1. First clarify the actual operating parameters
Design working conditions and normal working conditions should be provided before purchasing, instead of only submitting a maximum flow rate.
The main parameters include:
• Rated, minimum and maximum flow, unit m³/h;
• Total lift, including static lift, pipeline loss and outlet pressure;
• Normal liquid level, minimum liquid level and liquid level variation range;
• Tank depth and required underwater length;
• Medium name, density, viscosity and vapor pressure;
• Operating temperature and possible maximum temperature;
• Solid particle content, particle size and settling characteristics;
• Continuous operation or intermittent operation requirements;
• Power supply, explosion-proof level and on-site environment.
If the head is only estimated based on the tank height and the outlet back pressure and pipeline resistance are ignored, problems such as insufficient flow, motor overload, or deviation from the high efficiency area may occur after the pump is put into operation.
2. How to determine the flow rate and head?
The flow rate selection should be determined based on the actual processing capacity of the system. The long-term operating point should be close to the best efficiency point of the pump to avoid continuous low flow or excessive flow areas.
Small flow operation may cause internal backflow, vibration and temperature rise; excessive flow may lead to increased power, insufficient NPSH and increased shafting load. If the working conditions vary widely, frequency conversion control, return pipeline or multi-pump combined operation can be considered.
3. Why are the underwater depth and the minimum liquid level important?
The underwater length is not a simple copy of the tank depth, but the structural dimension from the installation datum to the pump suction inlet or the center of the pump body. When selecting, you need to confirm the height of the tank cover, the minimum operating liquid level, the distance between the suction inlet and the bottom of the tank, and whether there is any sediment.
The pump inlet must maintain sufficient submergence depth. Insufficient flooding may form vortices and suck in air, causing flow fluctuations, vibrations and cavitation. If the suction inlet is too close to the bottom of the tank, it is easy to inhale sediment particles and cause blockage or wear.
For deeper tanks, the long axis deflection and critical speed must be checked. If necessary, guide bearings, bushings and intermediate supports should be reasonably arranged to control the swing of the shaft system.
4. How to choose between VS4 and VS5 structures?
VS4 vertical submersible pump usually uses a long shaft and one or more submersible guide bearings, which is suitable for working conditions with large submersible depth and high continuous operation requirements. When selecting, confirm the guide bearing material, lubrication method and the impact of particles in the medium on the bearing.
The submerged part of the VS5 vertical cantilever pump usually does not have a guide bearing, which can reduce bearing failures caused by media contamination, crystallization or poor lubrication. However, the cantilever length is limited by the stiffness of the shaft system, so it is more suitable for applications within the specified underwater depth range.
Buyers should not only compare the prices of the two structures, but should make a choice based on the depth of the liquid, media cleanliness and maintenance conditions.
5. How do materials and structures match the medium?
For ordinary sewage, cast iron, carbon steel or stainless steel can be selected according to the degree of corrosion; for acid, alkali, salt solutions and organic chemical media, 304, 316L, duplex steel or other corrosion-resistant materials should be selected based on concentration, temperature and chloride ion content.
Media containing particles or crystals should also pay attention to the hardness and wear-resistant design of the impeller channel, flow-passing parts. For working conditions prone to sedimentation, semi-open or open impellers can be used, but the efficiency, throughput capacity and axial force must be checked at the same time. Under high temperature conditions, thermal expansion, shaft elongation, material strength and installation gap changes need to be considered.
6. Typical engineering applications
Vertical submersible pumps are commonly used in:
• Chemical tank drainage and process circulation;
• Petrochemical sumps and accident pools;
• Transportation of industrial wastewater and particle-containing sewage;
• Power plant, steel and mine drainage;
• High-temperature molten salt and special media transportation;
• Media that are easily volatile, easy to crystallize or are not suitable for ordinary shaft seals.
The main risks are different for different applications. For example, sewage working conditions focus on blockage and wear resistance, chemical working conditions focus on corrosion and leakage, and high temperature working conditions focus on thermal expansion and shafting stability.
9. Jiangsu Feiyue Pump Industry’s vertical submersible pump solution
Jiangsu Feiyue Pump Industry can conduct working condition analysis based on the medium properties, flow head, tank size, liquid depth and operating standards, and complete pump type selection, material configuration, shaft system calibration and motor matching. For corrosion, high temperature, particle-containing or deep groove working conditions, the impeller form, guide bearing, sleeve, flow-passing material and installation structure can be specifically designed, and the flow rate, head, power and operating stability of the pump can be verified through performance testing.
The ultimate goal of correct vertical submersible pump selection is not to choose a larger model, but to obtain stable transportation, reasonable energy consumption and controllable maintenance costs within the entire working condition range.
