Pipefitter Rigging and Hoisting Operations 2 — Questions and Answers
Question 1: What is the 'D/d ratio' in rigging, and what does a higher ratio indicate?
- The ratio of wire rope drum or sheave diameter to rope diameter; a higher ratio means less wire fatigue and longer rope life (Correct answer)
- The ratio of dead load to dynamic load on a rigging system
- The ratio of downward force to diagonal force in a sling angle calculation
- The ratio of drum diameter to hook diameter on a hoist
Correct answer: The ratio of wire rope drum or sheave diameter to rope diameter; a higher ratio means less wire fatigue and longer rope life
D/d ratio is the diameter of the drum/sheave (D) divided by the rope diameter (d). A higher ratio reduces wire rope bending stress and extends rope life.
The D/d (drum-to-rope) ratio describes the degree of curvature imposed on a wire rope as it wraps around a drum or sheave. Industry standards recommend a minimum D/d ratio of 18:1 for 6×19 class rope in general service. When the ratio is too low (rope bent too sharply), the individual wires must bend severely, causing accelerated fatigue and early wire breakage. Higher D/d ratios reduce wire stress and extend rope service life.
Question 2: What does 'proof load' mean for rigging hardware?
- A test load applied to hardware before service to verify it can handle its rated capacity without permanent deformation (Correct answer)
- The maximum load a rigging component can theoretically support before breaking
- The working load limit divided by the safety factor
- The load applied during hydrostatic testing of pipe
Correct answer: A test load applied to hardware before service to verify it can handle its rated capacity without permanent deformation
Proof load is a non-destructive test load applied to rigging hardware (typically 2× the Working Load Limit) to verify structural integrity without causing permanent set.
Proof load testing applies a load (typically 2× WLL for shackles and hooks, per ASME B30.26 and ASME B30.10) to rigging hardware to verify it can handle its rated capacity. The hardware must not show permanent deformation after proof loading. This is different from the breaking strength (ultimate load), which is typically 4-5× the WLL. Proof loading provides confidence that the hardware is free of manufacturing defects.
Question 3: What is the maximum angle from vertical that a two-leg bridle sling should form before the WLL is reduced to account for increased leg tension?
- 45 degrees from vertical (90-degree included angle) (Correct answer)
- 60 degrees from vertical (120-degree included angle)
- 30 degrees from vertical (60-degree included angle)
- There is no angle limit if the WLL of each leg is not exceeded
Correct answer: 45 degrees from vertical (90-degree included angle)
At 45° from vertical (90° included angle between legs), each sling leg tension equals 0.707 × load. Beyond 45°, tension increases rapidly; many standards limit use to 60° from vertical maximum.
In a two-leg bridle sling, leg tension = Load Weight / (2 × cos θ), where θ is the angle from vertical. At 45° from vertical: each leg carries Load / (2 × 0.707) = 0.707 × Load. The horizontal component of each leg also creates inward compression on the load. Most rigging standards (ASME B30.9) reduce WLL for slings used at angles greater than 45° from vertical and prohibit use beyond 60° from vertical due to the exponentially increasing leg tension.
Question 4: What is a 'tagline' used for during crane lifts of pipe or equipment?
- A rope attached to the load to control rotation and horizontal movement during the lift (Correct answer)
- The safety line attached to the crane boom to prevent over-extension
- The load rating tag attached to every rigging component
- A line used to manually measure the lift height
Correct answer: A rope attached to the load to control rotation and horizontal movement during the lift
Taglines are ropes attached to the load, held by ground personnel, to control load spin and lateral movement during the lift, keeping workers clear of the load's path.
Taglines are an essential safety device during crane lifts. Ground riggers hold taglines (typically 3/4" to 1" manila or synthetic rope) to: (1) prevent the load from spinning, (2) guide the load over obstacles, (3) position the load accurately at the landing point, and (4) keep workers at a safe distance from the suspended load. Taglines must never be wrapped around hands or body. At least one tagline is required per ASME B30.2 for loads that could rotate or swing dangerously.
Question 5: What is the primary purpose of a 'load cell' used during rigging operations?
- To measure the actual weight of a load in real time during lifting (Correct answer)
- To test the breaking strength of slings before use
- To detect moisture inside rigging wire rope
- To measure the electrical load on the crane motor
Correct answer: To measure the actual weight of a load in real time during lifting
A load cell is a strain gauge device placed in the rigging to measure the actual tension/weight in real time, ensuring the lift stays within equipment capacity.
Load cells are electronic force-measuring devices inserted into the rigging between the crane hook and the sling attachment. They display the actual load weight on a remote indicator. Load cells are used when: (1) the load weight is uncertain or estimated, (2) multiple crane lifts require precise load sharing data, (3) proof testing of lifting fixtures is required, or (4) regulatory requirements specify verified weights. They prevent overloading of cranes and rigging equipment.
Question 6: Before a crane or hoist is used, what inspection must be performed according to ASME B30.2 and OSHA 1926.550?
- A pre-operational (shift) inspection by the operator, checking controls, brakes, hooks, and warning devices (Correct answer)
- A full annual certification inspection by a third-party inspector
- A load test to 125% of rated capacity
- A lubrication service of all sheaves and drums
Correct answer: A pre-operational (shift) inspection by the operator, checking controls, brakes, hooks, and warning devices
ASME B30.2 and OSHA require a pre-operational (daily/shift) inspection by the crane operator before each use, covering controls, limit switches, hooks, wire rope, and structural components.
ASME B30.2 mandates three levels of crane inspection: (1) Pre-operational (shift/daily) — operator inspection before each use, checking functional controls, brakes, limit switches, hook latch, wire rope for visible damage, and safety devices; (2) Frequent inspection — periodic inspection (monthly or per use frequency) with documentation; (3) Periodic inspection — comprehensive annual or semi-annual inspection by a qualified inspector. The pre-operational inspection is the operator's responsibility every shift.
Pipefitter Rigging and Hoisting Operations 2
What is the 'D/d ratio' in rigging, and what does a higher ratio indicate?