I attended a selection day, held in Leeds, for a company specialising in power station overhauls. At the end of the process the consultant informed me that he would be recommending me for both positions, those being Planning Engineer and Sub-contract Manager.
The next stage was an interview with a company representative at their head office. When I was offered the Planning Engineer role I asked “what about the other job?” and was told I was being offered only the Planning role. I accepted and began work on the first Monday of March 1990.
Power stations do not generally operate at full capacity during the summer in the UK. Their operators take the opportunity to shut some of them down in order to carry out major overhauls. Most consist of two or more generating “sets” so the whole station does not shut down, only one set at a time. On a four set station, two sets will be shut down over a six month period, each for three months.
The first shut down is usually scheduled for late March/early April. That year the shut down of one of the four sets at Eggborough was brought forward because of a breakdown – the operator decided not to restart for a 2-3 week run but to commence the planned overhaul right away at the beginning of March. That is where I was sent on my first day.
In 1990 all UK power stations were still operated by the CEGB (Central Electricity Generating Board). The government had decided to privatise, dividing the enterprise into two businesses, National Power and Powergen. Neither privatised company wanted to takeover an enterprise that was not efficient, so the CEGB was investing heavily, on behalf of the government, ensuring the plant was in good condition, as well as installing modifications to make them less polluting.
This mostly concerned the boiler element of the set. All of the work had to be accomplished within 90 days. There was a penalty clause under which the contractor would have to compensate the operator for loss of revenue in respect of every day by which the restart was delayed. The role of the Planning Engineer was, therefore, an important one.
A power station boiler is the size of a city apartment block: 160 feet (50 metres) high, 80 feet x 40 feet in plan (25 x 12.5 metres). Access is provided at 40ft., 80ft. and 120ft. above ground. The inner chamber up to 80 ft. is constructed entirely from thick walled steel tubes containing water under pressure which is heated by the burning of powdered coal blasted in through 24 nozzles each about 4 feet in diameter.
One of the jobs being undertaken during this round of overhauls was to replace those nozzles with new ones designed to eliminate the production of nitrogen oxides (Nox), a principle cause of acid rain. The tubes in the front wall are shaped to surround the nozzles. Because the new nozzles were a different size to the original this whole wall had to be cut out and replaced.
Elsewhere the extent of erosion and corrosion on the other walls was measured. Where this was found to be excessive the defective sections of tube were cut out and replaced. All of these tubes are embedded in refractory cement, outside which is a sheet steel case, then a layer of insulation and an outer cladding of sheet aluminium, all of which has to be removed to provide full access to the tubes, and then replaced after all tube welding has been completed.
The nozzles are supported within a steel structure on the front of the boiler. The old nozzles have to be unbolted and lifted out and the new nozzles lifted in. A difficult operation that has to be co-ordinated with the removal and replacement of the matching tube wall.
At Eggborough that March it soon became apparent that this sequence of operations could not be completed within the permitted time. I was charged with the task of devising an alternative sequence that would meet the time constraint. This proved successful.
Meanwhile there was much other work taking place. In the upper section of the boiler chamber a series of “U” shaped tubes hang down, also filled with water under pressure which is heated by the hot gases rising out of the chamber. All of these required inspection, as a result of which many were shown to be in need of repair.
All of the tubes emanate from a series of large bore tubes, or headers, located above the chamber roof. These too are subjected to inspection and repair as required. All around the boiler valves are repaired or replaced. All of the large ducts conveying air and hot gases to and from the boiler are cleaned out and, where necessary, their walls repaired.
The coal pulverisers are stripped down and worn parts replaced. The turbines, too, are subjected to an overhaul. Progress on all these tasks has to be monitored to ensure that nothing prevents the re-firing of the furnace on the contract date. Additional labour is recruited if needed, and additional hours worked, more than the usual 60 hours per week.
The sub-contract manager’s role is to liaise with the many specialist sub-contractors – scaffolders, refractory and insulation specialists, cleaning and inspection teams – to ensure that they have sufficient resources allocated when and where needed.
Both roles require the incumbents to spend large parts of the day in the thick of it, clambering about in confined and dirty spaces as well as attending meetings with contract supervisors and the client’s team and, in the case of the Planning Engineer, time spent at the desk assessing where delays are occurring and coming up with possible strategies for correcting them when the original strategies for preventing them have plainly failed.