Availability analysis for the Electrabel - Lanxess Rubber ...b-dig.iie.org.mx/BibDig2/P11-0252/Track 3/Session 3...Availability analysis for the Electrabel - Lanxess Rubber cogeneration

CHOOSE EXPERTS, FIND PARTNERS

Availability analysis for the Electrabel -Lanxess Rubber cogeneration in AntwerpDe Vliegher Georges - Bollens Kris - Deknopper Karel

De Pauw Ivan

09/06/2010Availability analysis for the Electrabel - Lanxess Rubber cogeneration in Antwerp 2

TABLE OF CONTENT

1. Introduction & project context

2. Basic design & selected equipment

3. Methodology of availability study- SQUAD

- FMECA

- FTA

4. Results and changes

5. Conclusion

09/06/2010 3Availability analysis for the Electrabel - Lanxess Rubber cogeneration in Antwerp


• Cogeneration plant to replace the complete steam production of the Lanxess Rubber chemical plant in Antwerp

• Agreement between Electrabel-GDF SUEZ and Lanxess Rubber for the delivery of steam & electricity

• Tractebel Engineering in charge of:

- Feasibility study

- EPC-M of new CHP



• Main characteristics: - Average continuous steam demand 120t/h, peak demand 150t/h

- Availability of 99,7% for minimum 95t/h = less than 26,28 h/year < 95t/h

- Plant overhaul every 3 years, no other steam supply interruptions

- No condensates, only potable water from the grid

- GT electricity to public grid, ST electricity to Lanxess grid

- O&M by Electrabel – GDF SUEZ

• Hence the question:

Can we demonstrate that the plant will reach

99,7% availability ?



• Basic choices- made during feasibility

• Main equipment- GT - HRSG

- ST - Bypass

- Back-up Boilers

- Demin water plant

- FW system

• Auxiliaries- Gas station

- Air plant



• High level of redundancy in the basic design choices to satisfy profitability, budget, functional and availability requirements:- Beside the GT – HRSG – ST combination: N + 1 Back-up Boilers

- 3 x 50% demineralizers

- 2 x 100% instrument air production unit

- 2 x 100% fuel gas station equipment (counters – heaters – pressure reducers)

- Electrical system with connection on both the public grid (GT) and the Lanxess grid (ST)

- Redundancy for instrumentation (1°°2, 2°°3), pumps, FW equipment…

- Redundancy in control systems (DCS, PLC’s)



• Selected equipment data:- One GT – HRSG (without fresh air) – ST combination, 120t/h

- BUSG’s of 3 x 52t/h; Fire tube boilers instead of water tube boilers

- 3 demin units of 62t/h and 1 demin tank of 1000m³

- 2 FW tanks of 60m³ and 124 t/h each

- 4 LP FW pumps of 60t/h, 2 HP FW pumps of 150t/h

- BUSG and DEMIN with own redundant PLC control

- HRSG – BOP – AIR – GAS control in DCS system (HRSG BPS in redundant PLC)

- GT and ST with own control system


3. Methodology: SQUAD POWER

• “Semi-QUantitative Availability analysis for Design of Powerplants”

• Developed by Tractebel Engineering to evaluate expected availability and reliability of Power Plants during basic design phase

• Combination of 2 risk assessment tools:

FMECA (Failure Modes and Effects Criticality Analysis)

+

FTA (Fault Tree Analysis)


3. Methodology: SQUAD POWER

INPUTBasic design & design team knowledge

O&M and Engineering knowledge about failure frequencies & repair timesGeneric data on failure frequencies & repair times

FMECAExpert Group facilitation by risk analysis expert

FTAFault Tree Analysis by risk analysis expert

calculated availabilityrequired availability(steam supply 95t/h ->

availability 99,7%)

recommendations

recommendations


3. Methodology: FMECA

• Most efficient & complete way to get all necessary information -> individual expert input + input from interaction between experts-> how is system built up; possible interactions between sub-systems; how bad is it when a

sub-system fails (basic redundancies)

• (rough) Estimation of sub-system failure frequencies (MTBF)-> e.g. categories: n/year – 1/20 years – 1/100 years – 1/1000 years-> generic info exists but not always fully applicable

• Estimation of mean time to repair (MTTR)-> Attention! Implications for necessary spare equipment / manpower

• First idea about problems with basic design-> recommendations can already be made-> FMECA = kind of basic design review too


