Page 150 - Steam Turbines Design, Applications, and Rerating

Turbine Auxiliaries 131

Figure 7.7 Eccentric trip pin (top) and disk type overspeed trip device (bottom). (Elliott
Company, Jeannette, Pa.)

the action of springs and the steam pressure. These valves can be
“exercised” or checked for correct operation while in service. A built-in
steam strainer is usually provided to protect the blading against solid
particles from the boiler and pipework and also to distribute the flow of
steam more evenly.
Trip, or main stop valves, which incorporate the ability to manually
or hydraulically effect a progressive and precise valve opening for
starting up a turbine are called trip-throttle valves. Figures 7.3 and 7.4
show trip valves, and Figs. 7.5 and 7.6 depict trip-throttle valves.