Specialist maintenance companies provide comprehensive solutions

Paul Boughton
As downtime costs money, maintenance strategies have to be carefully planned and involve experienced specialists. Eugene McCarthy reports.

Rotork Site Services in Australia has completed the comprehensive workshop service of 28 Rotork IQ valve actuators within the critical four-week timescale dictated by a power station shutdown.

The actuators have been installed at the 487 MW Pelican Point combined cycle gas turbine (CCGT) power station near Adelaide in South Australia for seven years. On-site facilities to carry out the work were limited, so a decision was made to remove the actuators and transport them to Rotork's own fully equipped workshops at Ballarat, some 600 km from the power station.

Return, re-fit, re-commission

Rotork took complete control of the project, hiring a truck to transport the actuators rather than relying on a third-party when the precise timing of activities would not be known. The project was divided into four, week-long portions, involving removal, workshop service, return and refit and re-commission.

The actuators required only relatively minor repairs, mainly caused by environmental exposure. In all cases, only genuine Rotork parts were used, enabling the actuators to be tested and returned in as-new condition. All the work was completed within the strict timescale allowed, ensuring that Rotork Site Services' performance would not delay the power station's plans for re-starting.

MTU Maintenance Berlin-Brandenburg, for example, says it is renowned for excellent-value gas turbine maintenance. For a quarter of a century, the company has been a reliable partner for many customers in the power generation and other sectors. MTU says it offers a compelling choice of customised service packages and aims to repair rather than replace.

The company is one of the leading maintenance providers for General Electric's LM series of aeroderivative industrial gas turbines (IGTs) worldwide. MTU's maintenance experts have built a background of more than 25 years of experience in this market segment. The Ludwigsfelde location in Germany is the centre of excellence for the maintenance, repair and overhaul of industrial gas turbines within MTU's network of companies.

MTU is a licensed level IV depot for General Electric LM2500, LM2500Plus, LM5000 and LM6000 gas turbines. Its worldwide customer base is as varied as the range of applications for the products, and spans the gamut from power generation companies to marine users and operators of oil rigs and compressor stations, on-shore and off-shore.

Design and development

When it comes to the maintenance of industrial gas turbines, customers benefit from MTU Maintenance's worldwide service network and MTU's expertise in the design, development, production and repair of the aircraft engines from which they are derived.

Whether as part of a long-term service agreement or as a stand-alone mission, MTU offers the following on-site services: availability - 24 hours/365 days, 24-hours hotline for trouble shooting, local field service representatives in North America, South America and Asia-Pacific; inspections - periodic inspections and individual preventive maintenance concepts for reduced downtime; spare parts supply and management - complete range of GE LM-series spares available and rotable units and tooling available; vibration services - on-site trim balancing and vibration data analysis and laser alignment; combustor mapping and controls services - combustion and emission surveys, hardware upgrades/software updates, and controls services.

An extensive testing service covers proof of actual and true MW output, extensive combustor mapping capabilities and more.

Construction and decommissioning

Similarly, RWE Power International's specialist services cover every aspect of operations and maintenance, from construction and commissioning to eventual decommissioning. The company offers gas turbine services, risk assessment processes, power plant information systems, environmental management and power station maintenance management. It also provides plant rehabilitation, power generation training and asset development.

In terms of power plant operations and maintenance, RWE provides fully integrated power plant operations and maintenance services to optimise plant performance and generate higher profits. Its worldwide experience has been acquired on more than 45,000MW of power plant encompassing hard coal, lignite, gas, oil and nuclear power generation, cogeneration and renewables. Its technical support group (TSG) provides a broad spectrum of engineering services to the power industry and other heavy industries. The extensive workshop facilities include state-of-the-art machinery, which coupled with its long experience, enables TSG to offer a comprehensive, high quality service that includes: workshop services and support for plant refurbishment, including: overhaul, repair or modification of existing plant and machinery; manufacturing of new components, spare parts and assemblies; outage management and delivery; on-site machining; CNC and general machining; and gas turbine services.

