P008en Seamless Steel Tubes and Pipes for Boilers
1.1 This specification 2 covers minimum-wall-thickness, seamless carbon steel boiler and superheater tubes for high-pressure service. 1.2 The tubing sizes and thicknesses usually furnished to this specification are 1 / 2 in. to 7 in. [12.7 to 177.8 mm] outside diameter and 0.085 to 1.000 in. [2.2 to 25.4 mm], inclusive, in minimum wall thickness. Tubing having other dimensions may be furnished, provided such tubes comply with all other requirements of this specification.
Specifications: A179 A192 A210-A1, A210-C A209 T1, T1A, T1B A213 T2, T5, T9, T11, T12, T22, T23, T91 A334 Grade 1 and 6 A423
In other words, I believe that your reference to a 2 tonne boiler means a boiler that has a maximum steaming capacity of 2 tonnes of steam per hour from and at 100 degrees celsius and at atmospheric pressure. In other words, if your boiler is run at atmospheric pressure and is fed feedwater that is at 100 degrees celsius it will theoretically be able to produce 2 tonnes of steam/hour if you run it flat out.
ASTM A192 / A192M - 17 Standard Specification for Seamless Carbon …
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