26. Meeting in Swindon

Ageing of old power plants - Henk Wels, NRG
If after say 25 years of operation the forced unavailability of conventional power plant components changes systematically, it would be wise to take these components into account when considering life extension activities. Using the NERC data, VGB data and data from the client, generic ageing in components was investigated. The overall good news of the analysis is that given maintenance is carried out in a normal way, on the average forced unavailability will not rise. However, there is a limited number of components where forced unavailability will rise, especially if the construction is troublesome already and maintenance budgets are reduced (minimal repair). There is a large spread in the data that will be caused by differences in construction, management and market conditions, pleading for condition based maintenance and causing a roller coaster curve instead of a typical bathtub curve.

New Challenges facing ESB -
Vincent Ryan, Manager, Plant Performance, Power Generation, ESB
Market opening has not brought the expected competition in the Republic of Ireland. As a result Emergency Generation of up to 300 MW is planned. Plant which ESB expected to close when market opened is now expected to operate for the next 7 years and possible longer, with flexibility of operation a key requirement. Issues now being addressed include identification of the real cost of 2-shifting in order to make informed decisions re operation at minimum load versus shut-down and start up and the introduction of a benchmarking programme as a means of closing gap to best practice.

Markov Decision models for maintenance optimisation
By Henk Wels - NRG
Markov models are well known contrary to Markov Decision models. Based on simple spreadsheet models, Markov Decision was applied to electric motors in a coal fired plant, the bearings of which were causing trouble. By defining system states (1 = as good as new, 2 = light degradation, 3 = heavy degradation, 4 = failure), it was possible to draw up a Markov model using Monte Carlo modeling and @RISK in order to decide on optimum preventive replacement, condition based replacement and inspections for the bearings. Input data were derived from maintenance records. The use of RISKOPTIMIZER allowed discarding constant inspection intervals and optimising directly for the optimum times of inspections and/or strategy as a function of time. It is intended to apply the Markov models also to boiler components and gasturbine blades.

Plant Condition Assessment for Asset Management -
By Lynton Mogridge, Innogy
Innogy have developed a methodology called PLUS to collect data that can be used to:
Identify residual plant life;
Evaluate the effect that maintenance, refurbishment and operating regime are having on residual plant life;
Evaluate engineering costs for plant;

And is used to support:
Asset management;
Evaluation of generating costs.

The basis of the process involves scoring the condition of a plant on a scale of 0 to 10. Scoring is carried at a subsystem level (there being about 50 sub-systems on a unit). Data also collected for each sub-system includes:

Operating hours & Starts;
Plant condition assessment;
Rate of degradation;
Maintenance costs to achieve design degradation rate;
Current maintenance costs;
Cost to reinstate/refurbish.

Use is made of "structured application of judgement", with station and central engineering department engineers working together, to estimate data using a structured framework to ensure consistency.

The data can then be summated to give information on a unit, plant area, station or portfolio basis.

This data has significantly improved Innogy’s understanding of how plant costs and reliability change with plant condition and methods of managing plant end of life. Further techniques are being developed to exploit this knowledge especially in plant asset management.

Estimating the Hidden Costs of Two-Shifting - Alan Joslin, Innogy Generation Performance Engineer
Knowledge of the real cost of a two-shifting cycle is essential for determining optimum operating regimes. Some costs are obvious, notable that of the energy used during the period between de-synchronising and synchronising. However, some are less obvious. The presentation categories and describes the major items of these "hidden" losses, and describes methods that can be used to evaluate them.

The main categories of hidden costs are fuel, maintenance and engineering deficit, and reliability costs. For fuel, the hidden elements are changes in stored energy, both during de-loading prior to de-synchronising and after synchronising, and degradation of thermal performance of the unit as a consequence of the start. The cost of the former can be estimated based on results of extensive CEGB testing. For the latter, Innogy estimate the cost based on the long term correlation of operating regime and TEMP factor, a measure of thermal performance.

Maintenance and engineering deficit (plant life) costs can be estimated by considering the impact of changes in operating regime on maintenance budgets and investment needs. Where the plant has an established history and experienced staff, this is best done by those staff controlling the work and budgets. If not, extrapolations from similar plant and use of manufacturers’ guidance can be used.

Reliability costs clearly vary with market conditions. Innogy have methodologies for analysing the correlation between plant operating regime, plant condition, and breakdown rate. From this, the mean changes in breakdown rates per start can be determined. When combined with the market situation, costs can be estimated.

When the hidden costs of starts are taken into account, the total cost is frequently found to be several times the cost determined by consideration of the basic energy costs alone.

Inspection Management - A Specialist Inspection Business
By Roger Lyon, Corporate Engineer, Inspection Management, Innogy Plc
Historically, Innogy and its preceding companies have always been inward looking and have concentrated on servicing its own power plant, primarily situated in the UK but later the portfolio included overseas sites; money for research and development was readily available and staff numbers were high. Nowadays, staff numbers have been significantly reduced, concentrating on core skills; research and development has to have a funding customer; but equipment and technology has advanced considerably, thus providing high integrity inspections with improved accuracy and repeatability.

The product and service drivers that have lead to where we are now, in terms of techniques and equipment, include quality, efficiency, reliability, accuracy, repeatability and cost. We are confident that our new NDE Specialist Inspection Business will be successful because of: Capital Investment - most companies cannot afford to purchase modern equipment; Competency Development - Retention of essential staff and the employment of key contractors; Advanced Technology - our research and development programme supports the highest advancements in NDE; Customer Focus - high turnover, small profits - Validation - we have real components with real defects to validate our methods and techniques.

Some of our specialist inspection techniques include: End Ring Inspection - for the inspection of generator retaining rings in situ; Time of Flight Diffraction (TOFD) - for accurate positioning and sizing; Phased Array Inspection - for the inspection of non-uniform geometries, providing accurate, position, size and directional information; Thermographic Inspection - for detection of temperature variations; EMAT Technology - for inspections without surface preparation; Oxide Thickness Measurement - for profiling the condition of the boiler; LP Rotor Disc and Rotor Bore inspection - using TOFD and Eddycurrents.

Conclusion - NDE Inspections have advanced considerably over the past 15 years and although the research, development and equipment are very expensive, Service Inspection Companies can provide these services at competitive rates.

Remark: All items are strictly to be considered from a technical point of view only with regard to the support of the strategic work of EURELECTRIC.