A branch pipe conveys steam from the throttle to the input of a cylinder. Most steam locomotives have two branch pipes , one for each cylinder, that split off a single feed from the throttle.
The diameter of a branch pipe can be computed with the formula given below, from "A Treatise on the Steam Engine".
- The following rule gives the usual diameter of the branch steam pipe for locomotive engines.
- RULE - To find the diameter of the branch steam pipe for the locomotive engine - Multiply the square of the diameter of the cylinder in inches by 0.021. The product is the diameter of the branch steam pipe for the locomotive engine in inches.
- Example - Required the diameter of the branch steam pipes for a locomotive engine, when the cylinder's diameter is 15 inches. Here, according the rule, diameter of branch pipe is computed as:
- branch pipe diameter = 0.021 x 152 = 0.021 x 225 = 4.725 inches