The sketch on the right shows two Square Box Boilers (from HMS Thunderer) with four furnaces each. The damage was a result of an explosion on HMS Thunderer (sister ship of HMS Devastation). Cerberus had two 3 furnace boilers on one side of its boiler room and one 3 furnace boiler and two twin boilers on the other side.

Thunderer & Devastation had two boiler rooms each with two 4 furnace boilers per side. On the left is shown a model of the damaged boiler from HMS Thunderer.