Demolition - Vessel Safe Work Method Statement

Comprehensive atmospheric testing must be conducted before any vessel entry and continuously during work. Testing must include oxygen concentration (acceptable range 19.5% to 23.5%), combustible gas concentration measured as percentage of Lower Explosive Limit or LEL (must be below 10% LEL), carbon monoxide (below 30ppm), hydrogen sulphide (below 10ppm), and any specific chemical vapours relevant to the vessel's previous contents (below 50% of workplace exposure standards). Testing must be conducted at multiple levels within the vessel - at entry point, mid-level, and bottom - because hazardous atmospheres stratify by gas density. Initial testing should occur after ventilation has operated for minimum 4 hours. Use calibrated multi-gas detectors that have been bump-tested with calibration gas before each use. Install continuous atmospheric monitoring with sensors at multiple levels and audible alarms set to activate if readings move outside safe parameters. Retest atmosphere after any work break exceeding 30 minutes or if work conditions change including commencement of hot work operations. Document all atmospheric test results in the confined space entry permit including date, time, location, readings for each parameter, and tester name and signature. Never enter a vessel based solely on a single test result - multiple tests at multiple locations and continuous monitoring provide the safety margin required for this high-risk work.

No. Atmospheric monitoring using portable gas detectors is essential for identifying hazardous atmospheres, but detection alone does not provide respiratory protection. Workers entering vessels classified as confined spaces must wear supplied-air respiratory protection (Type 1 air-line respirators per AS/NZS 1715) regardless of atmospheric testing results. This requirement exists because vessel atmospheres can change rapidly due to disturbance of residual materials, release of absorbed chemicals from linings or coatings, heating during cutting operations causing volatilisation of residues, or failure of ventilation systems. Supplied-air respirators provide continuous flow of clean breathing air from an external source positioned outside the vessel, protecting workers even if the vessel atmosphere suddenly becomes toxic or oxygen-deficient. The air source must meet AS 2896 Grade D breathing air quality and be positioned in a clean atmosphere with high-pressure filtration. Filtering respirators (cartridge-type respirators) are not acceptable for vessel entry because they do not protect against oxygen deficiency, they rely on sufficient oxygen in the atmosphere to support breathing, their filters can be overwhelmed by high concentrations of contaminants, and they provide no protection if unknown contaminants are present. The combination of supplied-air respiratory protection AND continuous atmospheric monitoring provides defense-in-depth: monitoring alerts workers to deteriorating conditions while respiratory protection ensures breathable air regardless of vessel atmosphere. This dual approach has proven necessary through tragic experience - multiple confined space fatalities have occurred in vessels that initially tested safe but developed hazardous atmospheres during work.

Hot work on vessels that previously contained flammable materials requires an extremely rigorous permit system due to explosion risk. The hot work permit must document completion of the following mandatory prerequisites: comprehensive atmospheric testing showing LEL readings below 10% of lower explosive limit at all tested vessel locations conducted immediately (within 30 minutes) before cutting commences; removal of all flammable materials including insulation, coatings, plastic sheeting, timber, and combustibles from a minimum 10-metre radius of the cutting location; establishment and verification of continuous forced ventilation creating minimum 6 air changes per hour through the vessel volume; assignment of dedicated fire watch personnel who have no other duties and will monitor for fire during cutting and for 60 minutes after cutting ceases; positioning of appropriate fire extinguishers (minimum two 9kg ABE extinguishers) within 5 metres of cutting location; availability of emergency services either on-site or with confirmed response times; and communication systems tested and operational between cutting operator, fire watch, standby person, and supervisor. The permit must specify the exact location and scope of cutting operations, the cutting method (oxy-acetylene, plasma, grinding, etc.), the maximum duration of the permit (typically single shift), and the name of the competent person authorising the permit who has physically verified all control measures are implemented. Critically, if atmospheric testing shows ANY detectable flammable vapours even below 10% LEL, consider using alternative cold cutting methods including hydraulic shears, high-pressure water cutting, or mechanical cutting that do not generate sparks or heat. Hot work permits are valid only for the specified shift and location; if cutting moves to a different vessel location or continues on subsequent days, a new permit must be completed including fresh atmospheric testing. The permit must remain displayed at the cutting location and be available for inspection by workers and regulatory authorities.

