The alarm settings for high and low liquid levels in methanol tanks are inconsistent in the control interlock DCS, SIS, and operating procedures
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The following questions were raised during the expert examination today. The alarm settings for high and low liquid levels in the methanol tank are inconsistent in the control interlock DCS, SIS, and operating procedures. Upon review, it is stipulated in Section 4.4.1 of the “Specifications for Safety Risk Control and Hidden Danger Investigation and Rectification in Hazardous Chemicals Enterprises” that the indicated values on the field instruments, the DCS control values, and the control values specified in the process cards must be consistent with each other. The guidelines for inspections stipulated in Document No. 78 of the Work Safety Supervision also require that the indicated values on the field instruments, the DCS control values, and the control values specified in the process sheets must be consistent with each other. Therefore, I would like to ask the senior experts and masters: what are the specific requirements for ensuring that DCS and SIS remain consistent?
The liquid level control and alarm settings for the methanol tank should be consistent in the DCS (Distributed Control System), SIS (Safety Instrumented System), and operating procedures, in order to ensure the safe and efficient operation of the system. The “Specifications for Safety Risk Control and Hidden Danger Investigation and Rectification in Enterprises Dealing with Hazardous Chemicals” and Document No. 78 issued by the Work Safety Supervision Bureau indeed stipulate that the readings displayed on field instruments, the control values set in the DCS, and the control values specified in the process cards should be consistent. This requirement also applies to SIS. In practice, DCS is primarily responsible for process control, while SIS focuses on safety-related control. Although their functional focuses differ, the settings for level alarms should be kept consistent between the two systems. This ensures that in the event of a failure in one system, the other can effectively take over to maintain safety. Therefore, it is recommended to review and adjust these settings to ensure they are consistent across all systems, in compliance with security regulations and operational standards. .
The SIS system alarms are interlock-triggered alarms. Have you also set up numerical alarms for the SIS? The SIS system merely has one interlock value, which lies outside the DCS system.