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Management of Change

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Effects of Change

Change alters the basic relationship betweencomponents in a system (configuration) andintroduces new modes of failure.

All changes must bemanaged to ensure thatsystem integrity is notcompromised.

Plant

People

Process

Examples of Change

• New regulations• New facilities• New procedures• New tools and equipment• Increased job scope• Altered work sequence• Replacement parts• Inexperienced workers• Inclement weather• Deteriorating materials• Organisational Change

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Potential Risks

1) Are new or unknown failure modes introduced?

2) Are existing failure modes altered as a result ofthis change?

3) Are existing controls adequate for dealing with thenew failure modes?

4) Have changes been made in the organizationalinfrastructure?

Management of Change System

System to ensure that all changes are thoroughlyscrutinized prior to implementation.

Rational basis required to initiate the process.

All changes evaluated, communicated andcoordinated prior to execution.

Applies to physical plant, chemicals, operatingconditions, staffing

Special provisions for spare parts, training, drawings etc.

Flixborough - 1974

Case History - CH11

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Case History 11-Flixborough

1974 – Nypro Caprolactam Plant, Flixborough, UK

• Large site for caprolactam production by oxidation ofcyclohexane

• Two months plus prior to incident:

- Cyclohexane leaking from Reactor No. 5

- Plant shutdown. Reactor removed for repair

• OK to run with 5 reactors, bypass installed between No’s 4 & 6

• Powerful explosion and fire killed 28, seriously injured 36

Process Description

• 6 Reactors 160 ºC, 120psig (8.3 barg) - aboveatm boiling point

• 12 ft (3.7 m) Dia x 16 ft(4.9 m) high

• Carbon steel with

stainless steel cladding• 14 in (36 cm) elevation

change between reactors

The Incident

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What Happened

• Collapse of the temporary bypass caused releaseof cyclohexane

• Main cause of failure was effects of shearforces caused by internal pressure

• 1/8 of liquid flashed off as pressure was reducedto atmospheric, the remainder was carriedupward as a dangerous spray

One Theory of Why It Happened

Sudden pressure surge caused the pipe to fail– No. 4 reactor was equipped with an agitator

– Heel of water was left in the reactor aftershutdown

– On reheating during startup, temperature rose toboiling at the hydrocarbon-water interface

– Two phases mixed and created sudden evolution ofvapor and a pressure surge strong enough to rupturethe bypass arrangement

Damage Details

– People: 28 deaths, 36 seriously injured

– Environment: Onsite & offsite contamination

– Business: Plant totally destroyed, Nyproruined

– Reputation: 1,821 houses, 167 shops damaged

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Major Lessons Learned

• All changes requirecompetent design & carefulreview.

• The report of the Court ofInquiry stated:“ There was no overall

control or planning of thedesign, construction,testing or fitting of theassembly nor was anycheck made that theoperations had been properly carried out.” 

M a n a  g e m e n t  o f  C h a n  g e 

Baglan Bay Ethylene Cracker Cold Box

HPSEPARATOR

35 barg LP SEPARATOR

3 barg

LEVEL CONTROL

VALVE IS HP/LP

INTERFACE

SHELL OF HEAT

EXCHANGER

DESIGNED FOR

3 barg

RELIEF VALVESET AT 3 bargPROTECTS HEAT

EXCHANGER SHELL& LP SEPARATOR

New block valve installed

HPSEPARATOR

35 barg LP SEPARATOR

3 barg

LEVEL CONTROL

VALVE CLOSED

 AS NO LEVEL IN

HP SEPARATOR

NEW BLOCK

VALVE INSTALLED

 AND CLOSED

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Unit starts up

HPSEPARATOR

35 barg LP SEPARATOR

3 barg

LEVEL CONTROL

VALVE OPENS AS

LEVEL BUILDS IN

HP SEPARATOR

NEW BLOCK

VALVE CLOSED

PRESSURE IN

HEAT EXCHANGER

RISES TO 35 barg

Lessons learned

P r o c e s s  R i s k  A s s e s s m e n t 

O  p e r a t i n  g  P r o c e d u r e s 

P r o c e s s  S a f e t  y  I n f o r m a t i o n 

M a n a  g e m e n t  o f  C h a n  g e 

•Process safety informationcontains process equipmentspecification data

•A simple HAZOP wouldhave predicted the outcome

•All changes requirecompetent design andCareful review

•Operating proceduresshould have requiredthe new block valve tobe LOCKED OPEN

Pre-Startup Safety Review

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Pre-Startup Safety Reviews

Equipment considerationsWhat are some of the hazards and risks?

• Cleanliness

• Service testing (hydro test, flow test)• Refractory dry out

• Purging

• Calibration of instruments• Blanketing

• Dewatering

• Process line up (valves and circuits)

Pre-Startup Safety Reviews

Procedural considerations

• All actions complete, including HAZOP

• All PSI updated

• Operating procedures written

• Training complete

• Maintenance procedures written and spareparts available

• Emergency response plans updated

•Recommendations from PHSERS, HAZOPs, etc•Design integrity maintained?•Readiness of P&IDs and other documentation•Hand-over system for project to plant control is in place

•Procedures for startup up, shutdown, normaloperation, emergency shutdown of the facilities•Safe work practices procedures•Facility staffing adequate for startup?•Competencies and skills for safe operation•Punch listing is in place and that all high priorityitems have been completed•Loop Checks and Trip Checks completed?

Pre-Startup PHSSER: Key Activities

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Pre-Start Safety Review??