Replacement Of The Boiler Feedpumps During The Retrofit Of The 500 Mw Units At A German Power Station

Abstract

The Janschwalde Power Station consists of six 500 MW units that were commissioned between 1981 and 1989. These units, which were equipped with turbo feedpumps manufactured in Russia, had an average efficiency of only 78 percent and a mean time between overhauls of 25,000 hr. The test was to adapt these boiler feedpumps at the lowest possible cost (only minor modifications to the base and the pipework were envisaged), and to achieve a payback time of four to five years by improving the pump efficiency and reducing operating costs. This was accomplished by fitting new cartridges into the existing barrel casings. These cartridges consisted of six-stages of a well-proved hydraulic with a specific speed of 1700 operating at the nominated turbine speed of 5600 to 5700 rpm. The processing of the contract within the pump manufacturer’s organization is described, along with the extensive coordination and quality assurance within a tight production schedule (delivery time of only seven months before the trail operation of the first pump unit). The efficiency of the new pumps was determined onsite by means of thermodynamic measurement. The specific features of the pumps and the proof efficiency in the power station by means of thermodynamic measurement are defined in detail.