... OD:25---76mm 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 ... , DZ40, DZ50, N80, J55, GCr15, GCr15SiMn, GCr9, GCr9SiMn seamless tube and pipe for low and medium pressure boiler