Flow-Accelerated Corrosion

Transcription

1 Flow-Accelerated Corrosion Risk Assessment & Inspection Planning Risk Assessment Who is concerned? FAC can occur in boilers, HRSGs and air-cooled condensers of all sizes. Because it is a progressive phenomenon, there is real benefit in a proper risk-based inspection programme, by identifying imminent failures or high-risk components. FAC Inspection Plan Using the Risk Assessment in combination with engineering judgment acquired through extensive field experience, we identify components that will be most prone to FAC wear. An easy-to-follow and targeted inspection plan is developed showing the areas requiring UT and/ or borescope inspection inside the boiler and on external power piping. The plan includes sample detailed UT grid layouts to assure effective detection and trending of thinning. As an option, Tetra can deliver field inspection services or expert field supervision of 3rd party NDE contractors. Using our FACRisk software, Tetra Engineering assesses the risk of thinning in components for each critical HRSG/boiler system; taking into account all parameters that influence FAC progression: Temperature ph Dissolved Oxygen Flow rate Geometry Material Fluid Phase The analysis incorporates of boiler process conditions using advanced thermodynamic simulation software. This is an essential step in predicting wear in certain areas, such as LP evaporators. () S.A.R.L. FZ-LLC

2 Failure Root Cause Analysis How and Why Did It Fail? Context is key While knowing the failure mechanism is important, it is only by understanding the process conditions that led to failure that steps can be taken to prevent future failures. conventional thermal power plants for more than 25 years at client sites around Decisions and Actions on: Components are known to fail in a variety of ways and can have serious implications for the overall system. We call on an interdisciplinary team of accredited experts to identify the type of failure and to establish how and why it happened. Testing & Analyses Physical Testing: Visual Examination and Macro Photography Metallography Fractography Chemical Analysis Tensile and Fatigue Testing Hardness Tests Scanning Electron Microscopy Energy Dispersive Spectroscopy Supporting Analyses: Operating data Assessment Finite Element Analysis Thermal Modelling Along with identifying the cause, we follow through with clear advice: Fitness-for-Service Methods of Repair Changes to Operations Component Redesign System Modification () S.A.R.L. FZ-LLC

3 Power Piping Services Field Services PipeVue 2.0 Tetra has developed a 3D Knowledge Management System designed specifically to help Plant Operators keep track of their Power Piping integrity. conventional thermal power plants for more than 25 years at client sites around Compliance with B31.1 O&M requirements The Power Piping Code now requires Operators to develop a Covered Piping Systems (CPS) Maintenance Programme. This includes Assessing and mitigating risks by developing targeted inspection plans Keeping maintenance and inspection records Performing regular Condition Assessments Keeping operation records and capturing any operating excursions Keeping track of the condition of your Power Piping and its supports is critical to plant integrity. We offer : Field inspections of piping and supports Piping Condition Assessments Risk-based Inspection Plans for creep, (inc. P91), fatigue, FAC and other degradation mechanisms for NDT technicians to follow Engineering Analysis Just as important to plant integrity is assessment of inspection results. Tetra provides the necessary engineering analysis including: Remaining Life Assessments and Fitness-For-Service Piping Stress Analysis using Autopipe or Caesar II Knowledge Management Software for keeping track of historical records () S.A.R.L. FZ-LLC

4 Flexible Operation of the HRSG Get Prepared Typical Scenarios Low-load operation Two-shifting Seasonal Cycling Low-load with duct firing (for steam host or desalination) Load Following conventional thermal power plants for more than 25 years at client sites around The Right Approach Experiences in the power industry have shown that base-loaded HRSGs outlast those that cycle, two-shift or run at low load. The damage incurred in Flexible Service leads to reliability problems and controlling the degradation is critical to plant performance. Identify the risk Tetra s approach is to get a full picture of the HRSG s operation using DCS data, numerical analysis and industry-standard assessment procedures (ASME/ EN / FFS) to advise on: Control logic & ramp-up/down procedure changes Upgrading existing equipment Improving the HRSG design s suitability to flexible service Inspection Planning for outages Maintenance Planning for outages Different operating regimes accelerate different wear mechanisms depending on the HRSG design characteristics. We identify the damage mechanisms relevant to your HRSG s operation, and the affected components: Superheaters and Reheaters Low-pressure and High Pressure Evaporators Economisers Cold-end Corrosion Sprays, Control Valves and Bypass Valves Steam Drums Main Steam Piping () S.A.R.L. FZ-LLC

