MARKS ON BOILER PLATES.
Something has been said under another heading of the nature and requisite quality of the materials entering into the structure of the boiler. Too much emphasis cannot be laid upon the necessity for the use of the very best iron and steel that can be manufactured, and the most skillful and thorough workmanship that can be performed in constructing the boiler.
It is becoming the practice, both for land and marine boilers, for boiler plate makers to furnish “test pieces” from each sheet or plate that goes into the construction of a boiler, and a sheet showing the tensile strength of each sheet or plate that enters into its make up.
But irrespective of this practice each plate entering into boiler construction will be found to have one of the following marks, which designate its quality and method of manufacture. The name “Charcoal Iron” is used because in its manufacture wood charcoal is employed instead of mineral fuel.
“Charcoal No. 1 Iron” (C. No. 1) is made entirely of charcoal iron. It has a tenacity of 40,000 pounds per square inch in the direction of the fibre. It is hard, but not very ductile, and should never be used for flanging.
“Charcoal Hammered No. 1 Shell Iron” (C. H. No. 1 S.), although not necessarily hammered, has been worked up before it is rolled into plates. It has a tenacity of 50,000 to 55,000 pounds per square inch in the direction of the fibre. It is rather hard iron, and should not be flanged. It is used for the outside shell of boilers.
“Flange Iron” (C. H. No. 1 F.), is a ductile material which can be flanged in every direction. It has a tenacity of 50,000 to 55,000 pounds per square inch along the fibre.
“Fire Box Iron” (C. H. No. 1 F. B.), is a harder quality, designed especially to withstand the destructive effect of the impinging flame, and is used for boxes and flue-sheets.
The letters in the brackets exhibit the plate stamp.
Cast iron and copper were used in an early day for steam boilers and the former is still extensively used for certain forms of low pressure steam heaters made for various purposes, such as green houses, etc.