This standard stipulates that the rated steam pressure is greater than 0.04MPa. But less than 3.8MPa industrial steam boiler rated parameter series. This standard applies to industrial and domestic stationary steam boilers using water as the medium.
GB/T 1921-2004 history
2004GB/T 1921-2004 Parameters for industrial steam boilers
1988GB/T 1921-1988 Specifications for industrial steam boiler