Reactor Cleaning: A Permit Without Isolation and a Standby Who Leaves
A 3 m tall stainless steel reactor at a chemical plant has a 500 mm top manhole and a 450 mm side manhole. The last batch used toluene, and the vessel was 'washed with water' but not purged. Two workers are to enter and scrape residue from the internal baffles. The production supervisor issues the permit-to-work. There is no isolation certificate: the agitator is switched off and its key is in the supervisor's desk, but the agitator can be started from the control room. Gas readings at the top manhole are LEL 0%, O2 20.8%, toluene 20 ppm. The entry team has one SCBA set and one 10-minute escape set. The standby person is the production supervisor, who says he will 'keep an eye' but must answer the phone in the control room 40 m away. The rescue plan is 'call 999 and use the fire hose'.
1. Identify the failures in roles, isolation and permit arrangements.
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Failures include:
- No competent-person risk assessment or certificate for the entry as required; a production supervisor cannot simply issue a permit.
- No positive isolation of the agitator. Switching off and holding a key is not lockout/tagout; the agitator can be started remotely, so the key is not a control.
- No isolation of the toluene line. Water washing is not purging, and 20 ppm toluene at the top shows residue remains.
- The permit does not reflect atmospheric monitoring inside the vessel or the need for continuous monitoring.
- The standby is the permit issuer and leaves the entry to answer a phone 40 m away. The standby must remain at the entry.
- The rescue plan is not a plan.
The roles of competent person, authorized person and standby have been confused.
2. Would you allow entry with one SCBA and one escape set? Explain the respiratory and monitoring requirements.
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No. One SCBA set cannot protect two entrants and a standby or rescuer; an escape set is for escape, not for work or rescue. The vessel has not been purged, and the top reading of 20 ppm toluene does not prove the bottom or the residue surface is safe.
Entry should be with supplied air or BA for each entrant, with an independent escape set, and continuous monitoring at the worker's position. The atmosphere should first be purged or ventilated and re-tested. If entry is still necessary, respiratory protection must be selected for the actual contaminant and any oxygen deficiency. A written permit must specify maximum entry time, air supply, communication and rescue. If the vessel cannot be made safe, use remote cleaning or no entry.
3. What must the rescue plan include, and what should happen before the permit is reissued?
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The rescue plan must be site-specific and practised:
- identified rescuers trained in confined-space rescue and BA;
- a retrieval system such as a tripod or winch and harness for vertical entry;
- access to both manholes;
- communication between entrant, standby and rescue team;
- first aid and oxygen;
- a method to isolate the agitator and stop product ingress during rescue;
- a call to 999 with a clear location and hazards.
Before reissue: full risk assessment by the competent person; agitator and lines positively isolated and locked; purge, ventilation and multi-point monitoring; standby assigned and briefed; rescue team and equipment in place; permit signed and explained to all entrants.