS (Chief Engineer, Utah Fuel Company) : I would like to ask Mr. Emrick if he has any record showing the saving in power on using the alloy steel chisel bits. I know that several experiments have been made; I do not recall the figures now, but we had a very decided saving in power. MR. EMRICK: I haven't any of the records. Do you think that is because of the steel that has been used? MR. WATTS: Well, they were all sharpened by the same man and used in the same machine, and at the same shop. I do not know the composition. It is "Red Star" Vanadium that I had in mind. MR. EMRICK: I have not seen any records. Some companies are using the tool steel bits because they stand up a little bit better. MR. BENEDICT SHUBART (Secretary) : I was going to ask Mr. Emrick about that question. There is one company that does not recommend tempering the bits. They recommend using not exactly self-hardening steel, but one that is bard enough without quenching-they use 80-90-point car- bon but about a 70-point manganese, not exactly self-hardening steel, but they do not temper this at all. Will Mr. Emrick state if a steel of that kind could be worked in the bit sharpening machine that his company makes, as it

Jan 1, 1925

The second annual RMCMI Mine Rescue Performance Evaluation was held in conjunction with the 1993 RMCMI Convention at Beaver Creek. [ ] Six teams participated in this year's evaluation; BHP Minerals, Navajo Mine, Fruitland. NM; BHP Minerals - LaPlata Mine. LaPlata, NM; BHP Minerals - San Juan Mine. Waterflow. NM; The Coteau Properties Company - Freedom Mine, Beulah. ND; Cordero Mining Company, Gillette, WY; and The Falkirk Mining Company - Falkirk Mine. Underwood, ND. The Western Energy Company of Colstrip, MT was represented through observers and evaluators. [ ] Realistic industrial related scenarios, closely simulating the stress of actual rescue incidents, were provided by members of the Eagle Valley Ambulance Service. Five different scenarios were presented to each team on the first day of the evaluation and three on the second. Each team was given the pertinent information to solve the problem as they assembled at the scenario site. The scenarios were going on simultaneously and each team was unaware of the circumstances until they entered the scene. Interested onlookers were afforded the opportunity of viewing the actual simulated rescue operations as they occurred. The teams received valuable pointers and direction from the ream of evaluators following each scenario. They were are also given the opportunity to observe the other teams in action and to meet with the members of all the teams to share information and ideas during team meetings per the predetermined schedule. The primary goal is to recognize current rescue skills, knowledge, and abilities of participating teams. In doing this, each team was provided with individual evaluations and a path for improvement as needed. Each team was recognized for their efforts at an awards breakfast on the final day of the evaluation. New innovations in rescue equipment were introduced and demonstrated for interested teams following the awards program. The importance of progressive training such as what we are witnessing at evaluations during the RMCMI conventions cannot be stressed strongly enough. These teams are the providers of immediate rescue and medical care for victims of accidents at their respective properties. Every mining operation has the potential for very serious accidents due to immense size of equipment and mining logistics. These rescue teams must be prepared to act with the most immediate, professional and knowledgeable actions to save lives and prevent further injuries. Safety is a primary concern of every mining operation and the mine site rescue team is an integral part of that safety effort. The evaluation program is very appreciative for the financial support of the following businesses to enable this program to continue: Safety Master, Acme Welding, North American Coal, Triune. Cummins, OK Tire. Modern Industrial, The Industrial Company, Mine Safety Appliances (MSA), Biomarine, Personal Safety Enterprises, Inc., and Blattner Construction, Thank you again for your much needed assistance. Plan to be a part of next year's Mine Rescue Evaluation Program as a participant or an observer. You will be amazed at the skill levels of the Rescue Teams. See you next year! Linda G. Ash The falkirk Mining Company [ ]