3. Methodology: FMECA

1. Break down installation into systems and subsystems

2. For each subsystem: determine failure modes

3. For each failure mode: determine effects (consequences)

4. Identify safeguards

5. Recommendations

Additionally:

• Criticallity analysis (based on risk matrix)

• Determination of failure frequency (MTBF) and duration (MTTR)


3. Methodology: FMECA example

Break down: CHP plant -> Water supply system -> Ion exchangers (demin) subsystem

Failure modes Effects Safeguards Recommendations

Poisoning of resin no demineralisation

possible loss of steam

production

50% redundancy

demin water storage

tank 1000 m3 (8h)

quality control of

delivered chemicals

Provide separate

discharge point for

direct feeding


3. Methodology: FMECA risk matrix example

1/1000 yrs 1/100 yrs 1/20 yrs n / yr

Loss of steam production < 95 t/h IV IV I I

Loss of gasturbine or heat recovery boiler IV IV IV IV

Loss of backup boilers IV IV IV IV

Loss of redundant machinery IV IV IV IV

estimation of failure frequency

tailored to what you want to analyse

IV = AcceptableI = Unacceptable


3. Methodology: FTA

• All information necessary for Fault Tree Analysis is gathered in previous phase (FMECA)

• Fault Tree is built and analysed by risk analysis expert

• Use of specific software

• Output- Calculated availability

- Which sub-systems contribute most to unavailability

• Allows for sensitivity analysis-> e.g. different failure frequencies, different mean time to repair, influence of redundancies


3. Methodology: FTA example

Failure of steam supply 95 ton/h to Lanxess

OR

Failure of make-up water supply

Failure of steam production devices

Failure of normal steam supply from GTsystem

Failure of back-up steam

AND


4. Results & changes4.1. First output

• Basic case 95 t/h:- Calculations give an availability of 99.94% (5.4 E-04 failure rate = 4.7 h/yr)

- Above request of 99.7%

- Major part (28%) of unavailability is due to the make-up water system

- Decision to go more in detail for this system (new failure cases, frequency, MTTR)

- Lead to improvements in design

• Off design case 120 t/h- Availability of 99.4 % (6.0 E-03 failure rate)


4. Results4.2. Design changes

• Water production & make-up- Increase demin water production capacity: 3 x 60 t/h => 3 x 75 t/h

- By-pass of raw water tank

- Increase demin water storage capacity : 1 x 1000 m³ => 2 x 750 m³

- Redundant neutralisation pits

• Gas pressure reduction station- Separate high pressure and low pressure reduction units

• Electrical distribution panels- Individual electrical system for each boiler with feeders from two separate sources

- Specific electrical systems for the water production unit, also with two feeders


4. Results & changes4.3. Final output

• Basic case 95 t/h:- Calculations give an availability of 99.98% (1.8 E-04 failure rate; 1.6 h/yr)

- Above request of 99.7% (26.3 h/yr)

- Unavailability divided by a factor 3 (4.7 h/yr => 1.6 h/yr)

• Off design case 120 t/h- Availability of 99.4 % (6.08 E-03 failure rate; 53 h/yr)



4. Results & changes4.4. Final output – Sensitivity

GT unavailability of 5% instead of 10% (LM6000 fleet of Gdf Suez)

• Basic case 95 t/h:- Calculations give an availability of 99.99% (1.14 E-04 failure rate; 1.0 h/yr)




4. Results & changes4.5. Plant operation results

Over the period of 10 months since start-up of back-up boilers

• Availability = 99.99%- Corresponds to 3 steam interruptions < 42 minutes cumulated

- Incidents were consecutives to modification actions on software and test linked with commissioning of GT-HRSG-ST combination


5. Conclusion• For the project

- Confirmation of the basic design at early stage of project

- Only a few modifications to improve results

- Weak points of the plant design were identified (mainly on water supply)

- Importance of maintenance and availability of the spare parts (respect of assumptions)

• Attention points- The reliability of the results is directly related to the quality of the data

• MTBF and MTTR are sensitive elements

• Experience and diversity of participants are important

- The level of detail has to be carefully monitored. To much detail will result in very large FTA. It is better to reduce the level of detail and zoom in on weak points

- Applicable on large and complex installations with limited time efforts


Electrabel CHP Plant at Lanxess site

Documents

Availability analysis for the Electrabel - Lanxess Rubber ...b-dig.iie.org.mx/BibDig2/P11-0252/Track 3/Session 3...Availability analysis for the Electrabel - Lanxess Rubber cogeneration