When is a Turbine Flush Warranted?

Noria Corporation

"A boroscope inspection of the main turbine oil reservoir at our power plant revealed paint chips in the reservoir, puddles of water, red-iron oxide particles (rust) and babbitt material in one of the main return lines. The babbitt can most likely be attributed to a hydrogen fire that happened more than five years ago and wiped the bearings. As this fire occurred in the summer and electricity prices were high, a flush at that time was not performed.

Actually, the turbine lube oil system has not been flushed in more than seven years. Among other things, this has led to concern that if babbitt debris were to appear in a recent oil sample, it would not be possible to tell if the babbitt is from the fire five years ago or presently being generated by bearing wear.

Our plant is currently in a maintenance outage that will last for only a few more weeks. The system likely needs to be flushed, but the general feeling is why do it now since the babbitt has been in the return line for five years and thus far has not caused any problems. Likewise, it is believed that the paint chips will be caught by the filters located on the bearing supply line.

Operations would like to wait until the next outage (two years down the road) to flush the system. Plant maintenance thinks it would be wise to flush now. What would be your recommendation?"

The system should be flushed, the lines cleaned, and the reservoir emptied, wiped down and refilled with new turbine grade oil. If the general oil condition (based on oil analysis) is good, then running it through a dehydrator and filter could be an alternative. This would allow reclamation of the oil, thus lowering some of the cost.

The fire likely resulted in carbon in the unit and lines as well as the wiped bearings. That would have been the time to correct the babbitt left in the return lines, and flushing would have been in order.

Remember, a known problem should be addressed at the earliest opportunity. This particular unit may include a line of turbines with a central lube system supplying all the turbines. While taking the central lube system offline may not be an option now, cleaning the return lines and supply lines to the turbine would be. Flushing can also still be done.

Early identification of work (potential problems) is one of the tools that can be used to forecast and ward off catastrophic failures. One failure would justify all the work that needs to be done. Catastrophic failures often result in money being thrown at the problem, with all the components checked, cleaned and replaced as necessary, along with lots of overtime, contract costs and loss of revenue.

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