... WT:1.5--4.0mm Seamless tube and pipe for lowand medium pressure boiler-----American Petroleum Institute:Certificate of Authority to use ... the Official API Monogram. -----Boiler and Super-heater Pipes,Seanless Pressure Pipes had been approved by CCS-----The quality management system ... , N80, J55, GCr15, GCr15SiMn, GCr9, GCr9SiMn seamless tube and pipe for low and medium pressure boiler