# Guardian valve

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Valve used in marine steam turbine propulsion plants

A **guardian valve** is a [valve](/source/Valve) used in [marine](/source/Marine_(ocean)) [steam turbine](/source/Steam_turbine) propulsion plants to prevent steam from leaking into the [astern](/source/Astern) turbine while the vessel is operating in the ahead mode. It is normally installed between the astern [throttle valve](/source/Throttle_valve) and the astern elements of the low pressure (LP) turbine. Typically only the LP turbine of a steam ship's propulsion plant has reversing blade elements. Steam leaking in such a manner would result in a loss of efficiency and possibly overheat and damage the turbine blades.[1]

The guardian valve must be opened prior to any [maneuvering](https://en.wiktionary.org/wiki/maneuver) situation, in order to permit the astern turbine to be used to bring the vessel to a rapid stop or to back down.

Any similar arrangement of a stop valve used to protect leaking past a throttling valve could also be referred to as a guardian valve.

## References

1. **[^](#cite_ref-1)** ["T.S. Patriot State Engineering Manual"](http://weh.maritime.edu/campus/tsps/manual/mainSteam.html).

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Adapted from the Wikipedia article [Guardian valve](https://en.wikipedia.org/wiki/Guardian_valve) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Guardian_valve?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.