The Beam That Wouldn't Stop Swinging
Steel erection, fifth floor. You are the designated signalperson for a 60-ton crawler crane. The load is a 4,800 lb, 32 ft beam with a 14 in deep web - in an 18 mph wind gusting to 27, it is a sail. The operator sits 110 ft away and the pick point is hidden behind a stack of decking, so he works off your signals alone. One tagline is on the load, but the handler is 40 ft away and the line is slack. On the hoist the beam begins to rotate and swing toward the ironworkers at the deck edge. The operator is hoisting at full speed, cannot see the drift, and the load is 6 ft from the edge beams.
1. The beam is swinging toward people. What signals do you give, in what order, and why is the choice between STOP and EMERGENCY STOP not cosmetic?
Read the worked answer
1. EMERGENCY STOP first - both arms extended horizontally, palms down, swept back and forth. This signal exists for imminent danger to people: it tells the operator to halt all functions now, not to finish the current motion gracefully.
2. Hold. Stopping the hoist drum does not stop the pendulum. The beam will keep traveling after the drum stops, so the next command must not add energy to it.
3. Do not lower yet. A LOWER command while the load is swinging adds to the arc and puts the beam down off-target - on the ironworkers' side of the edge beams.
4. DOG EVERYTHING (hands clasped in front of the body) while the deck crew clears the landing zone, then a controlled lower using the SLOWLY modifier - one hand giving the lower signal with the other held motionless in front of it.
Why it matters: STOP (one arm, palm down, horizontal sweep) is a routine halt of a function. EMERGENCY STOP is a hazard-to-people command. Using STOP when a load is drifting into a crew burns the seconds that matter; using EMERGENCY STOP for every routine stop trains the operator to discount it. Also remember the stop signal is obeyed regardless of who gives it - your first job is to break the motion, your second is to re-establish control.
2. You cannot get an angle that lets you see both the load and the operator's cab from the deck edge. How do you fix the positioning before the next pick, and what must the operator do if he loses sight of you?
Read the worked answer
Neither half of the link is optional: you must be able to see the load, and the operator must be able to see you (or, on voice signals, maintain continuous communication). You cannot signal a move you cannot see.
Sequence: dog everything or land the load first - never 'walk' a load while you reposition.
Options, in order of preference:
- Change the pick so the operator has line of sight to the landing zone.
- Reposition yourself to a spot with a clear view of both the load and the cab.
- Add a relay signalperson (each person must see the next, and signals are repeated exactly, never interpreted) or switch to radios with one voice per crane.
- Re-set the crane so the geometry works.
If the operator loses sight of you or loses the radio: he stops and holds. He does not finish the motion, does not lower on assumption, and does not accept a guess from a bystander. The load stays where it is until communication is restored. A held load over a deck is a controlled condition; a load moved blind is not.
3. The tagline handler is 40 ft away with a slack line. If the load starts to rotate again, does the tagline control it, and what do you change before the next pick?
Read the worked answer
No. A tagline controls rotation only when the line is taut, the handler has room to walk, and the line runs at roughly 90 degrees to the load's long axis. Forty feet of slack line is a rope, not a control - in a 27 mph gust the load will outrun that handler every time.
Before the next pick:
- Move the handler close enough to keep the line taut and give them a walking path that tracks the swing.
- Plan for two taglines on a long, narrow member - one line lets the load rotate about the attachment point; two give you genuine control of orientation.
- Hold the pick during gusts. A beam with a deep web in gusting wind behaves as a sail, and gust loading is what breaks rigging and surprises operators.
- Coordinate swing speed with the handler. A taut line and a slow swing manage rotation; a fast swing and a taut line just lets the load drag the handler.
Reasoning to carry to the exam: taglines do not increase capacity, do not substitute for a controlled swing, and never justify sending a load over people.