5 Remaining Life Assessment How much life is left in your steam generator? Return On Investment Damage Mechanisms Fatigue Creep Thermal Shock Fireside Corrosion FAC Chemical Attack Poor Design / Build Operation and Maintenance of old plants can be a challenging. Key questions are: What is the right level of maintenance expenditure / investment? How much longer can your steam generator run profitably? The answers to these questions require careful analysis of the design and operating O&M history, with projection of the future operating regime. Operating Excursions Assessing the damage The damage mechanisms affecting your boiler s service life are varied and many. The assessment methods are just as numerous. We analyse historical records of failures, operating data and excursion records, and talk to plant staff to understand the challenges that the plant will face in the future. The scope of service can include pressure and non-pressure parts, such as: Superheaters and Reheaters Evaporators and Waterwall Economisers Firebox and Burners Gas-Air Preheaters Air Fans Other Auxiliary Components () S.A.R.L. FZ-LLC

6 Third Party Consulting Independent Advice Typical Scenarios Tetra focusses its expertise on key areas of the steamcycle: Steam Generators Power Piping Steam Turbines Condensers Desalination Plant The most important factor in making real-world decisions for high-value assets is the availability of unbiased advice. When parties have a financial interest in the outcome, independent advice can be essential in finding the right answer among differing opinions. Using a Third Party Engineer can be useful throughout the plant s operating life, including: Design Specification Fabrication Construction / Assembly Commissioning Operation Removal From Service conventional thermal power plants for more than 25 years at client sites around Specialist Engineers has a long history providing engineering advice in the Power Sector. We are regularly called to assist in cases of: Warranty Claims Legal Disputes Due Diligence Assessments Quality Systems Investigation () S.A.R.L. FZ-LLC

7 Inspection & Field Services Inspection Your HRSG or boiler should be inspected at every planned outage. We offer: Optimised NDE Let Tetra help plan your boiler outage to assure that NDE activities are performed on the high-risk areas. Riskbased inspection plans save you money by reducing unneeded work-scope Visual inspections of gas-path, drums, vessels & externals Remote Visual Inspection of internals by videoscope / borescope Full NDE Inspection Capability Risk-based Inspection Plans for in-house NDE teams Don t wait until you have failures to start checking for damage! Warranty & Baseline Inspection conventional thermal power plants for more than 25 years at client sites around Engineering Support Of equal importance to plant integrity is interpreting your inspection results. Results from inspections can be fed into analyses: Remaining Life Assessments Fitness For Service Stress Analysis Boiler Performance Evaluation Water Chemistry Audits Layup & Preservation Review Has your HRSG or boiler been thoroughly checked before handover or end of warranty? Have Tetra perform a Warranty Inspection. A full report will be provided with all the details needed to support your discussions with the OEM. () S.A.R.L. FZ-LLC

8 Boiler Preservation Engineering Preserve and Protect Let Tetra design and engineer a preservation system that fits your budget and operating constraints while assuring optimal protection of your steam cycle components. Scope of Preservation (Plant, Boiler, Turbine etc...) Requirement for Return to Service Local environnemental Regulations System Materials Plant Operating Chemistry From Strategy to Specification OEM or industry guidelines for Boiler or HRSG waterside and gas-side preservation (or layup ) are useful but typically don t go further than general advice on the different available options (wet vs. dry etc.). The difficulty is in moving from the general to the specific for a given plant. Tetra can define viable preservation options and help you choose an optimal strategy from among these that fits your budget and operational constraints. If desired, Tetra will then develop a detailed engineering specification for your preservation system. conventional thermal power plants for more than 25 years at client sites around Age and Condition of Unit Procurement and Installation Procurement and installation of the preservation equipment is typically done by plant staff supported by local contractors. Tetra can provide professional technical support to assure that the project meets budget and performance goals. Our field staff has extensive experience with installation of process modifications to thermal plant steam cycles. () S.A.R.L. FZ-LLC

