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Reg. 35-2
MATERIALS OF CONSTRUCTION

COPPER, BRASS AND STEEL TUBES

Brass Tubes

(a) Composition.- Brass for boiler tubes may be of either 70/30 alloy or 2/1 alloys as specified.

(b) Chemical analysis.- The tubes shall consist of an alloy of copper and zinc, and shall contain:-

70/30 alloy. Not less than 70 per cent of copper and not more than a total of 0.75 per cent of materials other than copper and zinc.

 

2/1 alloy. Not less than 66.70 per cent of copper and not more than a total of 0.75 per cent of materials other than copper and zinc.

 

The manufacturer shall supply when required free of charge, a copy of his works analysis* of the material.

(c) Freedom from Defects.- The tubes shall be clean, smooth and free from surface defects or longitudinal grooving, both internally and externally, and the ends shall be clean and square.

(d) Tolerances.- The tubes shall be solid drawn and shall be concentric within the working margins for thickness given below. The tubes shall be straight and unless otherwise ordered they shall be of uniform diameter throughout.

The working margins shall be as follows:

On length ± 1/16 inch.

On thickness ± half the difference between the Standard Wire Gauge (S.W.G.) specified and the next Standard Wire Gauge thicker.

On external diameter ± 0.005 inch.

(e) All test material shall be annealed before testing and shall comply with the following mechanical tests:-

(i)

Bulging or Drifting Test.- The test piece shall stand bulging or drifting cold (see Diagram 1 and 2 respectively) without showing either crack or flaw, until the diameter of the bulged or drifted end measures not less than 25 per cent more than the original diameter of the tube.
(ii) Flanging Test.- The test piece shall stand flanging cold (see Diagram 3) without showing either crack or flaw until the diameter of the flange measures not less than 25 per cent more than the original diameter of the tube.
(iii) Flattening and Doubling over Test.- The test piece shall stand the following test when cold without showing either crack or flaw. The rest piece shall be flattened down until the interior surfaces of the tube meet and then be doubled over, on itself, that is, bent through an angle 180° (see Diagram 4), the bend being at right angles to the direction of the length of the tube.

(f) Hydraulic Test.- Each tube shall be tested, before the tubes are presented for inspection, by an internal hydraulic pressure of 750 lbs. per sq. inch or by such internal hydraulic pressure as may have been specified by the Inspecting Authority and the Inspector may re-test 5 per cent or more as he may deem necessary.

The tubes shall withstand the test without showing any signs of weeping.

 

*A Works analysis is defined as the routine analysis taken by or for the manufacturer in order to control the quality of the material.

 

 
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