PED Workshop 07, Bucharest Annika Haglund, Inspecta Technology

1. RBI, Risk Based Inspection Results and experience from a Pilot study within the Swedish Pulp and Paper Industry PED Workshop 07, Bucharest Annika Haglund, Inspecta Technology

2. Introduction to RBI

3. The definition of Risk R = P × C P = the probability of failure for a component, over a given time period into the future. (Not constant with time for time dependent degradation) C = the consequence, given that the failure has occurred. (For example measured by probable costs, fatalities, discharge volume, or core damage probability.) R = the risk level (for the analyzed event), the expected value for the consequence. The metric of the risk (”the probable consequence”) is the same as the metric of the consequence.

4. Risk types Three main types of risk measures:

5. i) based on plant experience (statistics) ii) based on analyses of risk level, (probabilities, consequnces) Typical selections of components to inspect: Probability of failure, P [1/year] Consequence of failure, C [M€]

6. Changes in risk level due to different actions ¯inspection, change of material, load monitoring, … ¬consequence reduction; safety systems, redundancy, protection, … årebuild Probability of failure, P [1/year] The reduction at inspection is dependent on interval and the detection capability. Consequence of failure, C [M€]

7. Why should the Industry use RBI? • The current inspection planning is in practice based on rough thumb rules. There is a need to utilize more analytical approaches in order to focus inspection on high risk items and prioritise the efforts. • Inspection planning by Risk Based Inspection (RBI) methods imply a systematic assessment of all components in a system. For each component the damage mechanisms are analysed in detailed, based on the chemicals, material and loadings. • The safety consequence and economic consequence at failure of each component is analysed.

8. Why should the Industry use RBI? • Inspection intervals are determined based on the development of the damage mechanisms, the risk level, and the inspection effectiveness. Cost-benefit analyses are made for the economically driven inspections. • The industry will take benefit by developing more detailed and optimised inspection programs. The number of failures reduce and reliability increase. Savings are also made by the better optimisation of the inspection efforts and reduction of planned downtime.

9. Why should the Industry use RBI? • Traditional inspection according to Swedish regulations will give fixed intervals; 3 years, 6 years etc. Will not consider differences in materials and details for damage mechanisms for the equipment. • An example: - Pressure vessel A made from SS and pressure vessel B from CS - Both contain White liquor- Shall the inspection intervals be the same? NO!

10. % Total Risk compared with % Piping Components The Ethylene factory, 1958 Piping Components 100% 90% 80% 70% 60% % of the total risk 50% 40% 30% 20% 10% 0% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % Piping segment Where will the risks apear – An example 10% of the equipment stands for almost 100% of the risk

11. RBI pilot studySmurfit Kappa Kraftliner

12. RBI – The project Part 1 RBI Screening Rough assessment of possibilities by RBI for different systems • Improved safety (lower economic consequence in case of failure, improved personal safety) • Cost savings (increased intervals between planned shutdowns) Part 2 Implementation of detailed RBI • Implementation of RBI in a selected system

13. Part 1 – RBI Screening The three systems evaluated: • Pulp production line (digestery, bleachery) • Recovery systems (evaporator, causticising plant, lime sludge burning) • Energy plant (soda recovery boiler, bark boiler, steam system, feed water tanks, condensation cleaning and gas destruction) The Piping systems were excluded. The paper mill was excluded.

14. Data acquisition • Component data (material, pressure and temperature) • Chemicals • Present inspection intervals and history • Consequences from a failure (production stop, personal injury)

15. Data acquisition for the assesment of: • The probability of failure • The consequence in case of failure • The potential with RBI (Cost savings, increased safety)

16. Results from the RBI Screening • A potential to prolong the inspection Intervals in the bleachery (because of the low pressure and therefore low utilizations) • A potential to prolong the intervals for the evaporation plant. Especially for the Liquor vessels due to redundancy and favorable environment. • A potential to prolong intervals for parts of the pulp production line, introduce inspection for other parts as the pressure diffuser and the vessel for depressurization of pulp in L2 (non-pressurised equipment) • A potential to prolong the interval for the recovery boiler from 1 year to possibly 2 years. Most components have already today 3 years NDT intervals.

17. … 2 weeks later, The vessel for depressurization of pulp in L2 • The corrosion had gone throw the shell of the vessel! • The vessel carries the pressure diffuser. Reinforcements are necessary. • The RBI sreeening identified the equipment as a high risk object. • With RBI as a base for the inspection program this would never have happened.

