Improving the reliability of differential pressure level type instrumentation.

Case Study: Soku Gas Plant.

Shell Petroleum Development CompanyAkhibi, Osemhen Jennifer

Intern, Shell Assessed Internship Program 2008

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Project ObjectivesProject Objectives

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Approach & Resources

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Vapour

System OverviewSystem Overview

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Implications of Instrument FailureImplications of Instrument Failure

• Loss of income associated with trip of

equipment because of subsequent

production deferment.

• Compromises safety of people, equipment

and environment.

HP

LP

Liquid

Failure Rates AnalysisFailure Rates Analysis

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5-Whys Method5-Whys Method

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leak thermal

effect

Inherent nature of wet legs.

Fill System

•No barrier to seal out air or prevent fill fluid leaking into vessel.

Frequent maintenance wears out joints, making them leak.

Mixing ratio of water and glycol not guaranteed as ideal.

Viscosity of fill fluid vulnerable to temperature fluctuation.

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Sealed Capillary System•Records identify two CMs in last

twenty-four months.

Cost Balance Model for a typical month: Based on past failure trends, the production capacity of an AG compressor and vendor’s prices.

Running Costs, $

Fill System Sealed Capillary

Cost of unscheduled deferment, $

16,750 -

Cost of man-hours expended on CMs, $

600 -

Glycol, $ 160 -

Total 17,51017,510 -

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Initial Cost

RecommendationsRecommendationsReliability improvement plan

Highlights of proposed Maintenance Job Routine (MJR).

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• Replace transmitters with sealed capillary models.

• Forward MJR to instrumentation teams SPDC-wide.

• Train plant operators intensively on instrument operations.

• Record Trip Free Days and reward at target e.g. 100 days.

ChallengesChallenges• First project ever.• New environment.• No SAP access.• Time constraints.• Initial difficulty in communicating with the

manufacturers.• No work-station in IA.

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Learning & Skills developedLearning & Skills developed

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BACK-UP SLIDES.

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Occurrence of OSDs due to false alarms.

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Expectations

Challenges• Initial cost of replacing

transmitters.

Justifications• Investment pays for itself in

the long-run.

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