Improving Belt Conveyor Safety With Better Procedures and Training

Transcription

1 9 th International Conference on Bulk Materials, Storage, Handling & Transportation Improving Belt Conveyor Safety With Better Procedures and Training Larry Goldbeck Martin Engineering Neponset, IL USA Abstract Belt conveyors are critical elements in any bulk material-handling operation. However, they can also be dangerous, particularly when employees assigned with operating and maintaining them are poorly trained as to their potential hazards. A belt conveyor is essentially a giant rubber band, stretched tight and threaded through a maze of obstructions and pinch points. This band is then burdened with a heavy load and then pulled at high speed. The forces applied are significant and potentially dangerous. These forces create risks to personnel who are working on or in the vicinity of belt conveyors. Part of the problem is that conveyors have become part of the landscape. They are not seen as a hazard, but rather a fact of life, like driving a car or using a phone. The average employee does not see the risks inherent in the conveyor, because they have not been trained to see (and avoid) the risks. In this presentation, Martin Engineering s Larry Goldbeck looks at the safety record of conveyors and discusses the proper training to improve this record. He will review the general topics to be included in conveyor training and discuss the site-specific analysis required. He will show how this training can provide a double benefit by improving worker safety while boosting an operation s overall efficiency. Introduction A belt conveyor is essentially a giant rubber band, stretched tight and threaded through a maze of obstructions and pinch points. This band is then burdened with a heavy load and then pulled at high speed. The forces applied are significant and potentially dangerous. These forces create risks to personnel who are working on or in the vicinity of belt conveyors. Part of the problem is that conveyors have become part of the landscape. They are not seen as a hazard, but rather a fact of life, like driving a car or using a phone. The average employee does not see the risks inherent in the conveyor, because they have not been trained to see (and to avoid) the risks. In CFCR Part 46 and 48, the US Mine Safety and Health Administration requires training for all workers in mines and processing plants, above or below ground. Newly hired workers must receive 24 hours of specified training. In most cases, four hours must be given before work begins, while the remaining 20 hours given within 60 days while working under close supervision. All miners must receive 8 hours of specific refresher training each 12 months. The introductory 24 hour training program as seen in a typical training program--includes introduction to the work environment, hazard recognition, rights of miners, and electrical hazards health and safety aspects of assigned task. However, there is no specific equipment training mentioned, and that means there s no conveyor training specified. When one looks at the number of injuries and deaths, it becomes evident that the existing training programs have accomplished very little in preventing conveyor belt accidents. Conveyor-Related Accidents In Analysis of Powdered Haulage Conveyor Belt Injuries In Surface Areas of Metal/Nonmetal Mines From 1996 Through 2000, Harvey Padgett of the US MSHA Office of Injury and Employment Information, noted over the four-year period from 1996 to 2000, there were 459 reported injuries ranging from fatal (degree 1) to injury with days away from work (degree 3) to injury with restricted work activity (degree 5). Of these 459 reported injuries, 13 were fatalities. Another 22 were reported as permanent disabilities. Keep in mind that these were the reported incidents for the United States only and in metal/non-metal mines only. One could only wonder what the statistics would be worldwide. 1

