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Safety Driven Performance Conference 2013 Improving the Performance of Systems with RAM Analysis Danielle Chrun Senior Consultant Lloyds Register Consulting.

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Presentation on theme: "Safety Driven Performance Conference 2013 Improving the Performance of Systems with RAM Analysis Danielle Chrun Senior Consultant Lloyds Register Consulting."— Presentation transcript:

1 Safety Driven Performance Conference 2013 Improving the Performance of Systems with RAM Analysis Danielle Chrun Senior Consultant Lloyds Register Consulting Reliability and Asset Performance October 10, 2013

2 Safety Driven Performance Conference 2013 Agenda Lloyds Register Consulting RAM analysis Example 1: Risk assessment of gas deliverability Example 2: RAM analysis of subsea compressor station

3 Safety Driven Performance Conference 2013 Lloyds Register Consulting

4 Safety Driven Performance Conference 2013 Lloyds Register Consulting - Overview Is the consulting unit in Lloyds Register Energy division Acquired companies like Scandpower, ODS and Human Engineering are included in this unit No. of employees: 500

5 Safety Driven Performance Conference 2013 Your Local Global Expert for a Safer World

6 Safety Driven Performance Conference 2013 Risk based management Risk based management Risk analysis Technical safety and consequence modelling Technical safety and consequence modelling Human factors and working environment Human factors and working environment Risk management software Risk management software Reliability and asset performance Reliability and asset performance Services and Products from LR Consulting Engineering dynamics Engineering dynamics

7 Safety Driven Performance Conference 2013 Reliability and Asset Performance Reliability and SIL (Safety Integrity Level) Fault tree analysis SIL/IEC 61508/IEC61511 studies and compliance RAM and asset performance, incl. system optimisation FMECA (Failure Mode, Effect and Criticality Analysis) Decision support, Data and Uncertainty analysis

8 Safety Driven Performance Conference 2013 RAM Analysis

9 Safety Driven Performance Conference 2013 RAM Analysis RAM: Reliability Availability Maintainability RAM analysis is a structured analysis of the performance of a system to meet its deliverability/demand Quantitative analysis of a complete system / parts of a system / sub- system

10 Safety Driven Performance Conference 2013 Production Assurance Terms (Ref. ISO 20815)

11 Safety Driven Performance Conference 2013 Purpose of RAM Analysis Get an estimate of the expected system performance of concepts considered Identify major contributors to production loss / system unavailability Evaluate various measures to improve system performance / production loss (design and operational measures) Evaluate maintenance and spare parts planning It is not just the numbers that are important, but the analysis process itself will give valuable input both to design and operation of the systems analyzed It is more cost effective to implement regularity improvement in design than implementing measures after the plant is in operation

12 Safety Driven Performance Conference 2013 RAM Analyses / Production Assurance Analyses RAM analysis results in: Overall availability (system availability / production availability / deliverability) Availability for each component Overview of available and applied resources / spare parts RAM analysis can be used for: Production optimization Design optimization Spare part philosophy Maintenance planning Input for financial analyses and decision support

13 Safety Driven Performance Conference 2013 Example 1: Risk Assessment of Compressor Gas Station

14 Safety Driven Performance Conference 2013 Objective To perform a quantitative risk assessment of Compressor Station gas deliverability to a customer The risk assessment shall cover equipment and utility system failures at the Compressor Station, and will be based upon Client's operational data as well as industry failure data. Client wants to justify a new compressor station to be built to get LCU coverage (Loss of Compressor Unit coverage = Redundancy)

15 Safety Driven Performance Conference 2013 Flow Schematic A Compressor B Compressor Customer Max: 2.54 PJ/d

16 Safety Driven Performance Conference 2013 Assumptions: Sample Constant demand rates to customers Peak gas supply to Customer: 2.54 PJ/d Shutdown of compressor A implies a max gas delivery of 2.09 PJ/d Shutdown of compressor B implies a max gas delivery of 1.49 PJ/d Gas supply upstream compressors assumed to be 100% available OREDA assumed to be relevant although being offshore reliability database. Engineering judgment used when failure data considered inadequate + used for MDT

17 Safety Driven Performance Conference 2013 Methodology FMECA Reference all equipment included in Station (including utility) that lead to downtime in gas deliverability Identify failure mode, failure cause, effects, failure detection Likelihood, consequence, risk matrix MTTF, MDT based on OREDA and engineering judgment RAM Miriam Regina Almost certain Likely Occasional Rare Remote < 2 hours Between 2 and 8 hours Between 8 and 16 hours Between 16 and 24 hours >24 hours

