Robert KilroySr. Engineer Turbine-Generator Repairs Division
I graduated from the Massachusetts Maritime Academy with a Bachelor degree in Engineering and started my career as a design engineer for General Electric®. I then moved onto ALSTOM Power® as a repairs engineer, servicing and repairing ALSTOM and other OEM power generation equipment. Since 2007 I have been working for MD&A as a Senior Turbine Generator Repairs Engineer and have over 26 years of experience in the maintenance, service, and repair of steam turbine and generator equipment for all major OEM designs.
What do you do here at MD&A?
As a Senior Turbine Generator Repairs Engineer at MD&A, my job is twofold. I support steam turbine, generator, and valve repairs both at customer sites, as well as, in the MD&A St. Louis Repair shop. And, I provide on-site third party technical engineering consulting support for customers during major equipment outage overhauls and component repairs.
What is the most interesting challenge you have come across at a job site or in repair shop?
I developed a weld repair for a condemned generator rotor forging that was damaged by a double ground fault incident. What we found was that the rotor forging had some missing material and some that had hardened to a coil slot tooth. Both problems were due to severe arcing damage. I was part of a team that developed a plan to remove part of the coil slot tooth, perform a weld restore procedure, conduct a post weld heat treatment, and complete final machine work on the generator rotor tooth. Precise welding and heat treatment was important to ensure that the generator rotor suffered no distortion. Equally critical, the final machining had to be performed to make sure the newly machined surfaces blended with pre-existing surfaces, which included the tooth sidewalls, dovetail hooks, and cooling vent slot. Our plan resulted in the generator rotor forging being repaired successfully. It was a good feeling to know that the customer was very grateful to learn they would not have to procure a new generator rotor forging, and that the generator rotor was able to return to service without issues.
What are the signs of a bowed rotor?
A rotor bow can be caused either by long-term thermal yielding or by a quick thermal incident. The first can happen on high-temperature rotor elements and is more often seen in long rotor spans. The signs of a bowed rotor caused by long-term thermal yielding are a long-term trend of high vibration at operating speed due to a gradual increase in rotor runout over time. It’s important to note that vibration due to runout can be masked by balance shots and should be checked when evaluating a rotor’s overall condition. By contrast, a rotor bow due to a quick thermal incident can occur on high- and low-temperature rotor elements either because of a water induction incident or by heat that is generated by a hard rub that affects stationary components. In this case, the signs of a bowed rotor can include rubbing or locking of the rotor rotation on turning gear, excessively high vibrations at critical speeds, and high vibrations at operating speeds. At the extreme, a unit could even trip offline due to the high vibration. Fortunately, even severely bowed rotors can be repaired using options that can include machining, stress relieving, and thermal “hot spot” straightening methods.
Diaphragm Dishing is the axial distortion of a diaphragm, which roughly resembles the shape of a dish. How does dishing impact fossil-fired machines that have been re-purposed for combined cycle operation?
A diaphragm that is dished, or that shows signs of displacement of the inner web, can be caused either by long-term high- temperature creep or by a water hammer / steam flashing incident. Fossil machines that are seeing duty in combined-cycle operation that have been re-purposed for combined cycle operation may also experience an increase in diaphragm dishing due to increased start / stop cycles. For example, if stage operating temperatures, steam mass flow, or pressure drops have risen across the diaphragm from the original design intent of each stage, then diaphragm dishing due to high-temperature creep may become an issue. To minimize high-temperature creep, it’s important to review and evaluate how the turbine is being re-purposed, or reduce the inlet temperatures and steam mass flow. If an increase in incidents of water induction or drain blockage occurs due to the increased number of start / stop cycles, then diaphragm dishing due to water hammer or steam flashing may be an issue. To avoid this possibility, be sure to follow startup / shut down procedures and to perform regular maintenance on all valves. Fortunately, dished diaphragms can be repaired or modified to increase their stiffness, or materials can be replaced to improve creep resistance.
What is your personal motto?
My personal motto… there are so many to choose from: “Attention to Detail”, “The Right Tool for the Right Job”, “Measure, Check, Verify, Re-Check”. We work on high energy equipment, spinning at high speeds, with very tight tolerances and clearances, in an industry that is not very forgiving. Success in any endeavor requires single-minded attention to detail and total concentration.
Contact Rob today using our Contact form.