Confined-Space Entry on Ballast Tank at Pier 7
At 06:40 on a clear, 8°C morning, a deck crew at Pier 7 is scheduled to enter the forward ballast tank of a 180-ft deck barge through a 22-in manhole. The tank is 9 ft deep and was cleaned three days ago. The task is to inspect corrosion and weld a doubler plate. The initial reading at the manhole is O2 19.4%, LEL 4%, H2S 3 ppm, CO 12 ppm. A 900-cfm blower is running with 15 ft of duct, but the duct outlet stops 2 ft above the tank bottom. Two workers plan to enter with 30-min escape packs. The ladder has two rusted rungs. The attendant is a second-year apprentice who is also assigned as fire watch for hot work on deck. No retrieval tripod is set up. At 06:45 the general foreman says, "Those numbers are close enough; we need the tank back by 14:00."
1. Should the crew authorize entry at 06:45? State the decision and the specific readings, equipment, and staffing facts that drive it.
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Decision: do not authorize entry at 06:45. The controlling fact is O2 at 19.4%, below the usual 19.5% minimum; "close enough" is not an acceptable entry criterion. The reading was taken at the manhole, not at the bottom, and the blower duct terminates 2 ft above the bottom, so the lower tank may be worse. The 4% LEL and 3 ppm H2S are below common entry limits, but they do not cure the oxygen deficiency, and hot work may require a lower LEL and a separate hot-work permit. The rusted ladder, lack of retrieval tripod, and dual-role attendant are independent deficiencies. The entry supervisor should stop the job, ventilate with the duct extended to the bottom, and re-test at top, middle, and bottom before reassessing.
2. If the tank is re-tested and entry is later approved, what controls and rescue arrangements must be verified before the first worker breaks the plane?
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Before entry, verify: (1) energy isolation and line blanking; (2) ventilation reaching the bottom and continuous mechanical ventilation; (3) gas test at multiple levels after purging, with O2 19.5–23.5%, LEL within the entry permit (and hot-work permit, often lower), H2S and CO within site limits; (4) continuous personal monitors with alarm; (5) full-body harness, retrieval tripod/winch, and a rescue plan with trained rescuers; (6) repaired ladder and safe access; (7) dedicated attendant with no other duties; (8) communications and a means to summon rescue; (9) hot-work permit, fire watch, and fire extinguishing equipment for the welding; (10) pre-entry briefing. If any item is missing, no entry.
3. How should the attendant/fire-watch conflict be resolved, and what should happen if the general foreman repeats the instruction to enter?
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The apprentice cannot be both attendant and fire watch. Assign a dedicated attendant at the entry and a separate fire watch outside the tank; if staffing is not available, stop. If the general foreman repeats the instruction, the entry supervisor should exercise stop-work authority, refuse the entry, and escalate to the safety manager/competent person. Document the refusal, the readings, and the instruction. Do not let schedule pressure turn a known oxygen deficiency into a "close enough" entry.