Jiangsu Haifa Machinery Manufacturing Co., Ltd.

Title: Rotor Dynamics Design of VS4 Pump Long Shaft

In the field of industrial fluid transport, the rotor dynamics of long-shaft pumps have long been a hidden pain point for users. A petrochemical company once reported that the VS4 vertical long-shaft pump they used frequently experienced excessive vibration during operation, with bearing life less than three months, leading to production line shutdowns for maintenance and single direct losses exceeding hundreds of thousands of yuan. After our technical team conducted on-site diagnostics, the root cause was identified as the rotor system design failing to adequately account for the coupling effect of long-shaft deflection deformation and critical speed.

To address this pain point, we provided the company with a customized VS4 pump long-shaft rotor dynamics optimization solution, with the core design divided into three steps:

Precise Modeling and Simulation Analysis  Using multi-body dynamics software, a complete model including the shaft system, impeller, bearing housing, and sealing system was established. The simulation focused on the impact of different speeds and medium densities on rotor deformation under actual operating conditions, identifying the risk of the original design’s second-order critical speed coinciding with the operating speed.Optimization of Shaft System Structure and Support Layout  The original uniform-diameter shaft was replaced with a stepped shaft, and an auxiliary bearing housing was added at the midpoint of the support span enhance system stiffness. Additionally, the bearing preload was adjusted, reducing the rotor amplitude under rated conditions from 0.12mm to below 0.03mm.Introduction of Damping Vibration Reduction Technology  A high-damping alloy cushion layer was embedded at the connection between the bearing housing and pump body, combined with an optimized lubrication system, effectively suppressing low-frequency whirling.

On-site measurement data from the client showed that after the modification, vibration intensity dropped from 7.8mm/s to 2.1mm/s. “After six months of operation, the bearings are still in good condition, and the vibration data is more stable than that of a new machine,” the company’s equipment manager during a follow-up visit. “We used to think vibration was a common issue with long-shaft pumps, but we never realized it could be completely resolved through professional design.”

Common Issues and Precautions:  The rotor dynamics design of long-shaft pumps must account for specific installation environments, such as foundation stiffness and pipeline stress. It is recommended to conduct on-site vibration testing before installation to avoid “armchair engineering.” For shaft lengths exceeding 2 meters or operating speeds near the critical zone, finite element analysis should be prioritized for validation rather than relying solely on empirical selection. Damping vibration reduction components are consumable items and should be inspected every 12 months, with replacement as needed. We offer remote monitoring and early warning services to help users identify potential risks in advance.

We are honored to have elevated the reliability of the VS4 pump to a new level through this collaboration. Moving forward, we will continue to delve into the field of rotor dynamics to solve similar challenges for more users.

Jiangsu Haifa Machinery Manufacturing Co., Ltd. was restructured from Jiangsu Ligong Group Co., Ltd. and the Jingjiang Stainless Steel Pump and Valve Factory of the Iron and Steel Research Institute of the Ministry of Metallurgical Industry, originally established in 1958. The company primarily produces API610 chemical process pumps—OH1, OH2, OH3, OH4 pumps; BB1 to BB5 multi-stage pumps; VS1 to VS6 barrel pumps; HES chemical process pumps; sixth-generation ultra-low carbon stainless steel high-quality leak-proof molten urea pumps; urea hydrolyzer feed pumps; pitot tube pumps; rotary jet pumps; molten salt pumps; vertical submerged pumps; high-temperature magnetic drive pumps; magnetic pumps for conveying solid-containing media; industrial pumps; canned motor pumps; slurry pumps; titanium tetrachloride pumps; self-priming pumps; lined fluorine pumps; leak-proof pumps; alkali pumps; axial flow pumps; long-shaft vertical submerged pumps; CQC first-level energy-efficient chemical pumps; and high-pressure descaling industrial pumps. www.jslgpump.com Contact: 13905263417 E-mail: jslgpump@gmail.com E-mail: jsareva@163.com