Pronab Thermal insulation of pipelines in steam system is to serve two purposes viz., to reduce heat loss and also for personnel safety, Insulation thickness for hot surfaces (for safety of personnel working close by steam lines) will have to be designed to limit the outside lagging surface temp to a maximum of 140 deg F - 60 deg cent (generally speaking). This is based on 30 deg cent ambient temp and at 1 mph/hr air velocity Other insulation minium will have to be designed to limt the heat loss to approx. 80 Btu.hr-ft2 based on again 80 degeree F (26 deg cent) and an air velocity of 20 mph/hr. Thermal insulation will have as its main constituent calcium silicate, foam glass, fiber glass, or mineral wool, and will consist of pre-formed slabs or blankets, where feasible. Asbestos materials will be prohibited. An aluminum jacket or suitable coating will be provided on the outside surface of the insulation. Where a hard-setting compound is used as an outer coating, it will be nonabsorbent and noncracking. Thermal insulation will be chemically inert even when saturated with water. Insulation system materials, including jacketing, will have a flame spread rating of 25 or less when tested in accordance with ASTM E 84. Insulation at valves, pipe joints, steam traps, or other points to which access may be required for maintenance will be specified to be removable with a minimum of disturbance to the pipe insulation. At each flanged joint, the molded material will terminate on the pipe at a distance from the flange equal to the overall length of the flange bolts to permit their removal without damaging the molded insulation. Steam trap stations will be "boxed" for ease of trap maintenance and freeze protection. Above ground insulated piping will be clad with pebbled or corrugated aluminum of not less than 30 mil thickness and frame reinforced. At the joints, the sheets will be sufficiently overlapped and corrugated to prevent moisture from penetrating the insulation. Design temperature limits for thermal insulation will be based on system operating temperature during normal operation. Outdoor and underground insulation, if required, will be moisture resistant. Trust this will help you C.V.Srinivasan Nishi Engineers Pvt Ltd India June 24, 2007 E-mail: nishi@vsnl.com >Is there any regulations ( API or something like this) that >insulations not required in a steam line ( >pressure/Temperature are known) flange, union, expansions >joints, etc. if so which can lead to corrosion or other type >of failure of the pipe. > >Regards. > >pronab.