Basic factors to be considered in the selection of screw pump models
In the selection of screw pumps in the early stage, comprehensive technical and economic indicators such as investment and operating costs of pump units and pump stations should be considered comprehensively, so that it conforms to the principles of economy, safety and applicability.
Specifically, there are the following aspects:
1) According to the layout of the device, terrain conditions, water level conditions, operating conditions, comparison of economic plans and other factors
2) Consider choosing horizontal and vertical. The horizontal pump is easy to disassemble and assemble,
3) It has good anti-cavitation performance, which can not only reduce the excavation depth of the pump room but also prevent the pump from cavitation, stable operation and long service life. The pump station is built according to the selected water pump, the project investment is small, and the operation cost is low.
4) Selection steps of screw pump
a. List basic data
Characteristics of the medium: medium name, specific gravity, viscosity, corrosiveness, toxicity, etc. Contained in the medium depends on the particle diameter and content of the body. Medium temperature: (℃)
b. Required traffic
General industrial screw pumps can ignore the leakage in the pipeline system in the process flow, but the influence on the flow rate when the process changes must be considered. If the agricultural pump uses open channel water delivery, the leakage and evaporation must also be considered.
c. Pressure
Suction sump pressure, discharge sump pressure, and pressure drop in the piping system (head loss). Piping system data (pipe diameter, length, type and number of pipe accessories, geometric elevation from suction tank to pressurization tank, etc.). If necessary, the device characteristic curve should also be drawn.
Conditions of use of the screw pump
1) The screw pump must be used within the rated power range, usually 80%~110% of the rated power of the screw pump.
2) The temperature of the medium conveyed by the screw pump should not exceed 40 degrees Celsius, and the pH value of the conveyed substance should be between 2 and 12.
3) The volume ratio of sand or water-insoluble substances in the material transported by the screw pump does not exceed 0.1% of the total volume, and the grain size does not exceed 0.2 mm.
4) The substances in the screw pump transportation should not contain strong corrosive liquids, such as special chemical synthesis liquids and so on.
5) The frequent start of the screw pump should meet the relevant requirements.
What should be paid attention to before starting the screw pump?
1) Make sure that the connection between the suction pipe section and the instrument joint is kept sealed.
2) When the screw pump is started or has not been started for a long time, the suction chamber should be filled with medium first, and the pump shaft should be manually turned for a few turns before starting. To prevent dry friction between the stator and rotor, damage the stator or reduce the suction performance of the pump.
3) Before starting the single screw pump, the spacer layer of the pump should be heated to reduce the viscosity of the remaining medium in the pump.
4) Check the steering of the prime mover of the pump to prevent reversal.
5) To ensure that the pipe is unblocked before starting, it is necessary to open the valves on the inlet and outlet pipes.
What working conditions are general screw pumps suitable for?
The screw pump is a positive displacement pump with internal meshing and eccentric rotation. The main components of the pump are a single-head helical rotor and a punctual helical stator usually made of elastic material. When the rotor winds around the stator in the fixed cavity When the axis makes a planetary rotation, the airtight arm formed between the rotor and the stator produces displacement along the rotor spiral; therefore, the medium is sent from the suction port to the discharge port continuously, at a uniform speed, and with a constant volume. Based on this characteristic, single Screw pumps are especially suitable for the following working conditions.
1) Conveying high-viscosity media
Depending on the size of the pump, it can transport media with a viscosity ranging from 37,000 to 200,000 centipes.
2) Conveying media containing particles or fibres
The particle diameter can be up to 30mm (no more than the rotor eccentricity). The fibre length can be 350mm (equivalent to the pitch of a 0.4 rotor). Its content can generally reach 40% of the medium kiln. If the solid matter in the medium is in the form of fine powder, the higher content can reach 60% or higher, and it can also be transported. When the delivery pressure is required to be stable and the inherent structure of the medium does not like to be damaged, it is ideal to use a single screw pump for delivery.
Handling of common problems in the use of screw pumps
1) The pump body vibrates violently or produces noise
Causes
The water pump is not installed firmly or the water pump is installed too high; the ball bearing of the motor is damaged; the main shaft of the water pump is bent or is not concentric or parallel to the main shaft of the motor.
Treatment method
Install the water pump stably or lower the installation height of the water pump; replace the motor ball bearing; correct the bent main shaft of the water pump or adjust the relative position of the water pump and the motor.
2) Drive shaft or motor bearing overheating:
Causes
Lack of lubricating oil or cracked bearings, etc.
Treatment method
Add lubricating oil or replace the bearing.
