A shift supervisor received severe burns and later died after a flexible hose used to transfer hydrogen to the catalytic reformer was over-pressurised and caught fire.Hydrogen is supplied from three modules each consisting of 12 x 1m3 cylinders at 150 bar (2205 psig) pressure. Each cylinder is fitted with a needle valve and the twelve are connected together with steel tubing. Each module has a filling connection (with no pressure regulator) and a discharge connection equipped with a pressure regulator and a pressure safety relief valve set at 14 bars (206 psig) pressure. The Cat Reformer has two hydrogen connecting points to the recycle gas compressor's discharge line which is normally used to charge the unit. Only one of these connecting points is fitted with a pressure relief valve in addition to the PSVs fitted to the individual modules. Each hydrogen module is connected to the Cat Reformer's injection points with 1 inch flexible steel hoses from the outlet of the H2 module's pressure regulator. On June 9, 1997, No. 1 and No. 2 hydrogen modules were connected to the recycle gas compressor using the correct outlet points after the pressure regulators. No.1 module was emptied and replaced by No.3 module. Hydrogen from No.2 module was still connected to the injection without the PSV and 3 cylinders had emptied into the unit. The normal sequence of hydrogen injection is to open the block valves starting at the recycle gas compressor downstream from the injection point and then open the valve on the hydrogen module after the regulator. Whenever the operation is stopped these block valves are closed in the reverse sequence. On June 10, the process operators continued to empty No.2 module (9 cylinders were left). They noticed that the pressure in the unit was building up too slowly. The Shift Supervisor decided to switch the flexible hose from the end, after the regulator on the module, to the module's filling line which is not equipped with a regulator. The switch over was authorized under a cold work permit and carried out by maintenance department personnel who warned the Shift Supervisor against it. Six cylinders were then emptied one by one by the area operator in 35 minutes and the unit was pressured up to 7 bars (103 psig) . The area operator then closed the cylinder needle valve at the hydrogen module followed by the three block valves on the filling line to the recycle gas compressor. As the Cat Reformer's pressure decreased and as the area operator had other tasks in hand, the Shift Supervisor decided to discharge the remaining three cylinders alone. Failing to remember that the block valves downstream to the compressor were shut, he opened a cylinder discharge needle valve and the module's filling valve. The flexible steel hose was subjected to the full cylinder pressure of 150 bar. The hose connection flew off and hit the Shift Supervisor causing him to faint from a broken shoulder bone. The hydrogen immediately ignited whereupon the Shift Supervisor became exposed to flames. It was discovered that process operators had used the module's filling line connection before whenever they had difficulty with the pressure regulator at the module's proper discharge connection.The pressure regulator and some needle valves were dismantled. Broken pieces of Teflon seats from the needle valves were blocking the pressure regulator's passage ways. The needle valves were damaged due to over tightening with wrenches. The shift supervisor was wearing a cotton shirt with trousers (pants) made of special material at the time. Although these suits (jacket and trousers) are issued to all process personnel, many complain about wearing the complete suits in hot weather.There is no operating procedures manual covering the discharge of hydrogen from the modules to the plant. Only one of the connection points to the recycle gas compressor has a PSV fitted upstream of the block valves.Flexible hoses used for the transfer of hydrogen from the modules to the plant had been tested to 70 barg (4 times their normal working pressure) when they were originally received from the supplier. They had not been tested since. These hoses were placed in store when not being used for hydrogen transfer.The immediate cause of the accident was the use of the wrong connection at the hydrogen module which bypassed the pressure regulator. Major contributory factors to the accident were the absence of a pressure relief valve at the recycle compressor's injection point upstream of the isolation valve and failure to operate the system valves in the correct sequence.