I would like to ask my colleagues: how should the range values for alarm limits and interlock limits on the DCS process cards be set in accordance with standard procedures? Are there any relevant guidelines?
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I would like to ask my colleagues: how should the alarm values and interlock values on the process cards be set appropriately in accordance with the operating procedures? Generally, the interlock values are specified during the design phase. So how are the process cards in the DCS defined? Should a process card represent the smallest scope of operations for a company? Then, which one has a wider range of operating values provided by the design institute? For DCS alarm values: high level is indicated as H, very high as HH; low level is indicated as L, very low as LL. How should these be set reasonably? Another issue is whether the range on the process card is consistent with or conflicts with the overreporting and underreporting The interlock value is undoubtedly the one with the widest range. There’s no doubt about that. So, the display tables in DCS are usually different from the interlock tables in SIS as well? Our company has repeatedly encountered issues with operating procedures during inspections by the Petrochemical Association; the inspectors (who are mostly experts from CNPC and Sinopec) disagree with our views. Please ask an expert for an answer. Thank you.
Process card control range—alarm value—interlock value; the control range is the narrowest
First is the process control range, which is also the optimal range for controlling process parameters in a company. Next are the alarms: including low-level and high-level alarms. Then there are the DCS interlocks (high-high, low-low), and finally the SIS interlock values. The settings for the high-level and low-level alarm thresholds are determined by the company based on its own process conditions
Are there any latest standards or specifications available?
Article 8 of the “Guiding Opinions on Strengthening the Safety Management of Chemical Processes” (Safety Supervision General Administration Document No. San [2013] 88)
The document only states the requirements; it provides no guidelines on how to set these parameters
Under conditions that meet safety requirements, the range between the normal value and the alarm value should be sufficient to provide workers with enough reaction time to take corrective action.