2 It has been estimated the average cost of a fatality in an underground coal mine at $1.02 Million. This figure includes the costs of medical expenses, worker compensation, accident investigation, loss of family income, and lost production value. The cost for underground accidents of less severity was estimated at $237,000 for permanent disability accidents and $5,000 for lost time accidents. These cost estimates were originally published in Imagine how much these costs have climbed in the past 20 years; a reasonable guess might be they have at least doubled. The Causes of Conveyor-Related Accidents Analyzing the activities of the reported injuries, we would find 192 reported injuries (42%) occurred when the injured worker was performing maintenance, lubrication, or checking the conveyor. (Ten of the 192 were fatalities). Another 179 reported injuries (39%) occurred while the employee was cleaning and shoveling around belt conveyors. (Three of the 179 were fatalities.) The tendency is to send the new kid --the least-experienced, the most-recently hired--out to do the job that nobody wants to clean up around moving belt conveyors. And this is typically without an ounce of training about conveyors or the safe ways to work around them. The most common reported cause of accidents around belt conveyors is getting caught by the moving conveyor belt or pulley. This accounted for 290 of the 459 injuries and 10 of the 13 fatalities. The following activities were reported: Working under or next to poorly guarded equipment. Using hand or tool to remove material from moving rolls. Trying to free stalled rolls while conveyor is moving. Attempting to remove or install guards on an operating conveyor. Attempting to remove material at head or tail pulley while belt is in operation. Wearing loose clothing around moving belt conveyors. Not blocking stalled conveyor belt prior to unplugging (both flat and inclined belts) as energy is stored in a stalled conveyor belt. Reaching behind guard to pull V-Belt to start conveyor belt. Looking at this record, it is easy to see that both experienced workers and new employees are susceptible to injury or death. This is true because there has been no specific training on the hazards and the correct procedures when working around belt conveyors. The belt does not care how old the employee is, or how much experience he or she has. Preventing Accidents Through Conveyor Training So, what is the answer to preventing conveyor belt accidents? Well, it is obvious that dedicated belt conveyor training should be provided to all employees--- experienced and new--prior to any work being performed around a belt conveyor. This comprehensive training should include: General Safety Practices Around Conveyor. Performing Inspections and Maintenance Safely. Conditions of the Conveyor that Cause Problems (that Lead To Maintenance and Safety Issues. Matching the Belt to Structure and Conditions. Eliminating Fugitive Material (Dust and Spillage). Belt Tracking Procedures. The Double Benefit of Conveyor Training In fact, training in conveyor operations provides the best of both worlds. It presents an opportunity to provide training on worker safety that will in fact improve an operation s operating efficiency. By training in better conveyor practices (maintenance and operating) you can improve the results, and at the same time reduce the opportunities that require service that can lead to accidents anyhow. This double benefit provides some extra needed credibility in these operations where safety training is met by an eyes-rolled back-in-the-head you are wasting my time shrug from employees. General Conveyor Safety Practices Conveyor belt safety starts with the new employee. Prior to assigning a new employee to the task of working around a conveyor belt, the employee should attend a minimum of 4 hours of classroom instruction specific to conveyor belts. And do not forget the veteran employees. Keep in mind that the senior employee has probably had little or no training about conveyor belts or conveyor belt safety. 2

