Managers know that valves are necessary to plant operation. That’s why protecting them in prime situation is a precedence. Upgrading to superior valve designs and lowering stress on valve supplies are simply a few steps that may enhance outcomes.
It’s not an exaggeration to say that there are a whole lot, if not 1000’s, of valves put in in every utility-scale energy plant on the planet. The quantity in every plant varies, in fact, based mostly on the scale of the plant and the complexity of its programs, however each valve has a objective and its correct operation is necessary in making certain essentially the most environment friendly and most secure plant operation potential.
But, there are various valves at practically each plant that don’t carry out as meant. Typically, valves don’t seal as designed. In reality, valve seats and discs will be broken in the course of the preliminary hours of operation and by no means work correctly once more. It’s akin to having a automotive accident as you drive a brand new car off the present ground—how disheartening.
Moist Steam
Moist steam presents a specific problem for energy and course of plant managers. Moist steam kinds when saturated steam and condensate water molecules mix, which may consequence from elements akin to incorrect plant operation logic or poor drainage programs. Failure to manage moist steam can result in the erosion of vital valve trim parts, inflicting security hazards and substantial operational inefficiencies, which may in the end result in pricey unplanned downtime.
Examples of vital steam valve purposes which can be liable to condensate erosion are high-, intermediate-, and low-pressure bypass valves. Different purposes that face condensate erosion embody vent, steam letdown, and auxiliary steam valves. Erosion will be minimized and even prevented by admitting solely dry saturated steam into management valves, however typically, the presence of moist steam can’t be averted. This results in condensate erosion of sealing surfaces (Determine 1).
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1. A valve element broken as a consequence of moist steam. Courtesy: IMI Course of Automation |
Sealing floor erosion results in leakage and downstream temperature rise. In some designs, this ends in frequent opening and shutting of spray water valves, resulting in spray water valve trim harm, lack of controllability, harm to stress lowering levels, and potential cracking in downstream pipes. It might additionally result in water hammer and much more consequential system harm.
The EroSolve Answer
To counter the moist steam drawback, IMI Course of Automation launched an answer known as EroSolve Moist Steam in 2019. The corporate has been putting in the improved parts at energy and course of crops all through the world since then, and on July 10, 2024, it introduced it had put in its two hundredth EroSolve Moist Steam resolution.
EroSolve eliminates erosion issues via the mix of an revolutionary design that retains flashing fluids away from sealing surfaces and a particular materials that resists water droplet erosion. The answer is obtainable as a trim improve and will be carried out in each IMI Course of Automation and different producers’ valves.
A number of clients have raved concerning the outcomes. At one plant in India, for instance, annual value financial savings of £275,000 and a discount in CO2 emissions equal to 10,000 tonnes per valve, per 12 months have been attributed to the EroSolve Moist Steam resolution (Determine 2). In the meantime, at a significant U.S. energy facility, using EroSolve Moist Steam reportedly enabled considerably improved valve longevity. Previous to the improve, the valve in query would leak roughly three to 6 months after set up. Nevertheless, after implementing EroSolve Moist Steam, the plant has skilled no leakages in additional than three years, based on IMI Course of Automation.
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2. EroSolve Moist Steam trim instance. Courtesy: IMI Course of Automation |
In different buyer testimonials, managers at a 1,200-MW mixed cycle plant within the U.S. stated they had been proud of the answer’s efficiency and meant to improve two extra valves. At a 420-MW coal plant in India, managers stated IMI Course of Automation was an excellent accomplice able to analyzing the whole system and offering an acceptable resolution to get rid of their erosion drawback.
“Moist steam is a major environmental and financial drawback for energy and course of crops worldwide, which is why it was recognized as a key problem to unravel as a part of the primary spherical of our Development Hub initiative again in 2019. Since then, we’ve been capable of ship substantial financial savings to clients throughout industries, each when it comes to prices and emissions, on account of diminished leakage and downtime,” stated Kevin McKown, president for the Americas at IMI Course of Automation. “This can be a nice instance of our mission to ship ‘breakthrough engineering for a greater world’ in follow. EroSolve Moist Steam has made a really vital contribution to supporting the trade each in its industrial and environmental sustainability.”
Metallic Fatigue and Cracking
Past points attributable to moist steam, vital bypass valves are additionally inclined to metallic fatigue and cracking. The mixture of excessive vibration, frequent thermal biking, and excessive stress drops can result in metallic fatigue within the valve physique, water connections, and surrounding piping, leading to cracks and probably catastrophic failures, if not addressed.
Common inspections and non-destructive testing are necessary on these valves. Routinely examine the valve physique, welds, water connections, and surrounding piping, utilizing non-destructive examination strategies to detect growing metallic fatigue points earlier than they turn out to be vital.
Take into account upgrading to flow-up valve designs, which may cut back put on and lengthen service life in comparison with conventional flow-down designs. If flow-down valves are the one sensible choice, vertical mounting of the actuator may end up in diminished and extra even put on.
Utilizing superior supplies also can assist. Make use of extra erosion-resistant, hard-facing supplies for valve parts just like the plug-stem meeting, cage, and seat ring. Take into account high-temperature alloys for purposes in supercritical and ultrasupercritical crops.
DMWs
Dissimilar metallic welds (DMWs) may also be a supply of hassle. DMWs contain becoming a member of two totally different alloy programs or metals collectively, relatively than welding equivalent supplies. Widespread energy plant examples of DMWs embody welding carbon metal to chrome steel or becoming a member of totally different grades of chrome steel. DMWs are extra complicated than welding related metals as a consequence of variations in bodily, chemical, and mechanical properties between the supplies being joined. Key challenges are attributable to variations in melting factors, thermal enlargement charges, and formation of brittle intermetallic compounds on the weld interface.
When valves are put in utilizing DMWs, it’s necessary to find the connection in lower-stress areas, if potential. It’s typically greatest to make use of spool items for materials transitions relatively than welding on to the valve physique. The important thing to profitable dissimilar metallic welding is knowing the metallurgical compatibility of the supplies, and choosing applicable welding parameters and filler metals to create a sound joint.
Different Stress Discount Ideas
To scale back stress on valve parts throughout operation, implement superior management algorithms and precision actuation know-how. Valve our bodies and trim needs to be designed to face up to extreme thermal shock, akin to will be attributable to temperature adjustments of 200C or extra, whereas nonetheless making certain dependable operation. Vibration must also be restricted as a lot as potential, as this additionally contributes to metallic fatigue. Incorporating noise abatement know-how will help.
The significance of correct upkeep can’t be overemphasized. Substitute smooth items and spray nozzles usually to forestall harm to extra vital parts. It may be worthwhile to put in guide block valves upstream and downstream of bypass valves to permit for on-line repairs when essential.
For an intensive understanding of how a valve may carry out in a system, finite factor evaluation (FEA) fashions will be helpful. FEA is a computerized technique for predicting how a product or construction will react to real-world forces, vibration, warmth, fluid move, and different bodily results. FEA breaks down a fancy object into 1000’s, and even hundreds of thousands, of smaller parts (like cubes or tetrahedrons). Mathematical equations are used to foretell the conduct of every factor. Then, the pc combines all particular person behaviors to foretell the general conduct of the item. Superior FEA fashions can be utilized to investigate complicated geometries in management valve designs, find stress concentrations, and incorporate design modifications to attenuate stresses.
—Aaron Larson is POWER’s govt editor.
