Guide word | Deviation | Cause | Consequence | Safeguard | DMRA |
Less | 1) Level | 1) LIC (liquid indicator controller)in the scrub tower fails to open, causing liquid drainage | 1.1.1 Which may cause gas to flow through the bottom exit to unit 7 causing hammering | A low level trip at the scrub tower to prevent gas entering | Probability = 4 Severity = 3 Risk factor = P × S = 12 Type = undesirable |
More | 1) Level | 1.1. Malfunction of flow valve at bottom of scrubber | 1.1.1 Carry over at the scrubber as the gas flow would carry liquid with it, liquid may freeze with the low temperature causing dry ice on inner tubes causing lower production &corrosion | High alarm level at the scrubber | Probability = 4 Severity = 2
Risk factor = P × S = 8
Type = acceptable with controls |
Change | Composition change | 1.1. Loss of reflux in the scrubber | 1.1.1 Heavy ends directed to MCHE-Main Cryogenic Heat Exchanger-, causing corrosion & freezing | Low reflux alarm at entry of scrub column | Probability = 3 Severity = 2 Risk factor = P × S = 6 Type = acceptable with controls |