PAL Engineering pioneered a method of servicing or changing variable inlet guide vanes (VIGV) on GE gas turbines with the compressor rotor in place!

As owners of GE gas turbines have learned, it sometimes becomes necessary to service the VIGV.  Because of the OEM design and assembly procedures, it is difficult to remove the lower-half VIGV while the compressor rotor remains in its casing.  Difficult, that is, but not impossible. 

For a while, the manufacturer claimed it could not be done without removing the rotor.  The mistake they made was that they didn’t ask Charlie Pond, founding partner of PAL Engineering, if he could do it another way.  Or perhaps they weren’t as interested as PAL is in helping clients save over $200,000 by avoiding a major turbine disassembly.

Fig. 1: UH bellmouth and compressor forward casing removed exposing IGV

On the MS7001, this task is hard to do.  On the MS6001 it is even more physically difficult.  The MS5001 was thought to be impossible.  As we at PAL Engineering are inclined to say, the impossible just takes a little longer and a bit more dexterity!

Yes, working space is tight.  Removing the inner bushings is a nasty job.  Grinding the stake marks on the dowels takes perseverance.  As you remove one inner block, the work space slightly improves, but the next block is farther away.  The bottom inner blocks are usually the most difficult to remove.  Yes, patience, skill and dexterity are all required.

Fig. 2: LH inner IGV blocks removed with compressor rotor in place

Working on the lower half presents the biggest challenge.  Below, a mechanic struggles with a rusted IGV pinion gear.

Fig. 3: Mechanic working on the IGV Pinion Gears

Some things are better done by the technical advisor himself.  Below in Fig. 4, Charlie Pond sets the IGV angles from inside the “mouth of the whale.”  Every vane requires adjustment to the proper angle.

Fig. 4: Setting IGV angles from inside inlet bellmouth

The IGV angle is indicated on the compressor shell with a pointer.  It is important that each vane be properly positioned for optimum air flow and operation.

Fig. 5: IGV Angle Indicator

Fig. 6: IGV Inner Block with 4 vanes, bolts and staked dowels

For more information, contact Charlie Pond on 913-220-5316 or the PAL Engineering office at 518-371-1971.