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A Brief Discussion on Common Problems and Solutions for Vertical High-Speed Pumps! Author: Senior Expert in Coal Chemical Engineering, Su Zhiqiang. Abstract: Taking the GSB-L1 type vertical high-speed pump as an example, the equipment parameters are briefly introduced. The author highlights some common problems encountered in actual production processes and proposes some effective solutions for them. Keywords: high-speed pump ； Frequently Asked Questions ； Treatment measures 1. Equipment overview -1.1 Equipment composition and parameters The GSB-L1 vertical high-speed pump is a single-stage, single-suction partial-flow centrifugal pump, consisting of an electric motor, a gear speed increase gearbox, the pump itself, and its accessories. The performance range is shown in the table below: -1.2 Introduction to the lubrication system and oil parameters ① Composition and lubrication process of the gearbox lubrication system The gearbox lubrication system for high-speed pumps consists mainly of the following components: the gearbox oil sump, the main oil pump, the oil cooler, the oil filter, the pre-lubrication auxiliary system, and the associated piping. The lubrication process is as follows: ② The lubricating oil should possess the following physical and chemical properties: 2. Precautions during installation 2.1 When installing the pump inlet pipeline, efforts should be made to minimize flow resistance in order to ensure the pump’s net positive suction head. 2.2 After welding is completed in the liquid storage tank before the pump, thorough purging must be carried out to prevent the accumulation of impurities such as weld slag and rust, which could damage the impeller and inducer wheel when the pump is put into operation. During purging, disconnect the filter from the pump and cover it with plastic to prevent debris from being blown into the pump. 2.3 A filter is installed before the pump, and the mesh size of the filter is determined based on the requirements of the medium being transported. A check valve should be installed at the pump outlet; it is necessary to inspect the check valve before installation to ensure it is in good condition. Prevent reverse rotation caused by backflow after the pump stops. In addition, the inlet and outlet pipelines should have dedicated supports; the pump cannot bear weight. 3. Precautions for initial startup 3.1 Inspection items regarding the equipment ① Check that the connection between the pump and the motor has been properly adjusted, and that the anchor bolts of both the pump and the motor are firmly tightened. ② The motor’s power lines and ground wires are connected correctly, and the oil cooling pipe system is properly connected with no leaks. ③ The pressure, temperature, and oil level indicators related to pump operation should be in normal condition. 3.2 Inspection regarding the process and pump startup ① The inflow and return flow rates of cooling water for the oil cooler are normal. ② Start the electric oil pump or operate the manual oil pump up and down; the oil pressure should be no less than 0.25 MPa. Carefully inspect all the sealing points in the lubrication system; address any leaks promptly. ③ Check that the oil level is within the normal range, and open the inlet valve of the pump fully to fill the pump chamber with the fluid. ④ Open the exhaust valve to release gas, and open the bottom valve of the pump to remove some liquid in order to prevent the accumulation of impurities. ⑤ The manual disc pump operates without jamming. ⑥ Keep the outlet valve slightly open; it must remain slightly open when the pump is started. Test the motor by turning it on to check whether the rotation direction matches what is indicated on the pump casing; address any abnormalities promptly. ⑦ Start the main pump when the oil pressure of the lubricating oil pump is normal, and then stop the oil pump manually or automatically after starting it. ⑧ Adjust the outlet valve of the pump to the operating flow rate, and check that the oil temperature is between 60°C and 80°C and the oil pressure is between 0.25 MPa and 0.6 MPa. At the same time, check for leaks in each seal. 4. Shut down the pump: ① Normally, the pump should be shut down when it is necessary to switch pumps, or when parameters such as oil pressure, oil temperature, head, outlet flow rate, motor current, and voltage are abnormal after the pump starts up, or when there is noise during operation. ② When stopping the pump, gradually reduce the outlet flow; after the pump has stopped, close the outlet tightly. At the same time, take appropriate actions regarding the pump based on the reason for the shutdown. 5. Common problems during pump operation 5.1 Excessively high lubricating oil temperature Causes: ① The oil cooler has not been cleaned and is blocked; ② Insufficient amount of cooling water; ③ The lubricating oil has not been replaced for a long time and has deteriorated. Solutions: ① Clean the oil cooler; ② Adjust the cooling water valve; ③ Replace the lubricating oil. 5.2 The oil pump stops operating when the temperature is below zero in winter Causes: The extremely low temperature results in high oil viscosity, which leads to inadequate lubrication in certain areas even when the oil pump starts, and this can cause the bearings to burn out after the main pump begins to operate. The measure involves preheating the oil tank with steam; after the lubricating oil assists in starting the oil pump, it operates for about ten minutes longer than usual, and the main oil pump is started once the oil pressure stabilizes. Be sure to avoid prolonged preheating, which can cause the lubricant to degrade due to high temperatures. 