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

Safety Driven Performance Conference 2013

Improving the Performance of Systems with RAM AnalysisDanielle ChrunSenior ConsultantLloyd’s Register ConsultingReliability and Asset Performance

October 10, 2013


Agenda

• Lloyd’s Register Consulting• RAM analysis• Example 1: Risk assessment of gas deliverability• Example 2: RAM analysis of subsea compressor station


Lloyd’s Register Consulting


Lloyd’s Register Consulting - Overview

• Is the consulting unit in Lloyd’s Register Energy division

• Acquired companies like Scandpower, ODS and Human Engineering are included in this unit

• No. of employees: 500


Your Local Global Expert for a Safer World


Risk based management

Risk analysis

Technical safety and

consequence modelling

Human factors and

working environment

Risk management

software

Reliability and

asset performance

Services and Products from LR Consulting

Engineering dynamics


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


RAM Analysis


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


Production Assurance Terms (Ref. ISO 20815)


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


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


Example 1: Risk Assessment of Compressor Gas Station


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)


Flow Schematic

A Compressor

B Compressor

Customer

Max: 2.54 PJ/d


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


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

1 2 3 4 55 Almost certain 3 2 2 1 14 Likely 3 3 2 2 13 Occasional 4 3 3 2 22 Rare 4 3 3 3 21 Remote 4 4 4 3 3

1 2 3 4 5

< 2 hours Between 2 and 8 hours

Between 8 and 16 hours

Between 16 and 24 hours >24 hours


FMECA Spreadsheet

Drawing ref. EquipmentMain

functionEquipment

stateFailure

mode(s)Failure

cause(s)

Failure effects

Failure detection method

LikelihoodConsequenc

eRisk rank MTTF (years)

MTTF data reference/

assessment

Mean DowntimeLocal Global

XXSuction 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 lossInspection by chance

2 3 3 81 4.1.1 12 hours

Structural deficiency

Foreign objects and excess flow, fatigue failure of internal components

No impact None

Noise, following compressor problems

4 1 3 - 0 hour

PluggedSlug 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

1 1 4 100 4.4.1 0 hour

Instrumentation failure

Instrumentation failure

Shutdown of A plant

0.45 Pj/d loss PLC alarm 4 2 3 21.8 4.5.1 2 hours


Data Dossier

No.

Equipment taxonomy (OREDA / ISO14224)

Simulation model referenceFailure Mode

Number of failures

λcrit

MTTFcrit (years)

OREDAMTTR (hrs)

Failure data source Failure notesEquipment subdivision

Equipment description

Model reference

Item class description

3.1.1

Mechanical equipment

Vessel VE-SC B Scrubber

External leakage - Process medium

1 1.41 81.0 7.0OREDA 2009 3.2.7, p. 369 (25/7)

-

3.2.1External leakage - Utility medium

1 2.22 51.4 2.0OREDA 2009 3.2.7, p. 369 (25/7)

-

3.3.1 Structural deficiency 2 5.18 22.0 9.5OREDA 2009 3.2.7, p. 369 (25/7)

-

3.4.1 Plugged - 1.14 100.0 Assessment

Lack of failure data for specific scenario. Scenario is considered to have remote probability. MTTF of 100 years set.

3.5.1 Instrumentation failure 3 5.23 21.8 OREDA 2009 3.2.7, p. 369 (25/7) and p.371

Instrumentation is related to approximately 60 % of scrubber failures

4.1.1

Mechanical equipment

Vessel VE-SC A Scrubber

External leakage - Process medium

1 1.41 81.0 7.0OREDA 2009 3.2.7, p. 369 (25/7)

-

4.2.1External leakage - Utility medium

1 2.22 51.4 2.0OREDA 2009 3.2.7, p. 369 (25/7)

-

4.3.1 Structural deficiency 2 5.18 22.0 9.5OREDA 2009 3.2.7, p. 369 (25/7)

-

4.4.1 Plugged - 1.14 100.0 Assessment

Lack of failure data for specific scenario. Scenario is considered to have remote probability. MTTF of 100 years set.