9 Why choose? Benefit by working with highly-qualified consulting engineers Independent and Objective Service Areas Field Inspections Failure Analyses Fitness-for Service Life Assessments 3rd Party Experts Steam Cycle Training Unlike OEM s and some other boiler inspection houses, Tetra does not sell hardware or repair services We do not have formal partnerships with repair or hardware suppliers Recommendations to a client concerning using other suppliers for work are limited to providing a list of known contacts Reactive and Flexible Our team-based approach and relatively smaller size means we are much more responsive than larger OEM and consultant engineering organizations Solutions are always adapted individually to suit your project no one-sizefits-all prepackaged solutions Experienced Founded in 1989 by three mechanical engineers, all with advanced engineering degrees and experience acquired at a major OEM in nuclear and fossil power plant engineering Founders still actively working in the company Full focus on conventional radiant and CCGT plant steam cycle over the last 20 years Highly-skilled staff, all degreed engineers from major universities Present Worldwide an office founded in 1991, Dubai office in Projects including field work in over 60 countries to date means familiarity with the variety of plant configurations and regulatory constraints found in different markets Multilingual staff (English, French, German, Polish, Spanish, Swedish, Arabic) Technically Capable Capability to provide in-depth analysis at the same level as OEM s in nearly all areas of steam cycle engineering Field inspection is an integral part of our offering, there is continuous feedback between field experience and back-office analysis Field work such as inspections conducted by engineers () S.A.R.L. FZ-LLC

10 PipeVue 2.0 Knowledge Management System Covered Piping System Maintenance Management Who is concerned? New Mandatory ASME B31.1 requirement states that documentation of maintenance of pipe supports for piping operating within the creep regime as well as shall be maintained and easily accessible. These new requirements are of high importance to Plant Owners and Operators. New requirements demands better inspection control ASME B31.1 places practice requirements on Operators for the maintenance of their Covered Piping Systems (CPSs). Condition Assessments are required on a regular basis, associated with good record-keeping for traceability. Over time this generates large volumes of documentation and inspection history data, therefore a coherent solution to knowledge management is needed. PipeVue 2.0 was developed by to store and organize large amounts of inspection data in one networkbased solution, easy accessible for both plant operators as well as engineers planning yearly inspections. Functionalities PipeVue 2.0 has three modules covering: pipe hangers & supports flow-accelerated corrosion inspection data; and Grade 91 weld and thermal shock inspection data The software stores hanger/support setting information (hot/cold), inspection notes, photos, NDT data and associated design documentation (PDF drawings & manuals) in a simple and categorized manner, with 3D-visualization of all components. The user can add new data and save to a networked database, where it will be instantly accessible for other users. The software is provided on a yearly license basis. Engineering support from Tetra is available as an option, creating an instant channel between plant personnel and third party engineers. () S.A.R.L. FZ-LLC

11 Impact of GT Upgrade on HRSG Life & Performance Remember the HRSG! GT upgrades will affect the HRSG and steam cycle, therefore assessing post-upgrade thermal performance and the effects on component life is essential to assuring that the full impact of changed GT characteristics on a CCGT plant are considered. A competitive power market is pushing many combined cycle plant operators to invest in technology that increases plant efficiency and reliability. An upgrade of an existing Gas Turbine (GT) is one avenue for achieving this goal. Upgrades that increase GT output, improve efficiency, availability, reduce start-up times and lower emissions are on offer from the major GT vendors. These upgrades typically lead to changes in the exhaust gas temperature and mass flow, hence the effects on the HRSG performance and component life need to be carefully evaluated. offers an engineering evaluation package that considers the full impact that GT upgrades will have on your HRSG and steam plant: Thermal Process Simulations: Simulations are performed using advanced boiler software in order to evaluate changes in steam cycle process conditions. Results are used as input to subsequent mechanical design validations and component life assessments. Effects on HRSG Component Life: Changes in fluid pressure and temperature can lead to reduced creep life of hot-end components (SH/RH) and increased risk of thermal fatigue failures in thick-walled components such as steam drums. GT Exhaust Gas Flow Simulations: Computational Fluid Dynamics (CFD) can be used to evaluate the impact of changes in GT exhaust gas conditions on downstream pressure parts. Design Code Check: A review of original design is conducted to verify continuing design code compliance after changes in process conditions Effects on Duct Burner Performance: Changes in the GT exhaust characteristics can lead to operating parameters that are outside the original Duct Burner design envelope. The impact of these changes is assessed using results from thermal process and CFD simulations. Controls, Valves & Pumps: Changed in process conditions may require modifications to existing steam cycle piping, valve, drain and pump capacities as well as to the operation of control loops. These modifications are identified for action by the plant operating staff. () S.A.R.L. FZ-LLC

