Sharing of pump failure cases
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This post was last edited by 156026692 on 2019-8-11 at 10:25. As one of the most commonly used devices in the petrochemical industry, pumps can encounter various problems in daily use. I would like to create a dedicated thread to collect information on the faults that occur with pump equipment during regular production operations. To avoid using specific names such as the owner, the pump manufacturer, or the design institute, when sharing cases of pump failures, one can use terms like “Pump A” or “Manufacturer B” as substitutes. The goal is to gather information on issues related to the design, manufacturing, and daily use of pumps; it would be useful to include actual photos of the faulty components along with analyses of the causes of those failures. The collection is planned to take two weeks, starting from today, the 11th, and ending on the 25th. At that time, depending on the quality of what each person shares, rewards in the form of wealth, charm, or even HaiChuan coins will be given to them to varying degrees. It is hoped that through mutual exchange, everyone can gain useful insights in the daily use of pumps and in dealing with faults.
This building will be temporarily occupied; later, the best options will be identified and publicly listed as rewards: lol
This post was last edited by 156026692 on 2019-8-11 at 10:45. Let me start by offering some initial thoughts. In August 2016, an equipment engineer at a hydrogenation plant conducted an on-site inspection and found that the lubricant in the bearing housing at the non-drive end of the deaeration water pump was cloudy. The lubricant was replaced, but it remained cloudy after that as well. The problem persisted even after several replacements of the bearing housing lubricant, prompting calls for repairs. The pump is of horizontal multi-stage centrifugal type, designed for transporting deoxygenated water. It uses the PLAN 21 sealing and flushing scheme, and as of August, it had accumulated 12,312 hours of operation since the occurrence of faults. Due to the turbid lubricant in the pump bearing housing, the problem persisted even after the lubricant was replaced. It was initially suspected that there was a leak in the circulation water pipeline of the bearing housing; upon inspection after disassembling it, it was found that the circulation water pipeline was normal. The pump was disassembled for maintenance; inspections revealed the presence of impurities between the main shaft and the bearing shells, as well as severe wear on the alloy surface of these bearing shells. After a major overhaul involving the replacement of the main shaft and the bearing shells on the non-driving end, the pump was put back into operation and is functioning properly. The main reason is that the pump has been in operation for too long without being switched to a backup pump on a regular basis. During its prolonged operation, worn debris accumulates between the main shaft and the bearing shells at the non-driving end, causing the lubricating oil to become cloudy and leading to wear of the shafts and bearing shells. Draw inferences from one instance – regularly switch between the backup pumps and distribute their usage cycles reasonably. At the same time, taking into account any problems that arise during the operation of the facility, schedule preventive repairs for the pump equipment in a timely manner, so as to avoid letting minor issues develop into serious problems that could lead to abnormal operation of the equipment.
During the commissioning of a certain unit in 2018, fluctuations in the outlet pressure of the magnetic pump occurred, along with increased noise. After switching to the backup pump, it was disassembled for inspection; during disassembly, it was found that the sliding bearings and face bearings were damaged. Other rotating components of the magnetic pump are worn to varying degrees. It was found that the filter screen of the inlet filter was clogged; as a result of this blockage, insufficient liquid flowed in, causing cavitation inside the pump. After cleaning the filter, the repaired pump resumes normal operation smoothly, and users are advised to clean the filter regularly during operation. Such problems often occur during the commissioning phase of the equipment; it is recommended to pay close attention to them during this stage.
Magnetic pump thrust disc, pump inlet filter clogged and evacuated, thrust disc worn?
That’s right; when there is a disruption in the hydraulic balance of the magnetic pump during times when it is not in use, the rotor moves back and forth, and the sliding bearings as well as the thrust bearings are subjected to large axial forces. Another cause can be dry grinding of the sliding bearing, which leads to a sharp rise in bearing temperature and eventually the destruction of the sliding bearing. Did using a magnetic pump to evacuate it only damage the sliding bearing? Is the thrust disc not damaged?
In a certain gas processing unit, the methanol circulation transfer pump was a two-stage horizontal centrifugal pump of model A. Sealing leakage occurred during operation; upon inspection, cracks were found in the waveguide of the mechanical seal’s stationary ring. After replacing it with a new seal from manufacturer A, leakage occurred again within less than a day of operation, and the same problem was detected upon further inspection. A seal from manufacturer B was then used, but the same issue persisted even after one day of operation. Investigations revealed that after starting the pump, the operator reduced the flow rate by opening the outlet valve only slightly. The pump overheated due to prolonged operation, and it operated under vacuum conditions. The operator failed to conduct thorough inspections, and the sealing leakage was not detected until it became apparent. The pump outlet flow path was modified: the outlet valve was opened fully, and a return line was activated. Part of the fluid went to the next process, while the excess methanol was returned to the tank, thereby maintaining the flow rate and pressure in the downstream system and ensuring that the pump did not overheat or become vacuumed.
The thrust disc, bearings, and shaft sleeves are all worn out; the inner magnetic cylinder is severely damaged. Moreover, frequent starting and stopping also leads to wear
The new installation in the company’s southern area has been put into operation. The liquefied gas loading pump is a 30KW vertical single-stage shielded pump; its motor is started using an inverter. The frequency is increased by 5 hertz every 10 seconds, but vibration and abnormal noises gradually increase, and the pump has to be stopped after less than 20 seconds. Several attempts were made, but the problem persisted. After consulting with the electrical staff, the frequency was increased to 50 hertz, and the pump operated normally. The frequency was then adjusted to an appropriate level based on pressure and flow rates, but it could not drop below 70 revolutions per minute. The outlet valve and return line are used to regulate the pump’s outlet flow rate and pressure.