Dear gentlemen,

First of all I would like to thank you for this excellent Forum that provide to us an opportunity to share our question and problems.

In our thermal power plant we have the following:
boilers 850t/h
2x steam Turbine 700MW

The steam Turbine will trip at low condenser vacuum and LP Pressure Turbine bypass control valve kept closed when Turbine tripped at low vacuum in order to protect the mechanical integrity of the unit because The condenser is not designed to hold a pressure and as such must be prevented from any positive pressure above atmospheric. Often rupture discs are fitted as a mechanical prevention against any pressure surge.

My question is about High pressure turbine bypass control valve position OPEN OR CLOSE when Turbine trip at Low vacuum.

Note: This bypass system permits stable operation of the boiler when the turbine trips off line or during start-up operations.

Thank you for your immediate help

 

Dear Zouhen

In this case when Low vacuum Turbine Trip, both LP and HP pressure turbine bypass control valve kept lock close in order to protect the mechanical integrity of the unit. The condenser is not designed to hold a pressure and as such must be prevented from any positive pressure above atmospheric. Often rupture discs are fitted as a mechanical prevention against any pressure surge.

Also the boiler Tripped when Turbine trip by Low vacuum protection.

 

Dears,

Actually turbine hp bypass cv when Turbine low vacuum trip it will open and keep the boiler in service.

Can some one explain to how this system work when Turbine trip

thanks

 

Dear,

What type of boiler you have, reheater provided, hp bypass will provide steam to reheater in case of turbine trip. but if vacuum low, it should also trip, else where you feed steam generated into boiler.

 

first, I have never seen a CCP, nor a unit with multiple bypass. I have worked nukes with a single HP bypass from ahead of CVs to condenser.

their logic was a turbine trip occurred at 7"HgA. the sudden closure of the CVs resulted in a fast opening of the BPV to maintain the reactor (maybe).

the BPVs had a vacuum permissive to open so that condenser must be <15"HgA. so even though the turbine tripped on low vacuum, the bypass could stay in service as long as there was some negative pressure in the condenser. should the condenser vacuum continue to decay and the loss of permissive close the BPVs, the reactors safeties would lift.

In the event that the vacuum decayed completely and there was still steam being dumped into the condenser, the blow out diaphragms would rupture at 1Atm pressure to prevent from damaging the LP Hoods.

Now I can only guess how a dual bypass is arranged. It would be nice if a diagram was provided.

 

Dear Gutman

thank you for your reply.

the boiler is reheater boiler with hp bypass.

Please if you have any documents related to this operation
Of hp and LP bypass send to me [email protected].

In our power plant the lp bypass lock closed and hp bypass opened and the safety valves opened to release the pressure. Really I don't feel comfortable with this kind of logic.

dear all please help me.
thank you

 

Do you have any drawings? I would think there would be more to BPV logic than just a low vacuum permissive, like desuperheating availability or even the algorithm for their positioning.

do the bypass valves even allow boiler steam flow to the condenser during startup?

> Please if you have any documents related to this operation Of hp and LP bypass send to me.
> Really I don't feel comfortable with this kind of logic.

 

Please JEB send to me your Email

 

> Please JEB send to me your Email

I am a guest on this forum and not sure of the rules related to direct communications.

if you have additional comments/questions, can they be posted here versus going private. Going private would also limit my ability to present ideas due to liability.