MARC Steam Turbines The Modular Steam Turbine Generation

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Control mechanism The steam control valves of MARC turbines are of a diffuser type. Small valve dimensions allow a vast number of valves and nozzle groups. Consequently, the throttling losses are kept low also at part load. The cone form of the valve has been optimized regarding the flow. Valve spindles, valve cone and valve bar consist of heat-resistant steel with hardened, wear-resistant surface. The hardening is effected via a plasmahardening process. 12 Due to the small valve dimensions, the steam control valves can be actuated directly. This so-called group drive is a compact and reliable solution. The actuator is a single acting hydraulic cylinder which is fed by the control oil system at an oil pressure of 160 bar. On turbine tripping or full-load disconnection the valves are closed by the pre-loaded spring, thus, protecting the turbine plant at malfunctions. If the pressure in the control oil system decreases, both the control valves and the tripping devices will be closed automa- tically, as they act on the same principle (single-acting hydraulic piston against pre-loaded spring). This means double security for the turbine and the steam system. A lever system for parallel motion of both valve spindles precisely transmits changes of the controller output onto the valve bar and – depending on the valve lift – on one or more valve cones. The moving parts are made of non-corrosive and maintenance-free self-lubricating material. The valve spindles are sealed by maintenancefree, pre-compressed graphite laminated glands, and reinforced carbon guide bushes.
Gearbox/Generator module Gearbox and generator are installed as one compact unit. For the MARC 2 and the MARC 4, generally an epicyclic gearbox is used which is flanged directly to the generator. For the types MARC 6 and MARC 8 either an epicyclic or a helical gearbox is used, depending on power and speed. The application of epicyclic gearboxes bear the following advantages: The offset usually caused by a helical gearbox is avoided, which greatly facilitates the alignment. Moreover, one coupling and the high-speed gear bearing are omitted which improves the total efficiency. 13
Page 1 and 2: MARC ® Steam Turbines The Modular
Page 3 and 4: The first steam turbines under the
Page 5 and 6: The turbo generator unit comprises
Page 7 and 8: The new MARC 1 The success formula
Page 9 and 10: The following design features apply
Page 11: Reaction Part The multi-stage react
Page 15 and 16: Control oil module Control oil syst
Page 17 and 18: Control cabinet Field ISDN Router E
Page 19 and 20: Service Our experienced Turbine Ser

MARC Steam Turbines The Modular Steam Turbine Generation

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