TABLE OF CONTENTS Unfired steam boilers, that is, nominally termed "waste heat boilers" or "heat exchangers", which generate steam by heat interchange with other fluids (see ASME code [1] Par. U-1 (g)), should be equipped with pressure-relieving devices required by the ASME code, Section 1, as far as applicable; otherwise, refer Par. UG-125.
Vessels, as per Par. U-1(g), which follow Par. UG-125ff are as follows:
Evaporators or heat exchangers.
"Vessels in which steam is generated by the use of heat resulting from operation of a processing system containing a number of pressure vessels such as used in the manufacturer of chemical and petrochemical products" [1].
Par. U-1 (h) "Pressure vessels or parts subject to direct firing from the combustion of any fuel, which are not within the scope of Sections I, III or IV, may be constructed in accordance with the rules of Section VIII, Division I, Par. UW-2 (d)" [1].
To meet code requirements, the relieving device must be directly open to the system to be relieved, see Figures 9-10, 9-11, and 9-12. For Figures 9-10, 9-11, and 9-12, the rupture disk and the relief valve must be designed to handle the relieving capacity at the relieving temperature without allowing more than a 10% pressure buildup above the MAWP of the unfired pressure vessel (or corresponding overpressure for other code requirements). Figure 9-11 requires that the rupture disk be designed the same as for Figures 9-10, 9-13a and b and Figure 9-12 requires that the...
