METHODS FOR INCREASING LIFETIME OF OUTPUT ELEMENTS OF SUPERHEATERS.

Damage to the unheated output sections of high-pressure and low-pressure superheater coils where they are welded to the headers is a characteristic reason for failures of boiles in large power generating units. Damage to header welds (HW) is caused in most cases by premature exhaustion of the lifetme of the tube metal as a result of the action of elevated temperatures, stresses from internal pressure in stationary operating conditions, and cyclic temperature and compensation stresses during startups and shutdowns. The size of these loads depends on a group of operational and design factors, whose analysis enables us to take specific measures to increase the lifetime of convective superheaters (CSH). The general principles governing the lifetime of HW are considered on an example of the superheaters of TGMP-204, TPP-210A, and P-50 boilers.