WQD-S Oil-immersed Submersible Sewage Pump

Simply put, it's a submersible sewage pump based on the standard WQ (QW) series, but utilizing oil-immersed motor technology. This pump combines the dual advantages of "excellent heat dissipation from the oil-immersed motor" and "non-clogging sewage pump," making it widely used in industrial wastewater discharge, construction drainage, and other fields.

Core Structure and Working Principle
The most distinctive feature of this pump lies in its motor section.
Oil-immersed motor: Unlike ordinary dry-type motors, its motor cavity is filled with mechanical oil (usually No. 5 or No. 10). This oil film plays three key roles:
Cooling: Oil has a higher specific heat capacity than air, which can quickly dissipate the heat generated by the motor's operation, preventing the motor from overheating and burning out.
Lubrication: It lubricates the bearings inside the motor, reducing wear and extending service life.
Sealing protection: The oil fills the gaps inside the motor, so even if the external water seal leaks slightly, water is unlikely to directly contact the live windings, improving safety.
Pump section: It usually adopts a single-channel or double-channel impeller design (there are also cutting-type designs). The wide flow channels allow for smooth passage of solid particles and long fibrous materials, making it less prone to clogging.

Main Features
Excellent heat dissipation performance:
Due to relying on oil circulation for heat dissipation, it is more adaptable to frequent starts and high-load conditions than ordinary water-filled or dry-type motors, resulting in lower motor temperature rise and longer service life.
Non-clogging and strong passage capability:
The unique impeller design allows it to pass solid particles and long fibrous debris up to 50% of the pump's diameter, making it ideal for handling complex media such as domestic sewage and construction site mud.
Convenient installation and maintenance:
It is compact and can be directly submerged in sewage. It is usually equipped with an automatic coupling device, eliminating the need to build a pump house, and allowing for installation and maintenance without personnel having to enter the sewage pit.
Smooth operation:
The oil provides a certain damping effect, resulting in relatively low vibration and noise during pump operation.

Application Scenarios
Due to its "robust and durable" characteristics, this pump is widely used in the following scenarios:
Construction sites and piling projects: Used for dewatering of foundation pits and discharge of piling mud (this is also the scenario you were previously interested in).
Municipal Engineering: Urban flood control and drainage, rainwater pumping stations, sewer cleaning.
Industrial Wastewater Discharge: Mine drainage, factory cooling water circulation, discharge of industrial wastewater containing impurities.
Residential Facilities: Wastewater lifting and discharge from basements of hospitals, hotels, and residential areas.

Simple Comparison with Ordinary Sewage Pumps
Features Oil-immersed Submersible Sewage Pump Ordinary Dry/Water-filled Sewage Pump
Motor Cooling Method Mechanical oil circulation cooling Air/Water cooling
Heat Dissipation Effect Excellent, high temperature resistant General, requires attention to heat dissipation during long-term operation
Bearing Life Long (oil lubrication) Relatively short
Leakage Protection Performance Good (oil insulation) Depends on mechanical seal quality
Applicable Working Conditions Frequent starting, high load, sandy water General clean water or sewage

Selection and Usage Suggestions
Note on Material: Although called a "sewage pump," the standard model is usually made of cast iron. If your medium is seawater or strong acid/alkaline wastewater, be sure to order a stainless steel (304/316L) version, otherwise the pump body will easily corrode.
Prevent Dry Running: Although oil-immersed pumps have good heat dissipation, prolonged dry running is strictly prohibited. Although the thermal conductivity of oil is high, if there is no water as the final heat dissipation medium, the motor will still overheat and be damaged.
Regular Inspection: It is recommended to regularly check the oil quality and quantity in the oil chamber. If the oil turns milky white, it means that water has seeped in, and the oil needs to be replaced and the seals checked promptly.
In summary, the oil-immersed submersible sewage pump is a powerful drainage device with "good heat dissipation, long life, and no water limitations," especially suitable for drainage scenarios with harsh working conditions and requiring long-term continuous operation.