Entry into a 15,000-litre stainless steel water storage tank (3m diameter x 2.5m depth, single top-entry manhole 600mm diameter) for internal cleaning and visual inspection. Tank has been drained, isolated, and purged. Work involves high-pressure water cleaning of internal surfaces, visual and ultrasonic thickness inspection of tank walls and floor, and photographic documentation of any defects.
This SWMS does not cover any repair or welding works inside the tank, nor chemical cleaning processes. If defects requiring repair are identified, a separate SWMS will be developed.
| Hazard | Inherent Risk | Control Measures | Residual Risk |
|---|---|---|---|
| Atmospheric hazards Oxygen deficiency (<19.5%), toxic gases (H2S, CO), or flammable atmosphere within the tank |
5 x 5 = 25 Extreme |
Engineering Continuous mechanical ventilation (forced fresh air supply) maintained throughout entry, minimum 20 air changes per hour Engineering Continuous 4-gas atmospheric monitor (O2, LEL, H2S, CO) worn by entrant with audible/visual alarms Administrative Pre-entry atmospheric testing at multiple levels within tank — results recorded on permit; entry prohibited if O2 <19.5% or >23.5%, LEL >5%, or any toxic gas above WES Administrative Immediate evacuation if any alarm triggers; re-test and re-ventilate before re-entry PPE Escape-only self-contained breathing apparatus (SCBA) available at manhole entry point |
2 x 5 = 10 High |
| Engulfment Residual sludge or water accumulation at tank base; risk of partial engulfment if drainage fails |
3 x 5 = 15 High |
Elimination Tank fully drained and visually confirmed dry before entry; all inlet valves locked closed and tagged Engineering Sump pump positioned inside tank to remove any water ingress during cleaning Administrative Entry supervisor to confirm isolation register is complete; no entry if any isolation is incomplete |
1 x 5 = 5 Medium |
| Limited egress Single 600mm manhole entry/exit point; entrant unable to self-rescue in emergency |
4 x 4 = 16 High |
Engineering Rescue tripod with mechanical winch positioned over manhole; entrant wears full body harness with retrieval line connected to winch at all times Administrative Dedicated standby person stationed at manhole opening at all times during entry — trained in rescue procedures Administrative Rescue drill conducted before first entry of the day; emergency services pre-notified of confined space work |
2 x 4 = 8 Medium |
| Mechanical hazards Accidental activation of mixers, agitators, or inlet valves while entrant is inside the tank |
3 x 5 = 15 High |
Elimination Full mechanical and electrical lock-out/tag-out (LOTO) of all mixers, agitators, pumps, and inlet/outlet valves before entry Engineering Isolation points physically locked with personal danger tags; keys held by entry supervisor Administrative Isolation register verified by entry supervisor and entrant; zero-energy verification (try-start) performed before entry |
1 x 5 = 5 Medium |
| Heat stress Elevated temperature inside enclosed tank with limited ventilation, compounded by PPE and physical exertion |
4 x 3 = 12 High |
Engineering Mechanical ventilation provides continuous fresh air flow; schedule work for cooler parts of the day Administrative Maximum continuous entry time of 45 minutes followed by 15-minute rest and rehydration outside the tank Administrative Standby person to monitor entrant for signs of heat stress via communication system; cold water available at entry point PPE Cooling vest worn under harness during summer months |
2 x 3 = 6 Medium |
If the entrant becomes incapacitated, the standby person must NOT enter the tank. Activate the retrieval winch to extract the entrant via the body harness and retrieval line. Call 111 immediately and state "confined space rescue required." Administer first aid (including CPR and AED if required) once the entrant is recovered to the surface. If winch extraction fails, wait for emergency services with confined space rescue capability.
If any gas monitor alarm activates, the entrant must immediately exit the tank. If the entrant cannot self-rescue, the standby person activates the retrieval winch. Do not re-enter until the atmosphere has been re-ventilated and re-tested with satisfactory results recorded on the permit.
All workers must read and understand this SWMS before commencing work. By signing below, each worker confirms they have been briefed on the hazards, controls, and emergency procedures, and agree to follow them.
Describe your confined space entry task and get a complete, compliant SWMS with atmospheric monitoring and rescue procedures in under 60 seconds.
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