Gearbox diagnostics and consultancy of steam driven gearbox RENK TBE-630 plus generator

Challenge

Stork diagnostic service was invited by a power generation company in Turkey to investigate high vibrations on a steam turbine driven gearbox.

Unexplainable high vibrations occurred since a particular startup. The customer had checked many items but could not find the root cause. A diagnostic engineer from SGS was invited to come over and thoroughly investigate the problem.

Upon arrival, our diagnostic engineer was introduced to the vibration problems in a meeting with the engineers. Because the highest vibrations were measured on the gearbox, a gearbox failure was suspected and the gearbox top half casing was already disassembled by the customer.

The gearbox components were thoroughly inspected by our diagnostic engineer but no abnormalities were found. The entire machine train was equipped with fixed vibration transducers that could be used for vibration measurements in order to further analyse the problem. However a time consuming startup was not desirable.

Solution

Our diagnostic engineer advised to measure the shaft runout of the driven generator rotor. The 8 ton rotor was rotated manually. That revealed the root cause of the excessive gearbox vibrations: a permanent excessive rotor deflection appeared to be the problem.

The time consuming startup was cancelled and the generator was prepared for transportation to a workshop for repair.

A synchronization failure was suspected to be the root cause for the damage on the rotor but further inspections of the rotor is necessary to reveal the exact cause.

Benefits

The customer was very pleased with our approach:

• fast response time, our diagnostic engineer was onsite within a few days
• effective diagnosis, no need for an unnecessary shutdown and startup

Market segment: Power generation industry

Gearbox specifications: Manufacturer: Renk; Type: TBE-630; Ratio: 4.722; Input speed: 7.083 rpm; Power: 14,725 kW

Generator specifications: Manufacturer: Alstom; Type: A145A4, 4 pole; Specification: IEC 60034; Speed: 1500 rpm; Rating: 16218 kVA

Scope of work: Visual inspection of gears, magnetic particle testing of gears, visual inspection of bearings, tooth contact pattern check, shaft runout measurements and additional vibration measurments