main stop valve stopped by water induction. Is it possible?

Hi all,
I'm facing a failure problem where has been said that a huge water induction in a steam turbine prevents the main stop valve from close. I've searched and found nothing about that.
I'll be very thankful to any oppinion.
 
Hi Joca,

For sure water induction in steam turbine component , is BAD and can give serious damage on these components...

There are several articles on the web detailing why & how to prevent such things happening..., here is an very interetsing reel case article on How to prevent "Water induction in Steam Turbine":
https://www.powermag.com/replacement-instruments-improve-turbine-water-induction-protection/

Do not hesitate to share your feedbcak!

Controlsguy25.
Always glad to support you!
 
Joca,

Here some very interesting notes about "water induction in Steam turbine":

Water damage to modern saturated steam turbines can be roughly divided into
two categories: long-term erosion by wet steam and catastrophic damage due to
ingress of large quantities of water. The latter cause of turbine damage is covered
in this section.
Slugs of water can enter the turbine through a number of places, however, the
two most common sources of turbine damage are due to water induction
through the governor steam valve and through the extraction steam lines. Water
induction causes damage in three principle ways:
• direct impact damage on turbine components such as blading, diaphragms
and blade wheels,
• excessive thrust caused by water impingement leading to thrust bearing
failure or hard rubbing between components, and
• thermal damage to components due to quenching by water which may result
in excessive thermal stresses, thermal distortion, or permanent warping. This
is particularly true in the superheated section of the low pressure turbine.
Slugs of water which enter a turbine at high velocity will take the shortest path
through the turbine, possibly clearing out both fixed and moving blades in the
process. Because of the greater fluid density and the resulting impact on the
rotor, induction of water from the steam generator may result in thrust loads
much higher than design values. A failure of the thrust bearing can result in
excessive axial travel of the rotor and subsequent severe rubbing damage to
blading, blade wheels, diaphragms, glands and other components. Because of
its high heat capacity, water contacting hot turbine parts can cause severe
thermal stresses and distortion. This distortion can cause secondary damage if a
turbine is restarted before the distortion has dissipated. While thermal
distortion is not particularly severe in saturated steam portions of the turbine, it
can be a significant cause of damage in the superheated sections.
Prevention of water induction requires both proper operation of protective
features and careful avoidance of operating errors. The induction of water from
the main steam line is minimized by the steam generator level control system,
the high level alarm and by closure of the governor steam valve on high water
level. However, improper or inadequate draining of steam lines during startup
and subsequent loading can result in slugs of water being accelerated down the
steam lines and into the turbine.

Water induction into the turbine can have particularly severe consequences on
startup. While running under load, the steam flow can be of some benefit in
absorbing water and minimizing thermal distortion, particularly in superheated
sections of the turbine. Moreover, damage from rubbing can be increased when
rotor speed is in the critical speed range.
If high vibration or other serious problems necessitate shutting down the
turbine, the unit should not be restarted until all the water has been drained
from the unit and the cause of water entry found and corrected. In addition,
sufficient time should be allowed for relief of thermal distortion of the casing
and rotor. Experience has shown that the most serious damage from water
induction often occurs considerably after the first indication of water induction
and attempting to restart may result in extensive damage due to rubbing
between fixed and moving parts.
11.5 Moisture....
 
Hello, ControlsGuy25.

Thanks for your two answers.
Do you think that a large quantity of water inducted into a turbine can prevent the main valve to close properly? I mean, the valves do not close because the water is passing by it at the same time.
 
Hello, ControlsGuy25.

Thanks for your two answers.
Do you think that a large quantity of water inducted into a turbine can prevent the main valve to close properly? I mean, the valves do not close because the water is passing by it at the same time.
Hello Joca,

Thank you for your feedback!

Actually i can't state if " large quantity of water can prevent main valve to close properly", as I am not at site...

What did you do for knowing why this "water induction" occuring...,?
Are the drains lines ok "working properly"?
Do there is kind of extraction lines if yes are they ok?

That's what i can add for the moments...

Without be able to check P&ID , and also be present at site , this issue would be difficult to troubleshooting remotely..

ControlsGuy25.
 
Hello, ControlsGuy25.

Thanks for your two answers.
Do you think that a large quantity of water inducted into a turbine can prevent the main valve to close properly? I mean, the valves do not close because the water is passing by it at the same time.
Were any trip commands generated by the turbine's control system while the water was getting inducted into the turbine??
 
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