Importance of Matching Steam Temperatures With Metal Temperatures During Starting of Large Steam Turbines

Abstract

The best kind of operation for a steam turbine is to keep it continuously under constant load at constant steam pressure and temperature. However, system-load variations and present-day requirements call for daily starting and stopping of some units. Usually this type of operation has fallen on the older units built for lower pressures and temperatures than are common for new units today. The industry is reaching the point where the turbines subjected to this service are of the 1250-psig 950-F or even 1450-psig 1000-F level. This practice has proved to be the cause of some shell cracking. As a result, studies have been made to determine the factors occurring during the start-up period which produce cracking and what can be done to prevent trouble of this kind in the future.