The Locomotive - Lighthouse Survival Blog

PUBLISHED BY THE HARTFORD STEAM BOILER INSPECTION AND INSURANCE COMPANY.
New Skriks — Vol. XIV. HARTFORD, C'ONX., SEPTEMBER, 1893. No. 9.
On the Bracing" of Boiler Heads.
In flaj's when a GO-inch boiler was considered h\g, and a pressure of 75 pounds to the
square inch was considered high, boiler construction was a simpler art than it is to-day.
The tremendous growth of all kinds of industries in recent years, and the attendant com-
petition and consequent demand for economy, has given rise to a demand for larger
boilers and heavier ])ressures; till at the present day the boiler-maker often finds himself
hard pressed to satisfy the demands of his patrons, and yet turn out boilers that shall
have the necessary factor of safety. He has to provide specially designed joints for the
longitudinal seams, and has to consider the bracing of the heads with the greatest care.
Fig. 1.— A Tube Expanded into a Boiler Head.
In short, when a large boiler has to be designed so as to be safe under a high pressure, it
becomes necessary to proportion every part of it intelligently. We have frequently discussed
riveted joints in The Locomotive, and from time to time we have touched upon
bracing also; and in the present article we propose to give a sort of resume of what we
have published in past issues of the paper on the subject of braced heads.
Before discussing braced heads we may say a word about flat, unbraced ones, in
which the necessary strength is secured by great thickness of material. Flat cast-iron
heads are sometimes used in boilers, but we do not recommend them; nor dp we recommend
flat, unbraced heads of any kind, when they are subjected to any considerable
pressure. Braces are sometimes objectionable — as, for instance, in heaters that contain