American society of mechanical engineers u stamp (Section VIII, Division I)

Design pressures exceeding 15psig are generally ASME labeled and considered ASME pressure vessels. 

The maximum design pressure for ASME pressure vessels covered by ASME Section VIII, Division  I is 3,000 PSIG. 

A fired pressure vessel is any pressure vessel that receives heat. The vessel may be partially or fully subjected to the heat source and the heat may  be received either directly and indirectly. Fired pressure vessels require special precaution since they can overheat leading to safety concerns. 

Sheet type materials welded directly to the vessels. This method provides better heat and cooling transfer than clamp on style. Does not require an increase in shell thickness due to jacket pressure