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