Tower Crane Types, Components, and Setup

Types of Tower Cranes, Components, and Assembly

Chapter Introduction

This chapter covers all the knowledge required for the Red Seal exam concerning tower cranes: their classifications, structural components, mechanical and electrical systems, as well as assembly, disassembly, and stabilization procedures. You must master these concepts not only to pass the exam but also to apply safety rules on the job site. The tower crane is the most common lifting equipment on large construction sites in Canada, and improper handling is the cause of serious, often fatal, accidents.

Classification of Tower Cranes

Towing-Assembled Cranes (or Traditionally Rigged Cranes)

This type of crane is assembled piece by piece using an auxiliary mobile crane. The jib (or boom) is typically horizontal and supported by tie rods. The tower consists of modular lattice steel sections, joined with bolts or pins. These cranes offer high lifting capacity and significant hook height, but their installation is time-consuming and costly.

Self-Erecting Cranes (or Rapid-Erecting Cranes)

These cranes are equipped with an integrated hydraulic system that allows them to erect themselves without an auxiliary crane. They are often mounted on a concrete base or on rails. The erection mechanism uses a hydraulic cylinder to lift the upper portion of the tower, allowing new sections to be inserted from the bottom (a process known as "climbing from below"). This type of crane is preferred on urban job sites where space is limited.

Luffing Jib Cranes (or Inclined Jib Cranes)

The jib is articulated at its base and can be angled using a luffing cable. This design reduces the vertical clearance required during assembly and allows work in areas with limited headroom. Lifting capacity decreases as the angle of inclination increases.

Horizontal Jib Cranes (or Saddle Jib Cranes)

This is the most common type. The jib is held horizontally by tie rods attached to a slewing unit (or slewing ring). The trolley moves along the jib to position the load. Lifting capacity is at its maximum when the trolley is close to the tower and decreases as it moves further away (see capacity chart).

Comparative Table of Crane Types

Type	Assembly	Jib	Typical Capacity	Primary Use
Towing-Assembled	Auxiliary mobile crane	Horizontal or luffing	5 to 50 tons	Large job sites, great heights
Self-Erecting	Integrated hydraulic	Horizontal	2 to 12 tons	Urban job sites, confined spaces
Luffing Jib	Mobile crane or self-erecting	Inclinable	3 to 20 tons	Limited headroom areas
Horizontal Jib	Mobile crane or self-erecting	Horizontal	5 to 40 tons	General use, long reach

Main Components of a Tower Crane

The Tower (or Mast)

The tower is the vertical structure that supports the jib and the load. It is made up of lattice sections of steel, typically triangular or square in shape. Each section typically measures between 2.5 m and 6 m in length. The sections are connected with high-strength bolts or pins. The tower must be perfectly plumb; a verticality deviation greater than 1/500 of the height is unacceptable according to manufacturer standards.

The Jib (or Boom)

The jib is the horizontal structure that supports the trolley and the load. It is attached to the upper part of the tower via a slewing unit that allows it to rotate. The jib is held horizontal by tie rods (cables or bars) connected to a apex (or jib head). Jib length varies from 30 m to 80 m depending on the model.

The Counter-Jib

The counter-jib is located opposite the jib. It supports the counterweight, the hoist winch, and sometimes the slewing mechanism. Its role is to balance the overturning moment created by the load. The counterweight consists of concrete or cast iron blocks, with a total weight that can reach 20 tons or more.

The Slewing Unit (or Slewing Ring)

The slewing unit is a large-diameter ball or roller bearing located between the tower and the upper structure (jib + counter-jib). It allows the jib to rotate 360°. A slewing motor drives a pinion that meshes with the geared ring. The rotation speed is typically 0.5 to 1.0 revolution per minute.

The Trolley

The trolley is a mobile device that travels along the jib. It supports the return pulley and the hook. Movement is controlled by a trolley cable operated by a dedicated winch. The trolley's position determines the working radius and therefore the lifting capacity.

The Hook and Pulley Block

The hook is attached to a block (a set of pulleys) that multiplies the force of the hoist cable. The number of cable parts in the block determines the maximum capacity. For example, a 2-part block offers half the capacity of a 4-part block but doubles the hoisting speed.

The Hoist Winch

The winch is installed on the counter-jib. It consists of a drum, an electric motor, a gearbox, and a brake. The hoist cable winds onto the drum and passes through pulleys to the block. The brake must be capable of holding 125% of the maximum rated load.

The Counterweight

The counterweight is essential for stability. It is calculated to balance the maximum overturning moment caused by the load and wind. The total counterweight weight is specified by the manufacturer and must never be modified without written authorization.

