Some Intro to Gas Turbine Maintenance Philosophy

For industrial application, there are two distinct groups of gas turbines which require greatly different approaches of maintenance. They are the aircraft derivatives and the heavy duty industrial.

Aircraft derivative units, as the name suggest, are derived from turbines designed for aircraft use. Hence their maintenance, to a great extent, followed the practices of the aircraft industry.

Aircraft derivative users have three primary methods of maintenance:

1. Remove gas generators on a regular basis as determined by the manufacturer and their experience. Then send them back to the manufacturer’s facility for overhaul.
2. Operate a repair facility of their own for most of the routine overhaul procedures. For certain procedures which they were unable to perform, they could still be contracted to the Original Equipment Manufacturer (OEM) on a component basis.
3. Enter into a comprehensive service contract with the OEM that would included the first method, as well as periodic servicing and non-intrusive inspection activities on site.

There are advantages and disadvantages to each one of these approaches. Clearly if you only operate a few turbines and they are of different types, the second approach would not be very attractive. If however, you operate many identical units, the savings of the second approach could easily cut your maintenance budget in half.

The approach for heavy duty industrial turbines as mentioned before, is quite different. Heavy duty industrial turbines are more frequently installed in facilities which have some on-site maintenance forces and in many cases extensive engineering staffs.

There are four approaches to heavy duty industrial turbine maintenance, beginning with the approach requiring the least owner involvement:

1. A service contract with the OEM for all maintenance, including routine inspections and overhauls.
2. In-house maintenance supervision with engineering and service support from the OEM and a contract maintenance crew to perform the work.
3. In-house maintenance supervision and repair crew, with engineering from a third party (either a consultant or another part of the user’s company) and assistance from the OEM’s service engineering.
4. A multidiscipline team approach by the user, drawing from internal company resources (mechanical, metallurgical, instrumentation, maintenance planning and supervision, etc.) with minimal assistance by the OEM.

As was the case for the aircraft derivative engines, each approach has certain advantages and disadvantages. The approach taken is highly dependent upon the specific circumstances. As a general rule, the more units operated and the more time in operation, the further down the list the user progresses. Although there are still users who find an OEM maintenance contract attractive, as they gain more experience, users tend to seek more direct involvement in their gas turbine maintenance.

In deciding which approach the user should take, the objective of planned maintenance should be clearly defined in mind:

1. Minimize capital investment.
2. Maximize turbine reliability and availability.
3. Minimize operating and maintenance costs.
4. Maintain original design performance.
5. Incorporate appropriate product design improvements.

All should be prioritized accordingly based on relative importance to the business.

-Summarized from Major Process Equipment Maintenance and Repair, Heinz Bloch, page 442- 447

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