Image of the pump system in the water works

24 mar 20253 min read

SES System Efficiency Service makes resonant frequencies visible

High vibration levels were occurring at four newly installed variable-speed volute casing pumps in a water transport system when the pumps were operated at high speeds. Experts performed a system analysis to uncover the cause.

Multi-channel measurement with high sample rate makes vibration behaviour visible

Four pumps of the same type are installed in the water transport system, where they pump drinking water into one common main pipe. Two to three volute casing pumps are operated in parallel on frequency inverters for speed control; one pump is redundant. At low speeds, the vibration values were within the permissible range to DIN ISO 10816/7. However, at high speeds the values increased significantly.

Vibration measurement with high sample rate and several measurement channels

Vibration measurement with a high sample rate and several measurement channels initially showed the exact vibration development at several measurement points. The pump's operating range from 500 to 995 rpm (8.3 to 16.5 Hz) met the natural frequency of the system (at approximately 95 Hz). The reason for this was an overlap of the system's natural frequency and the blade passing frequency. This became clear via a frequency analysis. In order to determine further details about the natural frequencies, hammer excitation tests (bump tests) were carried out so that remedial measures could be derived.

New mountings lower the vibration values

The hammer excitation (bump) tests revealed that various reinforcements could be retrofitted to the frame. In addition, anchorage points were installed upstream and downstream of the pump, resulting in the system's natural frequency to move out of the pump's operating range.

Excerpt of the recorded measurement data — The vibrations in the lower speed range are within the permissible range. However, at speeds from 900 to 995 rpm (increase from 3 to more than 6 mm/s) the vibrations rose significantly at the non-drive end in the vertical direction.

Application: Water transport

Year: 2016

Duration: 3 month

Products used:

4 x RDLO 600-1200 B with 3.9 MW motors

RDLO

Documentos

Bomba de voluta partida axialmente, monoetapa, para instalación horizontal o vertical, con impulsor radial de doble aspiración, bridas de conexión según DIN, EN o ASME.

Detalles