4.5.1 Instrumentation failure - 5.23 21.8 OREDA 2009 3.2.7, p. 369 (25/7) and p.371

-

Safety Driven Performance Conference 2013Gas in

Gas to TCPL

To or from headers0 45 PJd

Valves to ultrasonicmeters 0 95 PJd

Valves to TCPLmetering 0 95 PJd

Bypass for 62 6 percent ofgas supply

Trafalgar crossover2 09 PJd

From cold recylcle to Bcompressor 2 09

Suction scrubberpackage 2 09 PJd

Valves to Bcompressor 2 09 PJd

BCompressor

Valves from B compressorto aftercooler

Valve to stationblowdown 2 09 PJd

Valve between C andF headers 2 09PJd

From cold recycleto Plant A 2 09 PJd

Failures in this section lead to a loss of 37 4 percent of the gas supply ie 0 95 PJ per day

Failures in this section lead to a loss of 82 3 percent of the gas supply which corresponds to 2 09 PJ per day

Valve from SC to CO inplant B 1 49 PJd

Headers 1 49PJd

To SC in B plant 149 PJd

From aftercooler toA plant 1 49 PJd

To SC in A plant 149 PJd

SC in A plant 1 49PJ

From SC to compressor inA plant 1 49 PJ

A compressor From A compressor toaftercooler 1 49 PJ

Between A plant andheaders 1 49 PJd


Bypass for 40 9percent of gas supply

Isolation valves toTCPL 1 5PJd

Ultrasonic meter 15PJd

Failures in this section lead to a loss of 59 1 percent of the gas supply ie 1 5PJd


Ultrasonic meters 0317PJd

Isolation valves forUM 0 317PJd

Failures in this section lead to a loss of 12 5 percent of gas supply ie 0 317PJ per day

Headers total lossof gas supply


Failures in this section lead to loss of 17 7 percent of gas supply ie 0 45 PJ per day



Failures in this section lead to a loss of 31 9 percent of gas supply ie 0 81 PJd



Failures in this section lead to loss of 8 3 percent of gas supply ie 0 21 PJd




Between A plantand headers 2 09

PJd

Headers lossdifficult to quantify

Aftercooler totalloss of gas supply

Valves to ultrasonicmeters total loss

To and from TCPLtotal loss

Utility for Plant A

Utility for Plant B

Utility common for Aand B plants

Gas deliverability to TCPL

Built-in redundancyfor aftercoolers

7 x 17%

Utility A in Utility A outSyst 8 Blowdownfor Plant A

Syst 10 Air Compressorfor Plant A

2 x 100%

Syst 10 Air Dryer forPlant A

Utility B in Utility B outSyst 7 Fuel Gas forPlant B

Syst 8 Blowdownfor Plant B

Syst 10 Air Compressorfor Plant B

2 x 100%

Syst 10 Dry AirDryer for Plant B

Syst 14 Heatmedium for Plant B

Syst 14 HM pumpand boiler for B

Utility common in Utility common outSyst 17 AuxiliaryGenerators

2 x 100%

2 x 100%

Syst 18 Controlsfor Plant A

Syst 18 Controlsfor Plant B

Syst 7 Fuel gas forPlant A

Safety Driven Performance Conference 2013Gas in

Gas to TCPL


Valves to ultrasonicmeters 0 95 PJd

Valves to TCPLmetering 0 95 PJd

Bypass for 62 6 percent ofgas supply

Trafalgar crossover2 09 PJd

From cold recylcle to Bcompressor 2 09

Suction scrubberpackage 2 09 PJd

Valves to Bcompressor 2 09 PJd

BCompressor

Valves from B compressorto aftercooler

Valve to stationblowdown 2 09 PJd

Valve between C andF headers 2 09PJd

From cold recycleto Plant A 2 09 PJd

Failures in this section lead to a loss of 37 4 percent of the gas supply ie 0 95 PJ per day


