Boom movement safety procedures

No—employees must not be under the boom, jib, or other components while pins are being removed except where the limited exception in 1926.1404(f)(2) applies. The general prohibition is in 1926.1404(f)(1), and Appendix B to Subpart CC explains that the only allowed exception is when the employer (through the A/D director) demonstrates that site constraints require employees to be under the boom while pins are being removed. (See the sample procedures in Appendix B to Subpart CC of Part 1926.)

The A/D director must implement procedures that minimize the risk of unintended dangerous movement and that minimize how long and how much employees are exposed under the boom. Appendix B gives practical examples—such as using an assist crane to support the boom section being detached, ensuring the end near the employee is well supported, removing the far-side pins first, and moving personnel out from under the boom as soon as possible—consistent with 1926.1404(f)(2) and the prohibition in 1926.1404(f)(1).

Yes—only when the employer demonstrates site constraints that make repositioning impossible and follows procedures to minimize risk and exposure. Appendix B describes a scenario where an aerial lift must move under the boom due to obstructing piping and explains that the A/D director must use controls (for example, an assist crane supporting the section) and minimize the time employees are beneath the boom in accordance with 1926.1404(f)(2) and the rule in 1926.1404(f)(1).

Remove the far-side pins first so personnel can move out from under the boom as quickly as possible, then move the aerial lift to the near side and remove the near-side pins. Appendix B specifically recommends removing far-side pins first, moving the aerial lift basket as soon as possible so employees are no longer under the boom, and then removing the near-side pins to minimize exposure, consistent with 1926.1404(f)(2).

An assist crane should be rigged to support the boom section being detached so that the section end near employees removing pins is well supported and unintended dangerous movement is minimized. Appendix B describes using an assist crane to support the section being detached and to take weight while employees remove pins from an aerial lift, consistent with 1926.1404(f).

Yes—1926.1404(h)(6)(i) requires that the center of gravity of the load be identified when that identification is necessary for the method used to maintain stability during assembly/disassembly. Appendix B reiterates this requirement and gives examples of when identifying the center of gravity is part of the stability method.

You must use measures designed to prevent unintended dangerous movement that account for the uncertainty in the center of gravity. For example, Appendix B advises keeping all personnel clear while you raise the section a few inches to see if it tips (indicating improper rigging), then repositioning the hoist and repeating until the section is stable—actions consistent with 1926.1404(h)(6)(ii).

Keep all personnel clear of the section and raise it a few inches to observe whether it tips; if it tips, reposition the hoist and repeat this incremental lift-and-observe process until the section remains stable. Appendix B describes this exact procedure as a practical method to confirm the hoist line is over the center of gravity when it cannot be accurately identified, in line with 1926.1404(h)(6)(ii).

The assembly/disassembly (A/D) director is responsible for developing and implementing procedures to minimize unintended dangerous boom movement and employee exposure during assembly/disassembly. Appendix B repeatedly refers to actions the A/D director must take (for instance, selecting controls, sequencing pin removals, and verifying rigging), consistent with the duties implied by 1926.1404.

Yes—1926.1404(f)(1) allows the exception only where 1926.1404(f)(2) is met, and Appendix B explicitly notes the exception can apply when one or more employees must be under the boom due to site constraints. Even then, the A/D director must minimize the risk and the duration and extent of exposure for all employees involved.

The A/D director should keep all personnel clear, raise the section only a few inches to check for tipping, reposition the hoist if tipping occurs, and repeat until the section is stable; use any additional measures (for example, supplemental tag lines or an assist crane) to prevent unintended movement. Appendix B gives this incremental lift-and-observe approach as an example of measures required by 1926.1404(h)(6)(ii) when the center of gravity cannot be accurately identified.

No—Appendix B does not change the rule; it provides sample procedures and examples showing how the limited exception in 1926.1404(f)(2) may be applied when site constraints make it necessary for employees to be under the boom. The underlying prohibition in 1926.1404(f)(1) remains the controlling requirement.