3.2 Climbing Procedures: Manufacturer Prohibitions, Notes & Warnings
Key Takeaways
- Under OSHA 29 CFR 1926.1435(b)(7), before and during all climbing procedures - including both inside climbing and top climbing - the employer must comply with all manufacturer prohibitions and must have a registered professional engineer verify the host structure can sustain the forces imposed through the braces, brace anchorages, and supporting floors.
- The universal manufacturer prohibition during a climb is that the crane must not lift any load other than the climbing operation itself: the slewing ring, trolley, and hoist are locked in the manufacturer-specified climbing position while the tower is discontinuous.
- A climbing crane is at its structurally weakest when the climbing frame carries the entire upper works and the mast is open at the splice, which is why climbing is a wind-limited operation with its own lower wind threshold.
- OSHA 1926.1435(b)(5) requires towers to be erected plumb to the manufacturer's tolerance verified by a qualified person; where the manufacturer specifies no tolerance, the default is at least 1:500, approximately 1 inch in 40 feet.
- After a climb is complete the top climbing unit must be returned to the position specified by the manufacturer before normal lifting resumes; leaving it parked in the climbing position is an out-of-service condition.
3.2 Climbing Procedures: Manufacturer Prohibitions, Notes & Warnings
Blueprint item D2.2 is "Know general notes and warnings to be applied during climbing procedures," and D2.11 is "Know proper position of top climbing unit after climbing procedures in accordance with manufacturer's specifications." Together they test one idea: during a climb the crane is temporarily not a complete structure, and everything an operator normally relies on is suspended until the tower is closed and pinned again.
1. The Two Climbing Methods
| Method | Where the Climbing Frame Sits | How Height Is Gained | Typical Use |
|---|---|---|---|
| Top climbing (external climbing, "jumping") | A climbing cage/frame wraps the outside of the mast, directly below the slewing platform | A hydraulic ram pushes the entire upper works up one mast section; a new section is rolled in on a monorail beam and pinned/bolted in | Freestanding and tied-in cranes on the outside of a building |
| Inside climbing (internal climbing) | The crane sits inside the building core on climbing collars supported by the floor structure | The crane is jacked up through a floor opening; collars are relocated to higher floors | Core-served high-rise where the crane comes out by helicopter or derrick at topping out |
OSHA's climbing rule at 1926.1435(b)(7) applies to both, and says so explicitly: "Prior to, and during, all climbing procedures (including inside climbing and top climbing), the employer must..."
2. The Two Mandatory Climbing Requirements
(i) Comply with all manufacturer prohibitions
Every OEM climbing chapter opens with a list of prohibitions. They vary in detail but converge on the same set:
- No lifting of any load other than the climbing operation. The hoist is used only to handle the mast section being inserted, at the position and radius the manual specifies.
- The slewing ring must be locked (swing brake set and, on most machines, a mechanical slew lock pin engaged). A crane that slews while the mast is open at the splice can shear the climbing frame guide rollers.
- The trolley must be parked at the specified balancing radius. This is the heart of it: the climbing frame can only carry the upper works if the moment about the frame is inside a narrow band. The manual gives an exact trolley position - often with the mast section itself hung on the hook as a deliberate counter-moment.
- No personnel below the climbing zone. For self-erecting cranes this is codified separately at 1926.1435(b)(2): employees must not be in or under the tower, jib, or rotating portion during erecting, climbing, and dismantling until the crane is secured in a locked position and the competent person in charge indicates it is safe - unless the manufacturer's instructions direct otherwise and only necessary personnel are present.
- Climb only within the manufacturer's wind limit (Section 3.3).
- Never leave a climb partially complete across a shift break or overnight without the mast pinned and bolted per the manual.
[!WARNING] The exam's favorite climbing question is some version of "may the crane make a production lift during a climb?" The answer is always no. During the climb the crane's tower is discontinuous and the entire upper works is riding on hydraulic rams and climbing frame pawls. Rated capacity in the load chart assumes a complete, pinned, plumb tower. It does not exist during a climb.
(ii) Registered professional engineer verification of the host structure
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.