Valve from SC to CO inplant B 1 49 PJd

Headers 1 49PJd

To SC in B plant 149 PJd

From aftercooler toA plant 1 49 PJd

To SC in A plant 149 PJd

SC in A plant 1 49PJ

From SC to compressor inA plant 1 49 PJ

A compressor From A compressor toaftercooler 1 49 PJ

Between A plant andheaders 1 49 PJd



Isolation valves toTCPL 1 5PJd

Ultrasonic meter 15PJd

Failures in this section lead to a loss of 59 1 percent of the gas supply ie 1 5PJd


Ultrasonic meters 0317PJd

Isolation valves forUM 0 317PJd

Failures in this section lead to a loss of 12 5 percent of gas supply ie 0 317PJ per day

Headers total lossof gas supply


Failures in this section lead to loss of 17 7 percent of gas supply ie 0 45 PJ per day



Failures in this section lead to a loss of 31 9 percent of gas supply ie 0 81 PJd







Between A plantand headers 2 09

PJd

Headers lossdifficult to quantify

Aftercooler totalloss of gas supply

Valves to ultrasonicmeters total loss

To and from TCPLtotal loss

Utility for Plant A

Utility for Plant B

Utility common for Aand B plants

Gas deliverability to TCPL

Built-in redundancyfor aftercoolers

7 x 17%

Utility A in Utility A outSyst 8 Blowdownfor Plant A

Syst 10 Air Compressorfor Plant A

2 x 100%

Syst 10 Air Dryer forPlant A

Utility B in Utility B outSyst 7 Fuel Gas forPlant B

Syst 8 Blowdownfor Plant B

Syst 10 Air Compressorfor Plant B

2 x 100%

Syst 10 Dry AirDryer for Plant B

Syst 14 Heatmedium for Plant B

Syst 14 HM pumpand boiler for B

Utility common in Utility common outSyst 17 AuxiliaryGenerators

2 x 100%

2 x 100%

Syst 18 Controlsfor Plant A

Syst 18 Controlsfor Plant B

Syst 7 Fuel gas forPlant A

Compressor B

Compressor A


Results

Event Results, operational time Results, calendar time*

Mean time between loss of gas deliverability 15 days (351 hours) 85 days (2029 hours)

Frequency of loss of gas deliverability 25 events per year 4.3 events per year

Compressor B failure frequency 17.3 per year 3.0 per year

Compressor A failure frequency 6.4 per year 1.1 per year

Full shutdown of both compressors 1.2 per year 0.2 per year

* Based on operational data from Union Gas, compressors are in use 17.3% of the time


Results (cont.)

Heat exchanger1.1 %

Valve2.5 %

Scrubber7.1 %

Gas turbine30.5 %

Compressor58.0 %

Other0.7 %

External leakage,

utility medium

2%

External leakage

3%

Spurious operation

8%

Failure to start11%

Aerodynamic damage

53%

Structural deficiency

21%

Other3%

Main contributors per equipment class Main contributors per failure mode


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

Equipment Failure mode MTTF Ref. MDT

Compressor B Aerodynamic damage8.9 years

OREDA 4 months

Compressor A Aerodynamic damage8.9 years

OREDA 4 months

Gas turbine, B Structural deficiency 20 years Based on lack of experience on Plant B 3 months

Gas turbine, A Failure to start0.5 years

Started more often than offshore unit. More reliable than B, based on experience (0.7 years for B)

8 hours

Scrubber Structural deficiency 22 years OREDA 59 days

Gas turbine, B Spurious operation0.2 years

Based on experience (0.5 years in OREDA) 8 hours


Example 2: RAM Analysis of a Subsea Compressor Station


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


Process Flow Diagram


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


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 2035. During series production and failure of one compressor train, the compres sors are configured back to parallel and production continues in one train. Switchover time is assumed negligible


Spare Part Philosophy

Case Spare part Quantity

Base case

Compressor module 1MV jumper 1Cooler bundle/cooler module 1Choke insert 1SCM 1

Sensitivity case

Compressor module 1MV jumper 2Cooler bundle/cooler module 1Choke insert 1SCM 1UTA transformer module 1CF jumper 1BF jumper 1CI jumper 1FO jumper 1LV jumper (from UTA to SCM) 1

