Between 1902 and 1907 Benson's scheme was altered when the Cornish beam engine was replaced with three triple extension engines made by Combe & Barbour of Belfast. Two Lancashire boilers were installed to supply the steam to power these engines. These are the engines and boilers seen at the site today.
The original engine house of Benson's 1860s scheme had to be altered and enlarged to house these engines and its original appearance was significantly changed. However, the original chimney stack was retained.