Low and Medium Pressure Wedge Gate Valves NKS, MKS For Use in Nuclear Power Plants
Introduction Gate valves are generally used in the nuclear power plant industry to securely isolate water and steam lines.the main advantage over globe valves is the extremely low pressure drop across the gate valves. Two main types are the wedge gate and parallel gate valves. On wedge gate valves the tapered configuration of the seat allows the generation of high additional sealing forces, thus ensuring increased safety during operation. Additional advantage over parallel slide gate valves: the sealing surfaces touch each other only in the final closed position. The guides in the body prevent a permanent contact during opening and closing, resulting in a longer, trouble-free service life. For low differential pressure ( p) applications the wedges are additionally spring loaded to ensure the gate is pushed onto the sealing surface for better sealing properties. The required spring force is individually calculated based on the case data, in particular the differential pressure ( p). Type Material Ferrite, Austenite Temperature range Max. 350 C Hard facing Stellite 21 Cobalt free: NIBORIT 40-P Sizes Pressure ratings DN 50-300 (dye forged shells) DN 350-600 (welded) Max. PN 160 (dye forged shells) High Pressure Gate Valves (DN 50-600, max. PN 350): see separate product sheet Gate valves can be hand or electrically actuated (or both). Special requirements such as tightness and functionality even after a malfunction of the actuator limit switches have been implemented in special designs, based on calculations and proven by extensive testings. Special hard facing of the seat either with Cobalt (Stellite 21) or without (NIBORIT 40-P) ensures long service life and excellent sealing properties over extended periods of operation. The bodies can be made of ferrite or from austenite materials as is appropriate. The bodies of low and medium pressure gate valves are made from dye forged shells that are welded together using the most modern arc welding technology and materials. The shell construction enables a perfect flow through the valve while reducing the overall weight of the valve body. 2 NKS, MKS
Design details Body Shell forged max. DN 300 Yoke tower Actuator Seat hard facing Stellite 21 or cobalt freei Wedge guide is either replaceable or a hard faced guide integrated in the body Body fracture protection (optional) Linear unit with axial bearing and stem nut Belleville spring column for the linear unit for setting the valve stiffness in the closed position Wedges Lateral guides in the body Stem with plunger connection between the actuator and wedges Adjustment of wedge position in the seat via thrust pad (optionally spring loaded) Seat hard facing Visual position indicator Anti-rotation device Stroke limiter Stem seal (live loaded packing) Yoke flange bolted to prevent rotation Flange seal with spiral wound gasket and tightness setting 3 Bevelled seat (3 ), fo higher pressures 4 6 3
Qualification Successful qualification of Bopp & Reuther gate valves by AREVA NP GmbH, Erlangen, Germany As part of a gate valve exchange program at a German nuclear power plant Bopp & Reuther s low pressure gate valves were subjected to an extensive qualification procedure. The qualification was carried out by the AREVA NP notified test labatory in Erlangen, Germany. The gate valves were DN 80 with bodies constructed from welded dye forged shells. Overview of the the test conditions: Functional tests at room temperature Endurance testing at 160 C Cycle testing of opening/closing, 50 cycles at p of 7 bar Tightness tests before and after each test run Failure testing, e.g. after actuator malfunction The results at the successful completion of the tests showed: Functionality during the entire test period and under all conditions Ample reserves in actuating forces at all loading cases Reliability, integrity and functionality in accordance with all requirements High resistance to wear Mechanical stability Seat tightness at low and high pressures Measuring parameter Effective actuator power Torque between the actuator and the gate valve Valve stem force (resistance strain gauges) Temperature of the valve stem during operation Temperature of valve body Pressure upstream and downstream of the gate valve 4 NKS, MKS
Qualification Test report of the AREVA NP GmbH, Erlangen, Germany 5
Cross sectional drawing 9 6 3 8 1 7 2 5 4 Table of components Component No. Description Component No. Description 1 Body 2 Guide 3 Stem 4 Wedge plate 6 Belleville springs 7 Bonnet 8 Stroke limiter 9 Actuator/ Hand wheel 5 Thrust pad 6 NKS, MKS
Gate Valve Enquiry Form (specifications) Size DN DN Dye forged shell body (DN 50 300) Welded body (DN 350 600) Actuator Hand wheel Electric Control: Position control Torque control Pressure rating Installation PN 10 PN 16 PN 25 PN 40 PN 63 PN 100 PN 160 Upright 45 90 180 Operating pressure [bar] Design features Seat hard facing: Stellite 21 Cobalt free Wedge positioning: Thrust pad Spring loaded with belleville springs Pressure drop ( p) [bar] Safety Class SC 1 SC 2 SC 3 SC 4 SC 5 Body fracture protection: Wedge plate guidance in the body: Seat ring drilled Wedge plates drilled External safety valve Not required Replaceable guides Integral hard faced Venting (of the body above the wegde plates) Medium Water Steam Belleville spring column for the linear unit for setting the valve stiffness in closed position Body Material C22.8 1.4550 1.4408 General requirements (Standard features) Integrity and functionality after actuator switch failure Seismic requirements EVA Piping connection Flange Welded end 7
Bopp & Reuther make industrial processes safe and efficient. We develop and manufacture shut-off valves, safety and control valves for the process industry, conventional power stations, the nuclear industry and other applications. Our products are supported by a worldwide service network. 03_2011 / NKS, MKS en FRANKFURT Bopp & Reuther Sicherheits- und Regelarmaturen GmbH Carl-Reuther-Strasse 1 68305 Mannheim Germany 70 km W N O Phone +49 621 / 76220-236 Fax +49 621 / 76220-130 www.bursr.com sales@bursr.com MANNHEIM S Bopp & Reuther Sicherheits- und Regelarmaturen GmbH. All rights reserved. Bopp & Reuther reserves the right to make technical changes without prior notice. All text and images are protected by copyright. Reproduction of any part of this document is strictly prohibited. We cannot be held responsible for any omissions or inaccuracies as a result of printing or composition errors.