3LIS/4LIS Screw Solar High-Lift Submersible Pump

Model Interpretation:
3/4: Represents the pump body diameter (3 inches ≈ 76mm, 4 inches ≈ 100mm).
L: Vertical.
I: Iron/Cast Iron – Core material identification.
S: Screw.

Core form: Single-screw submersible pump.
Core difference: Cast iron casing + stainless steel shaft + rubber stator. It retains the "durable" core of a screw pump, but the casing is replaced with lower-cost cast iron.
Core working principle: Positive displacement + low speed and high torque
The working logic of the 3LIS/4LIS Iron series is the same as the stainless steel version, which is "slow but powerful, accepting all comers":
Meshing seal: The core of the pump is a metal rotor (screw) and a rubber stator. When the rotor rotates inside the stator, a continuous sealing line is formed.
Axial propulsion: As the rotor rotates, the sealed chamber moves from the suction end to the discharge end. The liquid is enclosed in the chamber and smoothly "pushed" out of the wellhead.
Low-speed operation: Screw pumps usually operate at low speeds. Coupled with a brushless DC motor, it can provide a large starting torque, making it very suitable for solar power supply (low starting current).
Core features: Economical, wear-resistant, corrosion-resistant core

Feature Detailed Description
Extremely high cost-effectiveness Core advantage. Using a cast iron pump body, the cost is far lower than the 3LSIS/4LSIS series. It is the most economical option for entering the screw pump field, very suitable for small farmers or temporary projects with limited budgets.
Wear-resistant and impurity-tolerant Screw pumps are not sensitive to sand and particles. Even if the well water has a high sand content, the screw pump can still work normally. Although the casing is cast iron, the core rotor is usually made of stainless steel, which still has good wear resistance.
Corrosion-resistant core Although the casing is cast iron, the internal flow-through parts (such as the rotor) are usually treated with anti-corrosion treatment, and the rubber stator is resistant to acids and alkalis. As long as it is not a strongly corrosive liquid, it can handle it.
Stable Flow: Due to volumetric displacement, the water flow is very stable, without the violent water hammer phenomenon of centrifugal pumps, resulting in less impact on the pipeline.

Typical Application Scenarios
The 3LIS/4LIS Iron series is ideal for small and medium-sized projects, temporary water supply, and budget-sensitive projects:
Construction site drainage/sewage:
Construction site foundation pits often contain mud and cement residue. The Iron series is both wear-resistant and inexpensive, so damage is not a major concern.
Temporary agricultural irrigation:
Used to pump water containing sediment from rivers and ditches for irrigation.
Industrial wastewater/sludge discharge:
Used to discharge industrial wastewater containing impurities or sludge from sedimentation tanks.
Livestock farm manure treatment:
Used to clean manure and sewage from pigsties and chicken coops; screw pumps are not prone to clogging.

Selection and Usage Recommendations:
Strictly prohibit dry running (critical):
The rubber stator of the screw pump requires liquid for lubrication and cooling. It is absolutely forbidden to run the pump for extended periods without liquid, otherwise the stator will quickly melt and become unusable due to frictional heat. It is recommended to equip a water shortage protection controller.
Environmental adaptability:
Although the cast iron casing has high strength, it is not resistant to strong acid and alkali corrosion, nor is it as resistant to seawater corrosion as stainless steel. It is best suited for freshwater, sewage, and mud environments. If seawater or highly corrosive chemical liquids are involved, be sure to choose the 3LSIS/4LSIS series (all stainless steel).
Relatively low flow rate:
Compared to centrifugal pumps of the same power (such as the LZSU series), screw pumps generally have a lower flow rate, but their head (pressure) can be very high. It is more suitable for scenarios requiring a steady, continuous flow.

The 3LIS/4LIS Iron series is the "economical and practical workhorse" among screw pumps. It sacrifices the "noble lineage" of all-stainless steel for extremely high cost-effectiveness. If you need the impurity-resistant and wear-resistant characteristics of a screw pump, but have a limited budget, and the operating environment is freshwater or ordinary sewage, then the Iron series is the irreplaceable best choice.