Establishing a safe cutting sequence requires input from a qualified structural engineer who understands vessel design, stress distribution, and the effect of progressive cutting on remaining structure stability. The engineer must review original vessel design drawings including shell thickness, internal stiffening rings, support arrangements, and any modifications made during vessel service life. The engineer conducts a site inspection to verify current vessel condition, identify any corrosion or damage affecting structural capacity, and confirm the vessel matches original design documentation. Based on this assessment, the engineer develops a detailed cutting sequence plan that specifies the order in which cuts must be made, maximum dimensions of unsupported sections, requirements for temporary supports or bracing before critical cuts, and any sections that must remain intact until later demolition phases. The general principle is to work top-down removing weight progressively and maintaining load paths until final stages, remove non-structural elements including piping, platforms, and instrumentation before cutting primary structure, cut the vessel shell into manageable sections typically 2-3 metres maximum dimension to allow safe handling, install temporary bracing or supports before cutting any primary load-bearing members, and leave critical structural elements including base support rings and foundation connections until final removal phase. The engineering plan must be translated into clear site markings using high-visibility paint to number cutting sequences and mark cutting lines on the vessel external surface. All personnel involved in cutting operations must be briefed on the cutting sequence and understand they must not deviate from the specified order even if an alternative sequence appears more efficient or convenient. The structural engineer should attend site during critical cutting phases including removal of primary supports to monitor for any unexpected structural behaviour. If any signs of structural instability occur including unusual sounds, visible deformation, cracking, or movement of vessel sections, cutting must stop immediately and the engineer must reassess before work continues. This engineering-based approach prevents the uncontrolled collapse incidents that have caused multiple fatalities in vessel demolition projects where cutting sequences were determined by convenience rather than structural analysis.

Vessel demolition requires comprehensive emergency rescue procedures addressing the confined space nature of vessels and multiple potential emergency scenarios. Every vessel entry operation must have an emergency retrieval system capable of extracting an injured or unconscious worker without requiring rescuers to enter the hazardous atmosphere. This system typically consists of a tripod or davit arm positioned over the vessel entry opening rated for rescue loads (minimum 400kg dynamic load), a mechanical winch or rescue device with sufficient cable or rope to reach the bottom of the vessel, and full body harnesses worn by all entrants with dorsal D-rings connected to the retrieval system via shock-absorbing lanyards. The standby person positioned at the vessel entry point must be trained in operating the retrieval winch and must be capable of extracting an unconscious worker independently without entering the vessel. Before any vessel entry, conduct an emergency retrieval drill using a dummy or willing volunteer to verify the retrieval system functions correctly and the unconscious worker can be extracted through the entry opening while wearing all required PPE including supplied-air respirator. For medical emergencies inside vessels, establish communication protocols allowing the standby person to summon emergency medical services immediately while maintaining observation of the vessel entry. The standby person must never enter the vessel to attempt rescue unless wearing supplied-air respiratory protection, connected to a separate retrieval system, and backed up by an additional standby person - most confined space fatalities involve would-be rescuers overcome by the same atmospheric hazards. For fire or explosion scenarios, emergency procedures must include immediate evacuation signals (air horn or alarm audible throughout work area), designated assembly point at safe distance from vessel (minimum 100 metres for large vessels), accountability system to confirm all personnel have evacuated, and notification procedures for emergency services including fire brigade and ambulance. Maintain clear access routes for emergency vehicles at all times including during cutting operations when site congestion is highest. Site must have personnel trained in first aid readily available and first aid facilities appropriate to potential injuries including burns, trauma, and toxic exposure. Emergency contact numbers for ambulance, fire brigade, hospital, poison information centre, and senior management must be prominently displayed at the work site and included in all workers' site induction materials.