Solid drawn boiler tubes subject to internal pressure
66.—(1)  All tubes subject to internal pressure shall be solid drawn and made of steel, the ultimate tensile strength of which does not exceed 28 tons per square inch, and the elongation of which shall be not less than 30% measured on a standard test‑piece F when in the billet or bar form, and shall be certified as such by the makers of the steel and of the tubes.
(2)  All tubes under 1½ inches external diameter shall be cold finished; these and all other cold-drawn tubes shall be satisfactorily annealed before examination.
(3)  All tubes shall be free from defects, both within and without, and shall be tested as follows:
(a)all tubes up to 10 L.S.G. in thickness shall be capable of being flattened by hammering when cold until the inner surfaces are not further apart than 1/16 inch. For those over 10 L.S.G., and not exceeding 6 L.S.G. in thickness, the maximum distance apart shall be 7/32 inch; for those over 6 L.S.G. and not exceeding 3 L.S.G., the maximum distance apart shall be 3/8 inch; and for those whose thickness exceeds 3 L.S.G. the maximum shall be 9/16 inch. In all cases after undergoing such tests there shall be no signs of any cracking or other fracture; and
(b)all tubes when cold shall be able to withstand without cracking an enlargement of diameter at both ends by means of roller expanders or by drifts to the extent of: —
Thickness of Tubes
Enlargements of Diameters at ends by means of
Roller Expanders
Drifts
Up to 10 L.S.G.
12.5%
9.5%
Above 10 L.S.G. and up to 6 L.S.G
 
 
9.5%
 
7.0%
Above 6 L.S.G.
6.5%
5.5%
(4)  Tubes shall be presented for test in batches of 100 each. Two tubes shall be selected indiscriminately from each of at least two batches and one from each of any remaining batches. Each tube so selected shall be subjected to the above expanding tests and one tube from each batch, which may be a tube that has sustained the expansion test, shall also be flattened cold to the extent specified in paragraph (3)(a) at 3 different parts of its length of which one position shall be at or near the middle of the tube, and the flattened portions shall be in 3 different planes. The tubes shall pass these tests without signs of cracking.
Should one of the selected tubes fail to withstand either of these tests, two further tubes shall be selected from the batch and be subjected to both the prescribed tests. If further failure occurs the particular batch of tubes shall be rejected as unsatisfactory.
(5)  Every tube shall be tested at the tube maker’s works by hydraulic pressure to 3 times the maximum boiler pressure, but not less than 1,000 lbs. per square inch, except downcomer tubes, which shall be tested in accordance with the requirements for steam pipes.
(6)  The manufacturer’s certificate of the results of the foregoing tests shall be accepted, provided each tube is delivered with one inch in excess of the finished length, which excess shall be partly severed for flattening to the extent prescribed in paragraph (3)(a).
(7)  Every tube delivered is to be straight (unless otherwise specified) and is to be practically concentric throughout its length. The tolerance or deviation from the specified thickness is to be within the following limits:
(a)Cold Finished Tubes.—The tolerance in thickness shall be 5% below and 10% above the specified thickness; and
(b)Hot Finished Tubes.—The thickness of the tubes shall be within the following tolerances, measured at any point:
From 1½ inches up to and including
2½ inches {
-7½%
+17½%
Over 2½ inches up to and including
4½ inches {
-5%
+15%
From 1½ inches
2½ inches {
-7½%
+17½%.
The tolerances in external diameter from those specified are to be as follows:
(c)Cold Finished Tubes.—The external diameter of the tubes, measured at any point, shall be not greater than that specified, but may be less by a maximum of 1%.
(d)Hot Finished Tubes.—The external diameter of the tubes, measured at any point, shall be within the following tolerances of the diameter ordered:
For tubes from 1½ inches but below 2½ inches
{
+1/64 inch
-1/32 inch
 
 
 
For tubes 2½ inches diameter and over
{
+1%
-1%.