Key technologies for functional analysis and material selection of components of vertical multi-stage drum bag water pump (condensing turbine pump)

Vertical multi-stage drum bag type water pump (condensing turbine pump) is a special pump widely used in the fields of thermal power generation, chemical processes, etc. Its component functions and material selection need to be combined with specific working conditions. The following is a detailed analysis based on search results:
1、 Main component functions
1. Cylinder (outer cylinder)
Function: Form a closed pressure chamber, connect the suction pipeline, and stably guide the liquid to the suction horn mouth. Work often in a negative pressure (room temperature) or positive pressure (high temperature) state.
- Material: Carbon steel plate (Q235-A) or stainless steel (such as 304/316L), must be corrosion-resistant and meet vacuum/pressure sealing requirements.
2. Impeller
- Function:
• First stage impeller: Double suction structure design, expands inlet area, and enhances anti cavitation performance (such as Lijia Machinery JLDTN vertical multi-stage drum bag water pump).
Secondary impeller: a single suction structure that converts mechanical energy into liquid kinetic energy through high-speed rotation.
- Material: Stainless steel (such as ZG2Cr13) or special alloy, requiring wear resistance and resistance to medium corrosion.
3. Guide vanes and middle section
Function: Convert the kinetic energy of the liquid at the impeller outlet into pressure energy and guide it to the next stage impeller or outlet.
- Material: cast iron or stainless steel, ensuring smooth flow channels to reduce hydraulic losses.
4. Shaft and bearings
- Function:
• Pump shaft: transmits torque and supports the impeller. It needs to withstand axial force (partially borne by the balance drum) and radial load.
Guide bearing: Water lubricated sliding bearing (made of polytetrafluoroethylene or copper alloy), capable of withstanding radial forces from the rotor.
- Material: 45 steel, 40Cr or 42CrMo (high-strength), bearing material needs to be wear-resistant and self-lubricating.
5. Sealing system
Mechanical seal: Double end series design (such as the PLAN52 scheme) to prevent medium leakage. External flushing water cooling (pressure 0.4~0.6MPa) is required.
Packing seal: Suitable for low-temperature clean water, the leakage rate needs to be adjusted to around 40ml/min.
- Material: Silicon carbide/ceramic dynamic and static rings, fluororubber sealing rings.
6. Balance device
Balance drum: It bears 95% of the axial force, with the remaining force borne by thrust bearings (such as angular contact ball bearings or thrust self-aligning roller bearings).
- Material: Wear resistant cast iron, used in conjunction with a balance ring.
2、 Material selection skills
1. Select based on the characteristics of the medium
- Clear water/condensate (≤ 80 ℃): Carbon steel (cylinder), stainless steel (impeller, shaft).
Corrosive media (such as acids and bases):
Sulfuric acid: carbon steel can be used when the concentration is greater than 80%; Low concentration requires high silicon cast iron or fluoroplastic lining.
Hydrochloric acid: Non metallic materials such as polypropylene and fluoroplastics must be used.
Nitric acid: 304/316 stainless steel (at room temperature), titanium alloy for high temperature environments.
High temperature medium (>80 ℃): Stainless steel (316L) or special alloys (such as Hastelloy), with temperature resistant design for sealing.
2. Principles for selecting structural components
Wear resistance: When conveying media containing particles, the impeller and sealing ring are coated with high chromium alloy or ceramic.
Anti cavitation: The first stage impeller is equipped with a pre induced impeller (such as the LDTN vertical multi-stage drum bag pump from Lijia Machinery), made of tough stainless steel material.
Economy: Non critical components (such as the middle section) can be made of cast iron, while core components (shafts, impellers) prioritize performance.
3. Sealing system adaptation
Mechanical seal: Suitable for high temperature and toxic media, it needs to be equipped with a pressure reducing sleeve and a buffer tank (to prevent leakage).
Packing seal: Low cost operating conditions require regular maintenance and control of leakage.
3、 Key points of operation and maintenance
1. Pre startup inspection:
- Ensure that the pump is filled with liquid and thoroughly vented; The shaft seal cooling water is unobstructed; It is strictly prohibited to operate with the valve closed for more than 2 minutes.
2. Operation monitoring:
- Bearing temperature ≤ 75 ℃; The flow rate should not be less than 30% of the design value to avoid cavitation.
3. Material maintenance:
- Regularly replace lubricating grease; Check the wear of the sealing ring; Stainless steel components need to be protected against chloride ion corrosion.
Summary: The selection of vertical multi-stage drum bag pump (condensing turbine pump) requires comprehensive consideration of flow rate, head, medium properties (temperature, corrosiveness, solid content), and installation environment (such as NPSH restrictions). It is recommended to prioritize the use of efficient hydraulic models (such as the JLTDN series vertical multi-stage drum bag pump guide vane structure from Lijia Machinery) and strictly follow the manufacturer's maintenance guidelines to ensure longevity.