Plant operation databases improve system reliability

The advent of deregulation is being received with some trepidation, as well as with vision of opportunity. The common denominator for all in the industry is how the level of risk is assessed and quantified. Risk has various meanings and values depending upon who is making the assessment.

For insurers, risk is related to the relative frequency and severity of unanticipated events (losses). For project developers, risk is measured in terms of up-time and down-time, which becomes the required input for a pro forma evaluation of the expected profitability of a specific project. For equipment manufacturers, risk can be related to the cost and engineering effort associated with new technology development versus the potential level of margin, warranty and liquidated damages, as well as quality and reputation costs.

While the individual risks of the parties involved may vary, the key demands are to meet the budget, the schedule and for the power station to meet its design performance, durability, availability and reliability.

The increasingly competitive nature of both the industrial process and power generation markets has created an increased awareness of the impact that these factors have on plant profitability. To meet these requirements and to support the industry in the application and use of performance data as strategic business information, Strategic Power Systems Inc. (SPS) has developed ORAP (Operation Reliability Analysis Programme), a system for monitoring and reporting the reliability, availability, maintainability, and durability (RAMD) of turbomachinery plant equipment, including gas turbine (simple cycle and combined cycle), steam turbine plants, boilers, and balance of plant.

In order to reduce risks, particularly those of lenders and developers, the involvement of an independent consultant engineer could be very helpful. As an independent organization, the TÜV Süddeutschland Group with its more than 9500 employees and 60 branch offices world wide offers a comprehensive range of services spanning the entire power plant sector.

Reliability data management

The industry's focus on technology advancement for improved materials and coatings as well as advanced cooling techniques continues the drive for turbine systems with greater efficiency and higher output, at a lower first cost. Continuing requirements for the lowest achievable levels of NO_x and CO emissions, across varying loads, place an additional operating constraint on the design. Alternatives for the best available control technology include Dry Low NO_x, SCR (Selective Catalytic Reduction), as well as catalytic combustion system designs. The key requirement is that the technology must meet or exceed the durability and reliability levels of the current product offerings.

The risk associated with developing and introducing these advanced products would be acceptable if equipment capability, durability, and reliability is at worst constant, relative to the levels achievable by today's machine. So there appears to be a mutual goal across the industry, which can be characterized as a desire to understand and mitigate risk.

A substantial requirement to reach this common goal is a very detailed knowledge of the equipment operation data with a focus on product reliability. However, RAMD data, accepted to be a key issue to improve reliability, are not suitable or specific enough to characterize today's turbomachinery usage or capability. Simply put, the measures of reliability, availability, and maintainability, as defined by IEEE Standard 762 and ISO 3977, do not reflect the varying levels of operating demand which a given unit or plant must fulfil.

The measures are calculated and presented as indicators of time or capacity, and do not reflect actual performance against a given level of demand. Nor were the measures intended to reflect demand considerations. However, there is no answer to the question of what the data can tell us about the capability of the turbomachinery relative to its economic mission.

ORAP

Today, gas turbine plants have a broad range of operating missions: peaking; cycling; baseload; and continuous duty. Data available from ORAP, which can provide both the manufacturer and participating companies with a current and accurate perspective of power plant reliability for units in various MW ranges, applications, duty cycles, and plant configurations.

Major power generation equipment manufacturers, for example ABB Power Generation, ABB Kraftwerke, Siemens Power Generation, GE, GE Marine & Industrial, Westinghouse and United Technologies currently support the ORAP system, which means that this service funded by the manufacturers can be provided free of charge for many users and operators. At the moment, data of more than 1200 units with more than 10 000 unit years are stored in the SPS database.

It is clear that the ORAP data can be segmented into more classes of duty cycle. The information shows that a cycling mode of service is more severe relative to the effect on availability. And, in fact, there is even a difference between a baseload utility and a continuous duty cogenerator.

It reflects the contribution made to total plant unavailability as a percentage. Further breakdown by component is essential for a more precise understanding of what drives the levels of plant unavailability.

Reducing the effort

There is absolutely no doubt that in a competitive environment where resources are stretched, where reductions in staffing levels are occurring, where more contract labour is utilized to direct and perform major maintenance, that site reporting is a significant burden. The task of reporting operating data, recording and classifying forced outages and providing sufficient detail on a scheduled maintenance activity is a constraint which is normally minimized in the data recording and reporting process.

The effect of under-reporting is heightened by the fact that the 'rules of reporting' are not consistent from plant to plant. Readiness to serve rules and curtailment periods provide opportunity for maintenance to be performed at some plants when the unit is known to be 'not required' for some period of time. The elapsed time associated with these activities is typically not recorded as outage time.

