Ongoing process steam leakage in power plant control valves due to erosion from wet steam must be addressed to maximise uptime at a critical time for industry, says a power industry expert.
Continually rising gas prices caused by geopolitical events have put pressure on facilities to ensure continued, uninterrupted performance, and further heightened the impact of inefficient processes and unplanned downtime.
However, power plants with inadequate drain arrangements, incorrect bypass operation, improper valve calibration or inadequate pre-warming processes continue to be impacted by wet steam erosion, hampering productivity.
Specifically, these issues can lead to erosion of trim components on steam valves used in critical service applications caused by flashing condensate, otherwise known as wet steam. According to Mike Semens-Flanagan, Global Engineering Director at IMI Critical Engineering, this potentially chronic problem must be addressed if facilities are to remain efficient and cost-effective at a time when process costs are rising.
“Steam valve passing – or leakage – remains a common concern in power and processing plants that can lead to a whole host of issues, including downstream temperature rises, unplanned downtime, cracking pipes, and water hammer,” explains Mr. Semens-Flanagan. “The erosion of the valve plug and seat sealing surfaces are key reasons behind this, and must be addressed if the sector is to maximise performance at a time of great strain.
“While the common approach to mitigating trim damage involves the frequent repair and replacement of affected parts, the loss of energy and increased OpEx costs caused by this unplanned downtime is unacceptable in the current economic environment. Yet with major remedial steps such as adding drains to existing pipework often ruled out due to costs and logistics concerns, an innovative approach is required to alleviate this pressing concern.”
One such way to minimise wet steam erosion is to ensure that any condensate has minimal contact with sealing surfaces. IMI Critical Engineering, for example, has developed EroSolve Wet Steam, which upgrades the valve’s plug, stem assembly, cage, and seat ring. The solution has specially engineered sealing surfaces that optimise droplet impingement angles to reduce their impact. Its use of special, erosion-resistant hard-facing materials also enhances trim life in a solution that can be easily implemented in any make of control valves.
EroSolve Wet Steam’s impact can be seen at a Korean Combined Cycle Power Plant where operators experienced excessive trim erosion due to high condensate levels caused by frequent plant start-ups and shutdowns. The impact on the trim and subsequent issues with adjacent piping led to expensive unplanned facility shutdowns that were solved following EroSolve Wet Steam installation,
“Most traditional solutions to the problems posed by wet steam do not provide any added long-lasted benefits,” concludes Mr Semens-Flanagan. “Alongside this, the complexity of fully replacing a valve within power plants can make solving the problem more expensive that the hardware itself, and this is obviously unacceptable. If the valves are welded inline there may also be substantial additional costs incurred through engineering, scheduling, cutting and re-welding valves, and post-weld inspection, creating further complexity.
“However, replacing the trim with an innovative solution such as EroSolve Wet Steam can help delay degradation and extend the lifetime of valves operating in conditions where erosive wet steam is common. The fact that this upgrade can be carried out without changing the body, bonnet or actuator is also a key logistical benefit for these facilities, where any downtime for repairs can carry a large cost burden.”
For more information, visit our EroSolve Wet Steam webpage.