valve

Prevent valve delamination

If conventional power plants move from running at base load operation to more frequent cycling they need to consider potentially costly equipment problems, such as valve delamination, says Emerson’s Paolo Tomaini.
 
Article by David Sear
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Balancing the supply and demand of electrical energy is probably something that most consumers never stop to think about. We simply press the switch and the light comes on, whatever the time of day. However, ensuring there is sufficient electrical power being generated to meet fluctuating demand requires plenty of thought, especially considering that many power plants are designed to deliver a consistent, stable output.

And now it seems there is another factor that the engineers who deliver our power need to contend with. Namely the knock-on potential for damage to equipment caused by the increasing use of green or renewable energy. This was the issue that Mr. Tomaini was keen to highlight. “There are good reasons for using renewable energy sources. However, by their very nature, wind and solar power have inherently variable outputs and so cannot provide a consistent energy supply to the grid. In consequence, traditional plants are being increasingly cycled as a way to generate power on demand. This shift from running them at base-load power to cycling is causing increasing failures in certain items of equipment, such as valves.”

Mr. Tomaini explains that valves play a major role in plant uptime in conventional plants, but that valves manufactured ten to fifteen years ago were simply not specified to carry the intermittent or low-load duty of today’s operations. And this fact, he continues, is resulting in hard facing damages up to complete delamination. Mr. Tomaini: “therefore, one of the most impactful steps in minimizing failures is evaluating the plant’s critical valves to identify potential delamination issues.

I suggest that operators should consider three key questions when assessing the risks of premature failure. Firstly, what was the original design specification for the installed valve? Secondly, what was the original valve manufacturer’s practice for hardfacing? And finally, is repairing these valves a definitive solution, or should they be replaced?”

Avoiding costly repairs

Further discussing this problem, Mr. Tomaini says that signs of delamination in critical valves will necessitate a complete redesign of the hardfacing process to help reinforce the base material of the valve and ensure it can withstand the new operating conditions. “Steps that operators should follow for a successful hardfacing redesign include the following. Firstly, identify a trusted and experienced valve manufacturer to redesign this process based on application conditions, the base material/hardfacing combinations, and proper welding technologies and procedures. Secondly, inspect the hardfacing condition of the installed valves, and prepare a replacement plan and finally, specify a more robust hardfacing process for all new valves to be installed.”

End users who properly address delamination issues from the start can save substantial time and money, states Mr. Tomaini. “Improper valve repair can be highly costly - sometimes exceeding USD 100,000 per valve - only to leave the end user to experience the same issue again within a year’s time. The subsequent forced outages can cost end users as much as USD 250,000 per day in lost revenue in fossil power plants, for example. So in addition to bringing plant operations up to code with the ability to withstand new performance requirements, end users who properly implement a plan to prevent delamination will avoid forced shutdowns, prevent revenue losses, save money and time on maintenance and have the assurance of a long-lasting solution for the present and future service.”

Meet Mr. Tomaini

Paolo Tomaini is the Business Development Manager, Power and Gate, Globe Check Europe, with Emerson Automation Solutions. He is based in Italy at Emerson’s Rescaldina GGC Center of Excellence and has ten years of experience with valves and valve applications in addition to eight years of experience in steel materials and processes. He holds a Master of Science degree in Mechanical Engineering from ‘Politecnico di Milano’ University.

Mr. Tomaini will be speaker at the upcoming Valve World Conference. You can listen to his presentation on valve delamination at 11:50 a.m. in room 3 on Thursday, Nov. 29.

 

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