A legitimate rationalization and belief is that if the unit can be restored to a state of readiness in a certain acceptable period of time, if maintenance is performed when the unit is curtailed and will not be called upon to serve, that the maintenance should not be charged against the unit as unavailable time. The logic is, 'if it was not needed, why should the unit be penalized'. But these 'rules' do not apply across all plants, making the standard data recording processes and measurements more susceptible to individual interpretation.

There is no doubt that these activities are meant to ensure the operational readiness of a unit, and in fact are approaches for optimizing the performance of maintenance. However, the issue is that the details associated with the maintenance are typically not recorded simply because the activities are perceived to be outside the 'reporting rules' of unit unavailability. This process will make the availability and reliability values artificially higher, and in fact support the perspective that the standard measures need to be more directly related to unit demand. It is time to make the rules of reporting more uniform and improve the process.

In 1992, the Electric Power Research Institute (EPRI) initiated a research programme focused on the 'durability surveillance' of the latest state-of-the-art advanced gas turbine plant. The intent of this programme is to monitor, assess, and validate the achieved levels of operational RAMD against predefined expectations.

A valued-added out-growth of this programme has been derived through the manner in which the necessary data are obtained for support of the various durability evaluations. This progress has been achieved by SPS through the application of current information technology and data acquisition capability in three specific areas:

This successful demonstration project has lead SPS to continue the development of a product called ORAP-Link. The value and usefulness of ORAP-Link is achieved through a reassessment of how the 'transformed information' can be made available and presented to enhance the management capabilities of plant personnel.

The foundation for any data collection process is centred on the equipment breakdown organization of codes which plant personnel may use for event categorization. EPRI has contracted SPS to develop and implement a more uniform equipment coding structure to standardize and facilitate event recording and reporting from plant personnel. The coding structure, which has been implemented in ORAP, was designed to be flexible, allowing for additional 'growth' as advanced technologies are introduced to the market.

The coding structure design provides a uniform basis for categorizing the outage and maintenance events. The primary objective is to assist the plant in accurately attributing frequency of events, event duration, and corrective actions to specific components in the plant.

The standard coding structure allows for a cross-reference between manufacturers and turbine models.

The organization of the coding system is as follows: plant; unit; major system; system; component group; component.

The KKS (power plant classification system) could also be implemented in Europe. Both the EPRI system and KKS provide a structure which has been implemented in ORAP, and which allows information to be recorded and collected from the bottom-up.

The ORAP information system then converts the data into RAM statistics such as: detailed system and component outage factors; failure rates; starting unreliability; service factors; time to repair; and other outage factor information.

Additionally, ORAP provides outage description details, outage causes, failure modes, and corrective actions taken. This information provides the basis for assessing plant, system, and component RAM performance, as well as developing values to assess RAM growth.

It should be noted that the data reported from various utility and cogenerator participants are reviewed for accuracy, verification, and then entered into the database. The information is not modified by SPS unless the participating customer concurs and accepts a recommended change. This ensures that ORAP data reflect the specific operational, failure, and maintenance history for each machine in the database, and therefore the availability and reliability performance measurements are valid indicators of unit experience and capability.

Outlook

It is clear that the existing process for developing an understanding of current operating and maintenance costs is deficient. Primarily, it is deficient because there is no common methodology for measuring O&M cost (on a $/kWh basis) across varying plant arrangements and duty cycles. This issue is clearly seen by reviewing the most current Federal Energy Regulatory Commission (FERC) data, which is intended to be the 'uniform' O&M data reporting vehicle.

The FERC data shown in Figure 6 is a scatter of almost meaningless plant performance data which has limited use in planning and for comparative analyses. More importantly, the data constrains the ability of the user to establish realistic and meaningful expectations for O&M cost values across plant arrangement and duty cycle. In a constantly evolving and dynamic market place, the ability to understand and compare varying levels of O&M cost is essential; FERC data reporting requirements do not obtain sufficient detail to support these important assessments.

The market is becoming intensely competitive, and it is important to be able to identify and understand the nature and constituent elements of O&M costs. It is important to identify and understand the primary contributors to the cost levels which impact profitability, as well as the constituent elements which may be controlled and optimised by plant management. Additionally, it is clear that the inability to compare like operating plants on a more uniform O&M basis is a serious constraint. The industry needs to better understand what drives plant profitability. A measurement based solely on $/kWh is not an adequate reference.

It is time to create a standard. EPRI has undertaken a study of O&M costs, and has contracted with SPS to focus on the processes inherent in operating and maintaining a power plant.

The EPRI study is examining the fixed costs and the variable costs associated with the people processes and the non-people processes. Then, in the context of the plant configuration, mission, and size, some standards can be developed.