[Excerpt from a recent book detailing Sokolov's machines]
One of the advantages of the Sokolov's technologies is that they share the same magnetic socket for the tanks of processed whale oil they use as fuel. When a tank is exhausted, another can be plugged into place with ease, and the process is simple enough that any common workman or even the lower guardsmen of the City Watch can handle the task. This applies to the Arc Pylon and Wall of Light security systems, as well as the rail cars used for transport by those few who are wealthy enough to afford them. The only obvious downside of Sokolov's designs is the volatility of the oil itself. A few incidents have occurred, resulting in damage to property or bodily harm whenever one of the tanks has exploded.