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14. July 2017
Hot water recirculation pump without external cooling
Early in June 2014, KSB Aktiengesellschaft, Frankenthal, Germany, will
launch a new generation of hot water recirculation pumps for large
industrial heating systems as well as forced circulation boilers and district
heating systems. The horizontal, radially split single-stage volute casing
pumps feature a back pull-out design. Their ratings and dimensions comply
with ISO 2858; with regard to handling hot water, organic or synthetic heat
transfer fluids, they also meet the technical requirements of ISO 5199.
The HPK-L pump series, which comes in 49 different sizes, can be
operated at temperatures of up to 400 °C without any additional cooling
devices, and is designed for pressure classes of up to PN 40. This
temperature resistance is achieved by means of a generously sized heat
barrier which separates the pump set’s hot operating section from the aircooled mechanical seal chamber.
A fan impeller fitted at the pump shaft end generates a continuous flow of
air between the large cooling fins surrounding the mechanical seal
chamber. A service life of up to 25,000 operating hours is ensured by large,
product-lubricated silicon carbide plain bearings fitted close to the impeller
and by two angular contact ball bearings in back-to-back arrangement
sealed on both sides and mounted at the “cold” end of the shaft.
The patented venting profile, VenJet®, makes sure that the gas contained in
the fluid is separated near the mechanical seal and that it collects in the
venting chamber. The pump’s design provides space for the installation of
double mechanical seals in tandem arrangement without necessitating any
changes to the lengths of the cooling distances in the pump.
In this configuration, a quench fluid is provided between the two mechanical
seals. It prevents thermal degradation of the fluid handled at the sealing
clearance in cases of leakage at the inboard mechanical seal, and
discharges the heat transfer fluid into the quench system. This enhances
the system’s operating reliability, especially when using synthetic heat
transfer oils of up to 400 °C and with vapour pressures of more than 1 bar.
Discharge-side casing wear rings and drilled holes in the impellers help to
reduce the axial thrust and thus the loads on the bearings. With 49 pump
sizes on offer, a hydraulic system allowing the pump to be operated close
to the best efficiency point (BEP) can be selected for almost every
application. The pump manufacturer will also make sure to match every
impeller to the required operating point before the pump is supplied to the
customer.
Photo: HPK-L, the new hot water recirculation pump, can handle hot water
of up to 400 °C without external cooling. (Photo: KSB Aktiengesellschaft,
Frankenthal, Germany)