Investigate the T-105 high level alarm activation

What is going on

On 8 September a road tanker receipt of hydrochloric acid into tank T-105 reached 92 percent and activated the high level alarm before the operator stopped the transfer. The high high trip at 95 percent was not reached. The transfer register shows a planned receipt of 19.6 tonnes, the automatic gauge read 39 percent before the receipt and the weekly manual verification of the gauge was overdue. The tank data sheet gives the safe fill level and the receipt margin. The safety case lists the high level alarm and the high high trip as control measures for tank overfill. Declan Murphy wants a timeline, causes, an assessment of the safety case control measures and corrective actions for the process safety review on 23 September, and a view on whether the safety case needs to change.

Your brief

Investigate the safety system activation: gather the records and the accounts, build the timeline, identify the immediate and underlying causes including the ullage calculation and gauge verification, assess whether the safety case control measures performed as intended, recommend corrective actions and report to the process safety review.

Work through it

You do not need to do it all. Doing a few of these will show you what the work is like. Your ticks and notes stay on this device.

• Read the process safety and major hazard policy, the bulk fluid transfer and tank gauging procedure and the safety critical equipment register entries for the T-105 alarm and trip, and review PSE-26-067 and TR-26-3306.
• Gather the evidence: transfer checklist, gauge trend, manual dip records, delivery documents, alarm log and the tank data sheet, and interview Sam Whitford and the driver separately.
• Build a timeline from the pre-receipt gauge reading to the alarm and the stop, and reconcile the quantity received against the level change to test the gauge accuracy.
• Identify the immediate cause of the high level and the underlying causes, considering the ullage calculation, the overdue gauge verification, the checklist design, workload and supervision.
• Assess whether the high level alarm and the high high trip performed to their performance standards and whether the safety case relies on the ullage calculation as a control measure.
• Recommend corrective actions with owners and dates following the hierarchy of controls, including any management of change needed for the checklist, gauge verification or independent overfill protection.
• Write the investigation report for the process safety review with the timeline, causes, control measure assessment, actions and a recommendation on whether the safety case needs revision, and update PSE-26-067 in the incident register.

What someone in this role would produce

• Evidence file and interview notes
• Timeline with reconciliation of quantity and level
• Cause analysis
• Control measure assessment against the safety case
• Investigation report with corrective actions and register update