18 Safety Driven Performance Conference 2013 FMECA Spreadsheet Drawing ref.Equipment Main function Equipment state Failure mode(s) Failure cause(s) Failure effects Failure detection method Likelihood Consequenc e Risk rankMTTF (years) MTTF data reference/ assessment Mean Downtime LocalGlobal XX Suction scrubber Extract liquids from gas before gas enters compressor Operating External leakage Flanges, connections, tubing, dump valve fail open Shutdown of A plant 0.45 Pj/d loss Inspection by chance hours Structural deficiency Foreign objects and excess flow, fatigue failure of internal components No impactNone Noise, following compressor problems hour Plugged Slug most likely due to pigging Potential impact on A plant efficiency None, assuming that operation can proceed unless slugging is severe Differential pressure leading to PLC alarm hour Instrumentatio n failure Shutdown of A plant 0.45 Pj/d lossPLC alarm hours

19 Safety Driven Performance Conference 2013 Data Dossier No. Equipment taxonomy (OREDA / ISO14224) Simulation model reference Failure Mode Number of failures λ crit MTTF crit (years) OREDA MTTR (hrs) Failure data sourceFailure notes Equipment subdivision Equipment description Model reference Item class description Mechanical equipment VesselVE-SCB Scrubber External leakage - Process medium OREDA , p. 369 (25/7) External leakage - Utility medium OREDA , p. 369 (25/7) Structural deficiency OREDA , p. 369 (25/7) Plugged Assessment Lack of failure data for specific scenario. Scenario is considered to have remote probability. MTTF of 100 years set Instrumentation failure OREDA , p. 369 (25/7) and p.371 Instrumentation is related to approximately 60 % of scrubber failures Mechanical equipment VesselVE-SCA Scrubber External leakage - Process medium OREDA , p. 369 (25/7) External leakage - Utility medium OREDA , p. 369 (25/7) Structural deficiency OREDA , p. 369 (25/7) Plugged Assessment Lack of failure data for specific scenario. Scenario is considered to have remote probability. MTTF of 100 years set Instrumentation failure OREDA , p. 369 (25/7) and p.371 -

20 Safety Driven Performance Conference 2013

21 Compressor B Compressor A

22 Safety Driven Performance Conference 2013 Results EventResults, operational timeResults, calendar time* Mean time between loss of gas deliverability15 days (351 hours)85 days (2029 hours) Frequency of loss of gas deliverability25 events per year4.3 events per year Compressor B failure frequency17.3 per year3.0 per year Compressor A failure frequency6.4 per year1.1 per year Full shutdown of both compressors1.2 per year0.2 per year * Based on operational data from Union Gas, compressors are in use 17.3% of the time

23 Safety Driven Performance Conference 2013 Results (cont.) Main contributors per equipment classMain contributors per failure mode

24 Safety Driven Performance Conference 2013 Discussion Comparison with operational data Operational data reports 8.12 failures per compressor unit Our risk assessment shows 7.6 failures for A 18.6 failures for B Data uncertainty Main contributors to gas deliverability (red cells have great impact on results): OREDA applicability EquipmentFailure modeMTTFRef.MDT Compressor BAerodynamic damage8.9 yearsOREDA4 months Compressor AAerodynamic damage8.9 yearsOREDA4 months Gas turbine, BStructural deficiency20 yearsBased on lack of experience on Plant B3 months Gas turbine, AFailure to start0.5 years Started more often than offshore unit. More reliable than B, based on experience (0.7 years for B) 8 hours ScrubberStructural deficiency22 yearsOREDA59 days Gas turbine, BSpurious operation0.2 yearsBased on experience (0.5 years in OREDA)8 hours

25 Safety Driven Performance Conference 2013 Example 2: RAM Analysis of a Subsea Compressor Station

26 Safety Driven Performance Conference 2013 Objective Wet gas compression system 2 compressor modules 2 process coolers 1 flow mixer 3 bypass headers Compressor system will boost unprocessed gas well stream from 2015 to 2030 (production profile) Objective: Study the production unavailability caused by equipment failures in the subsea compression station System availability Recommendations on spare part philosophy

27 Safety Driven Performance Conference 2013 Process Flow Diagram

28 Safety Driven Performance Conference 2013 System Operation Natural production (bypass): Wells are producing naturally through the main headers with bypass valve (V3) open and valves in and out of the compressor station (V1 - suction and V2 - discharge) will be closed to prevent washout of inhibited volumes in the station Parallel compression: The two compressor trains can be operated in parallel with common suction and discharge. Used for high capacity Serial compression: Well flow is routed to compressor A train and then to compressor B train. Used for low capacity Single compression: If flow rates are low or if one compressor for some reason is out of operation, only one compressor can be operated while the other compressor is isolated and put in shut-in mode