Jan 1, 1993

Jan 1, 1981

Jan 1, 1987

CHAIRMAN LITTLEJOHN: Some of the members will want to question Mr. Farnham on some of the things he has brought tip, so we will throw the meeting open for discussion. I am quite sure Mr. Farnham will be willing and glad to answer any questions that may be put to him. MR. HOLMAN: I would like to ask Mr. Farnham a question in regard to the Duckbill: How wide a face will it operate without moving the bill? MR. FARNHAM: The Duckbill is a device that was developed in the Union Pacific Mine at Rock Springs, within the last few months, and it is shaped something like, a dustpan, with discharge throat in the rear. They made one seven feet wide and found it was too wide, and the one they are using now is between three and four feet in width. The front section of the conveyor, which attaches to the duckbill, meshes into it to form a sliding section, and the front end of the Duckbill is pushed by the upper segments. I saw one used in a room twenty-four feet wide, and they drew it back after they cleaned out one room and pushed it forward again. MR. HOLMAN: You have no arrangement other than ratchet work? MR. FARNHAM: The ratchet is for forward working and back; the sections are made 12 or 13 feet long, and the stroke of the conveyor automatically works the ratchet; they can ratchet it back; it is a hand device. MR. HOLMAN: They just swing the end of the conveyor across the face to pick up the loose coal? MR. FARNHAM: Yes; they are also planning to use it endwise along the panel face, that and the room work both are quite new in their application, and I do not think the Union Pacific is giving out any results as yet, because the system has not been in use long. MR. HOLMAN: We are planning on putting one in very shortly. MR. HALL: I understand they can swing it over 30 degrees one way or the other, and it goes the same way easily because of the continual jar of the back and forward motion on a 60-degree swing. SECRETARY SHUBART: Take on a comparatively long conveyor, you can get quite a sweep, a large part of the circle. The Duckbill could command quite a large range. For a 12-foot entry, take a four-foot wide advance through the middle of the shot coal, with a 12-foot advance, ratchet back, swing the Duckbill to the rib and repeat; but I do not think they could get as much as 60 degree. on the end of the Duckbill without curving further back. The conveyor is light and not normally set on any permanent foundation. I saw one of Mr. McCarty's first machines, a rather rudimentary one, clean tip a 12-trot entry, 21 tons of coal, in 16 minutes, three men at the face and one at the loading end. MR. FARNHAM: The average time to clean the entries is about an hour-to clean up good-it wouldn't take but a short time; that is why they get this record of several cuts a shift. CHAIRMAN LITTLEJOHN: Are there any other questions you would like to ask Mr. Farnham? MR. HOLMAN: We were discussing this entry driving in regard to the entry loader; an entry loader in advance work, just what you have to do to place the jackbars with the sheave-blocks? Do you dig along the ribs after the coal is shot or do you have any other scheme that could be worked out to a good advantage? MR. FARNHAM: This record is a report I have just received from our Chicago office, without the full details, which I have written for. I am sorry I cannot give you the details. This was an Indiana or Pennsylvania mine, near Pocahontas, not the one where they had an accident. I assume they set the jacks ahead and swung and dumped the coal partly out with a scoop and partly by hand, but the application for that for entry driving is entirely new. The reports stated that they anticipated using that as a standard method of entry driving in the future. I will be glad to see that you get a copy of it when I get the report completed. MR. MONAY: Mr. Shubart, did you say they loaded 12 tons in 16 minutes? SECRETARY SHUBART: Twenty-one tons. MR. MONAY: How long did it take to change the machinery out of there

Jan 1, 1926

By F. C. Miller

The briquetting of fuel is an industry centuries old and has followed the hammer and tongs method of making use of any by-product fuel by the simple process of sticking the mass together with anything that will stick. If fuel briquetting, as an industry, once in the lead over coal mining, had kept pace by introducing science, there would not at this time be the mad scramble to look up the fuel briquette family tree and accept every new method as fruit without the cultivation that makes fruit worth while. Cultivation of industry is a mass of evidence showing a tremendous expenditure of money for mistakes paving the way to success. Cultivation of the mining industry is practiced by nations and low temperature distillation and fuel briquetting will in the near future receive the same consideration. Fuel briquettes were used as a winter fuel in Ireland and Scotland before the discovery of America' or the introduction of coal as a fuel to replace briquettes in Ireland. This industry was practiced by the peasants who collected peat from the bogs and cut it into brick-shaped blocks, which were set up to dry in the sun and stored under cover for use or for sale. Demand for peat briquettes led to competition that resulted in a highly refined fuel. In some localities the peat was ground and purified from the earth by washing before placing in presses to squeeze out the excess moisture and form a block of peat about four inches thick. These blocks, after standing in the sun for a few weeks, were cut into briquettes about four inches square by twelve inches long and moved under cover where they remained until thoroughly dry. In this form peat makes an excellent fuel with considerable heat, small amount of smoke while burning, and tough enough to stand hauling in carts and boats without breakage. Slack from domestic coal, non-coking and anthracite, has until recently commanded a very low price and the attention of briquette men has centered on ways and means of preparing this class of fuel for the market in the form of briquettes. Industrial plants with automatic stokers have taken kindly to cheap slack or slack that was cheap because the price has been boosted to a figure where the cost of slack plus the cost of binder and operation makes fuel briquettes somewhat expensive. However, fuel briquettes are being turned out in commercial quantities to compete with prepared lump coal and the demand is in favor of the briquette man. Science has been called to aid the briquette and it is possible to purchase a complete coal briquetting plant that will turn out between four tons per hour and thirty tons per hour of briquettes at a calculated cost per ton to cover material and every item down to insurance on the plant. A few briquettes are being ' made with a mixture of- Portland cement and pulverized coal, where this class of briquette is cheap in the making, there is the increased amount of ash due to the cement to contend with and the briquette is not one that can compete with lump coal. Most binders have a fuel value, such as coal tar, pitch, asphalt residium, flour, glue and secret binders. Most briquettes are of an egg shape, weighing between one and one-half ounces and five ounces, pressed to form with a pressure varying between 1,000 pounds and 2,500 pounds per square inch. This' pressure, together with the binder, make a lump of fuel harder than most grades of soft coal. Most of the briquettes are free from pitch odor, and any tendency to leave a trace of the binder on the fingers, easy to handle, quick to, ignite, high in heat value and capable of indefinite storage without any change. Evaporative efficiency of briquetted fuel in stationary, marine and locomotive boilers has proved that a great many low-grade coals can be fired successfully in the briquetted form, where the same fuel without briquetting failed to give boiler rating.

