| 摘要 |
Security devices are provided to prevent or block unauthorized access through portholes formed in a protective housing assembly when the protective housing assembly is in its first, closed position and to allow access through the portholes when the protective housing assembly is in its second, open position. The protective housing assembly may be mounted on an upper portion of a railway tank car to protect valves, fittings and other components associated with loading and unloading of lading from the tank car. The portholes are typically formed in the protective housing assembly to allow access to an adjacent valve or other component. Each porthole cover may be engaged with a normal access cover of the protective housing assembly to block or restrict access through the respective porthole.
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