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Crane Limits & Hazards: Crane operation carries with it a greater potential for disaster than nearly any other activity on a construction project. Crane accidents are often the most costly construction accidents when measured either in lives or in dollars. All personnel involved in crane operations must understand their jobs, their responsibilities, and their part in the overall safety of each lift. In this section we will discuss: Crane set-up Load charts Working around power lines Hoisting personnel 1
Basic Types of Cranes Mobile Cranes- Found in all industries and range from small industrial cranes (such as Carry-Decks) to crawler cranes that have capacities over 250 tons. The key word is mobile and so the work environment continually changes from worksite to worksite. Tower Cranes- These dot the skyline in industrial and urban areas and because they are high profile they tend to attract the most attention when something goes wrong. Overhead Cranes- Used in most manufacturing plants, these are the most numerous. They can be as simple as a electric hoist on a trolley on an I-beam or multiple hoists on a bridge crane that spans the whole facility. Outdoors they come in the form of rubber tired gantries or a-frame gantries on rails. Pedestal Cranes- Mostly used in the maritime industry on docks and vessels. 2
Crane set-up: To completely understand why properly setting up the crane is so important it is necessary to understand crane stability. Crane stability is based on the principle of leverage. The crane can be viewed as a teeter-totter. The fulcrum, point A, is similar to the outrigger or tire over which the load is being lifted. When the leverage on side B is greater than the leverage on side C, the crane remains stable. When the leverage on side C becomes greater than on side B, the crane tips over. The leverage on side B basically depends on whether the crane is operating on rubber or with outriggers extended. When operating on rubber, the leverage is much less than when operating with outriggers extended. The amount the outriggers are extended also affects the amount of leverage generated. The leverage on side C depends on the horizontal distance the load is from point A and the weight of the load. Increasing the horizontal distance and/or increasing the weight of the load increases the leverage on side C. The horizontal distance from point A to the load can be increased by lowering the boom and/or extending the boom. 3
Crane set-up: Over 50% of all mobile crane accidents are the result of mistakes made when the crane was being set up. All of these accidents can be prevented by following the manufacturer s recommendations for assembly, dismantling, by using the correct components, and by observing the precautions outlined in this section. *When setting up the crane, the operator should refer to the operator s manual for specific directions. Consider the following: Is the crane in good working order? Has it been inspected and all deficiencies resolved? Are the outriggers fully extended and pads on firm footing? Is the crane level? The angle indicator and the load chart depends on it. Has the weight of the load been established? What is the radius of the pick and placement? Has the load chart been referenced to determine if the pick is within the capability of the crane? *Questions on written test: In order to use the load chart accurately, you need to make sure a. You know the weight of the load b. The crane is level c. You know the radius of the load d. All of the above are correct 4
Crane set-up: Is the crane in good working order? Has it been inspected and all deficiencies resolved? ASME standards require frequent and periodic inspections. OSHA requires cranes to be certified annually in the maritime industry. Many states and local municipalities require annual certifications. Crane safety begins with a safe crane. Never operate a crane in need of repair. 5
Crane set-up: Are the outriggers fully extended and pads on firm footing? 1. The first consideration is the quality of the surface the crane will be set up on. 2. Soils along the foundation of buildings are often poorly compacted and may contain drain pipe and other voids. Avoid setting up in such areas if possible. If such setup is necessary, use additional floats. 3. Floats larger than the outrigger pads should be used under each outrigger regardless of the type of surface being set up on. Float use will reduce the pounds per square inch loading on the surface which helps prevent the outrigger from sinking. 4. Blocking under the outrigger beam prevents full leverage of the outrigger being utilized. Such blocking increases potential for a tipover. 5. Always extend all outriggers. Not doing so can result in the crane tipping over. 6
Crane set-up: Is the crane level? The angle indicator and the load chart depends on it. All load chart ratings are based on the machine being perfectly level in all directions. This applies to cranes on crawlers, on rubber, on outriggers and when travelling with load. 7
Crane set-up: Has the weight of the load been established? We have already established the fact that the load chart can only be helpful if you have a pretty good idea of the weight of the load. The most accurate method of determining this is to weigh it. Often the weight of the load can be obtained from data on manufacturing label plates, manufacturer documentation, blueprints or drawings, shipping receipts, bill of lading, stamped or written on the load and other dependable sources. When such information is not available, it will be necessary to calculate its weight. Never use word of mouth to establish the weight of the load. 8
