High-reliability

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A wide range of pumps are utilized in power and desalination plants, all from which high reliability is demanded to ensure secure and stable plant operation. In order to ensure stable pump performance, factors such as bearing lifespan,
casing pressure, rotor stability and cavitation control, as well as the prevention of corrosion and occurrence of vortices around the suction tank, must all be taken into consideration.
Torishima’s R&D team is striving to conquer these issues through the use of advanced technology in fluid and structural analysis.

Cavitation

Regulating cavitation is a challenge that must be overcome when realizing both reduced sizes and high speeds in pumps. Using large scale cluster machines and the latest CFD technology, we can predict cavitation development,
which allows us to improve the cavitation characteristics of our products. (Ref. Fig. 1・2).

Fig.1 Results of cavitation analysis
Left:Existing impeller
Right:Improved impeller, the red colored areas indicate vapor phase

Fig.2 Photo of cavitation bubble
(Improved impeller which regulates cavitation)

Instability of Performance

Rotation stalls often happen when flow separation occurs at a partial flow rate due to pressure recovery of the stator vane, etc., of a compact-designed pump. When this happens, the pump operating range is significantly restricted due to the increase in vibration and noise.
In order to investigate the cause of diffuser rotating stalls, the internal flow was measured using a dynamic PIV measurement system.
Moreover, CFD was implemented to clarify the root cause of the diffuser rotating stall. Additionally, a design parameter study was performed on the diffuser to develop conditions in which pump instability characteristics are less likely to occur.

Fig.1 Static pressure fluctuation Fig.2 Measurement area of internal flow and static pressure
Fig.3 Vortec core of a rotating stall(PIV)

Fig.4 Instantaneous static pressure contour map(CFD)
Fig5. Instantaneous velocity vectors(CFD)
Fig.6 Pump performance charactaristics

Anti-vortex Devices

With large-size pumps, if the installation location and the shape of the sump are not adequate, harmful air and submerged vortices occur within the operation of the pump in the suction tank. We are able to predict the occurrence of vortices using a hydraulic model test or CFD (Computational Fluid Dynamics), allowing us to suggest a suitable shape.

Fig.1 Submerged vortex
(sump model test)
Fig.2 Surface vortex
(sump model test)
Fig.3 Vortex prediction
with CFD
Fig.4 Anti-vortex devices

Bearings

Thanks to optimized bearing design, Torishima Pumps can be maintained and kept running stably for a long time.
By monitoring the vibration of the bearing housing and the rotor bearings, bearing designs can be achieved that stand up against a wealth of operating conditions and environments.

Babbitt journal bearing

Bearing test and diagnosis

Rotor Dynamics

Consideration of the stability of the pump rotor is important when producing safety pumps.
For example (see multi stage high pressure pump : Fig. 1), natural vibration frequency and mode shape (Fig. 2・3) is investigated by using vibration analysis software to perform rotor stability and torsional vibration analysis, even before the pump rotor component is designed.

Fig.1 Structure of multi stage high pressure pump

Fig.3 Results of torsional vibration analysis (natural vibration mode shapes)
Fig.2 Results of rotor stability analysis
(natural vibration mode shapes)

Material

With the increasing demands of sea water pumps, corrosion resistance of the materials used has become more and more important. The elements and temperature of sea water can greatly affect the corrosion resistance of materials, and Torishima carries out corrosion tests according to the sea water conditions of the area to which the pump is delivered. We stand firmly behind our guarantee of reliability.

Corrosion test in seawater

Stainlless-steel RO
high pressure pump