Major Overhaul of an ABB Designed Marine Steam Turbine

"On October 12, 2014, I ascended the gangway of a Mexican crane ship B/G Tolteca for what would be a 2 week voyage from Freeport, Bahamas, to Campeche, Mexico. Little did I know what a massive undertaking this project would become." - Donald McNelly

This unit uses a saltwater condenser. Therefore, steam quality was poor since any cooling water leak in the system resulted in saltwater entering the steam cycle. The lube oil system was similarly cooled and also showed some evidence of water leaks into the system. Damp air from the sea caused corrosion and seizing of the carbon steel half joint bolting. Over the course of the next 55 days Reliable Turbine Services performed the following work at a drydock in the Bahamas.

Disassembly.

The carbon steel horizontal joint bolts were severely corroded due to time and damp, salty air. All of the bolts on the HP turbine had to be cut off, as well as many of the bolts on the LP turbine. The prolonged period between outages, combined with corrosion, resulted in most of the threads being completely seized. Destructive removal by drilling was the only way to remove them.

Disassembly

Remove, supply, and replace 47 rows of blades.

Due to the poor steam conditions, many blade rows required replacement. 47 rows of stationary and rotating blades were manufactured, delivered, and installed in time for the ship to sail as originally scheduled.

Replace Blades

Remove, supply, and replace all HP and LP packing gland seals.

The badly corroded, bent, and broken HP and LP packing gland seals were removed. New seals were manufactured, delivered, and installed. The rotor and casing seals were carefully measured and checked to ensure that the small clearances between rotor and casing were maintained.

Repair erosion damage on the LP half joint.

The LP casing was badly corroded near the half joint. A patch consisting of a strip of stainless steel was welded to the casing over the affected area to prevent the corrosion from developing into a hole.

Replace erosion damage

Repair HP and LP journal bearings and oil seals by rebabbiting.

The HP and LP bearings and oil seals were in poor condition due to less than ideal oil quality and lack of regular maintenance. The bearings and oil seals were shipped to the USA for rebabbiting. RTS prepared the procedure for cutting the elliptical bearings.

Repaired Journal Bearings

Reassembly.

The rotors were returned to the lower casing in the ship, the upper casings installed, and the casings were bolted closed using newly manufactured bolts.

Reassembly

Witness and advise on turbine startup and operation during first voyage.

Two RTS representatives, myself included, provided advice on startup and operations during the first voyage after the turbine overhaul. Once at full power, the turbine was able to propel the ship at speeds greater than the customer’s expectations. Bearing temperatures and turbine vibration was acceptable during all conditions on the voyage.

Startup

Major Overhaul of an ABB Designed Marine Steam Turbine Gallery


Project Dates:

October 12th, 2014 - December 8th, 2014

Project Location:

Campeche, Mexico

Project Outcome:

"On October 12, 2014, I ascended the gangway of a Mexican crane ship B/G Tolteca for what would be a 2 week voyage from Freeport, Bahamas, to Campeche, Mexico.  Little did I know what a massive undertaking this project would become." - Donald McNelly

After
 
 

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