Cutting the costs of valve maintenance

Cutting the costs of valve maintenance – how to make a big difference

Kovan, Dick

Maintenance programmes have always concentrated on reliability and safety with costs playing a minor role. Now costs are also a major part of the equation. To meet this challenge,

Siemens / KWU believes it is best to take big steps. Using its extensive world-wide experience and know-how in this field, it has developed an integrated valve maintenance concept aimed at reducing costs and plant down-time.

In this era of market liberalisation and growing competition, operators are looking to reduce costs with maintenance activities one of the main focuses. As Germany’s largest services provider in maintenance management, Siemens has put significant effort into optimising maintenance programmes by developing various technologies, methodologies and other tools. This work has led to the development of an integral valve service concept which the company believes will be useful to many nuclear plants.

According to Peter Gerdes, plant manager of the Krummel station, outages had previously used some 80 subcontractors and and a total of 1000-1200 people to carry out some 3000 jobs which includes work on some of the 800 safety-related valves and 70-80 pumps. Maintenance activities involved opening, inspecting and renovating a large number of safety-related valves.

Under the earlier maintenance regime, the plant used to replace old valve parts with new spares from its stores. The old parts went to waste, which was a very costly solution.

When it became urgent to cut costs, Gerdes realised that they needed experienced help and asked Siemens to develop a new maintenance plan for the plant.

The plant has now moved to an exchange (rotation) maintenance regime in which parts removed from valves are decontaminated and reseated in a special valve maintenance shop set up at the plant. These parts are stored and rotated as spares in their turn.

And with Siemens now acting as general contractor for valve maintenance, the number of people, sub contractors and amount of unnecessary work has been greatly reduced providing significant cost savings.

MAINTENANCE SERVICE GOALS

Josef Sprehe, head of Siemens’ Centre of Competence and Maintenance, explained the measures implemented over the past few years to reduce maintenance costs. As the graph on the following page shows, since 1992, overall costs have dropped by nearly 50%, mostly due to a reduction in outsourcing costs.

Examples of where improvements were made include: pressure vessel – reduction of testing time by up to 60%; steam generators – performance improvement by increasing number of tubes inspected from 220 to 500; and valves – cost savings for maintenance up to 30%.

Important improvements were also achieved in other areas, eg managing outages to reduce critical path times, introducing methods of condition-oriented maintenance and using innovative tools, such as BFS++, a plant management software package which provides operation and maintenance guidance, stores information, creates work orders etc.

There are three levels of maintenance services:

Complete service – eg plant outages, maintenance during power operations; spare parts supply, consulting.

System services – eg reactor building, turbine building, nuclear operating systems, safety systems.

Platform services – eg valves maintenance, ISI, steam generators, condition-based maintenance, maintenance manuals.

As Sprehe noted, Siemens seeks to develop strategic partnerships with plants on maintenance packages. Valve maintenance, located in the lower level, is one area where the company has had particular success.

According to Georg Zanner, director of the valve department, the challenge is to cut costs without reducing quality. There is no generally applicable solution for all stations, as every one is different: each has different structures; uses different methodologies; and has different families of vendors. To make a real difference, Siemens believes that the best solution is to have one supplier of valve maintenance services who forms strategic partnerships with the operators and key vendors and is in a position to develop an optimised maintenance process.

The objective is to lower costs and the main ways employed are to:

Reduce scope of work.

Identify cost cutting potential.

Group maintenance activities.

This has led Siemens to develop the Integral Valve Concept to assure that valves are able and ready to fulfil their functions. The concept rests on three columns:

Design calculation. Calculation of required parameters: stem thrust, actuator torque and maximum load.

Design evaluation. Verification of relevant design functions, mechanics and features.

Monitoring and maintenance. Monitoring to ensure the functional behaviour of valves and actuators within allowable ranges during the lifetime. Early detection of changes and root cause analysis gives indications for condition-oriented maintenance.

The columns (shown at right) list supporting activities needed to fulfil these tasks and show the range of knowhow and management capability needed to provide an optimised service.

MONITORING & MAINTENANCE

The monitoring & maintenance column is divided into three parts.

At the top is a valve diagnosis and evaluation method used to determine how fit the valve is for its purpose. To accomplish this, Siemens has developed the ADAM software package and SIPLUG(R), an innovative method of active power measurement from the switch gear cabinet which allows the monitoring of all relevant functional parameters (see panel).

