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Additional information about Pelton Turbines
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Pelton turbines produced by our Company can be supplied either with horizontal shaft, with one or two jets, and with vertical shaft, with a maximum of six jets, always controlled separately.
They are complete with all the items and accessories needed for their installation and commissioning and are made of a carbon steel case (6), a single bucket or monolithic wheel, mechaniccally secured (8), by a supporting shaft and one or more injectors (1) complete with needles (2) and deflectors (3).
The case, made of suitably stiffened steel, are equipped with a separate base to be secured to the foundation works and have inspection openings. They have also been designed to help water outlet with minimum interference to the rotating wheel.
The welded parts are given suitable stress relieving heat treatment, to remove internal stress; a cycle of sandblasting is also carried out and primer applied (according to SVENSK STANDARD SIS 1967 directives), to preserve the material from oxidation and to guarantee the paint a longer life time. All the parts to be secured to the foundation works are washed with lime or equivalent and all the parts in contact with the water are painted with a-toxic products.
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The generator is secured by flanges directly above the turbine case with vertical shaft groups, and the wheel can be lowered directly onto the shaft so that the result is a compact, single-block system, avoiding any serious non-alignment between turbine and generator.
Our Pelton turbines are also equipped with deflectors (3) which come between the wheel and the water jet in emergencies, deviating its course and preventing the machine from reaching dangerous runaway speeds, but without sudden changes in the flow capacity which would cause water hammering in the pipeline.
Hydraulic actuators drive the injector needle as well as the deflectors, with double effect for the needle and single effect with spring return for the deflector. A sensor detects the position of each actuator continuously and sends a signal to the turbine regulator.
The jets have distributor needles (2) in heat treated CrNi 17/4 PH stainless steel or similar, and inter-changeable nozzles; they are complete with central rib (4) holding the needle rod, with a profile designed to re-align the flow of water before it hits the wheel buckets.
The jet deflectors are made of high tensile stainless steel, assembled onto standard self-lubricating bushings and controlled by hydraulic actuators (9).
The distribution pipeline to the various nozzles, suitably reinforced at the branches, is connected to the machine valve and to the injectors by a flanged joint (5).
The Pelton wheel may be produced in a single piece wheel or with buckets fixed onto a central disk with special mechanical dovetailing.
Casting is usually done in highly qualified foundries using special stainless steels in highly accurate ceramic dies.
Each bucket is accurately hollowed and the wheel is balanced dynamically to the runaway speed conforming to ISO 1940-1973 standards.
Connections between buckets (8) and the central disk are perfectly aligned as the surface plates are made by numerically controlled mechanical working processes. Stay bolts are used for securing, which are only exposed to axial thrust, transferring necessary compression to the buckets and reaching the required interference values. Single cast pieces are of better quality using this technique and positioning the profiles and finishing the surface of the hollowed parts is highly accurate.
The high tensile steel motor shaft is equipped with a labyrinth sealing for water tightness.
Horizontal shaft turbines are supplied with their own bearings, a flexible joint is normally used to couple up to the generator and one of the half-joints may be enlarged to increase the rotating mass inertia.
If supplied, the bearings are lubricated with grease and are designed for a working life of over 100,000 hours.
The series of equipment for automatic control and protecting the group normally include measurement instruments such as opening indicators, gauges and pressure switches, sensors for temperature and vibrations.
Finally, pre-assembly works and any alignment possible of the entire group onto a frame, done in our workshops, considerably reduce erection time in the power station, resulting in a faster and efficient commissioning.
For further information about this product, feel free to contact us.
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