18. Del 2 – Implementation of the detailed RBI • Was implemented for one of the pulp production lines, L1(digester with associated piping, chip feeding systems etc) • What changes would RBI give to the current inspection program? • Include the whole system, also equipment that don’t have demands for in-service inspection from authorities.

19. Method Collection of data 1) Categorisation of components:- Existing ID-numbers for pressure vessels and tanks- Grouping of piping systems (ID-nr missing)- The Digester was split into three parts; top, middle and bottom end 2) Collection of data (pressure, temp, chemistry etc) 3) Estimate the cost for inspection, building of scaffoldings, removal of insulation from equipment, cleaning / per component 4) Estimate the consequence - stop in the production- repairs- personal injury

20. Method Assessments 1) Identify all causes of damage:- corrosion, erosion- internal Stress corrosion cracking (SCC) - corrosion under the insulation, external SCC- Fatigue; thermal and mechanical 2) Judge the rate of corrosion (general data, thickness measurements) 3) Damage tolerance analysis for the digester (LBB)

21. Method Analysis • Time to failure calculated with simplified models • Damage factors calculated based on- The materials susceptibility to damage- Variations in the process (chemistry, temperature etc)- History of breakdowns • Prepare an inspection program based on:- Equipment with high personal safety risk - Equipment with high risk cost per year- A broad cost-/benefit analysis

22. Results The highest personal safety risk level is for: • The digester • Steaming vessel • Some piping to/from the digester • Inline-mills (in-service inspection not mandatory) The highest financial risk level is for: • The digester • Some piping systems to and from the digester

23. Risk matrix (financial) - present inspection 1,00E+00 1,00E-01 Probability (1/year) 1,00E-02 1,00E-03 1,00E-04 100 1000 10000 100000 1000000 Consequense (kSEK) Result – risk matrix for present inspection Very high High Medium Low

24. Risk matrix (finansial) - alternative inspection 1,00E+00 1,00E-01 Probabalitity (1/year) 1,00E-02 1,00E-03 1,00E-04 100 1000 10000 100000 1000000 Consequence (kSEK) Result – risk matrix for alternative inspection Very high High Medium Low

25. Result - financial Total yearly expected cost with different inspection programs 45000 40000 35000 Riskcost 30000 Inspectioncost 42706 25000 Inspectionprogram kSEK/year 1: No inspection 20000 2: present inspection 15000 3: alternative inspection 10000 7503 5000 3512 1067 879 0 0 1 2 3 Inspectionprograms

26. Result – personal safety risk Personal safety risk 10 4,34 1 Digester included. 0,31 0,31 Digester excluded Probable fatalities per year 0,1 Inspection program 0,01 1: No inspection 4,49E-03 4,05E-03 2: Present inspection 3: alternative inspection 7,46E-04 0,001 0,0001 1 2 3 Inspection programs

27. Results - reflections Digester • High risk level due to the very high consequence → requires other actions in addition to inspection • LBB will decrease the consequence considerably. One has to have leakage supervision to be able to able to gain from LBB. Piping systems • Often high risk level due to financial consequence and lack of previous inspection

28. Conclusions The new proposal for inspection program • Fulfills the Swedish Regulations for personal safety • Will decrease the risk cost considerably and give improved total profitability for the plant • Leads to new inspections for most piping systems. A lot can be inspected during operation. • Leads to some new inspection methods to find ”new” causes of damage (for example EC/UT for internal SCC) • Leads to prolonged interval for some pressure vessels

29. Kappa thought that their documentation was complete Specifically documentation from reconstruction seems to be missing. Obtain information from the suppliers Material data was not always correct A new way of working, first time More detailed analysis reviled new knowledge for the systems Initially many new concepts Experiences from Smurfit Kappa Kraftliner

30. Experiences from Smurfit Kappa Kraftliner • Limited need for internal resources • From each division: engineers from operation and engineers from maintenance, in risk identification sessions and data gathering • A new inspection plan was developed • Focus on some new equipment. • For example Vessel for pressurization of pulp and Pressure Diffuser in L2. No demands for in-service inspection according to Swedish Regulations. These were pointed out in the RBI study to be high risk objects.

31. Quotation: Lennart Nordström, Pulp line manager, Smurfit Kappa Kraftliner Piteå ”Could we in the Pulp and Paper Industry afford not to use RBI?”

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