The second part involves analysing and optimising the maintenance process.

The third part is to manage the maintenance activities.

ADAM

The ADAM methodology tells you how near the operating limits you are which can help determine what margins remain, important information for applying a condition-oriented maintenance regime. The ADAM package includes a data base of master data with nominal and limit values and also provides: an evaluation of measured signals; a quantitative assessment of parameters (eg torque, thrust); and trending and statistical results (see diagram top far right).

ADAM provides a number of benefits: Reduces costs by:

– Prolonging periods between inspections. Reducing the number of preventive inspections required by knowing available margins.

– Reducing preventive replacement of parts.

– Optimising spare parts stocks.

Enables diagnosis during power operation.

Verifies ability for function.

Reduces possibility of mistakes during maintenance.

Reduces dose rates.

Process analysis

The first full plant process analysis Siemens undertook was at Krummel. The objectives of the analysis was to identify cost-cutting potential. It looked at the processes used at the plant, eg in organisation, planning, performance, documentation and follow-up of valve maintenance activities. It also examined how the contractors actually executed the work – how did they handle safety, how did they prepare for and carry out jobs, how were they treated, were they effective.

The analysis also included a cost evaluation of activities by monitoring costs and time schedule compliance on site; these were compared against ideal conditions in terms of expenditure.

Out of this came recommendations for a programme of long-term reductions of maintenance costs and also for how best to utilise maintenance knowhow.

Managing maintenance

Rather than managing everything itself, the operator can get many benefits from both putting together a maintenance package and appointing a general contractor on a fixed price basis to takes responsibility that work is done to time, to required quality, and at least cost.

The range of activities in an integrated program-me is shown in the figure below.

According to Zanner, it is vital to use staff and subcontractors effectively, especially during outages. In previous times, maintenance jobs had a fixed number of days to complete which inevitably led to much wasted waiting time. Work was often badly synchronised: for example, electrical and mechanical activities would not be co-ordinated, requiring extra set-ups when each group was scheduled.

It is also important to ensure that the right people are doing the right job, particularly to avoid the use of high cost people doing low-level jobs. One measure was the creation of a craftsmen pool.

The process analyses should identify important measures for cutting costs. For example, in many cases significant savings can be made by replacing low-cost items rather than removing and renovating them.

Siemens has now developed strong cooperative working relationships with many of the major valve mAnufacturers and contractors, including Sempell and KSB. Together it has been possible to optimise schedules and the use of resources, resulting in reduced costs, increased efficiency and working to time.

JOB OF GENERAL CONTRACTOR

Siemens’ first job as general contractor for valve maintenance was at Krummel. The company has since received contracts from Brunsbuttel, and, on a slightly different basis, Grohnde.

As to be expected, the company had to show that it could achieve good results. Generally, Siemens’ experience, plus its new valve maintenance concept and attractive integral package, have convinced the plant managers.

In the past, the valve manufacturers performed the maintenance on their equipment. There seemed to be no need to do things differently. Generally, too much was done, partly because there was more time, and charged for.

Gate valves provide a typical example. In the past inspecting and refurbishing these would be scheduled to last 2 weeks and always did. But, said Zanner, we saw that it took two days to open it, two more to examine /refurbish, and two days to close. This led to present 6-day schedule. Eventually the contractors have accepted that an independent look to see how to do things better was needed and, in the long term, good for them as well.

MAINTAINING KNOW-HOW

Another important element is maintaining know-how, an issue that the whole industry is facing as restructuring progresses and many experienced component vendors and service providers leave the market or consolidate. Furthermore, as the age profile of workers is relatively high, the industry is now losing many experienced staff through retirement.

Avoiding the potential loss of know-how has been a driver for Siemens to develop its valve maintenance concept. More generally, the company thinks it is vital that nuclear know-how is retained in major companies who can be expected to continue in the industry well into the future.

It also believes it makes sense in another way. Because it does not manufacture valves, it is not competition with the manufacturers. In addition Siemens has qualified most critical valves, so already has masses of test information and documentation.

FUTURE SCOPE

Finally, Siemens has found attitudes in Germany and other countries are continuing to change and are now quite positive to outsourcing this type of work (see panel). Although there are still some power plants whose approach to maintenance has not yet changed, in the long run, Siemens is certain that cost pressures will force them to.

Copyright Wilmington Publishing Ltd. Jan 2000

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