Sharryn Dotson, Online Editor, Power Engineering
Main steam and feed water isolation valves are an important part of nuclear power plants and the demand for them is expected to increase over the next 10 years.
There are two kinds of valves used in emergencies: Safety release valves and isolation valves.
The safety release valve is typically operated in a closed position, said Juergen Pick, global product director of nuclear power for Tyco Flow Control. “The purpose is to protect from over-pressure and bursting and it has to be opened to release pressure.”
Isolation valves do the opposite. Normally, they operate at 100 percent open and have no throttling purpose, Pick said. They open to allow steam or feed water to flow through and pressure loss should be very low. In case of an emergency, such as a heating pipe rupture in a steam generator, this valve is required to be closed.
There are other kinds of valves in nuclear power plants as well, such as gate and check valves, globe valves and medium-operation valves.
Frank Gihooly, global marketing director of the power unit with Tyco, said the company is beginning to shift its focus to cooling systems as more nuclear plants are moving in that direction, such as the new reactors being built at Southern Co.’s Plant Vogtle in Georgia.
|Tyco medium operated gate valve, courtesy Tyco Flow Control|
“We have been focused recently on providing large diameter quarter turn valves into cooling water applications especially in the U.S. market as companies such as Southern prepare their sites for these new units,” Gihooly said. “These companies are starting to install cooling water systems and look at where they need to upgrade or increase size.”
Joe Calabrese, marketing director with Velan, said utilities now have a lot more say in what they want when it comes to valves.
Calabrese also said the main steam and main feed water isolation valves as well as other safety-related valves are specified in the early stages of a nuclear power plant project so that the qualification and testing requirements become well-defined and understood by all over a period of time.
The European and Asia Pacific regions are expected to show strong demand for nuclear main steam and feed water isolation valves from 2010 to 2020, according to market analysis from GlobalData. The report, Global Nuclear Main Steam and Feed Water Isolation Valves Market Analysis and Forecasts to 2020, said Europe is expected to show highest demand with 1,143 main steam and feed water isolation valve units, Asia Pacific with 629 units and North America with 315 units.
Gihooly said he agrees with the analysis.
Having a long lead-time helps when the valves you have to build keep getting larger.
“Generally what we’re seeing relative to the 70s and 80s, these valves have increased in size, from 12 and 18 inches to 32- or 38-inch sizes,” Calabrese said. “It’s gotten a lot more complicated than it was to make the smaller valves in the past.”
Floyd Bensinger, product portfolio manager for nuclear valves with Flowserve, said valves are built to close faster now compared with earlier versions.
“Early on, valves were ‘slow reacting’ valves and most were motor operated,” Bensinger said. “Main steam valves may take 2 to 3 minutes to close while feed water valves may have taken a minute or minute-and-a-half.”
As requirements changed, so did the close time for valves, from minutes to 3 to 5 seconds.
“Within an accident scenario, (the slow close times) did cause some problems and that went into changing the technology,” Bensinger said.
Some of the changes include using mechanical springs instead of motor actuators to help the valves close faster and adding gate valves.
Another complication is that some vendors have difficulty testing the valves before sending them off to the plant.
“We have to go to specialized companies to perform some of the testing,” Calabrese said. “In the past, you could easily find companies in the U.S. and Canada to handle the smaller sizes, but the larger sizes limit the capabilities of current testing equipment, so you have to find specialized facilities. It’s really pushing the limits of valve manufacturers’ capabilities.”
Gihooly said a review of manufacturing codes, quality assurance and manufacturing techniques affects the specification of valves all the way until they are shipped.
“I think the market is in the developing world right now,” Gihooly said. “
Gihooly points to one country in particular as the example of a growing nuclear market.
“The government in China has announced that they would like to increase their nuclear power capacity to 70 GW by the end of 2020,” he said.
Gihooly said the United Arab Emirates, South Korea and Russia are also working on increasing their nuclear generation, while France and many Scandinavian countries are continuing to build and support their nuclear industries.
Preparing for the future
GlobalData identifies 57 nuclear reactors globally under construction that are expected to come online between 2010 and 2020. This indicates growth in demand for main steam and feed water isolation valves worldwide and demand for replacement valves once the units complete 25 to 30 years of operation.
To answer that expected demand, Tyco Flow Control opened its Advanced Nuclear Testing & Development Facility in Massachusetts.
Velan PHT transfer, courtesy Velan
“We needed to be ready for the next wave of increased capacity,” Gihooly said. “We have $50 million invested in our nuclear production facilities around the world.”
Flowserve’s Bensinger said, thanks to the company’s work internationally on gas hydraulic actuators, the increased demand domestically would not be a problem.
“Our actuators have been finely tuned thanks to the international market,” Bensinger said. “We have just finished testing for Generation 3 reactors such as Westinghouse’s AP1000 and Areva’s EPR design.”
Nuclear Power International Issue Archives
View Power Generation Articles on PennEnergy.com