Section 1435 – Tower Cranes

Tower cranes present unique issues that are addressed in this section. In general, all provisions of the standard apply to tower cranes unless this section specifies different or additional requirements,

Additional Requirements for Erecting, Climbing and Dismantling

To reflect industry terminology, “erecting, climbing, and dismantling” are used instead of “assembly/disassembly” when referring to tower cranes. The following requirements apply in addition to those specified in sections 1403-1406:

• Tower crane foundations and structural supports (including both the portions of the structure used for support and the means of attachment) must be designed by the manufacturer or a registered professional engineer
• The Assembly/Disassembly (A/D) director must determine that tower crane foundations and structural supports are installed in accord with their design
• The A/D Director must address the backward stability of self-erecting cranes or cranes on traveling or static undercarriages
• Wind must not exceed the speed recommended by the manufacturer or, where the manufacturer does not specify this information, the speed determined by a qualified person
• Towers must be erected plumb to the manufacturer’s tolerance and verified by a qualified person. Where the manufacturer does not specify plumb tolerance, the crane tower must be plumb to a tolerance of at least 1:500 (approximately 1 inch in 40 feet)
• On job sites where more than one fixed jib (hammerhead) tower crane is installed, the cranes must be located such that no crane can come in contact with the structure of another crane. Cranes are permitted to pass over one another
• Prior to, and during, all climbing procedures (including inside climbing and top climbing), the employer must comply with all manufacturer prohibitions and have a registered professional engineer verify that the host structure is strong enough to sustain the forces imposed through the braces, brace anchorages, and supporting floors
• Equipment must not be erected, dismantled or operated without the amount and position of counterweight and/or ballast in place as specified by the manufacturer or a registered professional engineer familiar with the equipment. The maximum counterweight and/or ballast specified by the manufacturer or registered professional engineer must not be exceeded
• The size and location of signs installed on tower cranes must be in accord with manufacturer specifications. Where these are unavailable, a registered professional engineer familiar with the type of equipment involved must approve in writing the size and location of any signs.

Particular Caution Required When Using Synthetic Slings

This requirement appears in section 1404 but bears repeating here: when using synthetic slings during erecting, climbing, and dismantling, 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.

Safety Devices

Different safety devices than those specified in section 1415 are required on tower cranes. Those required on tower cranes are:

• Boom stops on luffing boom type tower cranes
• Jib stops on luffing boom type tower cranes if equipped with a jib attachment
• Travel rail end stops at both ends of travel rail
• Travel rail clamps on all travel bogies
• Integrally mounted check valves on all load-supporting hydraulic cylinders
• Hydraulic system pressure limiting device
• The following brakes, which must automatically set in the event of pressure loss or power failure, are required:
  • A hoist brake on all hoists
  • Swing brake
  • Trolley brake
  • Rail travel brake
  • Deadman control or forced neutral return control (hand) levers
• Emergency stop switch at the operator’s station
• Trolley end stops must be provided at both ends of travel of the trolley

Proper operation of these safety devices is required before operations can begin.

Operational Aids

Different operational aids than those specified in section 1416 are required for tower cranes. Those required on tower cranes are:

• Trolley travel limiting device at both trolley end stops
• Boom hoist limiting device that limits the range of the boom at the minimum and maximum radius
• Anti two-blocking device
• Hoist drum lower limiting device on tower cranes manufactured after November 8, 2011
• Load moment limiting device
• Hoist line pull limiting device
• Rail travel limiting device
• Boom hoist drum positive locking device and control
• Boom angle or hook radius indicator readable from the operator’s station. (Required on all luffing boom tower cranes and on hammerhead tower cranes manufactured after November 8, 2011)
• Trolley travel deceleration device
• Boom hoist deceleration device
• Load hoist deceleration device
• Wind speed indicator
• Load indicating device on tower cranes manufactured after November 8, 2011

As with operational aids on other equipment, tower cranes may be operated for limited amounts of time with malfunctioning aids as long as the temporary alternative measures specified in the standard are taken.

Inspections

Additional inspection requirements for tower cranes are discussed under section 1412 (Inspections).