LV jumper (from compressor station to compressor module) 1

LV jumper (from compressor station to cooler module) 1


Retrievable Units - Sample

Retrievable unit Vessel Mobilisation times (hrs)

Intervention time (hrs)

Refurbish time (hrs)

Lead Times(hrs)

Compressor Station HLV 4320 8760 - -

Compressor Module IMR 72 24 2190 8760

Cooler Module IMR 72 24 1460 8760

SCM IMR 72 30 8760 10220

Choke Insert IMR 72 12 2190 7300


Compressor Production CapacityYear 2 compressors running 1 compressor running 0 compressors running2015 100 % 97 % 91 %2016 100 % 73 % 60 %2017 100 % 62 % 33 %2018 100 % 71 % 13 %2019 100 % 74 % 0 %2020 100 % 76 % 0 %2021 100 % 62 % 0 %2022 100 % 54 % 0 %2023 100 % 55 % 0 %2024 100 % 50 % 0 %2025 100 % 45 % 0 %2026 100 % 40 % 0 %2027 100 % 35 % 0 %2028 100 % 30 % 0 %2029 100 % 25 % 0 %2030 100 % 20 % 0 %2031 100 % 15 % 0 %2032 100 % 10 % 0 %2033 100 % 5 % 0 %2034 100 % 0 % 0 %


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


Spare Parts – Base Case

NameInitial 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 1.00 0.68 0.66 0.47 0.28 4584 0.02 87

Comp. module 1.00 3.58 3.41 0.80 0.62 23337 0.56 2243

MV Jumper 1.00 0.19 0.19 0.17 0.09 558 0.00 0.6

SCM 1.00 1.01 0.96 0.58 0.35 8928 0.06 272


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



Spare Parts – Sensitivity Case

Name Initial no. in stock No. used No. replen-

ishmentFinal no. in

stock Avg. stockEmpty stock

duration (hrs)

Shortage no. times

Shortage duration

(hrs)

BF Jumper with couplers 1.00 0.07 0.07 0.07 0.04 210 0.00 0.00

CF Jumper with couplers 1.00 0.01 0.01 0.00 0.00 12 0.00 10

CI Jumper with couplers 1.00 0.07 0.07 0.07 0.04 207 0.00 0.00

Choke Insert 1.00 0.68 0.66 0.48 0.28 4600 0.02 99Compressor module 1.00 3.61 3.43 0.79 0.62 23369 0.57 2242Cooler module 1.00 0.48 0.47 0.37 0.21 1349 0.00 5.8FO Jumper with connector 1.00 0.07 0.07 0.06 0.03 194 0.00 0.00

LV Jumper with connector (UTA - SCM) 1.00 0.06 0.06 0.06 0.03 184 0.00 0.00

LV Jumper with connector (stat - comp module)

1.00 0.18 0.18 0.16 0.09 515 0.00 0.9

LV jumper with connector (stat - cool module)

1.00 0.04 0.04 0.04 0.02 121 0.00 0.00

MV Jumper 2.00 0.20 0.02 0.18 0.18 51 0.00 0.00SCM 1.00 1.02 0.96 0.58 0.35 8957 0.06 280Transformer 1.00 0.11 0.10 0.10 0.05 1110 0.00 4


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.




Conclusions

• RAM: Reliability, Availability, Maintainability• RAM serves several purposes:

• Evaluate performance of a system• Meet customer’s requirement in terms of performance• Major contributors to unavailability• Spare part philosophy

• At design or operation stage

Services are provided by members of the Lloyd's Register Group. For further information visit www.lr.org/entities

For more information, please contact:

Danielle ChrunSenior ConsultantReliability and Asset Performance

Lloyd’s Register Consulting1330 Enclave ParkwayHouston, TX 77077

T +1 (832) 582-9870E [email protected] www.lr.org/energy

Documents

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