All material used in the construction of pressure parts shall be tested and shall conform with the following requirements:-

(a) The workmanship throughout shall be of the highest standard. All castings shall be well finished, free from defects porous placed and below holes, and true to dimensions without warping. Where chaplets are used, there must be satisfactory fusion with the metal. Chaplets must be properly tinned with metal free from lead.

(b) The screw threads of all bolts must be of Whitworth forms.

(c) All component parts shall where necessary, be manufactured to limit gauges to secure interchangeability throughout.

(a) The castings shall be cast from metal melted or refined in any suitable metallurgical plant other than an iron ore smelting furnace.

The minimum test results required on test bars 1.2 in. in diameter shall be in accordance with the table

NOTE.-Grade 16.5, 14 and 12 iron correspond to 26, 22 and 18.73 kg/cm² (16, 14 and 12 tons) minimum tensile strength respectively.

(b) On analysis, the sulphur and phosphorous content shall not exceed the following percentages:-

(c) Minimum Manganese content shall be related to sulphur content by the following formula:-

(% sulphur x 1.7) + 0.3=% Manganese.

Which must be shown to be satisfied by routine quality control laboratory analysis. In any event the Manganese shall not be less than 0.5% and shall be within the range 0.50-0.90%.

Phosphorous content shall be kept as low as economically possible but in no circumstances shall it exceed 1.0%.