The Pressure Equipment regulations 1999, which relate to the European Directive PED 97/23/EC should apply to any new pressure equipment. The DTI has a useful free publication - Guidance notes on the UK regulations - Pressure Equipment, URN 05/1074. My understanding is that as a minimum the...
The ASME 8 Div 1 2004 ed. has an errata dated Feb 2005 for the minimum temp for P1 materials - the errata corrects the temperature to 1100F/595C. (The same errata applies to P10B materials)
Trace Heating design takes into account many factors - including temperature required, pipe size, insulation type & thickness, max/ min ambient conditions, hazardous area type if applicable, criticallity of temperature control, pipe material to name but a few.
Raychem are one of the largest...