9 common problems and preventive measures during the commissioning of chemical plants after maintenance

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Equipment maintenance of chemical plants is a means to ensure the integrity of the equipment, but there are significant risks associated with starting up operations after maintenance, and safety accidents occur frequently. Based on my own experience, I have listed some common problems that arise while driving and proposed preventive measures for everyone’s reference and discussion. 1. Material leakage at the flanges, thread plugs, and other components of equipment and pipelines; for example, insufficient airtightness checks or pressure testing during maintenance of pipelines and equipment, which leads to leakage once pressure is applied ； Plug valves for heat exchangers, pipes, etc. were not installed properly or were not sealed tightly after maintenance, as they were left uninstalled or installed incorrectly ； The flange bolts of pipes with significant temperature variations were not tightened thermally (or coldly) as required. 2. Failures in moving equipment: For example, a lack of lubricating oil in such equipment can lead to excessive friction and damage to the bearing shells and bearings ； The monomer has not been tested or was not used properly, which prevented the issues from being fully exposed; failures occurred after long periods of operation ； The valves on the equipment’s cooling water pipes were not opened, resulting in overheating and damage to the cylinders and heat exchangers. Premature introduction of cooling water led to vaporization-induced overpressure and an explosion. 3. Incorrect operation of valves can lead to production and equipment failures; for example, if the valves in the process flow are not opened, it can result in pressure buildup in the system or interruptions in the flow of materials ； The pump’s drain valve was not closed, resulting in accidents such as material leakage ； The air supply for pneumatic instruments is not turned on, which results in the automatic valves not operating, etc ； Starting the pump with the outlet valve of the high-flow centrifugal pump in the open position causes the motor to experience overcurrent, leading to shutdown or damage. 4. Failure to conduct proper safety checks before starting the machine, or performing such checks merely as a formality; for example, inaccurate PID parameter settings on the various instruments in the DCS, which leads to abnormal adjustments in the control circuits ； Inadequate purging or displacement of flammable media results in the mixture reaching its explosive limit ； The blind flange for maintenance was not removed, forcing the system to undergo replacement and disposal procedures once again. 5. Insufficient support for driving operations in terms of materials and personnel; for example, inadequate preparation of materials needed for driving, such as an insufficient amount of catalysts ； There are faults in the shared utilities such as nitrogen, instrument air, and circulating water ； Issues with walkie-talkies, on-site broadcasting, etc., resulting in poor communication and information flow ； Personnel in charge of electrical and instrumentation tasks, as well as maintenance, are not adequately prepared, and cannot carry out maintenance and repairs promptly when abnormalities occur in the equipment. 6. Delays or mistakes on the part of operators: For example, if an operator opens a valve to a large extent, steam is released too quickly and the condensate cannot be discharged in time, resulting in pipe damage due to fluid shock ； In the early stages of operation, insufficient exhaust at the high points of the liquid pipelines and insufficient drainage at the points of the gas pipelines led to obstacles in material transportation ； The temperature and pressure increases for the process control parameters were not carried out in accordance with the procedures, resulting in over-temperature and over-pressure conditions ； Errors in the sequence of valve operation and material feeding, etc., can lead to production or safety accidents ； Mismatch between upstream and downstream components leads to overfilling of the storage tank or its emptying ； Due to inadequate communication between control room personnel and those on-site, operational errors occur ； Unclear handover of personnel shifts (especially key maintenance information) leads to operational errors. 7. Multiple commands while driving: For example, when the operator receives different instructions, they are unable to carry out the operations ； Giving instructions to the central control system that conflict with or are inconsistent with the instructions from the on-site personnel ； The operation instructions lack consistency; frequent changes make it difficult for information to flow properly, leading to operational errors. 8. Improper handling of abnormal operating conditions; for example, failure to correct deviations in process parameters in a timely manner ； The device issued an alarm, but it was not confirmed or addressed in a timely manner ； When the device encountered abnormal operating conditions, no risk assessment was conducted before taking actions blindly ； When dealing with abnormal operating conditions, factors such as upstream and downstream processes and personnel gatherings were not taken into account. 9. Emergency equipment and their locations are not properly prepared for use; for example, the valve in front of the safety valve is not opened ； The air respirator cylinder pressure is insufficient ； The eye washer in the production facility has no water, or the water pressure is insufficient ； Failures in emergency lighting, etc ； The pressure in the fire water supply network is insufficient. To address the above issues, the following preventive measures should be taken: 1. Conduct a assessment of the potential risks associated with driving, and develop measures to control those risks ； 2. Prepare the startup plan and ensure that all preparations for startup are completed ； 3. Organize training on the driving plan to ensure that relevant personnel are familiar with all its requirements ； 4. Organize the verification of driving safety conditions, including driving confirmation forms, personnel presence, emergency supplies, etc ； 5. Implement all the measures outlined in the driving plan, with particular attention to confirming key steps, as well as the sequence and speed of material intake and output ； 6. Handle abnormal conditions during driving; if risk assessment is not possible, revert to a safe state.