Creeping Change: Liquid Accumulation in a Flare System · 2019-05-28 · Creeping Change: Liquid...

Creeping Change:

Liquid Accumulation

in a Flare System

HAZARDS 29

23rd May 2019

Roger Berriman

2Creeping Change: Liquid Accumulation in a Flare System, Hazards 29, 23rd May 2019

Agenda

• Introduction to CSL

• Event overview

• Consequence

• Timeline

• Investigation

• Causes

• Conclusions


CSL Locations

Woodland House,

Hull, East Yorkshire

Blocks 47 & 48 of the Southern North Sea


5PUK Dimlington Terminal

CSL Easington Terminal

PUK Easington Terminal

GASSCO Langeled Terminal

NGG Area AGI

EASINGTON TERMINALS HUB


Event Description

13:48, January 17th 2018

Temp: 6oC

Wind: W, 37mph

POB 102

“Whilst lining out hot flash stabilisation route. A pulse of gas and liquid was

transferred to the ground flare which subsequently ignited, resulting in thick

black smoke and a small pool fire within the ground flare sterile area.”


Liquid Storage

Gas Processing

Control Complex

NO

RT

HInlet Facilities

Cold Vent

Gas Metering /Outlet

Ground Flare


Photos


Setting the scene

Unstabilised

condensate

from D-1502

E-2307

P2301A/B

Gas to ground

flare via vent

header

Liquid to

condensate

storage tanks

D-2

311

PCV-23351

PT

H-1501

D-1

50

3

P-1501A/B

FCV-1523

70oC

22oC

300 L/min

0.6 barg

10 barg

~180 kg/min

2 L/day

liquid

~120 kg/min

Flash gas

recovery (LTI)


Consequences - Actual

Category Severity Coding ReasoningPeople (P) 0P Event happened but resulted in no

actual injury or health effect.Environment (E) 0E Event happened but resulted in no

actual environmental effect.External complaint and regulatory (R)

3L A schedule 5 form has been submitted to the Environmental regulator for combustion of liquids in ground flare (breach of permit conditions)

Asset Loss (L) 1L Little equipment damage in ground flare area (production losses not included)


Consequences - PotentialCategory Severity Coding ReasoningPeople (P) 3P The ground flare has a restricted sterile area

which has controlled access limitations. Injury to personnel (LTI) could be sustained due to work parties escaping from work sites directly outside ground flare sterile area in the event of a large flare.

Environment (E) 1E Minor environmental damage.External complaint and regulatory (R)

3R Medium impact with potential to escalate to local media attention. Regulatory action for permit or licence breaches (e.g. Caution/Fine).

Asset Loss (L) 3L Significant damage where losses /restoration costs are £100k to £1m in a year


Investigation

• Terms of Reference

• Team

• Root Cause Analysis

• Pre-startup safety review

• Recommendations/actions


Problem solving -

5 step process

Gather data

• People, documents, hardware

Produce Problem

Statement

• Define issue, When, Where, Impact

Cause and Effect

Analysis

• Map of causes

Solutions• Potential

solutions to eliminate causes

Final Report

• Findings, share learning


CausesImmediate:

• Release to ground flare of gas and liquid (unstabilised condensate) that had

accumulated in vent header

• High forward flow to hot flash system

• H-1501 unreliability

Underlying:

• Condensation in wrong place

• Low points in vent header

• Normalisation of deviation

Root cause:

• Ineffective change management


Causes – High Flow to Hot Flash

• Flow control valve (FCV) remaining in ‘auto’ set at 100% at start-up

• Flow transmitter goes off scale and into error, FCV remains at set point

• 2-3 minutes high flow

• Pressure surge, no vessel overfill

Recommendations (31 in total):

• Software limits on FCV – maximum output

• FCVs to hot and cold flash to fail closed on signal error

• Re-range and re-locate pressure instrumentation on hot flash system


Causes – H-1501 unreliability

• 4 unsuccessful starts on heater on day of event

• Higher flowrate desired due to low flow trip and flow transmitter issues

• Normalisation of deviation

Recommendations:

• Flow transmitter recalibration

• Review multiple start attempts philosophy

• Remove group suppression alarms

• Review long term options for H-1501


Causes – Condensation in wrong place


Causes – Condensation in wrong place

• E-2307 was designed as a partial condenser for continuous duty

• One (out of two) fans on E-2307 was isolated

• Batch operation of hot flash at lower pressures

• Effective condensation in ground flare header pipework

Recommendations:

• Operate hot flash at higher pressure and low continuous flow

• Add running indication and temperature indication for E-2307 on DCS

• Routines required to remove and clear accumulated liquid in pipework

• Review condenser improvement options (water/brine cooled)


Causes – Low points in vent header• 6” vapour line from hot flash out of top of D-2311

and down to grade level PCV before going up to pipe rack (10m elevation)

• Tie-in to 16” old export line which was changed to ground flare header

• Line runs 100m across process island & drains back to knock out drum D-2311

Recommendations:

• Provide low point drain from hot flash to tie into condensate removal pumps

• Provide level indication on pipework

• Relocate PCV to vent header level


Root Cause – Management of Change (1)

• Creeping change within hot flash system (batch operation, connection of

ground flare vent header, removal of flash gas compressor system)



• Criticality of dual fan operation not appreciated

– 1 out of 2 fans on E-2307 found isolated

– No expectation that vapour would carryover from D-2311 and accumulate

in vent header

– System operating pressure reduction occurred over time



Full re-HAZOP of plant conducted 2017:

“Overfill of D-2311 with liquid which carries over into the vapour line off D-2311 to ground flare. Potential lute section downstream of D-2311 where discharge line rises into gantry before dropping back into ground flare. Upset flame conditions at ground flare and potential damage to burners. Smokey flame and possible injury at ground flare. Potential slugging flow through to ground flare.

Action raised:

“Review routing and design of line from D-2311 to ground flare and determine if there are operational and potential liquid slugging issues associated with this current design that may need to be resolved”

• Event occurred before action was closed.

• Recommendation priority and resource to complete actions from workstreams is key to combat changing risk picture.


Conclusions

• Event had no immediate process safety consequences but investigation provided

management team with opportunities to improve the safety and reliability of the

asset.

• Useful to combine ‘short’ term actions from RCA within a pre-startup safety review.

• Opportunities exist to implement further risk reduction options as part of longer

term plant upgrades.

• Challenges of creeping change are real as described in KP4. Creeping change

hazard identification (CCHAZID) methodology (Energy Institute Guidance) is

available to assist with future studies.

• Risk ranking of study recommendations and available resource to complete actions

remains fundamental to risk management activities.

© Centrica Storage Limited, 2018. This document, and its contents, are strictly confidential and may not be used for any purpose by any person other than the intended recipient, and may not be reproduced or distributed to any other person or published, in whole or part,

anywhere. Neither Centrica Storage Limited nor any of its affiliates, representatives or employees, makes any representation or warranty, express or implied, as to the fairness, accuracy or completeness of any of the contents of this document, and nor will they have any liability relating

to or resulting from their use.

25

Thank you,

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Creeping Change: Liquid Accumulation in a Flare System · 2019-05-28 · Creeping Change: Liquid...

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