CONDENSATE PUMP FEATURES C078

CONDENSATE PUMP FEATURES C078

  • Condensate pumps take suction from a condenser hotwell and discharge either to a deaerating heater in an open feed water system. or directly to the suction of a boiler feed pump in a closed system.
  • Because it is desirable to locate the condenser hotwell as low as possible to minimize the elevation of the power plant, the NPSH available is usually extremely low.
    • This may require the use of a deep pit for the condensate pump. The NPSHA, with absolute pressures in the condenser near zero, is only the sub- mergence (or elevation) between the water level in the condenser hotwell and the centerline of the pump impeller (first stage impeller for multistage pumps).
    • This value could be as low as 2-ft to 4-ft, which means that friction losses between the condenser hotwell and the pump suction must be kept to an absolute minimum to avoid reducing NPSHA further. To minimize friction losses, calculated velocities in the suction piping and within the suction can of vertical pumps should be no more than 4-ft/s.
  • Condensate pumps can be horizontal or vertical, single or multistage, depending on the system head requirements. Because of the low NPSHA, horizontal pumps operate at relatively low speeds, from 1800-rpm for low flow requirements to 900-rpm or even less for higher flow requirements. Vertical can-type pumps, which can be installed below ground and attain higher values of submergence of the impeller (higher NPSHA), can operate at higher speeds.
    • Vertical can- type pumps are available with single and double suction first stage impellers and typically operate to 3600-rpm for low flow applications and 1200-rpm for higher flow requirements.
  • To prevent air or CO2 leakage into the pump convert  the packing to a balanced o-ring mechanical seal.
  • Condensate pumps are designed or arranged such that they have discharge pressure (or at least a positive pressure above atmosphere) on the seal chamber to prevent flashing of the condensate
  • Keep friction losses between the condenser hotwell and the pump suction to an absolute minimum to avoid reducing NPSHA any further.
    • With absolute pressures in the condenser near zero, the NPSHA is only the submergence (or elevation) between the water level in the condenser hotwell and the centerline of the pump impeller (first stage impeller for multistage pumps).

Category

Posted

  • On February 15, 2018