Ground Conditions and Assembly/Disassembly

Who is responsible for ensuring the ground conditions are adequate at the site?

Importance of Ground Conditions

Adequate ground conditions are essential for safe crane operations because the crane's capacity and stability depend on such conditions being present. If, for example, the ground is muddy or otherwise unstable, a crane could overturn even if operated with the load limits specified by the manufacturer.

BASIC RULE (short version): You must not assemble or use a crane, unless the equipment manufacturer’s specifications for adequate support and degree of level of equipment are met.

BASIC RULE (long version): You must not assemble or use a crane unless ground conditions are firm, drained, and graded to a sufficient extent so that, in conjunction (if necessary) with the use of supporting materials (such as blocking, mats, cribbing, or marsh buggies (in marshes/wetlands), the equipment manufacturer's specifications for adequate support and degree of level of the equipment are met. The requirement for the ground to be drained does not apply to marshes/wetlands.

Responsibilities of the Controlling Entity

A contractor operating a crane on a construction site may not have the ability or authority to provide for adequate ground conditions at the site. The standard, therefore, places the responsibility for ensuring that the ground conditions are adequate on the "controlling entity" at the site. The “controlling entity” is the prime contractor, general contractor, construction manager, or other legal entity with overall responsibility for the project's planning, quality, and completion.

The controlling entity must also inform the user and operator of the equipment:

• of hazards beneath the equipment set-up area (voids, tanks, utilities),
• if those hazards are identified in documents (site drawings, as-built drawings, and soil analyses),
• if the documents are in the possession of the controlling entity (whether at the site or off-site), and
• of any other hazards known to the controlling entity.

If there is no controlling entity for the project, the responsibility for providing adequate ground conditions rests on the employer that has authority at the site to make or arrange for ground preparations.

Responsibility of the Company Operating the Crane

Although the controlling entity is responsible for providing adequate ground conditions, the company operating the crane will often be better able than the controlling entity to determine whether those conditions are adequate. If you are operating a crane and decide that ground conditions are inadequate, you must discuss the problem with the controlling entity and see that the problem is corrected before beginning or continuing operations.

Assembly and Disassembly

Are accidents during assembly and disassembly of lattice boom and tower cranes one of the major causes of crane-related fatalities?

Accidents during assembly and disassembly of lattice boom and tower cranes are one of the major causes of crane-related fatalities. These sections are designed to prevent such accidents by requiring safe assembly/disassembly procedures for lattice boom and tower cranes. Hydraulic-boom cranes are not generally assembled on-site, but these sections contain some provisions, such as the requirement (Standard 1404(q)) for proper setting of outriggers and stabilizers, which apply to cranes with hydraulic booms.

Required Procedures

When assembling or disassembling a crane, you must comply with either manufacturer or employer procedures, which must be developed by a qualified person.

Such procedures must, at a minimum:

• prevent unintended dangerous movement or collapse of any part of the equipment,
• provide adequate support and stability of all parts of the equipment, and
• position employees involved in the assembly/disassembly operation so their exposure to unintended movement or collapse of part or all of the equipment is minimized.

Regardless of which of these options you choose, you must follow any manufacturer prohibitions that apply to the assembly/disassembly operation.

The A/D Director

The A/D director must understand the applicable assembly/disassembly procedures.

All assembly/disassembly operations must be directed by an individual who meets the criteria for both a competent person and a qualified person, or by a competent person who is assisted by one or more qualified persons. The A/D director must understand the applicable assembly/disassembly procedures. The A/D director must take the following precautions to protect against potential hazards associated with the operation, including:

• Site and ground conditions must be able to support the equipment during assembly/disassembly.
• Blocking material must be the correct size, amount, and condition. The blocking must be stacked so as to sustain the loads and maintain stability.
• When used to support lattice booms or components, blocking must be placed appropriately to protect the structural integrity of the equipment, and prevent dangerous movement and collapse.
• When using an assist crane, the loads that will be imposed on the assist crane at each phase of assembly/disassembly must be verified as being within its rated capacity.
• The point(s) of attachment of rigging to a boom (or boom sections, jib, or jib sections) must be suitable for preventing structural damage and facilitating safe handling of these components.
• The center of gravity of the load must be identified if necessary for the method used for maintaining stability. Where there is insufficient information to accurately identify the center of gravity, measures designed to prevent unintended dangerous movement, resulting from an inaccurate identification of the center of gravity, must be used.
• The boom sections, boom suspension systems (such as gantry A-frames and jib struts), and components must be rigged or supported to maintain stability upon the removal of the pins.
• Suspension ropes and pendants must not be allowed to catch on the boom or jib connection pins or cotter pins (including keepers and locking pins).
• Steps must be taken to prevent unintended movement from counterweights that are inadequately supported or are being hoisted.
• Each time reliance is to be placed on the boom hoist brake to prevent boom movement during assembly/disassembly, the brake must be tested prior to such reliance to determine if it is sufficient to prevent boom movement. If it is not sufficient, a boom hoist pawl, other locking device/back-up braking device, or another method of preventing dangerous movement of the boom (such as blocking or using an assist crane) from a boom hoist brake failure must be used.
• Backward stability must be assured before swinging the upperworks, travel, and when attaching or removing equipment components.
• The effect of wind speed and weather on the equipment must be taken into account.

