The Boom That Won't Stow
After a week of work, a crew is disassembling a lattice-boom crawler crane. The boom sections were pinned in 90°F heat; the crew is now working at 40°F in the evening. The 40 ft butt section will not slide free of the 20 ft insert even after the connecting pins are removed. A worker suggests hooking the assist crane to the insert and pulling while two hands guide the joint. The site superintendent asks whether they can just leave the boom assembled overnight and finish in the morning, since the machine is parked inside the barricade.
1. What is the most likely reason the sections won't separate, and what is the safe approach?
Read the worked answer
Thermal contraction and binding: sections pinned at 90°F and now at 40°F can bind on the pins/lugs, and the joint may be cocked. Do not pull with an assist crane while hands are in the joint - a sudden release can crush fingers or drop the section. Safe approach: support both sections independently on blocking, verify all pins and keepers are out, use the crane's own boom hoist to slightly relieve load, and use a soft mallet or jacking per the manufacturer's procedure. Keep hands clear of pinch points and use tag lines. If it still won't move, stop and consult the manufacturer or a qualified mechanic.
2. Is leaving the boom assembled overnight inside the barricade acceptable?
Read the worked answer
Only if the machine is left in a stable, manufacturer-approved transport or parked configuration - boom lowered/blocked, controls locked, and the area secured. An assembled boom left in an unsupported or partially pinned state can settle, and wind or vibration can shift it. The superintendent should require: boom lowered and blocked per the manual, all pins accounted for, the machine isolated (keys removed, lockout), and the barricade maintained. If the manual requires disassembly for transport or storage, do not leave it partially assembled.