The core of the floating suction pipe (also known as a floating oil discharge/suction device) is to utilize buoyancy to make the suction port float with the liquid level, always extracting clean oil from the upper layer of the storage tank and avoiding sucking in water and impurities from the bottom. The following is an explanation from the aspects of principle, structure, working process, selection, and application.
Core Working Principle
Buoyancy drive: The buoyancy generated by the floating cylinder is greater than the self-weight of the device, making the oil suction port suspend about 100–300mm below the liquid surface.Follow-up lifting: When the liquid level rises or falls, the floating cylinder drives the oil suction arm/hose to rise and fall synchronously, so that the suction port always remains in the upper clean oil layer.Stratified extraction: Using the principle of gravity sedimentation-water and impurities settle at the bottom of the tank, and the upper oil is purer; the device prioritizes extracting the upper oil, which greatly improves the quality of the output oil.Anti-vortex design: The suction port is often equipped with a rectifying grid to avoid the formation of vortices during liquid extraction, and prevent the inhalation of air or bottom sediment.
Typical Structural Composition (Common for Storage Tanks/Marine Use)Floating cylinder/floating ball assembly Function: Provide buoyancy and drive the suction port to float with the liquid level.Types: - Fixed floating cylinder: Rigidly connected to the suction port, serving as the main buoyancy source.
Movable floating cylinder: Assist in stabilization, balance torque, and reduce pipeline deflection.Material: Stainless steel, aluminum alloy, high-density polyethylene (HDPE), suitable for oil products/chemical media.
Oil suction arm/oil pipe line Rigid arm (commonly used): Can rotate around the swivel joint with a maximum swing angle of about 75°, featuring stable structure and long service life.Flexible hose: Suitable for large liquid level changes, with flexible installation, but prone to wear and requiring regular replacement.
Oil suction nozzle/suction port: Duckbill-shaped, multi-hole type, with wide mouth and large flow rate, anti-vortex; its position is slightly lower than the bottom of the floating cylinder to ensure suction within the oil layer.
Swivel/rotary joint Function: Connect the fixed end (tank wall/ship wall) with the floating arm, realizing 360° rotation and up-and-down swing to ensure unobstructed pipeline.Key points: Reliable sealing, flexible rotation, and resistance to oil corrosion.
Fixing and supporting system Base/rotary support: Installed at the bottom of the tank/hold, providing a rotation fulcrum for the oil suction arm.Connecting flange: Docked with the oil outlet short pipe/passage part of the tank wall to realize the connection of pipelines inside and outside the tank.Limiting/guiding: Prevent the floating cylinder from drifting, limit the height of the suction port at the lowest liquid level to avoid touching the bottom.
Auxiliary components Rectifying grid/anti-vortex device: Installed at the suction port to suppress vort ices and reduce air inhalation.Static wire: Discharge static electricity to ensure safety.Adjusting mechanism: Fine-tune the depth of the suction port to adapt to different oil densities.Complete Working Process Installation in place: The fixed end is connected to the oil outlet of the tank wall through a flange, and the floating cylinder end is suspended
below the liquid surface.Buoyancy balance: The buoyancy of the floating cylinder offsets the self-weight of the device, and the suction port is stabilized in the clean oil layer.Liquid extraction operation: When the pump is started, the upper clean oil flows through the suction port → oil suction arm → swivel joint → oil outlet pipe → external tank system.Liquid level following: When the liquid level drops, the floating cylinder drives the suction port to move down synchronously, always extracting the upper oil; when the liquid level rises, the reverse action occurs.Low liquid level protection: When the liquid level drops to the lowest level, the limiting mechanism prevents the suction port from touching the bottom to avoid sucking in impurities.
Main Types and Selection Single-arm type: Simple structure, low cost, suitable for storage tanks where the liquid level change is ≤ the tank diameter.Double-arm type: Good stability, large swing range, suitable for high liquid level and large-diameter storage tanks.Marine special type: Equipped with rotary support and hold wall passage parts, adapting to ship shaking, commonly used in heavy oil tanks and diesel tanks.Floating roof tank adaptation: The suction port is directly fixed under the internal floating plate and rises and falls synchronously with the floating plate.
Applications and Advantages Applicable scenarios: Storage tanks with high requirements for oil cleanliness in petroleum, chemical industry, airport oil depots, ship oil tanks, etc.Core advantages: Ensure oil quality and reduce the load on downstream filters/separators. Shorten the oil static precipitation time and improve oil dispatch efficiency. Reduce the wear and corrosion of equipment caused by bottom impurities/water.
