Safety talk Confined space incidents

Sometimes it seems that vessels are more dangerous empty than full. Case #1 Contractors, unfamiliar with a company's rules, have often entered vessels without authority. For example, a contractor's foreman was found inside a tank which was disconnected and open, ready for entry, but not yet tested. He had been asked to estimate the cost of cleaning the tank. The foreman said that he did not realize that a permit was needed just for inspection. He had been given a copy of the plant rules but had not read them. If vessels are open, but entry is not yet authorized, the manhole should be covered by a barrier. One should not rely on contractors' reading rules.  Rules to be explained to  them.

Source : What Went Wrong? - Case history of Process Plant Disasters by Trevor A. Kletz.

Case #2 Two men went into a reactor to carry out a dye-penetrate test on a new weld using trichloroethylene. Because the weld was 8 m long the solvent was soon used up, and the man who was on duty at the entrance was asked to go for some more. He was away for 10 minutes. When he returned the two men inside the reactor had collapsed. Fortunately they were rescued and soon recovered. The amount of solvent that can be taken into a vessel for dye penetrate testing or other purposes should be limited so that evaporation of the complete amount will not bring the concentration above the TLV, making allowance for the air flow if the vessel is force-ventilated. Stand by workers should not leave a vessel when others are inside it. Source : What Went Wrong? - Case history of Process Plant Disasters by Trevor A. Kletz.

Source : Loss Prevention Bulletin Issue 158 April, 2001. Case # 3 A second-hand dual compartment road tanker was purchased for internal use within the factory. It was to be used as a single compartment tanker, so a welder was given the job of burning out the internal wall that separated the two compartments. As soon as he started burning out the separating wall, a fire broke out. The welder jumped back and escaped through the manhole before the inside of the tanker was engulfed in flames. It transpired that there were two dished-end dividing walls built nose to nose, and a solid wax had built up between the two walls through a leak over the intervening years during its use to transport heavy fuel oil. This was not apparent after checking and inspection prior to the modification work that was to be carried out. There are always hidden problems in confined entry that must be identified. Source : Loss Prevention Bulletin Issue 158 April, 2001.

Case # 4 A tank had to be entered for inspection. It had contained only water and was not connected to any other equipment so the usual tests were not carried out. Three men went into the tank and were overcome. Two recovered but one died. The atmosphere inside the tank was tested afterwards and found to be deficient in oxygen. It is probable that rust formation used up some of the oxygen. Never take short cuts in entering a vessel. Follow the rules. Source What Went Wrong? - Case history of Process Plant Disasters by Trevor A. Kletz.

Case # 5 (a) A contractor entered the combustion chamber of an inert gas plant watched by two standby men but without waiting for the breathing apparatus to arrive. While he was climbing out of the chamber he lost consciousness halfway up. His body was caught between the ladder and the chamber wall. The standby men could not pull him out with the lifeline to which he was attached. So one of the standby men climbed in to try to free him, without breathing apparatus or a lifeline. The standby man also lost consciousness. The contractor was finally pulled free and recovered. The standby man was rescued by the fire service but by this time he was dead.

Case # 5(b) In another incident, three men were required to inspect the ballast tanks on a barge tied up at an isolated wharf 20 km from the plant. No tests were carried out. One tank was inspected without incident. But on entering the second tank, the first man collapsed at the foot of the ladder. The second man entered to rescue him and also collapsed. The third man called for assistance. Helpers who were asked to assist in recovering the two men were partly overcome themselves.

Lesson on behavioral safety Representatives of the safety department 20 km away set out with breathing apparatus. One man died before he could be rescued. Tests on other tanks showed oxygen contents as low as 5%. It is believed that rust formation had used up the oxygen. Lesson on behavioral safety If we see another person overcome inside a vessel, there is a very strong natural impulse to rush in and rescue him, even though no breathing apparatus is available. Misguided bravery of this sort can mean that other people have to rescue two people instead of one. Source : What Went Wrong? - Case history of Process Plant Disasters by Trevor A. Kletz.

Case # 6 A welder complained that a reactor which had been cleaned and purged still smelt strongly of solvent. The reactor was checked and it was found that this was indeed the case, so it was washed out and re-purged a second time. When the welder went back to carry out the work inside the reactor, he complained yet again that it still smelt of solvent. After intensive investigation it was found that the stirrer inside the vessel was hollow and that a hole had been drilled into it to prevent hydraulic pressure build up. Solvent had accumulated in the hollow shaft of the stirrer during the course of time.

Loss Prevention Bulletin Issue 158 April, 2001. Although the general atmosphere inside the reactor immediately after the washing and purging was found to be clear, by the time the welder came to do his work ,solvent had vaporized to create a dangerous atmosphere inside the reactor. There are often hidden places where substances can hide. Always be critical in the examination of a vessel and check all possible hiding places. Source : Loss Prevention Bulletin Issue 158 April, 2001.

Case # 7 In the middle of a night shift in 1994 a well-trained, recently-appointed and particularly conscientious process operator decided to clear a blockage in the outlet chute of a centrifuge. The centrifuge and the product hopper were nitrogen inerted. He must have dropped the spade he was using into the product hopper and in order to retrieve it he opened the hopper man way, put on a canister respirator (presumably because of the solvent vapour), ignored all vessel entry permit procedures, and entered the hopper. He was discovered a few minutes later, already dead, asphyxiated by the nitrogen.

Canister respirators are of no use in a nitrogen atmosphere and the operator should have known this. He should also have known that entry into a confined space must be carried out only according to the procedure. Emphasising all aspects of vessel entry to all concerned on a regular basis is very important.