Guide word | Deviation | Cause | Consequence | Safeguards | DMRA | |||||
No/less | 1) No/less flow | 1.1 Water entry with gas 1.2 15-ESDV-1196 “-(emergency shutdown valve) at beginning of node” Malfunction, partially or completely close 1.3 Valve pre MCHE (Main Cryogenic Heat Exchanger) closes | 1.1.1 Water freezes and forms ice & hydrates on tube side causing less flow 1.2.1 Less flow “production” 1.3.1 Less flow “production” | 1.1.1.1 Inject dehydration liquid to prevent hydrate formation 1.2/3. 1.1 Bypass & maintenance applied | Probability = 3 Severity = 3 Risk factor = P × S = 9 Type = acceptable with controls | |||||
More | 1) More flow | 1.1 Low/medium/high pressure exchangers ruptured 1.2 Level controller on scrub column reads high level and malfunction open valve to drain liquid 1.3 Pressure release valve between scrub columns fails to open, and by pass blocked | 1.1.1 Causing propane system to merge with the NG stream 1.2.1 NG will come out from bottom of scrub tower with liquid causing hammering in pipes 1.3.1 Product loss | 1.1.1.1 Stopping propane cycle, & directing NG to bypass the ruptured exchanger 1.2.1.1 Adding a trip for the gas and alarm for gas entry 1.3.1.1 Maintenance on the cause of more flow | Probability = 4 Severity = 3 Risk factor = P × S = 12 Type = undesirable | |||||
Guide word | Deviation | Cause | Consequence | Safeguard | DMRA | |||||
Less | 1) Pressure less | 1.1 No upstream for the units | 1.1.1 No production | Low pressure alarm at beginning of the Node | Probability = 5 Severity = 1 Risk factor = P × S = 5 Type = acceptable with controls | |||||
More | 1) More pressure | 1.1 Reduction of cross section of the piping, in which gas passes, through due to hydrate formation 1.2 Increase in temperature | 1.1.1/2 Cause poisoning and pollution, due to release of gas into the air, may cause explosive mixture by mixing with air | 1.1.1.1 High pressure alarm at beginning of each unit | Probability = 3 Severity = 5 Risk factor = P × S = 15 Type = undesirable | |||||