12 Efficiency Audit of the Steam Cycle A Practical Approach The ultimate goal is to provide a comprehensive review with real recommendations for how to improve efficiency and avoid unnecessary costly losses. provides a broad, full-scope service for the modelling and evaluation of the overall efficiency of all types of power boilers and HRSGs. Along with several advanced software tools, Tetra brings its 25+ years of experience to locate aspects of efficiency that can be improved - reducing losses and increasing profitability. Our experienced engineers spend a total 3-5 days on site collecting data and information from plant staff to ensure that all aspects are considered. Analysis of plant losses will be based on ASME PTC 4.4 guaranteeing a reliable industry standard approach. A full account of plant losses will be collected and calculated leading to efficiency improving recommendations. Recent Tetra experience has shown that even a small increase in efficiency can lead to good financial gains for plants. The state-of-the-art Power Plant Simulator and Designer (PPSD) software package developed by KED software is a powerful tool used for this work. This sophisticated tool allows accurate simulation of both steady-state and dynamic behaviour with gas and steam/water flow, pressure and temperature profiles calculated down to the component level. A wide range of plant characteristics and operational scenarios are evaluated including: Calculating overall steam cycle efficiency (heat balance) Assessing efficiency impact of changes to operating conditions and equipment Analysis of past operation from historic and current DCS data Investigation of electrical power losses due to motor operating inefficiencies A census of plant losses including all major sources of inefficiency () S.A.R.L. FZ-LLC

13 Boiler & HRSG Water Chemistry Audit A Practical Approach The objective is not to turn the power plant into a chemistry research lab, but to help the operators to assure reliable and cost-effective control of water chemistry in the boiler, HRSG and plant water/steam cycle. The Water Chemistry Audit is designed to evaluate current water chemistry control practice at a power plant site with a focus on the in-boiler and condensate steam/water chemistry. The goal is to identify areas of improvement that might reduce corrosion and degradation in water- and steam-side surfaces. does not sell water treatment chemicals and therefore our recommendations are not biased to a particular commercial water treatment solution. Our engineers are experienced not only in plant chemistry but are also experts in boiler design, thermohydraulic processes and in the range of degradation mechanisms that can affect pressure part integrity. They will visit the site to perform a walk-down and gather information for the following activities: Specification Review: The current plant chemistry limits are reviewed as well as the water treatment programs employed. The plant practices are compared with OEM recommendations, warrantee requirements, industry norms, and Tetra experience. Operating Performance: The actual water chemistry performance, quantified from PI data or lab sample data, is compared with specification limits and water treatment vendor contractual requirements. Determination of Water/Steam Quality: An assessment is made of how plant personnel can ascertain that key water treatment parameters are within the desired limits given the existing equipment and procedures. Sampling points, sampling frequency, equipment type and calibration are reviewed. Makeup Water Systems: Makeup water quality and its impact on process water chemistry are reviewed. Plant Degradation: Past equipment failures that could be influenced by boiler water chemistry are identified. Layup Procedures and Requirements. Plant layup procedures and decision processes are reviewed. The deliverable is a report that provides a comprehensive assessment of the state of the water chemistry program at the plant in question along with clear guidance on potential improvements. () S.A.R.L. FZ-LLC