5.3 No flow or pressure, or abnormal conditions after the pump starts: Causes ① The filter before the pump is clogged or the inlet valve is not open; ② The pump is not filled with liquid medium before starting, resulting in cavitation. Solutions: ① Clean the filter or fully open the outlet valve; ② Start the pump after venting the air. 5.4 Damage to the pump’s mechanical seal: Causes ① Incorrect installation after maintenance; ② Changes in the quality of the fluid being transported. Solutions: ① Reinstall it correctly according to the assembly diagram provided with the pump; ② Identify the source of contamination that has caused changes in the fluid quality and take measures to eliminate it. 5.5 Change in the color of the lubricating oil: Causes ① Corrosion of the oil cooler, leading to leakage into the oil; ② Excessive leakage from the pump’s seals. Measures: ① Replace the oil cooler; ② Inspect and replace damaged seal components or deformed “O”-rings. 5.6 Excessive consumption of lubricating oil: Causes ① Leakage from the shaft seal; ② Leakage from the mechanical seal in the lower housing; ③ Faulty oil cooler. Measures: ① Replace the shaft seal; ② Replace the mechanical seal in the lower housing’s oil circuit; ③ Replace the oil cooler. 5.7 Motor overload: Causes ① The viscosity of the medium being transported exceeds the limits specified for the pump; ② Motor failure; ③ Mechanical faults in the gearbox; ④ Mechanical faults in the pump; ⑤ Severe wear on the pump cover or diffuser. Measures: ① Check the actual viscosity of the medium being transported; ② Repair or replace the motor as necessary; ③ Disassemble the gearbox and replace parts as required; ④ Inspect the impeller and replace it if necessary; ⑤ Replace the pump cover or diffuser. 6. Inspection process and common issues after inspection: Inspect or replace each type of seal. It is strictly prohibited to use hammers or spades, as this may damage the sealing elements. During maintenance, if the sealing elements are stuck by dirt or deposits, these deposits must be removed before the mechanical seal can be disassembled. Inspect and replace various vulnerable components such as O-rings and anti-rotation pins. It is important to clean the bearings before installation, and to carefully check their inner and outer rings, rolling elements, and retainers for signs of rust, burrs, damage, or cracks ； Check whether the bearing clearance is appropriate, whether it rotates smoothly, and whether there are any sudden sticking issues. 6.1 After the maintenance is completed, it is necessary to carefully check whether there are sufficient numbers of sealing parts, and whether any components are damaged; in particular, it is important to verify that there are no defects such as scratches, cracks, or deformation on the moving and stationary rings. 6.2 Check whether the chamfers on the shaft sleeve or gland are appropriate; if not, they must be trimmed. 6.3 All components of the mechanical seal, as well as the relevant assembly contact surfaces, must be thoroughly cleaned with acetone or anhydrous alcohol before installation. Cleanliness should be maintained during installation, especially the moving and stationary rings as well as the auxiliary sealing elements must be free from impurities and dust. Coat the surfaces of the rotating and stationary rings with a layer of clean engine oil or turbine oil. 6.4 Tightening the gland should be carried out after the coupling has been aligned. The bolts should be tightened evenly to prevent skewing of the gland cross-section; a feeler gauge or specialized tool should be used to check each point, with the error not exceeding 0.05 millimeters. 6.5 Check the fit clearance (and concentricity) between the gland and the outer diameter of the shaft or sleeve; it must be even around the perimeter, and a feeler gauge should be used to ensure that the tolerance at each point is no more than 0.10 millimeters. 6.6 The compression amount of the spring must be in accordance with the specified values; it is not allowed to be too large or too small. The allowable error is ±2.00 millimeters, as a larger compression amount will increase the stress on the cross-section and accelerate its wear. If it is too small, the pressure will be insufficient to provide a sealing effect; once the spring is installed, it must be able to move freely within the spring seat. When using a single spring, pay attention to its rotation direction; it should be opposite to the rotation direction of the shaft. 6.7 After installation, the moving ring must be able to move freely; it should be able to spring back automatically after being pressed against the spring. 6.8 First, fit the static ring seal ring over the back of the static ring, and then insert it into the sealing end cover. Be careful to protect the cross-section of the stationary ring, ensure its perpendicularity to the centerline of the end cover, and align the anti-rotation groove on the back of the stationary ring with the anti-rotation pin, ensuring that they do not come into contact with each other. 6.9 During installation, it is absolutely not allowed to strike the sealing elements with tools directly; if striking is necessary, special tools must be used to avoid damaging the sealing elements. 7. Conclusion In daily work, it is very important to operate high-speed pumps correctly, as well as to accurately identify the causes of failures in these pumps and know how to address those failures. Based on the actual circumstances, it is possible to identify the defects that occur in high-speed pumps; alternatively, the elimination method can be used by listing potential causes, and after analysis and elimination, the main cause can be determined. Moreover, when dealing with equipment failures, repairs must be carried out strictly in accordance with the requirements to ensure the quality of the maintenance work. Original article; please indicate the author and source when reproducing it