Crane set-up: What is the radius of the pick and placement? The capacities listed in the load chart also depend on and vary with the crane s load radius. *The load radius is the horizontal distance measured from the center of rotation of the crane (center pin) to the load hook (center of gravity of the load) while the boom is loaded. Because of boom and machine deflection and pendant stretch, expect the load radius to increase when the load is lifted off the ground. Expect even larger increases in radius when the crane is on rubber because of tire deflection. *Question on written test: The radius of the pick is the distance a. From the outrigger to the load b. From the front of the crane to the load c. From the center of rotation of the crane to the load center d. From where the load is to where it will be placed 9
Load charts: Has the load chart been referenced to determine if the pick is within the capability of the crane? Everything in the set-up of the crane points to the load chart. It is imperative that it be used for every pick and everyone know how to use it. It is more than just a load chart. It will list different configurations, parts line, deductions, jib use, on rubber picks, and limitations. Don t wait until the crane is on its side to refer to it. 10
Discussion: Studying this picture what went wrong? According to accounts, this crane was working on rubber on this bridge and after the pick while they were swinging the crane around to put it away and it tipped over. 11
Discussion: On-rubber picks are prohibited with the jib un-stowed. While swinging the crane over the side (probably with more boom out than it shows) it tipped over. It is very possible that wind had a hand it this is you notice the swirling waters below. It is very clear that the load chart was not referred to for this lift. The reason for not extending the outriggers was probably to keep from blocking traffic. Luckily, no one was injured in this tipover. 12
Crane limits & hazards exercise #1: Here is a very simple load chart from a Hiab articulating boom crane. The only information you need is the radius of the pick, so 1) What is the maximum capacity of this crane? Where must that load be in order to be within this capacity? 2) What is its capacity with the boom completely extended? 3) What is its capacity at 21 feet? 13
Crane limits & hazards exercise #1: 1) The maximum capacity of this crane is 22,040 lbs at 6 7, which is right over the side or the truck. (remember, the radius is measured from the center of rotation so the outrigger might be out further than 6 7. 2) At full radius (32 2 ) it can pick 5,880 lbs. 3) Its capacity at 21 is 7,760 lbs. When the radius falls between capacities on the load chart then you must always use the lower capacity. You may not average the two. 14
Load charts: Here is the range diagram for this crane. It is useful for determining the amount of boom needed and at what angle for the radius of the pick. For example, if the radius of the pick was 65 feet the referring to the load chart we could see that the minimum boom length needed would be 78 feet at a 30 angle. Another consideration is the number of parts of line needed for the pick. The crane is limited by the hoist line capacity. For example: If you are using the crane in a one-part reeving then the most you could pick would be 7,700 lbs. If the load weighed 8,500 lbs, then you would need to use the one-sheave block and go to two-parts line. 15
Load charts: This is a typical load chart that is found on a National 690E boom truck. This load chart coupled with the range diagram will help you to determine if the crane has the capability to make the pick. Found below are the deductions that must be added to the load weight. For example, if you are using a two sheave block then you would need to add 355 lbs to the load before referring to the load chart. (Many load charts also make deductions for a stowed jib) 16
Crane limits & hazards exercise #2: 1) What is the maximum capacity of this crane? How many parts line would you need? What radius could you go out to? 2) What is the maximum radius the crane can reach? What would be its capacity? If you were using a two-sheave block how much could the load weigh for this maximum radius pick? 3) If you had a load that weighed 9,600 lbs, what would be the maximum amount of boom you could have out? What would be the maximum radius? 17
Crane limits & hazards exercise #2: 1) This is a 40,000 lb capacity crane but rarely would you pick that much since you could only go out 5 feet which wouldn t even get if off the back of the truck. The stabilizers of this truck go out 8 feet, so forget about it. You would need to go to 6 parts, so in order to do that you would need a three-sheave block. This crane won t even ship this block for this crane. The next radius out is 8 feet and you could pick 25,750 lbs which is more manageable but still right where the outrigger is, so, for all intents and purposes, this is a 20,000 lb capacity crane. 18
Crane limits & hazards exercise #2: SAMPLE 2) The maximum radius for this crane is 80 feet and its capacity out there is 800 lbs. After the deduction for a two-sheave block the maximum the load could weigh is 445 lbs. Not much and it s a critical lift since it would be 100% of capacity. 19
Crane limits & hazards exercise #2: *3) If you were picking a load that weighed 9,600 lbs you would need a one-sheave block which would add 200 lbs, so the gross load would be 9,800 lbs. The maximum amount of boom would then be 66 feet and the maximum radius would be 29 feet. *Question on written test: Using the load chart in your Practical Exercise Handbook the maximum load (including deductions) you could lift with 90 feet of boom out at 45 feet radius would be 3,550 lbs. a. True b. False 20
