Electrokinetica The Electro-mechanical Museum

ECC 1400 ampere mercury-arc rectifier plant

ECC 350A bulb

ECC 350A bulb

Big bulbs in high places

Mercury arc rectifiers often turn out to be located in the most inconvenient places. And with lovely big bulbs like these, you can imagine they were cunningly arranged to be as awkward as possible to get out. In this steelworks, the scrapyard was served by two large gantry cranes which docked under cover in an open-fronted building. On the top floor of this building adjacent to the crane bay was the HV / LV switchroom and rectifier room supplying not only the cranes but various other DC plant nearby in the works. Under the switchroom was an enclosed loading bay with its own gantry crane. Access to the switchroom consisted of a catwalk from the crane dock (for man-access) and a hatch in the floor down into the loading bay complete with load-rated I-beam above for rigging a hoist (for equipment access). 'Where's the catch?' I hear you ask. Naturally, the rectifier cabinets and transformer were too large to go through the hole. And the hole couldn't easily be enlarged because the defunct and immobile loading-bay gantry crane was trapped underneath it. So we had to rip a big chunk out of the side of the building and pluck them out with a mobile crane instead! There were a few obstacles there too: there was a trench by the side of the building which had to be filled in with rubble to get a good footing for the crane, and a couple of uprights in the way once the cladding was pulled off. All in a day's work for the Electrokinetica bulb-wranglers!


Recovery

View of complete plant

View of complete plant

The process was masterminded by Gordon Eastwood and Mick Novak of EDS, the contractors responsible for dismantling the disused scrapyard facility. Lucien had inspected the rectifiers some years before, while they were still in service, and had marked them down as examples of ECC's largest glass-bulb recs. The switchroom included two almost identical rectifier plants of slightly different ages, each rated to supply 1400 amps at 250 volts DC, using four 350 amp bulbs fed from one transformer at the end of the unit. One plant had been in operation until recently, and contained four working bulbs. The other plant contained only three of unknown integrity. Gordon invited us back to take a look, and we worked out the recovery programme to include five cabinets, one transformer and all the bulbs and control gear. Lucien and Alex built wooden cases for the bulbs, which on account of their size and specific design were best transported right-way-up. Two days before craning, Lucien and Janusz went up to Sheffield to prepare the plant by removing the bulbs and separating the cabinets. On the recovery day, Mick himself took the controls of the demolition machine and prepared the access in a matter of minutes. Unfortunately one of the rectifier cabinets scheduled for recovery became entangled with the dislodged cladding and buckled, but this was simply replaced by another cabinet from the second unit.

In the second instalment we will have pictures of the exciting 'flying bulbs' performance that followed; in the meantime we would like to thank the EDS team, including John Wilson, Gordon, Mick, Mark and co. for a safe, efficient and successful recovery.

Mercury-arc rectifier links

Further reading

  • Teago, F.J. and Gill, J.F. Mercury arcs. London: Methuen, 1936
  • Cotton, H. Electrical technology. London: Isaac Pitman, 1957
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