This is the requirement people forget, and it is squarely on the exam. A tied-in or internally climbing crane transfers enormous horizontal reactions into the building. Those forces land on braces (the struts), brace anchorages (embeds, through-bolts, collar connections), and - for internal climbing - the supporting floors themselves. Concrete that has not reached design strength is the classic failure path: a climb scheduled for a floor poured four days earlier can exceed the capacity of green concrete even though the finished structure would carry it easily.
Note the roles: a competent person cannot make this determination, and neither can the crane's A/D director acting alone. It requires a registered professional engineer.
3. General Notes and Warnings Common to Every Climbing Manual
| Note / Warning | Reason |
|---|---|
| Verify the climbing frame guide rollers and pawls/dogs are seated before any hydraulic movement | The pawls carry the entire upper works between ram strokes |
| Verify hydraulic system pressure, hose condition, and integrally mounted check valves | 1926.1435(d)(2)(v) requires check valves integrally mounted on all load supporting hydraulic cylinders precisely so a hose burst cannot drop the upper works |
| Confirm the new mast section orientation before insertion | Mast sections are directional on most machines; ladder side, cable guide side, and reinforced chord faces must align |
| Torque all splice bolts to the specified value in the specified sequence | Covered in Section 3.4 |
| Re-verify plumb after the climb | 1926.1435(b)(5) |
| Return the climbing unit to its specified post-climb position | D2.11, below |
| Do not climb with ice, snow, or standing water on the climbing frame walkways | Fall exposure and pawl seating |
| Suspend the climb if wind rises above the limit mid-operation and secure the mast in a pinned condition first | The mast must never be left open |
4. Plumb Tolerance - 1926.1435(b)(5)
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).
Three testable details:
- Manufacturer's tolerance controls first. The 1:500 figure is the default when the OEM is silent, not a universal number. Many OEMs specify tighter values, and some specify different in-service versus erected tolerances.
- A qualified person verifies it - not simply "someone checked with a level."
- 1:500 = 0.2%, or about 1 inch in 40 feet. On a 200 ft tower that is roughly 5 inches of permitted top-of-mast offset. Candidates often mis-convert this; carry the 1 inch per 40 feet form, because the exam permits no calculator.
Plumb is re-verified after every climb because each new mast section can introduce error, and error accumulates upward.
5. Position of the Top Climbing Unit After Climbing (D2.11)
Once the mast section is inserted, pinned, and torqued, the climbing frame is not simply abandoned in place. Manufacturers specify a defined post-climb position for the climbing unit, and it matters for three reasons:
- Load path. In the parked/secured position the climbing frame's load-transfer components are disengaged so that operating loads pass through the mast splice as designed, not through the climbing frame.
- Slewing clearance. The frame must sit where the counter-jib, cable guides, and tie-in collars can pass or clear.
- Structural rating. Some machines derate capacity, or prohibit operation entirely, while the climbing unit is in the climbing (rather than parked) position.
[!IMPORTANT] On the exam, the correct answer to "where should the top climbing unit be after the climb?" is always some form of "in the position specified by the manufacturer's specifications, with the climbing components secured and disengaged." Distractors offering "lowest possible position," "directly below the slew ring at all times," or "operator's discretion" are wrong because they replace an OEM specification with a rule of thumb.
Before returning the crane to production after any climb, the operator should confirm: mast splice bolts torqued and marked, plumb re-verified by a qualified person, climbing unit in the specified position and secured, slew lock released, trolley and hoist limits re-checked, and the height/radius limit switches re-set for the new mast height.
An internal climbing tower crane is scheduled to jump to a floor that was poured five days ago. Under 29 CFR 1926.1435(b)(7), who must verify that the host structure can sustain the forces imposed through the braces, brace anchorages, and supporting floors?
A general contractor asks the operator to make one quick pick of a bundle of rebar while the climbing crew is midway through inserting a mast section. What is the correct response?
A tower crane manufacturer's manual is silent on erected plumb tolerance. The tower is 240 feet tall. What is the maximum out-of-plumb offset permitted at the top of the mast under 29 CFR 1926.1435(b)(5), and who verifies it?