Jan 1, 1923

By F. T. Baker

The Primero mine, operated by the Colorado Fuel & Iron Company, is located 17 miles west of Trinidad, Colorado, in Las Animas County. Unusually bad roof conditions, along with heavy side pressure and other conditions causing rapid decay of timbers, all combine to create a very serious timbering problem. The height of the coal averages six feet six inches. It is a heavy coking coal and has a tendency to become easily crushed and broken down in the seam. The seam lies about 35 feet below the sandstone and the intervening formation is composed of loose shaly rock, and as the coal is extracted, the air slackens this rock to such an extent that within 24 hours, roof falls varying from five to fifteen feet in height are likely to occur. Under these conditions it is necessary to use cross bar sets in both rooms and entries, and they must be spaced no further apart than three and one-half foot centers, and be maintained within a distance of three feet of the face. Rooms are spaced on fifty footcenters, and cannot with safety be driven to exceed 14 feet in width, and 200 feet in length. The large pillar must be maintained to protect from side pressure, and the rooms must be driven up and retreated with as quickly as possible to avoid the squeeze caused by the intense side and roof pressure. Best results in extraction have been obtained by driving rooms for only a distance of 150 feet. Under these circumstances, it is readily seen that timbers of small diameters cannot be utilized in timbering any development work of a permanent nature. Entries are driven nine feet wide, and special peeled piling with an average diameter of 12 inches are most commonly used. It, is necessary to use lagging between each set of crossbars . Conditions such as these necessitated an immense expenditure for mine timber. In addition to ordinary seven and eight foot props, we used a yearly average of 65,000 feet of heavy peeled piling, averaging in diameter from 10 inches to 12 inches. Annual expenditures for timber of all classes was in excess of $60,000.00. Timber costs per ton averaged around 29 cents. In view of these exceptionally severe timber conditions at Primero, the company, in 1920, had a survey made with a view of providing some remedy to this problem. A comparison of the life of main entry timber at other bituminous mines was made, and an average life of four years was established. The actual data collected at Primero indicated an average of less than two years in the manway or "return" airways, and up to five years on the haulageways or "intake" airways. While some of this timber will stand up for a much longer period than this, a close inspection will reveal in most cases that its period of usefulness is spent. It is very essential when discussing the life of timber, especially that used on, main haulageways and aircourses, that a distinction be made between the point of service, that is, the point where it is sound, serviceable and able to carry weight, and the point of breakdown or failure, where it is no longer sound and able to carry weight. In figuring the life of timber, the point of service only should be considered as timber will frequently stand for a considerable length of time when it is entirely decayed and unserviceable. The larger part of the timber used for our permanent work was Alpine Fir, or what is locally termed Red Spruce, and the supply of this I is gradually becoming depleted and has to be obtained at a point so distant

Jan 1, 1926

By James J. Bryja

The production capabilities of today?s longwall systems have resulted in significant increases in retreat rates. This has in turn resulted in a heightened demand on panel development rates to assure that subsequent panels are completed in time to avoid a longwall production outage. As a means of reducing the pressure on the panel development activity a trend has developed towards the use of wider face lengths. The aim of using a wider face is to reduce the longwall retreat rate without sacrificing productivity and thereby reduce the pressure on increasing panel development rates. However, as the face width increases so too does the number of hydraulically powered roof supports that are required to control the longwall face roof. This increase in the number of units inherently translates into increases in the level of required maintenance relative to the multitude of mechanical and hydraulic components, and an increase in the time required for tear-down and installation time during the moves between panels. An obvious method of mitigating the maintenance and move-time impacts of wider faces is to employ the use of individual roof supports having a wider center-to-center spacing. This practice would serve to minimize the number of roof supports and maximize the time availability for longwall face production. With this target in mind a joint research project with DBT was initiated in 1998 to study the feasibility of using 2 m wide shields to replace the then standard 1.75 m wide shields. After four years of comprehensive work, the technical team from DBT and RAG American Coal completed the design and development of a prototype shield that would later become part of the world?s widest longwall face employing the use of shields having a spacing of +2 meters. The final spacing of the shields actually became 2.058m in order to match the standard pitch of the rack bar shearer haulage elements on the conveyor. In July 2002, the 2 m wide shields were successfully installed in LW-46 panel at RAG Cumberland mine in the U. S. The authors in this paper summarize the design considerations of and operational experiences with the world?s widest longwall face using +2 meter wide roof supports.

Jan 1, 2008