Answer / kaizad

As soon as steam stop valves are closed there is no control on coast down speed of turbine unless vacuum break valve of condenser is opened. Normally it takes approximately 55mins to coast down from 3000rpm to 20-30rpm barring gear speed. We keep watch on all turbo visors parameters in such times

Answer / m saqib

there is no control on coast down speed of turbine except vacume breaker.when turbine trip the steam stop valve should be closed.when turbine speed reaches 2800 rpm then we open the vacume breaker .then turbine speed reduce > than under vacume.

Answer / sbr

First off all we have to  close prds line valve due to prds pre low and vaccume also low that meens condenser pre high in the case turbine was tripped with low vacume after that close the esv. Why turbine shaft free fall in down when ever having vaccume in condenser  rpm slowly dicresed even that time shft having some load then we crose the critical speed some vibrations are coming so first shaft free only can crose the critical speed

Answer / chinmay kumar patra(npti)

open the vacuum breaker so speed retardation will be high and it will cross the critical speed rapidly.so no danger

Answer / sappy

Max speed at which turbine can rotate with load of maximum load

Answer / chanchal rajput

As we closed esv after that speed of the turbine goes to
slow down automatically we can not any thing as it cross the
critical speed , for short time vibration increase but after
that goes slow down and turbine stop .Some turbine run above
the critical speed and some below the critical speed .

Answer / ankit

barring gear motor is used to cross the critical speed which is 20-25% of rated speed

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