Engineered Services: Steam Turbine Rebuilt after Fire


After a fire at a specialty chemicals manufacturer, Maintenance Partners was asked to inspect, repair and commission the steam turbine and generator within 6 months. Read the full story below:

Specialty Chemicals Manufacturer

Our client is a manufacturer of a specialty chemicals and performance materials that specializes in the production of carbon black. Carbon black has many applications, ranging from pigment in coatings, inks and plastics to the enhancement of materials to be more conductive or UV-resistant.

Energy Recuperation

In the client’s manufacturing process, gas is generated as a byproduct. The gas is used by a boiler to generate steam that drives the steam turbine which powers a generator. By doing so, a significant amount of electricity is produced using waste gas. This reduces the client’s ecological footprint and lowers the costs of energy that are required to operate the facility.

Catastrophic Failure

Due to a malfunction in the generator’s control system, the generator started to drive the steam turbine (instead of the steam turbine driving the generator). This caused the steam turbine to vibrate excessively and to leak oil. The combination of oil and high temperatures led to a fire in the powerhouse building, resulting in severe damage to the entire turbine generator train and its auxiliaries:

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Inspection

Immediately after the fire, Maintenance Partners was asked to inspect the entire turbine-generator train in a short time frame. The goal of the inspection was to determine if repair was a possible option.

Severe damage to the steam turbine

The inspection showed that the coupling had absorbed most of the vibrations when the breakdown occurred. This left the gearbox and generator relatively undamaged. However, the steam turbine was severely damaged:

Diaphragms

  • Cracked welds
  • Bent vanes
  • Nozzles completely torn off & bent

Casing

  • Deformation of casing (combination of heat, vibration and damage to rigidity pillars)
  • Cracks
  • Damage on all diaphragm places, bearing places and all oil seal places caused by vibration

Valve bodies

  • Heavy damage
  • 1 valve broken off
  • Nozzle buckets bent

Rotor

  • All blades significantly damaged – stage 7 partly torn off and stage 6 completely torn off
  • Heavy damage to bearing journals
  • Heavy damage to seals
  • Rotor was bent (up to 0,2mm)

 

Renewal vs Repair

Awaiting the outcome of the inspection, our client considered ordering a new steam turbine. However, delivery, installation and commissioning a new steam turbine was estimated to take up to 2 years.

Maintenance Partners’ repair proposal offered a solution in which the steam turbine would be running within 6 months. A downtime of another two years was unacceptable, so Maintenance Partners was awarded the contract for the repair. The repair works began in January.

Repair | Steam Turbine

To ensure that the steam turbine would operate again, Maintenance Partners had to completely redesign, rebuild and re-align major components:

Rotor

  • Full rotor reblade
    • Complete re-engineering of the 6th row turbine blades
    • Reverse engineering of all other blades
    • Upgrading of material specifications to be more durable
  • Straightening of rotor
  • Repairing the bearing journals and seal places
    • Machining off the damage
    • Laser cladding by Maintenance Partners’ welding robot
    • Machining
  • Re-engineering the steam seals & completely redesigning the steam sealing system
  • Applying special coating on rotor surface in order to prevent corrosion and extend the rotor’s durability

Casing

  • Straightening
  • Repairing of cracks
  • Machining the damaged parts of the casing

Diaphragms

  • Rewelding the cracked welds
  • Straightening the vanes
  • Realigning the vanes in the casing

Redesigning of safety systems

  • Replacing of manual hydraulic extraction actuation system with an electronic system

Repair | Generator & Gearbox

Although the generator and gearbox had only sustained minimal damage,  both machines were cleaned and overhauled to ensure safe and reliable operations.

Repair | Auxiliary pumps and motors

The fire had also damaged the steam turbine’s auxiliary pumps and motors (5 oil pumps, 3 AC motors and 1 DC Motor). The 2 control oil pumps, bearing oil pump and emergency oil pump were overhauled and the DC motor had to be rewound. All AC motors were replaced by new ones.

Onsite Rebuild & Startup

All repair works were Maintenance Partners Steam Turbine Rebuilt after fire 00acompleted in May and one of our specialized field service teams started rebuilding the steam turbine and generator. The team’s activities included:

  • Realigning entire turbine generator train
  • Regrouting the generator and exciter
  • Renewal of  all the probes and sensors
  • Installation of an online monitoring system in the generator
  • Reprogramming the safety trips on the turbine
  • Replacing the hydraulic actuator with an electronic system
  • Realigning the rotor in the casing

Finally, the steam turbine was started up on July 16.

Result for Customer: Steam Turbine running better than before

Our customer experienced an increase in efficiency compared to operating data from before the crash:

  • Steam leakages fully resolved
  • Vibration
  • Less temperature losses
  • Better vacuum pressure

In conclusion, the repairs and improvements that the turbine and generator underwent have resulted in a machine that is running better than before the breakdown:

 

More information

For more information about repairs of steam turbines, generators or auxiliary equipment, please visit the pages below:

If you have any questions, please contact us via +32(0)3 541 71 40 or send us a message using the form below:

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