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Common practice at CTS is to completely disassemble the turbine, breaking apart both the horizontal and vertical split lines. Split lines are then ground to remove steam cuts and any other damage. Split lines are to be cleaned up to have at least an 80% contact. 100% is desirable but not always attainable if the damage to the case was indeed too severe. The horizontal split lines on the bearing housings are also cleaned up. The housings have to be lined up with the case and the ID’s need to be re-bored to make up for metal that was removed from the split line of the housing.

Several types of sealant have been used over the years. These include Copaltite, SilverSeal and Linseed Oil. Each type of sealant has its merits, but at CTS we primarily use Copaltite. There are cases where the split lines have been too badly pitted to clean up. In this case, Temptite String is added to the split lines (inside of the bolt holes) in order to better fill-in imperfections and improve sealing. Copaltite, as with other sealants, has one inherent problem. In order to be effective, the sealant has to be properly cured. In many cases where there was initial leakage at the split lines, it was found that the sealant had been “blown out”. This is a good indication that the sealant was never properly cured in the first place. There is the assumption (and we know what that word means) that the sealant will be properly cured in the field as part of the start-up procedure. This was not always the case.

Grade “8” is used for bolting
Grade “B-7” is used for studs.

Bolt Torquing and sequencing is a critical part of turbine assembly. It is often either overlooked or performed improperly. Most manufacturers specify Torquing sequences and procedures in their turbine manuals. Beyond the manufacturer’s instructions, a few other steps must be taken in order for the procedure to be completed.

1. First hand – tighten ALL bolting until they are snug.
2. Following the “crisscross” pattern as illustrated below.
3. Torque each bolt (or nut) to 50% of the desired torque.
4. Following the same pattern, begin again, this time
   Torquing to 100% of desired amount of torque. As each bolt is tightened, mark each bolt with a paint pen or Sharpie to indicate that the bolt is tight.

Completed turbines are “run test” on air to check for leakage, vibration, misalignment, and over-speed trip.
Considerations for “Run Test”

• Do not over pressurize – you can blow out sealant
• Since this test is run on air, you may introduce moisture
  into the interior of the case

In MANY cases proper start-up procedures are not followed once the turbine is ready to run in the plant. Has the turbine been pre-heated properly to allow for a uniform distribution of heat throughout the case?! This is important in that improper start – up can cause distortion leading to steam leakage or leakage due to not having cured the sealant properly. As a turbine re-builder, we have to assume that the turbine will not be properly pre-heated.
So – HERE IS WHAT WE HAVE IMPLEMENTED!

CTS – Our Better Mouse Trap

There is a Better Mouse Trap – a better way of sealing turbines. It doesn’t involve any single item listed above, but a combination of ENHANCED repair procedures and techniques.

The Better Mouse Trap – The Oven

Compressor and Turbine Services has carefully reviewed leakage problems on small turbine split lines and has ultimately changed our method of small turbine repair. Our thoughts are that turbine repair procedures must be changed in order to facilitate the proper sealing of small turbines.