Working around power lines: Typically, they higher the lines are from the ground, the more voltage. *For 50,000 volt lines no part of the crane should come within 10 feet. If there is a chance for any part of the crane will get close to that distance, protective measures must be taken. You must take these measures unless you have controlled the hazard by de-energizing or moving the lines, or by re-routing the electricity around the work. *Question on written test: No part of the crane should be within feet of a 50,000 volt power line. a. 10 feet b. 15 feet c. 20 feet d. 25 feet 21
Working around power lines: High voltage electrocution is the largest single cause of fatalities associated with cranes. All can be prevented. The power company or utility may consider (if given advance notification) shutting down the line temporarily or moving the line. If that is not possible the following procedures should be enforced: 1. Keep your distance. Surrounding every live powerline is an area where an electric arc is capable of jumping from the powerline to a conductor of electricity. So you must keep all of your equipment and its load at least the minimum permitted distance away from the powerline. 2. Treat all powerlines as live until reliable information assures you that the lines are de-energized. 3. A competent worker must be designated as a signaler to warn the operator when any part of the equipment, load, or hoist line approaches the minimum permitted distance to a powerline. The signaler must be in full view of the operator and have a clear view of both the equipment and the electrical conductor. 4. Avoid using tag lines. Unless it is necessary to prevent the load from spinning into the minimum distance to a powerline, the tag line itself can be a hazard because it can swing into the minimum distance. Note: All ropes are capable of conducting electricity, but dry polypropylene has better insulating properties than most commercially available ropes. 5. Slow down the operating cycle of the machine by reducing hoisting, booming, swinging, and travel speeds. 6. Exercise caution when working near overhead lines having long spans as they tend to swing laterally in the wind and accidental contact could occur. 22
Working around power lines: If you make contact with power lines: *Stay on the equipment. Don t touch the equipment and the ground at the same time. In fact, touching anything in contact with the ground can be fatal. Only if a new hazard develops that could be life-threatening, should you consider leaving the machine. Keep others away. No one else should touch the equipment or its load including buckets, outriggers, load lines, or any other part of the machine. Beware of time delayed relays: Even after electrical contact trips the breakers, relays may still try to restore power. They may come on automatically two or three times. Break contact. If possible while remaining inside the machine the operator should try to break contact by moving the equipment clear of the wires. This may be impossible if contact has welded conductors to the equipment. Leaving the machine. If the operator decides to leave the machine, he must jump clear. He must never step down allowing part of his body to be in contact with the ground while any other part is touching the machine. Ground around machine may be energized. The ground around the machine may be energized make sure no one approaches the machine and if the operator leaves the machine he must not create a voltage path from one leg to the other by taking long steps. Shuffle your feet or hop, keeping both feet together. *Question on written test: If the crane comes into contact with a powerline the operator should: a. Slowly dismount the machine b. Wait for the power breaker to shut off then dismount c. Wet his pants d. Stay on the machine and warn others to keep away 23
Hoisting personnel: Anytime you are going to hoist personnel, there should be a safety meeting to discuss the hazards. Crane suspended personnel platforms are difficult to maneuver and should not be used unless there is no other practical way. The platform should be load rated and built to OSHA/ASME standards. *The platform should be load tested to 125% of maximum capacity to the location that needs accessed before the live lift is made. The operator shall only respond to the signal-giver inside the platform. The crane must be equipped with an anti-two-block device. Fall protection must be worn by those in the platform. The slings used with the platform must be dedicated for that use and be rated to at least twice the capacity of the platform. *Question on written test: It is required to load test the manbasket and do a trial lift to where you want to hoist personnel each time you move the crane to a different location. a. True b. False 24
Discussion: What do you see in this picture? What would you do different? 25
Discussion: Wow, this looks bad! Climbing a ladder placed inside a manbasket that is lifted by a forklift is so dangerous. Add to that, the ladder not being extended high enough and no fall protection for the worker. This is a recipe for disaster. Basically, after setting this hopper, no provisions were made to unhook the rigging. It is critical that lifts are planned properly and in advance. The crane company knows the challenge of removing the rigging after a high placement and an aerial lift should have been on hand for this purpose. 26
Conclusion: Safety is the responsibility of everyone involved. Labor and management both have a responsibility to ensure the safety of all parties involved in hoisting and rigging. Major rigging operations must be planned and supervised by competent personnel to guarantee that the best methods and most suitable equipment are employed. It is imperative that all workers who prepare, use, and work with or around hoisting and rigging equipment are well trained in both safety and operating procedures. 27