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| Introduction Valves with absolute shut-off capabilities in high pressure and high temperature steam are required in a number of areas in a fossil fueled power plant. Copeland ball valves are so successful because they supply long term cost savings by eliminating steam leaks to the atmosphere or downstream. In many areas where traditional globe valves have been used, Copeland Power Valves have lasted longer and performed more reliably. A harder sealing surface, a forged body to prevent the possibility of body leaks and a unique, live loaded packing assembly are a few of the primary reasons for the Power Valve's tremendous acceptance. Typical Applications Applications for severe service ball valves in power plants typically involve high-pressure steam, ash slurries or corrosive liquids. Key areas where these valves are most often used include the following: Turbine The turbine and main steam drains need high pressure; small bore valves during start-up and shutdown of the unit to drain away condensation. The valves are open until the turbine is brought on-line and closed until the next shutdown. Similar applications are found around the feed water heater, the economizers and in by-pass lines of larger valves. The turbine seal steam supply system also utilizes them for isolation of the turbine bearing glands. Condensate Drain Valves Above and Below Turbine Throttle Valves Turbine Intercept Before and Seat Drain Steam Drum Vents and Drains Steam Supply to Vacuum (Air Ejector) Steam Trap Bypass and Isolation Attemperator Steam Sampling Isolation Feedwater Heater Isolation Typical operating conditions of feed water heater isolation valves are 350 - 400°F and 3500 psi for a sub-critical plant and 4500 psi for a super-critical station. Reliable isolation is important to prevent feed water from leaking and overloading the heater drain system. Maintenance personnel must be able to plug, replace or rod out the tubes without shutting down the whole unit or as much as 33% of the plant's thermal efficiency can be lost. Reducing the time it takes to repair the heaters by just a few hours can result in savings that quickly pay for the initial cost of the valve. The valves remain in the open position most of the time but must close tightly when the heater is brought off-line for maintenance. Rust, scale build-up or thermal expansion are often issues that can cause rising stem or valves with soft sealing surfaces to fail. An extra hard sealing surface and an over sized stem and actuator are important to insure that the valve will operate properly and reliably. Steam Sampling Isolation Boiler Feed Pump and Heater Systems Boiler circulating pumps are often found in plants larger than 350 mw to circulate water through the boiler. During start-up, fill valves are used to pressurize the pump and associated piping. Once the pump is brought on-line, the fill valves are closed. The same types of valves are used to vent or drain pumps during routine maintenance. Warming, Drain and Recirculation Blow down & Vents Pump Recirculation Bypass & Isolation Valves Heater Gauge Glass Isolation and Drain Valves Sample Stop Valve Heater Drain High Level Dump High Pressure Feed Pump Bypass Valve Feed Pump Discharge Return to De-Aerator De-Aerator Drain Condensor Drain Economizer Economizer Drain Economizer Sampling & Vent Valves Economizer Inlet Pressure Connection (Root) Valve Superheater Header Inlet Leader Drain (Primary) Bypass Systems Drain and Vents Power Operated Safety Relief Valve Sampling Isolation Valve Steam Drum and Boiler Steam drum vents require valves for venting the steam drain and isolating boiler drum or steam drum controls such as the water column and level alarms. They are also used to remove boiler sludge or water deposits during start-ups and shutdowns. Other applications include mud drum drains, continuous blow-down, fly-ash/gas vents, spray water and soot blowers Mud Drum Drains Drains Continuous Blow-Down Fly-Ash & Gas Vents Loop Vent Main Steam Start-Up Mixing Header Pressure Connection Valve Spray Water and Steam Supply Isolation |
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