Two Differences Between the Single Stage Pump and the Double Suction Pump

Centrifugal pump is divided into single stage pump (SSP) and double suction pump (DSP) according to suction method. Seen from appearance, the SSP has one water inlet on its impeller whereas the DSP has two on the two sides of the impellers. However, differences between the two pump types are far more than the number of water inlet.

Structure
The fundamental parts of a single stage pump, also called an end-suction pump, are an impeller which rotates with high speed and a fixed pump case in the shape of snail. The impeller with some backward bent vanes is tightened on the pump spindle and revolves with the spindle at a high velocity under the drive of the dynamo. The suction inlet in the center of the pump case is connected with the suction line which has a one-way foot valve in the bottom. And the outlet aside the pump case is combined with the discharge line loaded with a regulating valve.
The double suction split case pump has two back-to-back impellers which have symmetrical structures and the water flowing out of the impellers gathers into one volute. What's more, the inlet and the outlet of the DSP are in one direction and are perpendicular to the pump spindle. Some other chief units of the DSP are: pump body, pump cover, pump spindle, double suction sealing ring, spindle sleeve, shaft bearing and so on, among which the pump body and the pump cover constitute the work room of the impeller. On the flanges for water inlet and outlet there are pipe screw holes loaded with a vacuum gauge and a pressure gauge. And the pump spindle is supported by two single-row-radial-ball shaft bearings that are installed in the bearing bodies at the two ends of the pump body.
Advantage
For the single stage pump, there are two prominent advantages. Firstly, it is energy efficient, because during design the relationship between the pressure distribution and the velocity distribution is analyzed and counted out on the basis of computational fluid dynamics and the runner design of the pump is optimized, thus a high-efficiency hydraulic line is ensured and the productivity is prompted. Secondly, it is heat resisting, since the pump body is centrally supported. Therefore, the problems of press concentration and change of coupler center resulted from inconsistent thermal expansion of the pump package in high temperatures are solved. In addition, there are cooling chambers in the pump stand, the pump cover, the suspension body and the machine-sealing gland, and so they can be cooled down by the cooling water or the cooling air in different temperatures.
As to the double suction pump, it owns mainly four merits. To start with, its compact structure and good stability help for assembling. Then, it operates steadily, for the optimized double suction impellers reduce the axial force to a minimum, the blade profile has an excellent hydraulic performance, and through precision casting the inner surface of the pump case and the surfaces of the impellers are especially smooth, bringing about outstanding cavitation resistance and high efficiency. Third, the shaft seal of the double suction pump is chosen from the BURGMANN mechanical seals and the BURGMANN packing seals, and thus it can work for 8000 hours without leak. At last, its shaft bearing is of a SKF or a NSK bearing, making the operation more stable, the working noise lower, and the service life longer.
This article comes from: http://www.pacificpumpgroup.com/news/41160.html