210

MODERN STEAM PRACTICE.

at the fircplacc.

Fig. 134.—Engine at Goldthorn Hill Water-works. Elevations and Plan.

The pressure of the steam is about 15 lbs. persquare inch.

To avoid the almost constant trou-ble caused by leakage at the steamvalves on the boiler tops, from ex-pansion and contraction of the mainränge of steam pipes, the main steampipe should have a quadrant curvebetween the boilers, so as to allow forexpansion and contraction without athrust sufficient to break any joints.This arrangement is useful and effi-cient when there is one steam pipeleading off from between two boilers;when, however, the steam pipe leadsoff from one side, or where there is aränge of more than two boilers, it isnot applicable, and in such cases, inthe absence of packed expansionjoints, no plan is so simple and effec-tive as the wrought-iron diaphragmjoint, consisting of a couple of circu-lar wrought-iron plates, about twoand a half times the diameter of thepipe, dished out about 3 inches, andrivetted together at the outer rim andio Hanges on the main ränge of thesteam pipe.

Another useful, although frequentlyoverlooked, point of detail in Connec-tion with the boilers, consists in lead-ing the hot and cold feed and blow-off into and out of the boiler throughthe same pipe. This arrangementavoids the numerous holes usually cutin boilers for these purposes, and anyimpurity which may enter the boilerwith the hot and cold feed is de-posited near to the blow-off. In thepresent instance the pipe is of wrought