The Crew

Crew members need to know their tasks and the hazardous positions to avoid.

Before the operation begins, the A/D director must ensure that the crew members understand all of the following:

• their tasks,
• the hazards associated with their tasks, and
• the hazardous positions/locations that they need to avoid.

Before a crew member goes to a location that is out of view of the operator and is either in, on, or under the equipment, or near the equipment (or load) where the crew member could be injured by movement of the equipment (or load), the crew member must inform the operator that he/she is going to that location. Whenever the operator knows that a crew member is in such a potentially dangerous position, the operator must not move any part of the equipment (or load) until the operator is informed in accord with a pre-arranged system of communication that the crew member is in a safe position.

The Rigger

When rigging is used for assembly/disassembly, the employer must ensure that the rigging work is done by a rigger who meets the requirements as a qualified person and successfully demonstrates the ability to solve/resolve problems relating to rigging.

A rigger is required when:

• Rigging is part of assembly or disassembly work involving a crane
• Workers are within the fall zone and are hooking, unhooking, or guiding a load

A rigger doesn't have to be qualified to do all rigging jobs. You must determine whether a person is qualified to perform specific rigging tasks. Each qualified rigger may have different credentials or experience. (Oregon OSHA)

Working Under the Boom, Jib or Other Components

When pins (or similar devices) are being removed, employees must not be under the boom, jib, or other components, unless site constraints require one or more employees to be in such a position. In such a case, the A/D director must implement procedures that minimize the risk of unintended dangerous movement and minimize the duration and extent of exposure under the boom.

Real World Event

A crew of ironworkers and a crane operator were unloading a 20-ton steel slab from a low-boy trailer using a 50-ton crawler crane with a 90-foot lattice boom. The operator was inexperienced on this crane and did not know the length of the boom. Further, no one had determined the load radius. During lifting, the load moved forward and to the right, placing a twisting force on the boom. The boom twisted under the load, swinging down, under and to the right. Two crew members standing 30 feet away apparently saw the boom begin to swing, and ran. The boom struck one of the ironworkers in the head, causing instant death. Wire rope struck a management-trainee and caused internal injuries. He died two hours later at a local hospital.

Synthetic Slings

When using synthetic slings during assembly or disassembly, you must follow the synthetic sling manufacturer's instructions, limitations, specifications and recommendations. Synthetic slings must be protected from abrasive, sharp or acute edges, and configurations that could cause a reduction of the sling's rated capacity, such as distortion or localized compression.

Outriggers and Stabilizers

Outrigger and stabilizer blocking must be the correct size, amount, and condition.

When outriggers or stabilizers are used:

• The outriggers or stabilizers must be either fully extended or if manufacturer procedures permit, deployed as specified in the load chart.
• The outriggers must be set to remove the equipment weight from the wheels, except for locomotive cranes. This provision does not apply to stabilizers.
• When outrigger floats are used, they must be attached to the outriggers. When stabilizer floats are used, they must be attached to the stabilizers.
• Each outrigger or stabilizer must be visible to the operator or to a signal person during extension and setting.
• Outrigger and stabilizer blocking must be the correct size, amount, and condition. The blocking must be placed only under the outrigger or stabilizer float/pad of the jack or, where the outrigger or stabilizer is designed without a jack, under the outer bearing surface of the extended outrigger or stabilizer beam.

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Dismantling Booms and Jibs

The following precautions must be taken to prevent dangerous movement of boom and jib sections that are being dismantled.

• None of the pins in the pendants are to be removed (partly or completely) when the pendants are in tension.
• None of the pins (top or bottom) on boom sections located between the pendant attachment points and the crane/derrick body are to be removed (partly or completely) when the pendants are in tension.
• None of the pins (top or bottom) on boom sections located between the uppermost boom section and the crane/derrick body are to be removed (partly or completely) when the boom is being supported by the uppermost boom section resting on the ground (or other support).
• None of the top pins on boom sections located on the cantilevered portion of the boom being removed (the portion being removed ahead of the pendant attachment points) are to be removed (partly or completely) until the cantilevered section to be removed is fully supported.

Fall Protection

During assembly/disassembly work, fall protection is generally required when a worker is more than 15 feet above an unprotected side or edge. See Standard 1423.

Video

This is a a very informative video on crane safety developed by the Department of Defense.

Instructions

Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

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