d - failures

8/20/2019 D - Failures

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D – Equipment Failure

How does equipmentfail?

How Can Equipment Fail?

• Internal Upset e.g.– High pressure

– High temperature

• Structural Failure

• Material Failure• Specific Equipment

(Component) Failure

• Human Error !

Some common immediate causes

• Non Return Valve doesn’t hold

• Closed valve passes fluid

• Level float sticks

• Freeze up in dead leg

• Deposit builds up on thermowell

- false temperature indication.

• Wear and tear

• Low point drain plugs when needed.

• Poor link between sensing element and controlpoint.


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Causes of Equipment Failure

OTHER

IMPROPER

PROCEDURES

IMPROPER

MAINTENANCE

OPERATING

ERRORS

INADEQUATE

INSPECTION

POOR DESIGN

Internal Upset - Pressure

Can you get hurt with low pressu re?

Force = Pressure multiplied times Area

Lets review the details.

It’s like many small weights

sitting on a surface which add

up to a big weight.

So at a given pressure,

the LARGER the area

The LARGER the force.

Example 1Force = pressure multiplied by area so:

0.7 bag pressure on a 300mm X 300mm square surface area (90,000mm 2) is 650

kg of force!

This is equivalent to an object that w eighs 650 kg or1,400 lbs.

300mm X

300mm Square

Door

0.7

barg

650 kilogrammes of Force

And as th e doo r wei ghs about 50 k g lb s -- if s udd enly releas ed it goes

flying!


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Be Aware

Can you get hurt with low pressure?

ABSOLUTELY !

Beware of large surfaces as even 0.05 bar which

may not even register on the pressure gauge but

it’s enough to send a hatch flying.

Vacuum Safety

• Same concepts

• In vacuum systems thepressure is pushinginward, not outward.

• The pressure comesfrom the atmosphere

– We don’t feel it but

a tank does when youpull a vacuum on it!

Vacuum

Atmospheric Pressure

Atmospheric Pressure (at sea level) is 1 bar g

(1 kg/cm2), therefore full vacuum is -1 kg/cm2.

Covered VentThis tank collapsed while being pumped out!

Painters had covered the vent with plastic sheeting.


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Materials of Construction Failure

Leading Contributors

Erosion / CorrosionPittingTemperature gradientCrackingStress fatigueStress impactStress corrosion

Materials of Construction Failure

Elbow Thinning

Humber Oil Refinery - UK

Case History – CH6


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Case History 6 - Humber Refinery

2001 – Humber Oil Refinery, UK

• Saturate Gas (C3/C4) Plant overheads pipe

• Catastrophic failure at a 6 in (152 mm) diameterelbow just downstream of water-into-gas injectionpoint

• Refinery shut down for several weeks

• Widespread damage to houses and businesseswithin a 1 kilometer (1.6 mi) radius of the site

The Incident

The Incident – Cont’dPiping Failure


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The Incident – Cont’d

Failed Elbow

What Happened

• The elbow failed due to “erosion-corrosion” damage.

• 180 te of LPG vapour escaped; ignited after c.20secs

• Fireballs 30 m (100ft) in height

• Wall thickness was reduced from 7-8 mm (0.25 in)

to 0.3 mm (0.01 in)• Water injection point returned to use (from

intermittent to permanent) without full MoC

• Failed elbow had not been inspected in 20 years

Damage Details


7/177

Major Lessons Learned

• Management of changeprocedures must be robustand involve all functions

• Pipework integrity must bemanaged and critical pointsmonitored

• Corrosion data must bemanaged and trendsanalysed

M a n a g e m e n t o f C h a n g e P r o c e s s & M e c h a n i c a l I n t e g r i t y

A typical plant has miles of Piping• Transports large inventories

• Transmits pressure and temperature

Piping Design

• Size – Must accommodate range of flow rates• Orientation – Must disengage vapor from liquid

- Low points, dead legs, under roadcrossings• Support – Static and dynamic stress• Material – Must resist failure under range ofexposures• Wall thickness – Compatible with system designpressure

Piping System Failure Modes

• Material failure / Corrosion / Erosion

• Joint failure – insecure assembly• Blockage• Bending / stress• Incorrect closure of valves• Freezing and Expansion• Vibration• Local Eddy currents• Metallurgical defects• Human error / Complexity


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Oil Refinery - Alberta


Case History 7-Oil Refinery, Alberta

1984 - Large oil refinery, Alberta, Canada

The Process

Flow Schematic

M

M

M

M

M

INITIAL

FAILURE

G-2

RECYCLE SLURRY PUMPAROUND

G-3

HGO

FRACTIONATOR

G-1

BITUMEN FEED

FEED

RINGS

SCRUBBER

REACTOR

FEED

SURGE

DRUM

LGO

STRIPPER

BOTTOM

PUMPAROUND

M

TO GAS COMPRESSSOR

LGO

NATURAL GAS

BITUMEN


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The Incident

• Coker 8-2 was operating normally with noapparent problems. Feed rate 82 KB/SD.

• Line failed on overhead pipe rack betweenreactor structure and compressor house.

• Hot oil release accompanied by a large fire inunit and explosion in compressor house.

• Intense fire burned for 4 hours.

• Total physical damage $120 million. Fourmonths to rebuild.