29 Safety Driven Performance Conference 2013 Assumptions: Sample Only critical component failures that lead to shutdown or loss of production are considered in the RAM analysis Constant failure rates are used for all equipment, assuming exponentially distributed lifetimes The assumption "as good as new" is used for failure events. This assumption implies that all maintenance operations have the ability to restore the product to a state which is "as good as new The RAM analysis is simulated over a 20 years period, from beginning of year 2015 to end of 2034 Compressors are run in parallel from beginning of 2015 to end of 2023, and in series from 2024 to During series production and failure of one compressor train, the compres­sors are configured back to parallel and production continues in one train. Switchover time is assumed negligible

30 Safety Driven Performance Conference 2013 Spare Part Philosophy CaseSpare partQuantity Base case Compressor module1 MV jumper1 Cooler bundle/cooler module1 Choke insert1 SCM1 Sensitivity case Compressor module1 MV jumper2 Cooler bundle/cooler module1 Choke insert1 SCM1 UTA transformer module1 CF jumper1 BF jumper1 CI jumper1 FO jumper1 LV jumper (from UTA to SCM)1 LV jumper (from compressor station to compressor module) 1 LV jumper (from compressor station to cooler module) 1

31 Safety Driven Performance Conference 2013 Retrievable Units - Sample Retrievable unitVessel Mobilisation times (hrs) Intervention time (hrs) Refurbish time (hrs) Lead Times (hrs) Compressor StationHLV Compressor ModuleIMR Cooler ModuleIMR SCMIMR Choke InsertIMR

32 Safety Driven Performance Conference 2013 Compressor Production Capacity Year2 compressors running1 compressor running0 compressors running %97 %91 % %73 %60 % %62 %33 % %71 %13 % %74 %0 % %76 %0 % %62 %0 % %54 %0 % %55 %0 % %50 %0 % %45 %0 % %40 %0 % %35 %0 % %30 %0 % %25 %0 % %20 %0 % %15 %0 % %10 %0 % %5 %0 % %0 %

33 Safety Driven Performance Conference 2013 Results – Base Case Gas export availability The estimated gas export production availability for the wet gas compression station is 98.2 % Relative unavailability contribution per retrievable unit/location

34 Safety Driven Performance Conference 2013 Spare Parts – Base Case Name Initial no. in stock No. used No. replen- ishment Final no. in stock Avg. stock Empty stock duration (hrs) Shortage no. times Shortage duration (hrs) Choke Insert Comp. module MV Jumper SCM

35 Safety Driven Performance Conference 2013 Results – Sensitivity Case The estimated gas export production availability for the wet gas compression station is 98.7 %. The sensitivity case shows that the increased amount of spare parts significantly increase the expected gas export production availability. The differential between base case and sensitivity case is 0.5 % for the production availability Relative unavailability contribution per retrievable unit/location

36 Safety Driven Performance Conference 2013 Spare Parts – Sensitivity Case Name Initial no. in stock No. used No. replen- ishment Final no. in stock Avg. stock Empty stock duration (hrs) Shortage no. times Shortage duration (hrs) BF Jumper with couplers CF Jumper with couplers CI Jumper with couplers Choke Insert Compressor module Cooler module FO Jumper with connector LV Jumper with connector (UTA - SCM) LV Jumper with connector (stat - comp module) LV jumper with connector (stat - cool module) MV Jumper SCM Transformer

37 Safety Driven Performance Conference 2013 Example 2: Conclusions Highest unavailability contributors were failures at the compressor station/or leading to retrieval of the station Valves were the most critical component type, which cannot be resolved by spare parts. Recommendation to have full compressor module as spare, or spare parts of the most critical components within a compressor module can be considered Other major contributor: cooler module, decreased by the introduction of spare part in the sensitivity case. Relative unavailability contribution per retrievable unit/location

38 Safety Driven Performance Conference 2013 Conclusions RAM: Reliability, Availability, Maintainability RAM serves several purposes: Evaluate performance of a system Meet customers requirement in terms of performance Major contributors to unavailability Spare part philosophy At design or operation stage

39 Services are provided by members of the Lloyd's Register Group. For further information visit For more information, please contact: Danielle Chrun Senior Consultant Reliability and Asset Performance Lloyds Register Consulting 1330 Enclave Parkway Houston, TX T +1 (832) E w


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