Table of Contents
4.3 Maintenance and overhaul in the "shop"
Overhaul and maintenance is finally a matter of confidence! Which car owner is aware of this. In former times it was possible depending from skill and expertise, to make some things oneself. A precautionary visual inspection was practicable because everything could be to a large extent open inspected. So the owner could assess the costs. Today in the era of the „total electronics“ and the incapsulated motors, this is largely gone. Therfore we can get the feeling to be total at the mercy of the shop owner or the OEM. The estimation of costs from the shop as far as the necessity of activities we can hardly check. The uncertainty rises. So comes the fatalism of a blow of fate. In the case of doubt we will have to accept the offer of the shop.
Why this trend should be spared for the owner of a gasturbine? Rather even more money, high tech and highest loaded components matter. However an advantage has the competent operator. Borescope inspections give in advance the chance of an assessment. Later in the repair shop the owner can look at the parts/components which are earmarked for evaluation and exchange. So it ‘s possible to comprehend the recommendations of the OEM to some degree. Also the assessment of the insurance company can be helpful. During the decision about repaired or new parts the competent operator can more certain estimate his risk and better take the responsibility for his decision. This should be benificial for the two-way trust of the partners, operator and shop.
The decision about exchange or repair of the components/parts depends in a high degree from the operation profile (Lit 4.3-1, "Ill. 2.2-4" and "Ill. 2.2-5"). A peak load operation has other priorities than a base load engine or an engine which produces primarily for heating respectively production processes. Thereby also the consequences of an early blackout must be considered what influences the acceptable repair costs.
As one has already made clear in the Chapter 0, overhaul and maintenance is finally a matter of confidence.
In this sense, the repair shop is “a place of confidence”. In order to acquire this confidence, technical requirements have to be fulfilled (Lit. 4.3-2). Naturally as much experience as possible should exist with gasturbines of our type. The required spare parts should be present in the store, or should be produced in time. The shop must also have knowledge of the necessary, specified repair technologies themselves or made available by the OEM or through competent subcontractors as well as experienced technical personnel, through whom the technologies in our gas turbine, especially the new ones, can be optimally implemented:
- welding and brazing techniques
- thermal spray process
- drilling procedures, electrochemical and with the help of laser
- cleaning processes
- non destructive test procedures
All work should be comprehensible in specified and accepted work scopes (root cards) and documented in inspecton reports. At first, there is the question as to which component must be exchanged at all? Is it worth repairing the parts, or is it more sensible to operate them until the next overhaul, even if the repair limit has been exceeded and one is forced to install new parts.
On the one hand, the operator has interest to install new or as good as new spare parts, on the other hand, one has also to pay attention to the costs and avoid ( "Ill. 4.3.1-1"), that the life of new parts cannot be used due to other components. Here, for one thing, the advice of the manufacturer is important. As this may possibly not be in the interest of the operator, an independent expert could be a help. Questions arise such as:
- Is there competent, trained personnel present?
- New part or repair?
- What kind of repair technology?
- Are there operation specific technological and /or design improvements possible?
- Alternative sources for components and services?
- Is there safe life of the parts exchanged?
On the one hand the consultation by the OEM and the insurance company is important. If those have no congruent interests an independent expert consultation can be helpful. The decision will be safer, the more information there is available, with regard to operation and failure mechanisms of the parts to be exchanged. That is, why it is particularly helpful when the damaged parts are available for a failure analysis, which can be handed to the operator on demand, exactly as one can demand at every garage.