Rigging, Hoisting and Cranes

Rigging, Hoisting, and Cranes

Module Introduction

This chapter covers all the knowledge required for the Red Seal exam in ironworking (structural and ornamental) concerning rigging, hoisting, and the use of cranes. You must master not only the calculations and procedures, but also the Canadian standards that govern these operations. This module represents a significant portion of the exam — approximately 15 to 20% of the questions — and is an absolute prerequisite for safety on any ironworking site.

Fundamental Principles of Hoisting

The Lifting Chain

Every lifting operation involves a complete lifting chain: the anchor point (structure, crane hook), the sling (cable, chain, strap), the lifting accessory (hook, shackle, ring), and the load itself. The failure of a single link in this chain causes the total failure of the operation. You must always verify each element individually before use.

The Three Fundamental Forces

Any suspended load is subject to three forces that you must calculate:

Load Factor

The load factor is the multiplier applied to the weight of the load to determine the actual tension in each leg of a sling, based on the sling angle. This concept is fundamental and will be the subject of exam questions.

Calculating Tension in a Sling

The tension in each leg of a two-leg sling is calculated as follows:

T = (Weight of load ÷ Number of legs) × Load factor

The load factor depends on the horizontal angle between the leg and the vertical:

Calculation example: A 2,000 kg load is lifted with a two-leg sling forming an angle of 60° between the legs (therefore 30° from the vertical). The tension in each leg is:

T = (2,000 kg ÷ 2) × 1.16 = 1,160 kg per leg

Golden rule: Never exceed an angle of 90° between the legs (45° from the vertical). Beyond this, the load factor increases exponentially and the stability of the load becomes critical.

Types of Slings and Their Applications

Wire Rope Slings

Wire rope slings are the most common in structural ironwork. They are manufactured from stranded cables (typically 6 × 19 or 6 × 37, meaning 6 strands of 19 or 37 wires each).

Advantages: high strength, abrasion resistance, heat resistance, ability to withstand dynamic loads.

Disadvantages: low flexibility, risk of sudden failure without warning, requires protection at sharp edges.

Configuration factors (hitch modes) :

Caution: The configuration factor applies to the sling's rated capacity, not to the weight of the load. A basket hitch sling can carry twice its rated capacity in a vertical configuration, but only 0.75 times its rated capacity in a choker configuration.

Chain Slings

Chain slings (Grade 80 or Grade 100) are used for abrasive loads, high temperatures, and loads with sharp edges.

Characteristics:

Rejection criteria for chains (according to CSA standards):

Synthetic Web Slings

Synthetic web slings (polyester, nylon, polypropylene) are lightweight, flexible, and will not scratch finished surfaces.

Important limitations:

Color coding (according to CSA standards): each color indicates the sling's load capacity.

Lifting Accessories

Shackles

Shackles are classified by type (straight or screw pin) and by capacity. The capacity is stamped on the body of the shackle. Only forged alloy steel shackles are accepted for lifting.

Usage rules:

Hooks

Lifting hooks must be equipped with a functioning safety latch. Rejection criteria include:

Rings and Lugs

Lifting rings (lifting lugs) are welded to the load. The weld must be performed by a qualified welder and inspected according to the requirements of CSA W59 (welding of steel). The angle of the ring relative to the direction of the load must be verified — a ring designed for a vertical load cannot be loaded laterally without a reduction in capacity.

Crane Signals

Standardized Hand Signals

The Canada Labour Code and CSA Z150 (Safety for mobile cranes) require that all crane signals be standardized. You must know the following signals perfectly:

Essential rule: Only one signal person at a time. The signal person must be clearly visible to the crane operator. If the signal person is no longer visible, the operator must stop immediately.

Radio Signals

Radio signals must use standardized vocabulary: "Hoist," "Lower," "Stop," "Extend," "Retract," "Swing right," "Swing left." The signal person must identify the load by name before giving commands. In the event of loss of communication, the operator stops all movement immediately.

Inspection and Verification

Daily Inspection

Before each use, you must inspect:

Rejection criteria for wire rope (according to CSA standards):

Periodic Inspection

A complete inspection by a competent person must be performed at least once per year (more frequently for equipment subjected to severe conditions). This inspection includes disassembly of accessories, magnetic particle inspection of hooks, and verification of documentation.

