G - Engineering Design

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Engineering Safety

G - Engineering Controls

Layers of Safety

PPE

EMERGENCY RESPONSE

PHYSICAL

SAFEGUARDS

OPERATING PRACTICES

CONTROL STRATEGY

ENGINEERING

PRACTICES

TECHNOLOGYOP CONDITIONS

Stages of safety

Research Phase Engineering Phase Operating Phase

Conception Approval Startup

E f f e c t i v e n e s s i n R i s k

R e d u c t i o n

Inherent

SafetyEngineered

SafetyProcedural

Safety

Appraise Select Define Execute Operate

~ 4 years 25+ years


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• Intensification – Less inventory• Substitution – Lower hazard materials

• Attenuation – Reduce operating severity

• Simplification – Simplify design

Inherently safer systems are less likely toincur serious process incidents.

Inherent Safety Principles

Typical 30-year old platform design

Single platform

Some risers beneathaccommodation module

No subsea check or block valveson import / export pipelines

Limited fire and blast proofing

Wind-walls

All piping in carbon steel

Large hydrocarbon inventories.


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Inherently Safer Design PhilosophyHAZARD ELIMINATION is better than

PREVENTION is better than

CONTROL is better than

MITIGATION is better than

EMERGENCY RESPONSE

AND

PASSIVE controls are more reliable than

ACTIVE controls are more reliable than

OPERATIONAL or PROCEDURAL controls.

Inherently safer design: Tangguh

No hydrocarbon

processing to reduce leaks

and inventories

Open layout and grateddecks to increase gas

dispersion

No helicoptersphi losophy to

minimise hazards

No platform power

generation to avoid

hazardous storage and

operations

NUI with no overnight

accommodation to avoidpersonnel exposure

CRA piping to eliminate

corrosion

Topsides rated for

WHSP to simplify andavoid overpressure

Export riser locatedwithin structure

Corrosion resistant well flowlines


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Which is inherently safer?

Stainless steel wet gas line

Carbon steeldry gas line

• Balance of process / maintenance, ergonomics andsafety vs. economics.

• Process incidents with widespread effects willdictate maximum spacing.

• Industry spacing guidelines are a bare minimum.

• Industry spacing is generally based on firescenarios.

• Separate large inventories from potential ignitionsources.

Layout and Spacing

Layout and Spacing

Property Line

Maintenance

&

Warehouse

TankageBlock

Flare

N

S

W E

Prevailing Wind

Mid Tier

Pelletizing

And

Packaging

Lower Tier

Unimproved Land

Upper Tier

Main Road

Cooling

Tower

Ethylene

Low Pressure

Polyethylene

Ethylene

Glycol

Offices

Offices

Parking

Control

Room

Gate Gate

Process

Block

Offices

Office

Block


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Layout and Spacing

Systematic evaluation of building occupant risk as aresult of various external hazards.

Building poses risk to occupants because of:

1. People congregated near hazards

2. Structural integrity

3. Internal hazards

Facility Siting Studies


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• Examine strength of buildings – How blastresistant?

• Examine other physical hazards resulting fromdamage to buildings. i.e. Glass, toxic vapors intoducting, office furniture.

• Is a plan in place to evacuate and relocatepersonnel in an emergency?

• Is the facility suitable for shelter-in-place?

Facility Siting Studies

Major Concerns?

• Cover glass windows with protective film.

• Remove windows.

• Remove light temporary buildings.

• Relocate personnel.

• Apply structural modifications.

-------------------------------------------------------

• Demolish / replace with more robust structure.

• Erect new blast resistant structure.

Strategy for existing buildings


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• Grading should slope away from fuel sources orcritical equipment.

• Sewer system should be sized to handle– storm runoff, or– firewater, and– maximum release from major equipment

failure.

• Multiple catch basins reduce the travel time /distance and reduce the surface area for apotential fire.

Drainage

• Need to segregate incompatible materials.

• Sewer design must recognize plugging potential.provide means of clearing.

• Sewers must not permit the passage of flammablevapor (use traps).

• Integrated approach to layout, grading and sewersis required.

• May impact relief system sizing.

Drainage

System Isolation

• An essential safeguard for any hazardousprocess

• Permits safe inspection and maintenance

• Prevents the interaction of hazardous and nonhazardous materials

• Isolates energy sources from hazardousmaterials

• Reduces the size of a hazardous release –isolatable inventories


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Process Plant and Equipment

• Commit to quality engineering standards

• Material selection to match conditions

• Design to full range of service conditions

• Quality control during fabrication andconstruction

• Operate within safe operating envelope• Routine inspection and maintenance

Engineering Design

SAFE – RELIABLE - SUSTAINABLE

Krechba

Case History – CH13


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Case History 13-Krechba

2004 – BP Krecha (In-Salah) Gas Gathering Center,Algeria• Two nearly identical gas processing trains that treat

gas from remote production centers.• Facility provides glycol dehydration and CO2 removal

to sales gas spec for export via pipeline to Hassi R’Mel.

• Plant was in final stages of commissioning.• 6 in (150 mm) line taking gas off the top of the glycol

contactor to the flare header failed catastrophically .• Wind was blowing away from the plant and gas did not

ignite.

What Happened

• Train 1 had been flowing gas for a couple ofweeks, Train 2 was brought on stream the day ofthe incident.

• Within hours of start-up, problems with the CO2plant resulted in gas being diverted to flare.

• During Train 1 start-up, the flare system seemedexcessively noisy.

• As Train 2 started to send gas to flare thesituation became worse.

• Within hours the 6 in (150 mm) line taking gasoff the top of the glycol contactor to the flareheader failed catastrophically at the header.

Damage Details


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Why It Happened

• The 6 in (150 mm) line connecting the glycolcontactor to the flare header was too small (itshould have been 12 in (300 mm)).

• The under-design caused sonic velocities resultingin excessive vibration and very rapid fatiguefailure.

• Design failed to appreciate the importance of theblow down system to the safety of operations.

• No follow through on PHSSER/HAZOP findings.• Commissioning team did not adequately respond to

excessive noise and vibration in the blow-downsystem.

Major Lessons Learned

• The basis of design and pipingcalculations for the system mustconsider all operating modes.

• A sound design QA/QCprocedure must be available andfully utilized.

• Project HAZOP reviews mustinclude all systems, and allHAZOP recommendations mustbe closed out beforecommissioning.

E n g i n e e r i n g S y s t e m s T r a i n i n g / C o m p e t e n c y

P r e - s t a r t u p S a f e t y R e v i e w s


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• Determined by inventory requirements and holdupconsiderations.

• Limited by transportation systems.

• Large size equipment is more prone to failure fromlocalized stresses.

• Difficult to establish process control within allparts of large complex systems.

• Difficult to establish equilibrium in large vesselsand reactors.

Equipment Sizing

Documents

G - Engineering Design