LEEA Foundation Certificate Workbook

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Questions and Answers

What voltage range is commonly utilized for low voltage control in modern electric hoists?

24 to 50 volts AC or DC (correct)

50 to 100 volts AC or DC

120 to 240 volts AC

12 to 24 volts AC or DC

Which materials are considered the principal lifting media for power-operated hoists?

Plastic straps and rubber belts

Aluminum chains and carbon fiber ropes

Nylon cables and composite chains

Short link round steel chain and steel wire rope (correct)

Why might a collecting box for slack chain restrict the lifting height of loads?

It is positioned above the hoist where loads may get caught

It contributes to the overall weight of the hoist

It interferes with the motor's lifting capacity

It hangs below the hoist, limiting available vertical space (correct)

Which type of control is often used in older or special purpose hoists compared to modern designs?

Mains voltage control Signup and view all the answers

What is known as 'Extra Low Voltage' in the context of electric hoists?

Voltage derived from a transformer within the hoist Signup and view all the answers

In what configuration does the chain behave in hoists that use chain lifting media?

The slack side of the chain hangs loose over a pocketed wheel Signup and view all the answers

What is a common feature of modern electric hoists regarding their power source?

They utilize low voltage control derived from transformers. Signup and view all the answers

Which of the following is NOT an aspect of modern electric hoists as per the specifications provided?

Use of high voltage control Signup and view all the answers

Which type of crane is recognized for running on the top of rails that are part of the crane's supporting structure?

Top running bridge crane Signup and view all the answers

What is a common characteristic of the under-slung bridge crane?

It operates on the bottom flanges of its tracks. Signup and view all the answers

Which type of crane is typically supported by legs and operates on a low-level track?

Portal bridge crane Signup and view all the answers

In light-duty applications, what shape is the rail often configured as?

Square bar Signup and view all the answers

What happens if the rail is not securely clamped during welding?

Cracking may occur in service. Signup and view all the answers

Which of the following cranes can transfer loads between two running on parallel tracks?

Under-slung bridge crane Signup and view all the answers

Which crane type typically requires manual effort for its motions?

Bridge and gantry cranes in general Signup and view all the answers

Which crane design allows a bridge to have a cantilever at one or both ends while running on the bottom flanges?

Under-slung bridge crane Signup and view all the answers

What is the primary purpose of the structure of an ‘A’ Frame Gantry?

To ensure lateral stability through its shape Signup and view all the answers

What is the key feature of an Adjustable Height Gantry?

It allows height adjustments without load Signup and view all the answers

What is the primary purpose of runway switches and turntables in lifting systems?

To allow lifting appliances to be easily transferred between runway systems Signup and view all the answers

Which of the following statements is true about the Foldaway Gantry?

It is intended for applications requiring frequent storage and transport Signup and view all the answers

What maximum load capacity is typical for an ‘A’ Frame Gantry?

5 tonnes Signup and view all the answers

In which scenario is a slewing jib crane most effectively used?

In sites requiring limited moving operations combined with lifting Signup and view all the answers

Which of these is a design consideration for the Adjustable Height Gantry?

Adjustability to suit varying lifting height needs Signup and view all the answers

What characteristic distinguishes a slewing jib crane from other cranes?

The extensive coverage provided by the jib arm's slewing radius Signup and view all the answers

In what context would a Foldaway Gantry be preferable to an ‘A’ Frame Gantry?

When occasional use with frequent storage is required Signup and view all the answers

Which of the following is true regarding the design and installation of slewing jib cranes?

They may be supplied and tested independently of lifting appliances Signup and view all the answers

What is a limiting factor in the use of Foldaway Gantries?

They can only lift light loads Signup and view all the answers

What determines whether a slewing jib structure is over-braced or under-braced?

The location and intended use of the crane installation Signup and view all the answers

What distinguishes the ‘A’ Frame Gantry from the other types?