Load Calculations and Capacity

Rated Capacity and Safety Factor

The rated capacity (Working Load Limit — WLL) is the maximum load that equipment can support under normal operating conditions. The safety factor is the ratio between the breaking strength and the rated capacity.

Calculating Load Weights

You must be able to calculate the weight of a load from its dimensions and the density of the material.

Formula: Weight (kg) = Volume (m³) × Density (kg/m³)

Example: A steel beam with an HEA 300 section (linear mass of 88.3 kg/m) that is 12 m long weighs:

88.3 kg/m × 12 m = 1,059.6 kg

Centre of Gravity

The centre of gravity is the point where all the mass of the load is considered to be concentrated. For a stable lift, the crane hook must be directly above the centre of gravity. If the load is unbalanced, it will tip.

Calculation method for a compound load:

Where Wi is the weight of each part and Xi is its position on the axis.

Safe Lifting Procedures

Lift Plan

Before any lift, a lift plan must be established. This plan must include:

Fundamental Safety Rules

Lifting Long Loads

For long loads (beams, columns), use a basket hitch or a two-sling configuration with a spreader bar to maintain the correct angle. The spreader bar reduces horizontal compression on the load and keeps the legs vertical.

Lifting Loads with Multiple Attachment Points

When the load has four attachment points (e.g., a beam with four rings), the load distribution is never perfectly equal. In practice, it is considered that only three points carry the load (the load is distributed over three points, the fourth being in cantilever). For calculations, use the most unfavourable configuration.

Cranes: Types and Configurations

Mobile Cranes

Mobile cranes are classified into several categories:

Tower Cranes

Tower cranes are used for high-rise buildings. They are anchored to the ground or to the structure. Capacity decreases with reach and height. The load chart of the tower crane must be consulted for each configuration.

Load Charts

The load chart is the most important document for the crane operator. It indicates the maximum capacity based on:

Critical rule: The capacity indicated on the chart is the net capacity (without the weight of lifting accessories). You must subtract the weight of the hook, slings, and accessories from the indicated capacity.

Applicable Canadian Standards

CSA Z150 — Safety for Mobile Cranes

This standard is the primary reference for the use of mobile cranes in Canada. It covers:

CSA Z248 — Tower Cranes

This standard specific to tower cranes covers design, installation, use, and inspection.

CSA B167 — Overhead and Gantry Cranes

This standard applies to overhead cranes used in workshops and structural steel fabrication plants.

CSA W59 — Welding of Steel

This standard covers welding requirements for welded lifting attachments (rings, lifting lugs). Any weld on lifting equipment must comply with this standard.

Canada Labour Code — Safety Regulations

General safety requirements for construction sites under federal jurisdiction are set out in the Canada Occupational Health and Safety Regulations (COHSR), Part II.

Capacity Reduction Factors

Sling Angle

As previously discussed, the sling angle increases tension in the legs. This is the most frequent cause of sling failure.

Temperature

Wire rope slings lose strength at high temperatures:

Grade 80 chain slings can be used up to 300 °C without reduction, but beyond this, capacity must be reduced.

Dynamic Loads

Dynamic loads (shocks, accelerations, decelerations) can multiply the effective force on the sling by a factor of 2 or more. A sudden lift can create a force far greater than the static weight of the load. Always lift slowly and gradually.

Sharp Edges

A sharp edge can reduce the capacity of a wire rope sling by 50% or more. Use corner protectors or protective sleeves.

Pitfalls to Avoid

Exam Tips

Summary

Practice Questions

Answer: Load factor at 45° from vertical = 1.41. T = (3,500 ÷ 2) × 1.41 = 2,467.5 kg per leg.

Answer: 5,000 × 2.00 = 10,000 kg.

Answer: 97 × 9 = 873 kg.

Answer: No — the rejection criterion is an increase of more than 15%.

Answer: 90 °C (some special slings up to 180 °C).

This chapter provides you with the essential knowledge to succeed on the rigging, hoisting, and crane questions on the Red Seal exam. Review the tables, practice the calculations, and memorize the rejection criteria. Good luck with your preparation!