(1) Hydraulic Components
Shielded pump hydraulic components can be used with the same type of seal pump. They are designed to seal the hydraulic pump motor and the shielded motor, forming a combination that includes a general centrifugal pump impeller, volute casing, and flange structures for inlet and outlet. This design ensures efficient and safe operation in various industrial applications. If you're interested in the latest order information or buyer details, feel free to reach out. Don't miss the chance to grab this opportunity now!
(2) Bearings
Due to the longer rotor length, shielded pumps typically require two sliding bearings—one at the front and one at the back. Precise alignment of these bearings is crucial for diaphragm pumps. Poor alignment can lead to bearing failure. Shielded pump sliding bearings rely on liquid lubrication. To enhance this process, the inner walls and end surfaces of the bearings that come into contact with the thrust plate are often equipped with groove channels. These grooves can be straight, spiral, or a combination of both, depending on the design.
Common materials used for sliding bearings include:
①Graphite: This material is soft and self-lubricating. To improve its wear resistance, it is usually impregnated with resin or metal. Some graphite bearings are coated with hard alloys like tungsten, chromium, or diamond, or have plasma-sprayed silicon nitride sleeves, which significantly extend their service life—up to one year.
â‘¡ Silicon Carbide: Known for high strength, excellent wear resistance, and hardness, silicon carbide is an ideal bearing material. When used properly, pure sintered grade A silicon carbide bearings can last up to three years.
â‘¢ PTFE-Filled Materials: For handling highly corrosive media, sliding bearings made from PTFE filled with carbon fiber or glass fiber are commonly used.
â‘£ Ceramic or Metal Bearings: In special applications, ceramic or metal bearings may be chosen. Since shielded pumps do not use oil lubrication, they are limited in their ability to handle large radial and axial loads. Therefore, the design must incorporate methods to reduce bearing load.
To reduce radial force, common approaches include:
â‘ Double-volute casing: This design divides the fluid flow into two equal parts, creating symmetrical opposing radial forces that help reduce the load on the bearings. However, manufacturing such structures is complex and rarely used in practice.
â‘¡ Circular pump body: At the shut-off point (when the outlet valve is fully closed), the radial force is minimized. While this design performs slightly worse than a volute casing, it is more efficient at the optimal operating point.
â‘¢ Multi-channel pumps: Theoretically, multi-channel pumps can balance radial forces to zero. However, due to manufacturing imperfections, complete elimination is difficult.
For axial force reduction:
①Automatic thrust balancing devices: These use fixed and variable throttling rings to balance pressure on the impeller’s backside, reducing axial force. Under normal conditions, the thrust bearing remains unloaded, only engaging during start-up or unexpected situations.
â‘¡ Back-impeller mechanism: Installing a back-impeller with radial blades can significantly reduce axial force.
Each method has its own advantages and disadvantages, and the choice depends on practical experience and overall pump design.
(3) Shielding
Shielded pumps typically feature two shielding sleeves: one for the stator and one for the rotor. These sleeves prevent the working medium from reaching the stator windings and rotor core. However, the presence of shielding sleeves increases the air gap between the stator and rotor, leading to eddy current losses and reduced motor efficiency. Generally, shielded motors are about 5% less efficient than conventional centrifugal pump motors.
To minimize these losses, the shielding sleeve should be made from corrosion-resistant, high-strength, non-magnetic materials. The motor's diameter should be small, and the shielding sleeve thickness should be kept thin. Non-magnetic materials like austenitic stainless steel, Hastelloy, Hastelloy C, and titanium are commonly used.
Hastelloy is preferred for the stator shield due to its lower eddy current loss, while the rotor shield can be made of Hastelloy or austenitic stainless steel. The typical thickness of the shielding sleeve ranges from 0.4 to 0.7 mm. While thicker sleeves offer better structural integrity, they also increase energy loss. Therefore, a balance between safety and efficiency is essential in actual design.
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