Safety Devices

Load limiter (or moment limiter): a mechanical or electronic device that stops hoisting when the load exceeds the rated capacity for the given radius.

Overturning moment limiter: monitors the combined moment of the load and wind.

Hoist limit switch: stops the hook at the upper or lower position.

Trolley limit switch: stops the trolley at the ends of the jib.

Anemometer: measures wind speed; triggers an alarm and stops operations beyond the limit (generally 72 km/h, but varies by manufacturer).

Slewing limit switch: prevents excessive cable twisting (to avoid cable rotation).

Foundations and Anchoring

Types of Foundations

The tower crane must be securely anchored to the ground. Three types of foundations are commonly used:

46.Cast concrete foundation: a reinforced concrete block, typically 4 m × 4 m × 1.5 m, into which anchor bolts (threaded rods) are embedded. The crane is bolted onto these rods.

47.Rail foundation: the crane is mounted on rails laid on concrete sleepers. This system allows the crane to move horizontally but requires a perfectly level ground.

48.Pile foundation: used when the soil is of poor quality. Concrete or steel piles are driven down to a load-bearing layer, then a concrete footing is poured on top.

Ground Pressure Calculation

The pressure exerted by the crane on the ground must not exceed the bearing capacity of the soil. The maximum pressure is calculated as follows:

P = (Total crane weight + Maximum load + Counterweight) / Contact surface area

The contact surface area is the base of the tower or the surface area of the footings. For a concrete foundation, the surface area is that of the block. The typical bearing capacity of compacted soil is 150 to 300 kPa. Clay soil may only offer 50 to 100 kPa.

Intermediate Ties (or Guying)

When the free-standing height of the tower exceeds a certain value (generally 40 to 50 m), it becomes necessary to anchor the tower to the building under construction. These anchors are steel frames attached to the tower and connected to the building structure with tie rods. The maximum distance between two anchors is specified by the manufacturer, typically 20 to 30 m.

Assembly and Disassembly

Assembly Procedure for a Towing-Assembled Crane

58.Site preparation: level the ground, verify bearing capacity, install the foundation.

59.Base assembly: place the first tower sections onto the anchor bolts.

60.Lifting the slewing unit and upper structure: using a mobile crane, assemble the slewing unit, apex, jib, and counter-jib on the ground, then lift the entire assembly.

61.Securing the jib and counter-jib: once the upper structure is in place, attach the tie rods and install the counterweight.

62.Verifications: check verticality, tighten bolts to the specified torque, test limiters, perform a no-load test lift followed by a loaded test.

Assembly Procedure for a Self-Erecting Crane

64.Base installation: the base is placed on the foundation.

65.Initial assembly: a few tower sections are installed, then the upper structure (slewing unit, jib, counter-jib) is assembled on the ground.

66.Hydraulic climbing: the hydraulic cylinder lifts the upper structure, creating space to insert a new tower section from the bottom.

67.Inserting sections: sections are inserted one at a time, bolted in place, then the cylinder is repositioned.

68.Ties: when the maximum free-standing height is reached, ties are attached to the building.

Disassembly

Disassembly follows the reverse procedure. It is imperative to:

Remove the counterweight gradually, following the order prescribed by the manufacturer.

Lower the jib to the ground using the auxiliary crane.

Carefully unbolt, starting with the upper sections.

Verify that the wind does not exceed the permitted limit (generally 30 km/h for disassembly).

Weather Conditions

Assembly and disassembly are prohibited when wind speed exceeds 30 km/h (or the value specified by the manufacturer, often 40 km/h). In service, the crane can operate up to 72 km/h, but operations must cease beyond this limit. Beyond 100 km/h, the crane must be put into "weathervane" mode (free rotation) to minimize wind exposure.

Capacity and Stability Calculations

Overturning Moment

The overturning moment is the product of the load multiplied by the horizontal distance between the center of the tower and the load suspension point. It is expressed in kN·m (kilonewton-metres).

M = Load (kN) × Radius (m)

The maximum allowable overturning moment is specified by the manufacturer. It must never be exceeded, even when unloaded with strong winds.

Rated Capacity as a Function of Radius

The rated capacity of a tower crane is given by a load chart (or capacity table). This chart indicates the maximum allowable load for each working radius. For example:

Radius (m)	Capacity (t)
10	12.0
20	6.5
30	4.0
40	2.8
50	2.0

Capacity decreases with radius because the overturning moment increases. The maximum load is always limited by the most restrictive of three factors: jib strength, cable strength, or overturning moment.

Calculating Hook Height

Hook height is the vertical distance between the ground (or reference level) and the lowest point of the hook in its highest position. It depends on the tower height, the trolley position, and the length of the block.

