The steam-controlled solenoid valve integrates the functions of dual safety protection and timing release, and is safe and convenient for use.

本实用新型集双重安全保护和定时泄放为一体，使 用方便、安全。

youdao

All it means is that the Piston is not the Steam Box that Valve plans to release.

FORBES: Xi3 Is Committed to Piston, While Valve's Steam Box Remains Elusive

In February 2009, pressure levels spiked inside Reactor 1, forcing the release of steam through an emergency valve.

WSJ: Japan Plant Had Troubled History