Dogging and Rigging Basics

Crane Lifting Basics – Dogging and Rigging Basics

You’re trying to get into rigging as a profession, but you don’t know the basics? In this post, we’ll look at the fundamentals of rigging and break down exactly what rigging is all about.

One of the most important tasks for which the ‘rigger’ will be responsible is the safe raising and rigging of various materials.

These materials must be safely lifted off the ground and elevated to various elevations based on the specifications of each project.   It is important for both the crane operator and rigger to understand the fundamentals of crane rigging and how lifting materials of different shapes and sizes at various angles can have a direct effect on the type of crane and rigging equipment needed.

This goes beyond understanding how to attach the rigging to the crane. The operator must be completely aware of the operation of the crane, its maximum load limits, and other such factors. The crane itself must also be in good working order without any defects whatsoever. Otherwise, if there is a lack of operator expertise or equipment efficiency, it may lead to extreme, expensive and hazardous incidents.

To learn more about what the basics of dogging and rigging are or to secure your future in the industry enrol in a basic rigging course in Perth.

What’s Crane Lifting & Rigging Used For?

Lifting and rigging are most commonly done with portable or mobile cranes. There may be all-in-one cranes, where the crane is mounted on the back of a large truck-like vehicle or is a portable vehicle of its own.

Some cranes are semi-permanent structures, where the crane is transported to the construction site and then set up in a specific position where it can provide the most value. For example, in the case of high-rise construction projects, a Spyder crane may be temporarily mounted on the upper floors of the structure and relocated regularly as the height of the building increased.

The primary function of lifting and rigging is to move critical equipment and materials to places where they are easily accessible to staff. This method helps to reduce the risks of needing to move scaffolding equipment and materials manually, which can be complicated and hazardous.

In addition, lifting and rigging were designed to lift extremely heavy loads that would otherwise be difficult to handle manually. For example, a heavy portable generator needs to be raised up to ten floors where staff can use it to supply electricity. Manual transport of the generator is not feasible due to the weight of the generator.

In addition, the generator must be correctly rigged in order to allow offsets in load-bearing limits that adjust on the basis of the angle of the generator as ten stories are lifted. In our example, the best option would be to use a mobile crane. The crane could quickly lift the generator after it had been correctly rigged and attached to the crane.

Security of Rigging Equipment

Lifting and rigging require proper safety measures to ensure a safe working environment. In the case of construction firms owning their own cranes, it is important that routine maintenance is carried out to ensure that all parts, including the lifting mechanism, are in good working order.

When companies want to employ cranes for projects, they need to use a reputable and reliable company. It is perfectly appropriate for the project manager or the person responsible for securing the crane to request maintenance reports to demonstrate that the crane has been well maintained.

If you own your own crane or hire one, the next safety measure, once you have it on the job site, is to ensure that it is correctly set up before it is lifted. Mobile crane trucks must be adequately supported to prevent them from falling over due to shifts in the center of gravity when materials and equipment are raised and transferred.

Supports are also part of a crane truck and can be extended and lowered in place. Until deploying the supports, called outriggers, the cranes should be parked on a level and stable floor. Outriggers must also be on stable ground to keep the crane from falling over or collapsing into the soft ground. In the past, there have been incidents where the crane was not level or the floor on which it was parked was not secure.

If the crane is fully parked, supported, and configured, the next safety measure is to decide the most suitable rigging construction system to be used. There are various types of sling and hitch configurations that could be used, depending on the type of lift required, as follows:

The Different Types of Rigging Configurations

Basket Hitching – This approach is where each end of the sling is attached to the hook of the crane. It helps prevent the added burden on the load. Depending on the size of the object being raised, a single or double wrap sling configuration can be used. However, this approach is not so perfect to use with items that are difficult to keep balanced.

Choker Hitching – The sling is wrapped around an object, then tightened to hold it in place. This method of lifting is well suited for large cylinder items, but it should be lifted one at a time, not in loose bundles.

Vertical Hitching – This form is where one end of the sling is tied to the crane and the other to the item to be raised. However, one common problem is that an object can start rotating and rotate freely when it is lifted, so this approach is almost never used with a crane. Variations using other techniques can be used to make vertical lifting safer and safer.

If the rigging method has been determined, the next thing the operator would need to know is the weight of the materials or equipment to be lifted. Slings have overall stress limits for their weight. Exceeding these could cause the slings to snap and break, causing the object to fall to the ground below.

The operator must also realize that, as the angle increases, the overall tension limits also change, causing even higher rigging weight limits. To explain the results, let’s look at how the maximum stress changes:

90 degrees (vertical lift) – At this angle, the weight is evenly distributed, so if you were to lift a 1,000-pound object and use a dual configuration of two slings, each with a 500-pound maximum, it would be secure to lift the object.

60 degrees – At this angle, the performance of the slings is reduced to 86.5 percent of the full load limits. In other words, each sling now supports a maximum of 432.5 pounds or a total of 865 pounds. But it wouldn’t be safe to lift a 1,000-pound piece.

45 degrees – At this angle, the performance of our dual-sling setup is reduced to 70% of the maximum load limits. Now, each sling can only carry a total of 350 pounds or 600 pounds. Again, the lifting of a 1,000-pound weight will be risky.

As you can see, as the degree of lift increases, the load-bearing stress decreases. As a result, using our example, higher rating slings or additional slings will be needed to lift this load safely.

Please keep in mind that these are just general examples for comparison purposes, and other factors can affect load stress. It is your duty, as an operator, to educate yourself and learn how to correctly measure load limits and stress to ensure safe rigging and raising of the crane. Learning and following company procedures will help mimimise the risk of human error or accidents involving employees and other workers onsite.