Millions of Rands saved through improved Turbine maintenance practices by Eskom Rotek Industries.

Background: In the past major performance and vibration problems were experienced by clients following major outages.

Eskom Rotek Industries engineering department worked tirelessly with clients within the power utility sector to address vibration problems on turbines, which was leading to distortions on these rotating machines. The challenge was further aggravated by machine aging as well as general misalignment. Vibration problems had become a norm on these machines, following every outage (planned or unplanned).

It is quite normal for high temperature turbine cylinders to distort over time due to operational stress and age.  During  this period however it was observed that conventional cylinder alignment methods were proving to be unsuccessful during major turbine over haulage.  

With many of these clients’ fleet   operating on longer hours in a drive to meet customer’s energy demand, distortion becomes a major challenge and had been a major driver for higher maintenance costs as well as longer duration outages.  The industry norm for power plants with similar conditions would be to replace the turbines or remove the distortion by machining or heat treatment.  These options are very costly and time consuming and would often mean material life exhaustion of major components, which in turn would drive costs.

Solution:

An alternative solution was investigated and implemented by ERI (Eskom Rotek Industries).  This solution involved retaining the distortion of the casing as it often is a function of the operational temperature distribution in the casings.   Doing so improved the life expectancy of the assets’ major components, as the casing  was retained for longer in the secondary creep zone cycle.

Furthermore the team went on and investigated solutions that were to ensure a reliable operational turbine without any vibrational or process problems.  To this end, a method was designed to execute accurate cylinder alignment in the presence of distortion.  The distortion causes cylinder components to move relative to each other during the assembly. These movements affect the small internal clearances and can lead to mechanical contact between rotating and stationary components which in turn may lead to major vibration and mechanical damage.

The Outcome:

The development of the new technology was completed within ERI and has been executed successfully on three units to date.  By utilizing this method the turbines were refurbished, assembled, and returned to service successfully.  The distortion compensation method will in future be the norm for cylinder alignment of cylinders with above normal distortion.  One of the major advantages of the new method is that it can be executed within a shorter period than the conventional methods and tends to be much more accurate.

How to contact us:

General Enquiries: 011 629 4000
Rosherville: Latitude: 26.23575S and Longitude: 28.11992E
www.rotekindustries.co.za

ndwamitp@eskom.co.za
ERIinfo@eskom.co.za