SNF660ER40U3-W1-FA5,0

Pumped liquid：ISO VG 320

Kinem.viscosity v[mm*/s：320，0

Temperature t（℃）：40

Suction pressure ps[bar]：0，0

Nominal speed n[1/min] ：1500

Capacity Q[I/min]：509，0

Discharge pressure pd[bar]：7,0

Power absorbed P[kW]：11,9

NPSH[m]：3,1

Differential pressure dp [bar]：7,0

Power driver P[kW]:0,0

DNs/DNd [mm]:125/100

Screw Pump: The Positive Displacement Workhorse for Viscous Fluids1. Basic Definition

A screw pump is a type of positive displacement (PD) pump that uses one or more meshing screws (rotors) to move fluid along the axis of the screws. As the screws rotate, they form a series of sealed, discrete cavities that trap the fluid and transport it steadily from the suction side to the discharge side. This design makes them exceptionally effective for handling viscous, non-lubricating, and delicate fluids.

2. Key Components & Working Principle

The core components of a screw pump are:

· Rotor (Main Screw): The central, powered screw.

· Idlers (Stationary Screws): One or two counter-rotating screws that mesh with the main rotor. They are driven by the rotor via timing gears and do not make metal-to-metal contact.

· Timing Gears: Located outside the pumping chamber, these gears synchronize the rotation of the rotors, maintaining precise clearance and preventing contact. This is crucial for handling non-lubricating fluids.

· Pump Casing: The housing that contains the screws and creates the pressure boundaries.

· Bearings and Seals: Support the shafts and prevent fluid leakage.

Working Principle:

1. As the screws rotate, fluid is drawn into the inlet port at the suction end.

2. The fluid is trapped in the sealed cavities formed between the meshing screws and the pump casing.

3. These cavities move axially along the screws as they rotate, acting like a continuous, progressing "pocket" of fluid.

4. The fluid is conveyed smoothly and continuously to the discharge end without any internal turbulence or change in volume.

5. At the discharge port, the fluid is expelled as the cavities collapse.

The key is that the fluid moves axially in a laminar flow, without the churning or pulsation common in many other pump types.

3. Main Types of Screw Pumps

· Single-Screw Pump (Progressive Cavity Pump):

  · Consists of a single metallic rotor rotating within a stationary elastomeric stator.

  · Known for handling fluids with high solid content, sludges, and very high viscosities.

  · Often used in wastewater treatment and food processing.

· Twin-Screw Pump:

  · Features two intermeshing screws. They are timed by external gears, which means the screws do not touch.

  · Excellent for pumping non-lubricating, corrosive, and multi-phase fluids.

  · Highly versatile and common in industrial, chemical, and oil & gas applications.

· Three-Screw Pump:

  · Consists of one central power rotor and two idle idler screws that seal against the central rotor and the pump housing.

  · The idlers are not gear-driven but are turned by the fluid film.

  · Primarily used for pumping clean, lubricating fluids like fuel oil, hydraulic oil, and lubricating oil at high pressures.

4. Key Advantages

· Handles High Viscosity: Excels with thick fluids that would stall centrifugal pumps.

· Low Shear: The gentle, laminar flow is ideal for pumping delicate, shear-sensitive fluids like latex, fruit juices, and polymers without damaging them.

· Non-Pulsating Flow: Provides a smooth, constant flow rate, which is critical for metering and process stability.

· Self-Priming: Has excellent self-priming capabilities and can handle vapor or entrained gases.

· High-Pressure Capability: Can generate very high discharge pressures, even at low flow rates.

· Handles a Wide Range of Fluids: Effective with lubricating, non-lubricating, corrosive, and abrasive fluids (depending on the type and construction materials).

5. Common Applications

Screw pumps are vital in industries that move challenging fluids:

· Oil & Gas: Crude oil transfer, fuel oil burning, pipeline boosting, and hydraulic systems.

· Marine: Fuel transfer, lube oil service, and cargo pumping.

· Power Generation: Pumping heavy fuel oil, lube oil, and asphalt.

· Chemical & Process Industries: Transferring resins, polymers, paints, solvents, and adhesives.

· Food & Beverage: Pumping chocolate, syrups, dough, cream, and fruit concentrates.

· Wastewater Treatment: Moving primary and digested sludge.

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