These new boilers were the recently introduced Thompson dish-ended types. They were raised above the boiler-house floor with the fire-doors at about head height and firing must have been quite tricky. They were insulated by layers of bricks and flued on the Hyde - Bennett principle whereby the hot flue gases were allowed to circulate between the covering brickwork and the top of the boiler. The boiler-house itself was not enclosed when the photo was taken - some time between 1900 and 1905 - although the corbal stones which suported the original roof timbers can be seen on the engine-house wall level with the boiler tops
The engines supplied by these boilers were said to operate at 100 psi and they were protected by dead-weight safety-valves carrying ten plates. The pressure-gauge reading on the nearest boiler which is venting steam from the safety-valve, although somewhat indistinct,, seems to be reading at about the 10 oclock position, suggesting that the guages could read up to 300 psi.
They do not seem to have been fitted with low-water safety valves which is rather surprising. The water-level sight glasses were not protected by glass casing either - this only became mandatory in 1911.
The feed water was supplied along insulated pipes and the steam main was also well insulated although the flanges were unprotected. There was no superheating of the steam. The boilers were hand fired and the ash disposal arrangements are not obvious.