It is the most common and has a specific structural design Signup and view all the answers

What is a critical requirement for a slewing jib arm to function effectively as a crane?

It must be fitted with a hoist, hoist and trolley, or similar appliance Signup and view all the answers

Which of the following describes a typical application of slewing jib cranes?

Performing lifting and limited movement over machine tools Signup and view all the answers

How do slewing jib cranes complement overhead traveling cranes?

By covering areas where installing overhead cranes is impractical or costly Signup and view all the answers

What is the primary function of tower cranes at construction sites?

To lift and transport materials like steel and concrete. Signup and view all the answers

Which statement accurately describes offshore pedestal cranes?

They are used to move materials and personnel to marine vessels. Signup and view all the answers

How does a delivery method using an elevating device differ from traditional methods?

It eliminates the need for specialized lifting equipment like forklifts. Signup and view all the answers

What characteristic differentiates tower cranes from other types of cranes?

Their considerable height and outreach. Signup and view all the answers

What advantage do elevating and rotating lifting devices offer in offshore settings?

They allow for safe transfer of both materials and personnel. Signup and view all the answers

Why are tower cranes considered essential at major construction sites?

They can lift heavy materials to great heights. Signup and view all the answers

What is a common limitation of using traditional delivery methods that elevating devices overcome?

Inability to reach remote areas. Signup and view all the answers

Which of the following factors is crucial when designing offshore cranes?

Environmental and operational safety standards. Signup and view all the answers

Study Notes

Electric Chain and Wire Rope Hoists

Modern electric hoists typically employ low voltage control, generally between 24 to 50 volts AC or DC, known as 'Extra Low Voltage.'
Older and specialty hoists may lack low voltage control; some European countries use mains voltage control instead.
Principal lifting media for power-operated hoists include short link round steel chain, steel wire rope, and HMPE/textile belt materials.
In chain hoists, the chain runs over a pocketed wheel while the slack side hangs loose, potentially using a collecting box that restricts maximum lift height.

Switches and Turntables

Runway switches and turntables facilitate the transfer of lifting appliances between different runway systems.

Crane Systems

Slewing Jib Cranes

Commonly used in industrial settings for manual or powered lifting with limited movement.
Commonly found over workstations, machine tools, and loading bays, covering a wide floor area within the jib radius.
Often supplement overhead travelling cranes; function as cranes only when fitted with a hoist or trolley.
Wall or column-mounted designs are available, featuring either over-braced or under-braced structures depending on usage needs.

Mobile Gantry Cranes

The 'A' Frame Gantry is prevalent, utilizing a standard rolled steel runway beam supported by ‘A’ shaped legs, stable for loads up to 5 tonnes.
Adjustable Height Gantries provide telescopic support for varying runway heights without load, accommodating different lifting height requirements.
Foldaway Gantries are designed for easy storage and transportation, primarily limited to loads of up to 2 tonnes.

Crane or Track Rails

Rails often feature a square bar profile for light duties, installed via intermittent welding to avoid service cracks.

Bridge and Gantry Cranes

Serve to lift and transport loads across the crane's coverage area, typically powered electrically for all motions.
There are four main types:
- Top Running Bridge Crane operates on the top of the rail structure.
- Under-Slung Bridge Crane operates on the bottom flanges of the track, allowing for cantilever extensions.
- Semi-Portal Gantry Crane and Portal Gantry Crane support loads on low-level tracks, enhancing operational efficiency for truck loading.

Tower Cranes

Tower cranes are essential at major construction sites, with significant height and outreach capabilities.
Used for lifting various materials including steel, concrete, and equipment.

Offshore Pedestal Cranes

Defined as pedestal-mounted cranes that elevate and rotate to transfer materials and personnel between marine vessels and structures.

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Description

This quiz focuses on electric chain and wire rope hoists as part of the LEEA Foundation Certificate (Global). Learn about low voltage control systems, their operation, and safety features relevant to modern electric hoisting. Expand your knowledge and prepare for certification with this insightful quiz.