Inspection Of Cast-Iron Columns

All building castings, and especially columns, should be carefully inspected before being placed in the building. Air bubbles and blowholes are a common and dangerous source of weakness, and should be searched for by tapping the casting with a hammer. Bubbles or flaws filled in with sand from the mold, or purposely stopped with loam, cause a dullness in the sound. The casting should be free from flaws of any kind, with the exterior surface smooth and clean, and the edges sharp and perfect. An uneven or wavy surface indicates unequal shrinkage. Cast-iron columns should be straight, and cored directly through the center, the metal being as nearly as possible of uniform thickness throughout. It is not unusual to find cast-iron columns, designed to be 3/4 in. thick throughout, l\ in. on one side and 1/4 in. on the other.

The base and cap of a cast-iron column should be turned accurately, being true and perpendicular to the center line.

Fireproofing Of Cast-Iron Columns

Cast-iron columns subjected to the intense heat of a conflagration are liable to destruction when water is played upon them. In consequence, especially when located in important situations and when their failure in case of fire would practically destroy the building, they should be thoroughly fireproofed. There are several means employed to accomplish this. The columns may be incased in a light cast-iron shell, an air space of from 1 to 3 in. being left between the column and the casing; this space is sometimes, but not usually, filled with a incombustible, non-OOndctetive material. Two rough and one finish coats of good hard mortar plaster laid upon an expanded metal casing, surrounding the column, with an air space between, make a good fireproof protection. Terra-cotta tile is also much used.

Table XXIV. Breaking Loads For Square Cast-Iron Columns. In Thousand Pounds. U = 81,000