A systems approach for maintenance and renewal efficiency

A systems approach for maintenance and renewal efficiency

Facing a competitive environment production utilities are forced to rethink their maintenance strategies. Since the deregulation of the Swedish electrical market in 1996 energy sales have become a competitive market, while distribution and transmission became natural monopolies. For electric production companies the income is a result of the prices for electricity set by supply and demand. The hourly margin cost sets the price for the whole market. Before the change the

tariff was essentially the sum of cost of utilities and a reasonable profit: Tariff= Cost + Profit. Under the new regulation the tariff is determined independently of the cost of utilities. Hence, the profit is what is left when utilities costs are subtracted: Profit=Tariff−Costs.

A utilities earnings is the difference between incomes andcosts, the incomes can be increased by selling more power orby raising prices. To sell more power new investments must be made, either by purchasing other utilities or by building more power production facilities. But even if this approach is adopted the new investments must be maintained as effectively as possible. To increase the price of electricity is beyond the control of a utility. This means that a utility must

be as cost effective as possible to survive on a deregulated power market.

Cost effectiveness means minimizing costs and in the same time still live up to the demand of reliability from costumers and regulatory. In this paper we divide costs into cost of failure, cost of preventive maintenance and capital costs.

To reduce costs by making new investments to reduce capital costs. A manager has to face the fact that he has to manage the assets he is responsible for; he can make new investments just to meet the d of today. The question is what will happen in a long-term perspective of e.g. 25 years? What will the be and what condition will the technical system be in?

Asset management is the ability to model and compare

operational, maintenance and capital options with the goal, to find the overall most cost effective solu provide the required capability over time. Asset management is how to exploit the asset most profitab Maintenance in general consists of preventive and corrective maintenance. Preventive maintenance is at planned intervals, while corrective maintenance is carried out at the time of equipment failure.

Three approaches to maintenance are well established at present :

Time Based Maintenance (TBM) Condition Based Maintenance (CBM)

Reliability Centred Maintenance (RCM)

Every manager’s intention is to run the equipment as much as possible without costly breakdowns. T way to increase earning in a short-term perspective is to cut down on maintenance and postpone rene Because of the long operative lifetime of many components, often 50 to 100 years, and the inherent re such an approach will in most cases be successful. However, in a long-term perspective this might not effective. It is also difficult.

However, neither of these maintenance approaches alone can be used as decision-making tools for a m when making decisions about long-term asset management. Aspects like short-term and long-term co condition and risk can’t be dealt with using these approaches. As stated earlier a manager must minim present value of the costs for failures, preventive maintenance and capital costs. When managing asse operative lifetime we propose that maintenance management on technical systems are divided this int condition, and total costs.

This interpretation regards only physical assets and does not include issues like organization, operatio etc.What we want to point out with out definition of maintenance management is that in order to beco both long and short term effects of different maintenance strategies it is not enough to cover one or tw parts, all three must be included in an analysis. Today there is no general methodology that can cope complex issue. In this work a case study based evaluation of a methodology.

TBM is based on preventive maintenance and is carried out at regular time intervals suggested by the manufacturer. CBM is a method that tries to find the most efficient intervals between preventive main checks and measures. This method requires additional equipment to monitor the condition. RCM focu on the physical assets of the company and the functions they fulfil. It considers how assets could fail t their required function and what decisions must be taken when any reduction in performance takes pla method seeks to establish failure modes and the consequences of failure .

set up to handle this complex issues is carried out. The methodology was applied on a feed water pum Forsmark nuclear power plant. The object of this study is to examine pros and cons and use the result

the methodology. Detail vs. scope. When working with the proposed methodology one important issu is the approach for the study. In order for a study to be possible to carry out,a system can’t be divided

components, e.g. nuts and bolts. On the other hand, it is also very difficult to use too large systems an components. The idea of this methodology is to make a top to bottom analysis and divide a large syste components. Large systems can be e.g.generators, section of distribution or transmission grids,refiner transformers etc. These large systems consist of components selected by experts that together represen condition of the system. This means that in this study we call the lowest level where we collect data

METHOD

In this study the methodology has been applied to feed water pump system at Forsmark nuclear plant. This system was chosen because of three aspects: importance for production, access to data and system construction. These factors are

described in greater detail below.

System construction

The feedwater pumps are built with relatively few inputs and it is relatively easy to measure different values. Also, the three pumps together formed the system we applied the methodology on. Since only two pumps are needed in order for the system to function it was also possible to test the methodology on a system with redundancy

Many technical systems, the production, distribution and power industry often have redundant systems, so in order to make this validation of the methodology a fairly simple system analysis will show strengths and weaknesses.

The highest level of system consists of three feedwater pumps. Each one of them is divided into four subsystems,centrifugal pump, motor, oil system and gearbox. These four subsystems are then divided into a number of components. In this study we choose only to use the components representing the centrifugal pump. These are, oil pressure, axial bearing oil pressure, axial bearings 1 and 2 temperature, radial bearings 1 and 2 temperature and axial bearing 1 and 2 cooling water temperature. The maintenance personnel at Forsmark nuclear plant have chosen these components.

RESULT

The results from this study consist of a presentation of each part in the asset management methodology, risk, condition,and costs. These results are then combined and presented in a wider context in an effort to make a systems approach on maintenance and renewals strategies.