Design concept and technical core of vertical multi-stage submerged semi submersible long shaft deep well turbine pump

The design concept and technical core of the vertical multi-stage submerged semi submersible long shaft deep well turbine pump revolve around the core goal of "stable water delivery with high head in deep wells", and an engineering system consisting of four pillars: segmented long shaft transmission, multi-stage centrifugal boosting, axial force balance, guide bearing support, and downhole sealing. The design logic of the vertical multi-stage underwater semi submersible long shaft deep well turbine pump follows the industrial principles of "structure maintainability, high reliability operation, and high efficiency and energy saving".
Design concept: Modular layered architecture
·Drive layer above the well: The motor is placed on the ground and directly connected to the long shaft through a coupling to prevent the underground motor from being affected by moisture, high temperature, and corrosion, thereby improving maintenance convenience and safety.
·Transmission shaft layer: Adopting segmented 45 # steel chrome plated or 316L stainless steel long shaft, water lubricated guide bearings (made of graphite or engineering plastic material) are installed every 3-5 meters to form multi-point rigid support, effectively suppressing shaft deflection, ensuring radial runout ≤ 0.08mm/m, and preventing vibration and friction wear.
·Hydraulic working layer: Multi stage closed centrifugal impellers are connected in series in the guide shell, and the pressure is gradually increased. The single-stage head is 10-50m, and the total head can reach more than 250m (such as the LVG series vertical long shaft deep well pump of HUNAN PERFECT industry, which has a maximum head of 450m). The impeller material is selected from silicon brass, 304/316L stainless steel or duplex steel 2205, which balances corrosion resistance and wear resistance, and is suitable for water with sand content (sand content ≤ 0.01%).
·Water lifting channel layer: The water lifting pipe is connected by flanges or threads, and is equipped with shaft sleeves and sealing rings to ensure the sealing and structural rigidity of the water flow channel, avoiding leakage and displacement.
Technical Core: Four Key Technological Breakthroughs
Axial force balance technology:
Balance holes or balance disks/drums are installed on the front and rear cover plates of the impeller to counteract the axial thrust generated by high-pressure liquid; Part of the design is supported by motor bearings to bear residual axial forces, reduce bearing loads, extend shaft life, and improve operational stability.
Underground sealing technology;
The mainstream adopts double end mechanical seals (silicon carbide static ring+graphite dynamic ring), supplemented by fluororubber O-rings, with a leakage rate of ≤ 0.001mL/h; Partial operating conditions use a secondary impeller power seal to block medium leakage using reverse centrifugal force, achieving "drip proof" and suitable for high lift, corrosive media such as seawater and acidic water.
Vibration and deflection control technology:
Using flame straightening technology to eliminate internal stress in the shaft material, and mirror polishing the surface of the shaft body; The guide bearing adopts a maze type anti sand ring design, centrifugally separating sand particles to prevent them from entering the lubrication zone, ensuring smooth operation at a liquid depth of over 100 meters, with a noise level of ≤ 75dB and a lifespan of over 15000 hours.
Hydraulic efficiency optimization technology:
Based on CFD simulation, optimize the impeller wrap angle (affecting head) and guide vane outlet placement angle (affecting efficiency) to improve hydraulic efficiency by 5-8%; The high-efficiency zone is wide, with a comprehensive efficiency of 75-88%, energy-saving of 10-20%, reducing long-term operating costs, and complying with IE3 energy efficiency standards.
Design standards and industry norms
·Core standard: Implement the industry standard CJ/T 235-2017 "Vertical Long Axis Pump", covering type parameters, material requirements, test methods, and installation specifications, clarifying key parameters such as minimum submergence depth, allowable eccentricity, and maximum bearing span.
·Water quality adaptation: The conveying medium is clean water or a liquid with similar physical properties, with a temperature of ≤ 55 ℃ (special design can reach 90 ℃) and a sand content of ≤ 0.01%. A cyclone sand remover is required to extend the life of the impeller.
·Selection criteria: Total head=dynamic water level+pipeline friction loss+5-10m safety margin; The flow rate is determined by multiplying the daily water demand by a coefficient of 1.1, and the motor power matches the optimal efficiency zone (75-110% load).
Technology Trends and Engineering Practice
·Intelligent Drive: Variable frequency control and permanent magnet high-speed motor (6000r/min) have been applied to high-end products such as Hunan Lijia Machinery, achieving constant pressure water supply, energy saving of 20-40%, and supporting remote monitoring and fault warning.
·Material upgrade: The overcurrent components are widely made of duplex stainless steel 2205, ceramic coating or fluoroplastic lining, which improves corrosion resistance by 3-5 times and is suitable for seawater, geothermal, and chemical media.
 
Current Problems and Challenges
·Ultra deep working conditions (>200m): The difficulty of controlling long axis deflection and vibration increases exponentially, requiring reliance on multi-point bearings and high-precision machining, resulting in a significant increase in cost.
·Sand/corrosive media: Traditional seals and impellers wear out quickly, requiring continuous investment in research and development of wear-resistant materials (such as silicon carbide and nano coatings).
·Low penetration rate of intelligent operation and maintenance: Most small and medium-sized projects still rely on manual inspections, and online monitoring systems for vibration, temperature, and flow have not yet been standardized.
·Standard lag: CJ/T 235-2017 does not cover emerging technologies such as permanent magnet high-speed pumps and intelligent control, and the industry urgently needs to update its standards.