(151e) Securing the Control System against Improper Change after Alarm Rationalization

In the past, operators and engineering staff were accustomed to changing DCS alarm settings as they saw fit. Recently, an alarm rationalization project was executed to determine proper settings for every alarm. When these settings were implemented, the system was locked down to ensure that unauthorized changes were no longer possible. DCS lock-down created its own operational issues that had to be dealt with. This paper examines the method used for lock-down, the issues it created, and their solutions.