Perhaps the most critical aspect of any crane operations is the rigging. While it is crucial to keep the crane and the other equipment safe at all times, rigging remains an integral part of safety precautions for crane operations and lifting heavy loads. Everyone who operates cranes and responsible for rigging tasks should be qualified, professional, experienced, and has a full understanding of what rigging is about and how it affects the overall safety of the operations. In this article, we aim to go back to the basics of rigging to inform everyone about the different facets of rigging safety. Our goal is to reduce the risks associated with crane operations because they are often catastrophic and costly. We will look into various aspects of rigging, including the elements that affect the overall safety of the operation.
The hoisting triangle is fundamental when it comes to rigging safety. It is comprised of the crane, the mechanism of the crane, and the rigging of the materials to the crane.
One of the most important things you have to make sure of is that the crane should be in top working condition. The crane is an integral aspect of a safe lifting procedure. Before using it, the crane should be thoroughly checked by the employer or anyone in the same authority. Cranes should be regularly inspected and maintained to ensure it has no damage that can impact the safety of the operation. Another important element is the understanding and knowledge of operating the crane. Always get an operator who has an in-depth knowledge of the load charts. He is responsible for checking whether the crane is set up properly, and skilled in the use of outriggers as needed, and able to run the equipment to handle shock and ever-changing loading. He should consider any potential threat, including overhead obstruction, weather conditions, and other elements that can affect the safety of the crane operation. The operator should have good communication and signaling skills that are crucial in the task.
The last yet equally important element is knowing the weight of the load. The weight of the load is crucial to the safety of the operation. The person attaching the load should know the accurate weight and its center of gravity. He should make sure the rigging equipment is in good condition. These three factors should be considered every time, and when they are all in sync and in good condition, you will have a safe and successful lift.
Given that the crane is in good condition, and the operator is fully-skilled and knowledgeable in running the machine, the next thing to look into is rigging responsibilities. The operator must have a full understanding of sling angles, centers of gravity, and other critical information. Without these skills, it will be difficult and even impossible to rig the load correctly.
Let’s begin with the law of gravity. Keep in mind that the center of gravity of an object is the area where it will balance. The weight of the load is centralized during this time. If you look at some loads, you will realize that the center of gravity varies for each one. The center of gravity for unusual-sized loads will vary, which means the type of sling necessary will also differ. There is no way you will locate where the center of gravity is until the load is lifted. Once the load is lifted, you can correct the rigging until you finally locate the exact center of gravity of the load.
You should also look into sling angles, which are equally critical in rigging safety. Sling angle is the angle between the load in a horizontal angle and the sling body. When using a sling, several variables will directly impact the load rating, such as abrasion, distortion, and nicking. These things should be considered when planning the lifts for safety reasons. One should consider at which angle the sling will be used because the rated capacity significantly declines as the angle of the sling goes smaller.
For instance, a two-legged sling at a 90-degree angle working on a 700-pound load supports 350 pounds of stress on each leg. If the legs of the sling form a 45-degree angle on the same weight of the load, the rated capacity will decrease. For safety purposes, sling legs should not exceed 45 degrees. Perhaps the most critical thing to consider is that sling angles can dramatically impact the safe capacity of the load. Every type of sling, such as fiber rope, wire rope, and synthetic sling, comes with different load capacities.
Let’s now delve into the basic rules of rigging and rigging equipment. All rigging equipment should be evaluated before and during a lifting operation to make sure it is in good, serviceable condition. Faulty rigging equipment should never be used in service. Rigging equipment should not be loaded more than what is recommended. They should be removed and kept from the worksite, when not in use because they can still present a hazard to the workers. Every equipment shall be proof-tested before they are used, including hooks, clamps, and other lifting accessories. Get them inspected and evaluated by a professional for defects before they are used. Another inspection should be carried out while the sling is being used. Faulty and damaged slings should be removed from the service right away.
Alloy steel chain slings should have affixed identification with the information about its size, rated capacity, grade, and the manufacturer. Other accessories and attachments such as rings, hooks, and mechanical coupling links should have a rated capacity equal to the chain.
You should never use shop hooks and links, rods, or makeshift fasteners. If the chain-link goes beyond the allowable wear, in accordance with the standard rigging charts, the equipment should be taken away from service. Visual inspections are critical before every lift. Chain slings should be assessed prior to being used. It is never advisable to presuppose that the chain is in top condition because any damage can take place while and in between lifts. The professional inspector should check for bent and worn out links. Stretched links will present the look of an hourglass, and the links bind on each other. To correctly inspect multi-leg slings, you can hang them on a hook and look if they are of the same length. Alloy steel chain slings should be thoroughly checked routinely based on the frequency of its use, the extent of the service condition, the types of lifts being made, and the number of times the sling is used in the same condition. These inspections should be done in not more than a year of an interval. It is the employer’s responsibility to keep a log of the schedule of maintenance of every alloy steel chain sling. This record should always be available for examination.
The manufacturer determines the safe working loads of plow steel wire rope and wire rope slings of different sizes and classifications. This information is also available in approved rigging charts. Whatever the manufacturer recommended in terms of the safe working load must be strictly followed.
All strands on slings that stick out and bridles should be roughened. Wire ropes should not be fasted by bolts unless use on back lines on scrapers. The U-bolt should be utilized for eye splices to make the U section touch the deadlock of the rope. Makeshift tools such as knots or bolts should not be used to reduce the length of slings. You should make a habit of checking if the sling legs are bent or flawed. To avoid slippage, the materials loaded to a basket hitch should be balanced correctly. Protect the slings from any sharp objects by placing paddings on them. Be careful not to place your fingers in between the load and the sling while it’s being secured around the load. A sudden increase in load or shock loading should never be done anytime. Once the load is placed on the sling, the sling should not be removed from beneath the load. All welding of end attachments, except for thimble covers, should be done before assembling the sling. No welded end attachments shall be utilized without the permission of the manufacturer or any authority that proof-tested the said attachments. They should not be used twice their rated capacity before the first time they’re used. The certificate of the proof test should be maintained by the employer, and again make it available for assessment. There are several techniques used to evaluate the standards of rigging equipment, including fiber ropes, manila ropes, and synthetic materials. It depends on the professional inspector on what method to use, in accordance with your company’s procedures concerning the use of these rigging materials. Again, the quality of the crane, the operator’s knowledge about crane and rigging safety operation, and the rigging equipment make up a successful and safe lift. It is a must to perform visual inspections of rigging equipment prior to each lift for a safe and secure job.
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