3 Many operations forbid working ON the conveyor while it is running. But the same operations will require working AROUND the conveyor while it is in operation. If maintenance or other work needs to be done, the conveyor should be locked out and tagged out. Failing that that is, if the chores need to be done and the conveyor needs to run--extreme caution should be exercised when working in the vicinity of the conveyor system. And there s a more complicated problem with locking out a conveyor s energy source. What is NOT common knowledge is the fact that even if the belt conveyor is properly locked out and tagged out there is a potential for accidents or fatalities. Belt conveyors have shown to harm employees even though they were locked out and tagged out. Lock-out, Tag-out, Block-out During normal operation of a belt conveyor, the belt is usually under considerable tension. The belt is stretched just like a rubber band. The amount of tension is based on factors such as length and width of the belt, size of the drive; amount of conveyed material and the weight of the gravity take up. There are places along the conveyor system where the tensions are considerably higher than other areas of the system. The arrangement of the drive system determines where the tensions are high and where they are lower. This concept must be understood by all employees required to work around the conveyor belt. This MUST be included in the safety training along with lock out and tag out procedures. Most of the time it is not included and only after some one is killed or injured do we understand the need for this type of training. We must educate the employees on where the tensions are located based on the conveyor drive configuration. Most belt conveyors have the drive located at the discharge or head end of the belt conveyor. On these systems, the highest tensions are located at the point where the belt is against the drive pulley. Directly behind the drive pulley the belt tensions are considerably lower. On a head-driven conveyor, the tension on the belt is highest just before the belt leaves the drive pulley which in this case is the head end. The lowest tension areas of the belt are located on the return side of the belt. When the driven pulley is located at the tail end of the conveyor, the lowest tension areas of the belt then move to the upper side of the belt system. The highest tension area of the belt is still just before where the belt leaves the drive pulley. The same principles hold true for a belt that the drive is located in the center of the belt. Again the highest tensions are located just before the belt leaves the drive pulley. After the belt leaves the driven pulley, the belt tensions drop drastically. As the belt travels toward the driven pulley again, the tensions increase and increase, until it passes through the driven pulley and relaxes. Even if a belt has been properly locked out and tagged out, these tensions may be present when the conveyor belt is shut down. One easy-to-understand scenario is if an inclined belt has an emergency shutdown with material on the belt, the weight of the material will cause the belt to roll back wards, risking injury to the unwary employee. Properly installed brakes and backstops may help the roll back situation. However, if employees are required to be on the conveyor or near pinch points on the conveyor, the belt must be physically restrained from moving under its own power. This is called BLOCKING the conveyor belt. One should not rely on the backstops or brakes to prevent the belt from moving on its own. Lifting the gravity take-up MAY OR MAY NOT release these tensions. Other potential hazards may not be so obvious. There have been instances when the belt is empty, and it has moved due to the internal tensions by the belt stretch. Blocked chutes, material trapped at load zones, material under the belt or bad bearings may stall the belt sufficiently to cause considerable belt tensions. It is extremely important that the list if employees described above be properly trained on where the tensions are low and where they are high. It is also important that employees are educated about this potential hazard PRIOR to being assigned to work around belt conveyors. Many times our youngest, least experienced employee is assigned the task of cleaning up around belt conveyors with little or no knowledge of the dangers the belt conveyor may have. Lock-out, Tag-out, and Block-out We certainly recommend continuing the practice of lockout and tag out, but there are instances when the belt conveyor must be restrained from moving under its own power. A pre-job analysis should be performed prior to assigning employees to work around belt conveyors. This will determine if a block-out procedure is required. This pre-job analysis should ask: A. Will any work be performed in pinch point areas? This includes all pulleys, all troughing rolls, return rolls, drive components, belt cleaners, and sealing systems along the load zone. B. Will the belt need to be cut? The weight of the belt alone can make the belt travel forward or backwards. 3

4 C. Will several crews be working on the belt system at the same time? If so will the work performed by one crew affect the safety of another crew working someplace else along or around the belt? D. Have all personnel being assigned the task been properly trained on the potential stored energy that may exist in the belt system? E. Have all personnel been properly trained in the correct blocking procedures to prevent the belt from traveling under its own power? F. Is the correct blocking equipment available? Once the determination has been made that a block out procedure is required, how can this be accomplished? Belt clamps, chains, and comealongs (ratchet lever hoists) can be used to physically restrain the belt by securing it to a substantial member of the conveyor s structure. (FIGURE X) Keep in mind that the belt may move in either direction based on the conditions present at the time of the work. Also keep in mind that these conditions can and do change as the work progresses. Training in How to Work Safely Around Conveyors 4 Figure X An engineered belt clamping system should be connected to the conveyor structure to block belt movement. A common problem, of course, comes when somebody says they are just going to take a look, to inspect something, and tries to fix a situation they see, without bothering to shut down/lock out the system. As Richard J. Wilson of the United States Bureau of Mines Twin Cities Research Center noted in a paper Conveyor Safety Research, published in August, 1982: Most procedures require locking out the main power switch at the head pulley or control room. As this could be quite some distance from the work site, compliance could require a considerable amount of time and effort. It is not difficult to imagine maintenance personnel rationalizing that it is all right to quickly perform some routine repair work without locking out the belt when to implement the lockout procedure would take much longer than the job itself. It is important that the worker knows the location for all emergency stop buttons or shut down pull ropes. That way, if something goes wrong, you ll knew how to quickly shut down the system to reduce the chance of injury. And certainly personal protection devices should be discussed. It is the responsibility of the employer to provide the dust protection apparatus correct for the dusty environment. But it is the responsibility of the employee to use the equipment provided. These include hard hats, hearing protection, and dust masks. Even proper personnel grooming and apparel should be covered. Long hair should be tied up and placed under a scarf or hardhat to prevent being caught in moving conveyor parts. Today s style of loose, baggy clothing can be a cause of conveyor accidents. Something as simple as a hooded sweatshirt can become entangled in a belt conveyor with life-threaten consequences. Even something as simple as proper shoveling techniques should be taught to the employees. This includes never shoveling onto a moving conveyor belt. If a shovel would get caught in a moving conveyor belt, the shovel could either spear the handler or tear their arms off. Even when a conveyor belt is traveling as slow as 150 feet per minute (0.75 meters per second), the mind cannot respond quickly enough to for a worker to let go without injury. Belt Conditions The training should include a thorough understanding of belt conditions. By understanding different conditions of the belt exposure to conveyor accidents can be reduced. The training should include explanations of: Belt cupping (curve to the face of the belt, either up or down) Belt camber (a banana-like curve to the belt along the length of the belt) Crooked splice (often confused with a belt camber) Impact damage (causes belt failure and additional carry back)