Damage Details

What Happened• Initiating failure was in 18 in (0.5 m) section of 6

in (150 mm) carbon steel pipe that had beenwelded into 5Cr½ Mo line.

• Operators were unable to shutoff other hot oilpumps or isolate piping circuits to and from reactor.

• As fire spread, several other lines ruptured andthis further aggravated the fire.

• Abrasive solids in slurry was a contributing factor.However improper metallurgy made failureinevitable.

• Pipe wall thinning had pre-existed prior to fire.

• Initial failure attributed to hot sulphidationcorrosion.


10/1710

What Happened – Cont’d

Point of Failure


• Piping circuits which supply largequantities of highly hazardousmaterial must have remoteisolation capability.

• Systems must be in place toverify the material and quality of

all materials installed in the field.• Emergency shutdown procedures

are critical to avoidingcatastrophic losses and must bepracticed regularly.

P r o c e s s & M e c h a n i c a l I n t e g r i t y

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

Pipe Failures

Pinhole leaks

Corrosion


11/1711

Pipe Failures – cont’d

Did you know that 60% of major accidents inplants involve piping system failures?


Brittle fractureThinning


Pitting


12/1712


Stress crack

Fired Heaters

•Provides high level heat to processstreams or incinerate waste streams.•Critical operating parameters /hazardous conditions.

Major fuel release source in manyplants.

- high throughput- moderate to high pressure-high temperature

Source of major loss in many plants.

Fired Heaters – Common Incidents

• TUBE FAILURE– Metal creep, sustained high tube temperature.– Erosion on process side from solids or 2 phase flow.– Poor flow distribution or a blocked pass.– Direct flame impingement.– Mechanical stresses on coil assembly.

• FIREBOX EXPLOSION– Procedural error or inadequate monitoring.– Inadequate purging

• FURNACE TUBE FOULING– Contaminated fuel or inadequate flow in tubes.


13/1713

Tankage

Hazards• Largest inventory of hazardous material on sites.

• Significant vapor space and high confinement.

• Tank defects and upsets are difficult to detect.

• Tank incidents are difficult to isolate.

• Remedial action is usually only partly effective.

Often regarded as low to moderate in severity/riskand don’t receive prime attention.

Buncefield


Case History 8 - Buncefield

2005 – Buncefield Oil Storage Depot, UK

• Vapour cloud explosion caused massive damageand additional explosions.

• Resulting fire engulfed a high proportion ofthe site.

• No fatalities, more than 40 people injured

• Significant damage to both commercial andresidential properties in the vicinity.


14/1714

The Incident

What Happened

• Tank in Bund (containment dike) A was beingfilled with unleaded motor fuel at a rate of550 m3/hr (2,422 U.S. gpm)

• Level gauge recorded an unchanged reading,the tank continued for more than 2 hours.

• Continued pumping caused fuel (300tes

(661,380 lbs)) to cascade down the side of thetank.

• Escaping fuel formed a massive vapour cloudwhich eventually found an ignition source.

Overflowafter05:20 (appx300 t)

?

14’’ T/KSouth pipeline

Tank 912 (fittedwithInternalFloatingRoof)

Staticafter 03:00

Gasolinevapour clouddevelops

Ignition at06:01

BPA HOSL West

Open

Pumping rate intotank: 550 m3/h from19:00 to appx. 05:50890 m3/h from05:50 to incident

(Unleaded gasoline)

Graphicinterpretation of 3rd investigation report

SCADA: HighLevel Supervisory

Control andData Acquisition system

ATG: AutomaticTa nk Gauging

system

?: data not availablefromreport

HLA

LI

TI

ATG Alarm panel

Substation

SCADAOverride

switch

for tests

ESD Trip

?

?

T E S T

E D A F

T E R I N C I D

E N T : O

K

Buncefield summarised


15/1715

Notice car

(source Hertfordshire F&RS Report)

22 minutes later

(source Hertfordshire F&RS Report)

Picture credit: local Police website

Catherine House

Fuji

Source: 3rd investigation report

‘’Intensity of blast still unexplained’’

HSE level of overpressure for planning advice: BUNCEFIELD:

600 mill ibar = 50 per cent fatalit ieswithin occupiedbuildings 700 to 1,000 mbars


16/1716

Damage Details

Damage Details – Cont’d


• Instrumentation and control oftransfer systems is critical.Communication between remotelocations.

• Maintenance of levelinstrumentation and high leveltrips in tankage areas just asimportant as process areas.

• The location of commercial andresidential developmentsaround sites like Buncefieldmust be carefully analyzed.

P r o c e s s R i s k M a n a g e m e n t

P r o c e s s a n d M e c h a n i c a l I n t e g r i t y

E n g i n e e r i n g S y s t e m s


17/17

Offshore Failure Mechanisms

• Vessels, Piping, Machinery• Structure

– Ship collisions– Sea states– Earthquakes

• Transport– Helicopter

• Sub Sea Operations• Wells

– SimOps

• Dropped Objects

Offshore Failure Mechanisms

Riser JtNo.1againstBOP

Lower Risersupported bydrill pipe

Mud fallingfrom brokenupper riser

Top of LowerMarine RiserPackage (BOP)

Riser Jts

resting onother wellhead

Riser Jt #1against BOPcontrols

This is not a drillThis is not a drill……

Riser Break

d - failures

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