Vacuum-Lift Pick on a Windward Corner With a Single-Source Lite
A three-person crew is setting a 5 ft × 10 ft laminated glass lite, weighing about 400 lb, into a second-floor storefront opening on the windward corner of a building. The lite arrives on a boom truck with a four-cup vacuum lifter; each cup is marked 500 lb capacity. The forecast calls for sustained wind of 15 mph with gusts to 22 mph, and the general contractor wants the lite in before a 2:00 p.m. dry-in inspection. One journeyman and one apprentice are on the deck at the opening. The apprentice is wearing a harness, but the lanyard is clipped to a temporary rail that was removed on the far side of the opening and never replaced. There is no guardrail on the open edge near the opening. The lite is the only unit of its size on the job, and the supplier cannot replace it for three weeks.
1. Should the pick proceed as planned? Walk through the load and wind numbers, the vacuum lifter capacity, and the decision authority.
Read the worked answer
No - this is a stop-work situation, and the reasoning has to rest on more than the wind forecast.
Vacuum capacity. Four cups × 500 lb = 2,000 lb nominal against a 400 lb load, which looks like 5:1. But the governing number is the lifter's rated capacity, not the sum of the cup decals. Even at 5:1 nominal, a vacuum lifter needs a 4:1 minimum safety factor with the pads correctly positioned so no single cup is overloaded, a functioning vacuum gauge, a pump with a check valve and reservoir, and a non-porous, clean sealing surface. Verify the data plate before the pick.
Wind. Sail area is 50 sq ft; at 22 mph the dynamic pressure is roughly 0.00256 × 22² ≈ 1.0 psf, or about 50 lb. That is small next to 400 lb, so the real hazard is not the static force - it is loss of control: a gust catching an edge, pendulum swing, boom dynamics, and tag-line hands getting pulled into the path. A single-source lite that cannot be replaced for three weeks raises the consequence of any loss of control to project-critical.
The competent person controls the lift, not the GC's inspection schedule. Hold the pick, monitor wind at the glass, and reschedule for lower gusts or use a different handling method.
2. What fall-protection and personnel problems exist on the deck, and how should the pick be sequenced once it is cleared to restart?
Read the worked answer
Two separate failures sit on the deck.
Anchor point. The apprentice's lanyard is tied to a temporary rail that no longer exists as a system. A personal fall arrest anchor must support 5,000 lb per employee or be designed and certified by a qualified person, and it must be independent of the platform being modified. A rail that has already been partially removed is not an anchor. The apprentice comes off the edge immediately and the harness/lanyard is inspected for damage from prior use.
Guardrail. The open edge needs a guardrail system (top rail ~42 in, midrail, toe board) or the deck is a controlled access zone with a written fall-protection plan and a rescue plan. Guardrails also protect the pick: a rail keeps people from instinctively grabbing the lite as it swings.
Sequence once cleared. Pre-lift meeting and updated JHA; barricade and tag lines on the ground; nobody under the suspended load; the journeyman positions the lite at the opening while the apprentice stays back from the edge with a tag line, never standing between the lite and the opening; set the lite on setting blocks and shim before releasing the cups; verify vacuum gauge reading on the ground and at the opening.
3. What must be documented and communicated before the crew lifts again?
Read the worked answer
Documentation is what makes the hold defensible and prevents the repeat.
- Updated JHA / lift plan naming the wind limit (typically a written threshold such as 15 mph sustained at the glass), who monitors it, and who has stop-work authority.
- Equipment verification: lifter data plate capacity, current vacuum test and inspection tag, sling and rigging inspection, boom truck annual inspection.
- Anchor point sign-off by a qualified person, plus a rescue plan with a means of retrieval - a 911 call is not a rescue plan on a second-floor deck.
- Notification to the GC in writing stating the reason for the delay (wind, anchor, guardrail) and the corrective actions, so the schedule pressure does not simply reappear tomorrow.
- Toolbox talk sign-in covering the wind limit, tag-line hand positions, and the no-hands-on-glass rule during the pick.
If the GC directs the crew to lift anyway, that direction is refused and escalated - safety and health, not schedule, governs.