5 Impingement damage (polishing of the top cover or object puncturing the belt) Heat damage Chemical damage Junction Joint Failure (caused by too short a transition distance) Edge damage (from belt tracking problems) Entrapment point damage (unsupported belt in the load zone) It is these conditions that can lead to conveyor problems. And it is these problems that cause workers to be working around the conveyor--inspecting, adjusting, cleaning fugitive material, tracking the belt,--attempting to correct the problems and improve operations. Identifying the Sources of Fugitive Materials By analyzing the accidents it is easy to see that the majority of the accidents occurred because of material spillage. Training employees on where fugitive material escapes a belt conveyor and correcting the problems will certainly reduce the exposure to conveyor accidents. Typical spillage sources from a belt conveyor include Dust skirting leakage along the sides of the load zone Carryback (material sticking to the belt after the discharge point, and then dropping off conveyor belt) Material rolling down the conveyor from the load point out the back of the conveyor Holes in the chute Belt tracking problems Bad Mechanical Splices (or holes in the belt) that allow material to sift through. Procedures for Tracking the Belt Belt tracking the manipulation of conveyor components to get the belt to run in the center of the structure has been regarded as a sort of black art known only to senior employees. But in fact, belt tracking is a science. There is always a reason a belt does not track. Educating employees on the correct method of tracking and why a belt does not track can reduce the exposure to conveyor belt injuries. Belt tracking is a three-step process. First a visual inspection must be made to identify the reason (or reasons) a belt is not tracking properly. There are numerous problems that may cause a belt to wander. These could include the alignment of various conveyor components, such as the structure, the rolling components, idlers and pulleys, or the gravity take-up. They could include belt condition, with problems such as belt camber, or belt cupping. The mistracking could be caused by material accumulations in a chute or off center loading patterns. It could even relate to the weather. Or it may well be combinations of these factors. The second step is usually the most difficult. The conveyor must be shut down, and the problem(s) found in the first step must be corrected. Most people look for some magic, quick easy fix. There is none. Many times management will not shut the conveyor down long enough to correct the problems. This certainly increases the risk of injury if the worker is required to track a belt that cannot be track with out the proper corrections. The last step is to make the physical adjustments, starting at the lowest tension area of the belt, (directly behind the driven pulley) working towards the higher tension areas of the belt. (FIGURE Y) Typically, the solution calls for turning the rolling components slightly in an attempt to steer the belt into the proper path. FIGURE Y When tracking a conveyor, start at the lowest tension area, directly behind the driven pulley. 5

6 The Benefit of Conveyor Education Can we totally eliminate conveyor accidents? Probably not, but we can work towards zero accidents by: Educating new-hires and veteran employees (and provide refresher courses) prior to assigning tasks around belt conveyors Eliminate many of the problems that require the employee to work in close proximity to belt conveyors. Bear in mind that the cost of one accident will easily exceed the cost for a training program brought into the organization, or even a full time training person s annual salary. The cost of a fatality might be the total career salary for fulltime training coordinator. Effective training of employee on operating and maintaining conveyors safely will pay for itself very quickly. The good news is that eliminating the problems in conveyor operation that require employee attention will in fact improve the efficiency of the conveyor, and the entire operation. That gives you a double payback. ## 6