Analysis of operating conditions of vertical multi-stage semi submersible long shaft deep well turbine pump with ultra long underwater depth

The vertical multi-stage semi submersible long shaft deep well turbine pump with ultra long underwater depth is mainly used for extreme working conditions such as deep wells, deep seas, and large storage tanks. Its operational stability and safety highly depend on structural design, material selection, and system matching. Overall, vertical multi-stage semi submersible long shaft deep well turbine pumps with ultra long underwater depths (usually exceeding 30 meters, up to 80 meters to 100 meters) face greater challenges in high head, corrosion resistance, vibration resistance, and sealing reliability. They require segmented shaft systems, multi-point supports, high-performance materials, and intelligent monitoring to ensure long-term stable operation.
1、 Core structural design: addressing the mechanical challenges brought by depth
As the depth of the liquid increases, the length of the pump shaft significantly increases, which can easily cause problems such as increased deflection, intensified vibration, and excessive radial runout. Therefore, the following structural optimization schemes are commonly adopted for ultra long submersible pumps:
·Segmented long shaft design: The shaft body adopts multiple high-strength steel shaft sections connected by sleeve couplings, which is convenient for transportation and installation, while reducing the risk of deformation of single section shafts.
·Multi point support system: Multiple sliding bearings (guide bearings) are installed in the underwater part, with a spacing of generally ≤ 3 meters. They are matched with wear-resistant shaft sleeves and lubricating water films to effectively absorb swing energy and control radial runout ≤ 0.08mm/m.
·Three point support or adjustable rotor structure: For example, the LVG series vertical long shaft pump of Lijia Machinery adopts three-point support+water lubricated graphite bearings to achieve smooth operation at a depth of 100 meters.
2、 Materials and Corrosion Resistance: Suitable for Complex Media Environments
Ultra deep working conditions often involve highly corrosive, high sand content, or high-temperature media, which require higher requirements for materials:
·Axis material: 316L stainless steel or titanium alloy is preferred, with high strength (tensile strength ≥ 550MPa) and excellent resistance to chloride ion corrosion (Cl ⁻ ≤ 50000ppm).
·Impeller material: duplex stainless steel 2205 or ceramic coating, can withstand 565 ℃ molten salt environment, with a measured wear of only 0.15mm after 8000 hours.
·Bearing lubrication method: External cooling lubrication or self cooling lubrication can be selected to avoid excessive temperature rise of the bearing due to poor heat dissipation.
3、 Sealing and Leak Prevention System: Ensuring Safety under Extreme Pressure
Traditional mechanical seals are prone to failure due to high pressure and high temperature under ultra deep working conditions. High end imported pumps adopt multiple protections:
·Multi stage series mechanical seal: equipped with 3 layers of SiC sealing rings, pressure bearing ≥ 10MPa, leakage rate<0.1ml/h.
·Sealing chamber protection: Inject anti scaling lubricating fluid (such as ethylene glycol solution) to prevent deep well high-temperature scaling and extend sealing life.
·Explosion proof certification: In flammable and explosive environments, ExdeIIBT4 explosion-proof rating is required to ensure the safety of the motor and sealing system.
4、 Adaptability to operating conditions
·Startup advantage: The impeller is always immersed in the medium and can be started directly without exhaust, avoiding air resistance problems.
·Head and flow matching: Multi stage impeller combination can achieve high head (up to 100m) and high flow (up to 1500m ³/h) transportation, suitable for deep-sea ballast water discharge, subsea pipeline cleaning and other scenarios.