In addition, RWE says that its plant rehabilitation engineers are specialists in evaluating and upgrading generation plants to prolong asset life and improve performance. They have experience in refurbishing power stations around the world and can devise and implement investment strategies that deliver enhanced asset value. In terms of training, the company says it can meet the staff training and development needs of power plant operators, using state-of-the-art learning approaches. It offers development programmes in all aspects of power generation and mining, whether on-site or at our training facilities in the UK and Germany.

Gas turbines

Turbine Services (TS) is a total provider to owners and operators of industrial gas turbines worldwide, with particular specialisation in the heavy-duty frame range of gas turbines designed by GE.

The company's products and services include: spare and replacement parts; component manufacture and repair; turbine blade repair and coatings; rotor repair and overhaul; complete gas turbine refurbishment; field maintenance and engineering services; condition monitoring and diagnostics; and training services.

In terms of spare parts, TS maintain a substantial computerised inventory for the GE type heavy-duty gas turbine. The parts inventory is continuously monitored to ensure that the majority of customers' spare parts requirements are satisfied ex-stock for both scheduled and unscheduled maintenance.

Repair services

The company's extensive range of repair services cover stationary and rotating parts, rotor overhauls and specialised services including coatings, metallurgical evaluation, special laser and machining operations. TS also offers a component exchange arrangement, giving customers the possibility to minimise their own inventories. This service is available for most capital spares parts.

Complete management and maintenance services required for scheduled maintenance, unscheduled breakdown maintenance - with access to the TS strategic spare parts stockholding and rotor club - part repairs, plant modifications, condition monitoring, diagnostic trending, fault finding, plant improvements, and inspection planning for an agreed duration are available.

TS works with customers to develop and implement the most cost-effective way of running gas turbines in the current market. This includes the option of recycled repaired combustion and hot gas path components, using the latest technology to extend maintenance periods and investigating peak firing possibilities.

So far TS has trained over 2000 engineers and employees, along the way devising specialist courses and comprehensive training programmes for management, maintenance and operation personnel.

Combined cycle plants

Operación y Mantenimiento Energy (O&M Energy), a 100 per cent subsidiary of Gas Natural Fenosa, offers professional services in the operation and maintenance of a wide range of power and industrial facilities. These include power generation plants - combined cycle plants, diesel plants, hydraulic and other renewable energy plants - cogeneration plants, water treatment plants, industrial facilities, gas turbines, and LNG plants.

O&M Energy can provide a variety of operation and maintenance services ranging from full operations and maintenance contract provision to discrete operation and maintenance activities. The company's services range from project development support through mobilisation services to operations and maintenance contracts from start-up of commercial operation, supporting the whole project life cycle (Fig.1).

Recent projects include the Hermasillo and Naco Nogales CCPPs in Mexico, the Sogama and Eneralco industrial power plants in Spain, the Rabigh thermal power plant in Saudi Arabia, and the La Joya hydroelectric power plant in Costa Rica.

Maintaining accessories

Tedeco is a specialist in the early and real-time detection of failure in propulsion and mechanical transmissions in the power generation and other industries.

Its products include real-time failure detectors for transmission and gas turbine engine gears and bearings, on-line lube system wear particle monitors, chip collectors and detectors, plus various sensing and gauging products.

A particular speciality is on-line debris monitoring, which Tedeco says is particularly important in the diagnosis of three major problems: spalling, bearing cage failure and skidding.

Spalling occurs as a result of sub-surface cracks in gear teeth or bearing rollers, balls or races which propagate just under the work hardened surfaces; where these microscopic cracks intersect the surface, flakes begin to form. The flakes are generated in very small quantities, early in the failure cycle. Failure to halt this process will eventually result in cracked ball, roller, cage or race and potential catastrophic failure.

Bearing cage failure results from overloaded bearings, misalignment, excessive heat, particulate contamination, or poorly toleranced components. Whatever the cause, small fractures result in bending, melting or cracking of the bearing cage, leading to generation of ferrous and non-ferrous debris. Early detection of these particles could prevent the bearing cage from catastrophic failure.

Skidding results from lightly loaded bearings or poorly toleranced bearing components where there is a type of sliding motion between the balls/rollers, raceway and cage. This can generate very fine, almost chalk-like, debris particles that grind away at the bearing element surfaces. Eventually, this grinding results in a loss of tolerance and eventually, warns the company, bearing seizure and subsequent catastrophic failure.

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