Derricks & Cableways
1.5 hours
Learning Objectives
- •Identify the major types of fixed derricks and describe the structural role of each component
- •Explain the operating principles of a cableway system, including traction cable and track cable functions
- •Describe the load chart requirements for derricks under OSHA 29 CFR 1926.1436
- •State the inspection requirements specific to guy derricks and stiff-leg derricks
Topics Covered
- •Guy derrick: vertical mast held by a minimum of 6 guys equally spaced; rotating boom; common in structural steel erection
- •Stiff-leg (stiffleg) derrick: mast supported by two rigid legs and a base frame; does not require guys; limited rotation arc
- •Gin pole: simple single-mast derrick used for moderate lifts; no boom; load hangs from top
- •Chicago boom: attached to a building column or framework; boom pivots at a cleat on the structure; common in high-rise construction
- •Mast: primary vertical structural member; carries compressive load
- •Boom: pivoting member that positions the load horizontally; angle determines radius and rated capacity
- •Guys (guy lines): wire ropes from mast top to anchors; carry tension that stabilizes the mast; minimum 6 for guy derricks
- •Load chart: must show rated capacity at corresponding boom angles and operating radii; required by 1926.1436
- •New/reinstalled derricks: tested by competent person through full range of motion before first use
- •Derricks with capacity >6,000 lbs manufactured after Nov 8 2010 must have load-weighing or rated-capacity indicating device
- •Cableway systems: used to transport materials across a span (rivers, valleys, job sites)
- •Track cable (static cable): fixed cable spanning the distance; the carriage rides along it
- •Traction cable (haul cable): moving rope that pulls the carriage and load back and forth
- •Tower geometry: height, span, and sag determine capacity and clearance
- •Cableway carriage: the traveling trolley; rated for a specific suspended load
- •Operating from cableways: load must not exceed rated capacity; dynamic loading from swing must be accounted for
Resources
Self-Check Questions
Question 1: A guy derrick requires a minimum of how many guys, equally spaced?
- A. 3
- B. 4
- C. 6(correct)
- D. 8
Show Explanation
Explanation:
OSHA 29 CFR 1926.1436 and ASME B30.6 require a minimum of 6 guys, equally spaced, for a guy derrick. Variations in spacing require approval from a qualified person. Know this number — it appears on exams.
Question 2: Where must the load chart for a permanently installed derrick be located?
- A. In the general contractor's office trailer
- B. Posted where it is visible to personnel responsible for operating the equipment(correct)
- C. Kept in the operator's possession at all times
- D. Filed with the local building department
Show Explanation
Explanation:
OSHA 1926.1436 requires permanently installed derrick load charts to be posted visibly for the operating personnel. For non-permanent derricks, the chart must be readily available at the job site.
Question 3: Which type of derrick is attached to an existing building column or framework and pivots at a cleat?
- A. Guy derrick
- B. Stiff-leg derrick
- C. Chicago boom(correct)
- D. Gin pole
Show Explanation
Explanation:
The Chicago boom is mounted directly to the building structure — a cleat or bracket on a column — and the boom pivots around a limited arc. It is commonly used for hoisting materials during high-rise construction.
Question 4: In a cableway system, what is the function of the track cable?
- A. It pulls the carriage back and forth across the span
- B. It is the fixed, static cable that the carriage rides along(correct)
- C. It connects the load hook to the carriage
- D. It is the guy line that stabilizes the cableway tower
Show Explanation
Explanation:
The track cable (also called the static cable) spans the distance between towers and serves as the rail for the carriage. The traction (haul) cable moves the carriage. Knowing the difference between these two cables is a common exam topic.
Question 5: A new guy derrick has just been assembled on a construction site. Before placing any loads, what must occur?
- A. The operator must drive the derrick under a test load for 30 minutes
- B. A competent person must test the derrick through its full range of motion with no hook load(correct)
- C. The general contractor must sign off on the assembly log
- D. No pre-use testing is required if the derrick was used on a prior project
Show Explanation
Explanation:
OSHA 1926.1436 requires new or reinstalled derricks to be tested by a competent person through the full operational range — raising/lowering the hook, full boom travel, full swing range — with no load before first use. Documentation is required.