H = Tower height + Jib height − Block length

Effect of Wind on Capacity

Wind exerts a horizontal force on the load and on the jib. This force creates an additional moment that adds to the overturning moment. Lifting capacity must therefore be reduced in windy conditions. The reduction is generally 10% for a wind of 30 km/h, 20% for 45 km/h, and 50% for 60 km/h. Beyond 72 km/h, lifting is prohibited.

Applicable Standards and Codes

Canadian Electrical Code, Part I (CE Code) (C22.1-21)

This code governs the electrical installation of cranes. The main rules are:

Rule 8-200: supply conductors must be protected against overcurrent.

Rule 36-100: lifting equipment must be grounded in accordance with grounding requirements.

Rule 36-102: flexible conductors (power cables) must be of a type approved for industrial use.

CSA Z248-17 – Tower Crane Code

This standard is the primary reference for the design, installation, inspection, and use of tower cranes in Canada. It specifies:

Design and manufacturing requirements (Section 4).

Installation and assembly requirements (Section 6).

Inspection and maintenance requirements (Section 8).

Operator training requirements (Section 10).

CSA B149.1 – Natural Gas and Propane Code

This standard applies if the crane uses a gas or propane engine (rare for tower cranes, but possible for auxiliary mobile cranes). Rules 5.1 to 5.5 address the installation of tanks and piping.

Canada Occupational Health and Safety Regulations (COHSR)

The COHSR, under the Canada Labour Code, imposes general requirements for lifting operations. Sections 14.1 to 14.10 deal specifically with cranes and hoists.

Inspection and Maintenance

Daily Inspection

Before each use, the operator must check:

The condition of the hoist cable (wear, corrosion, broken wires).

The condition of the hooks (deformation, cracks).

The operation of limiters and limit switches.

The oil level of the gearbox and hydraulic system.

The condition of the tower bolts (visible tightness).

The operation of the anemometer.

Periodic Inspection

A thorough inspection must be carried out by a qualified person:

Monthly: check welds, electrical connections, and brakes.

Quarterly: check tower verticality, measure pulley wear.

Annually: complete inspection by an engineer, load test at 110% of rated capacity.

Records

All inspections must be recorded in a logbook. This logbook must be kept for at least 5 years and be available upon request.

Common Pitfalls to Avoid

Confusing maximum capacity with capacity at maximum radius: maximum capacity is always at minimum radius (near the tower). Never use maximum capacity for a distant radius.

Forgetting about wind: wind reduces capacity. Do not neglect capacity reduction in moderate wind.

Ignoring verticality: a tower leaning more than 1/500 is dangerous. Check with a theodolite after each climb.

Modifying the counterweight: never add or remove counterweight without the manufacturer's written approval.

Using a damaged cable: a cable with more than 6 broken wires over a length of 8 diameters must be replaced.

Exceeding free-standing height without ties: the maximum free-standing height is specified by the manufacturer. Exceeding it creates a buckling risk.

Confusing the standards: the Canadian Electrical Code applies to electrical installations, CSA Z248 applies to tower cranes. Do not mix them up.

Forgetting the wind brake: in strong winds, the crane must be put into weathervane mode. Do not leave the jib locked facing the wind.

Summary

Tower cranes are classified into four types: towing-assembled, self-erecting, luffing jib, and horizontal jib.

The main components are: the tower, jib, counter-jib, slewing unit, trolley, hook, winch, and counterweight.

Stability is ensured by the counterweight and the foundation. The overturning moment must never exceed the allowable value.

Lifting capacity decreases with radius and with wind speed.

Assembly requires an auxiliary crane (for towing-assembled cranes) or an integrated hydraulic system (for self-erecting cranes).

Intermediate ties are mandatory beyond the maximum free-standing height.

Applicable standards are CSA Z248-17, the Canadian Electrical Code (Part I), and the COHSR.

Daily and periodic inspections are mandatory and must be recorded.

Wind limits operations: 30 km/h for assembly/disassembly, 72 km/h for service, 100 km/h for weathervane mode.

Self-Assessment Questions

149.What is the main difference between a towing-assembled crane and a self-erecting crane?

150.What is the role of the counter-jib?

151.How do you calculate the overturning moment?

152.What is the assembly procedure for a self-erecting crane?

153.What are the wind limits for assembly, service, and weathervane mode?

154.What should be checked during a daily inspection?

155.Which Canadian standard governs the design and use of tower cranes?

156.Why does lifting capacity decrease with radius?

157.What is an intermediate tie and when is it necessary?

158.What is the Canadian Electrical Code rule regarding the grounding of lifting equipment?

This chapter prepares you for the Red Seal exam questions on tower crane types, components, and assembly. Review the tables, formulas, and standards until you can recite them without hesitation.