Plant Referred to in Section 51

1. A construction affixed to a relevant property (whether on or below the ground) and used for the containment of a substance or for the transmission of a substance or electric current, including any such construction designed or used primarily for storage or containment (whether or not the purpose of such containment is to allow a natural or chemical process to take place), but excluding any such construction used solely to induce a process of change in the substance contained or transmitted (in paragraph 2 referred to as the "substance concerned").

2. For the purposes of paragraph 1 the following shall not be regarded as a construction used solely to induce a process of change in the substance concerned, namely any individual item of plant used or primarily used—

(a) for containment or transmission, or

(b) for one or more actions or a series of actions,

that may take place, before or after, the occurrence of action that induces, in a separate construction affixed to the property, a process of change in the substance concerned.

3. The fact that particular plant is not used on its own, but rather is used in conjunction with one or more other items of plant, does not disbar it from being regarded as an individual item of plant for the purposes of the preceding paragraphs.

4. All fixed furnaces, boilers, ovens and kilns.

5. All ponds and reservoirs.]