What should be paid attention to in the maintenance of pressure vessels?

1. Daily inspection
1. Appearance inspection
Check the appearance of the container every day to check whether there is deformation, corrosion, wear, cracks, etc. Focus on the cylinder, head, pipe, flange and other parts, which are prone to problems. For example, if rust is found on the surface of the container, it may be an early sign of corrosion, and the degree of corrosion needs to be further evaluated.
Check whether the paint coating of the container is intact. The paint not only has an anti-corrosion effect, but also reflects the use status of the container. If the paint peels off, it may indicate that there is a problem with the surface of the container or that it has been hit by external force before.
2. Connection inspection
Check the sealing of the connection parts between the pipe and the pipeline, valve, etc. Check whether there is leakage at the flange connection. You can judge by observing whether there is medium leakage or smelling whether there is a special smell. If leakage is found, tighten the bolts or replace the gasket in time.
Check whether the opening and closing state of the valve is normal, whether the operation of the valve is flexible, and ensure that the valve can work normally. For manual valves, check whether the handwheel is intact and whether there is any damage or stuck.
3. Operation parameter monitoring
Pay close attention to operation parameters such as pressure and temperature to ensure that they are within the specified operating range. Real-time monitoring is carried out through the pressure gauge and thermometer installed on the container. If abnormal pressure or temperature fluctuations are found, find the cause and deal with it in time. For example, a sudden increase in pressure may be caused by a pipe blockage or an internal reaction out of control.
For storage containers, it is also necessary to pay attention to changes in the liquid level to prevent the liquid level from being too high or too low. Too high a liquid level may cause the container to be overfilled and cause a safety accident; too low a liquid level may affect the subsequent production process or the normal operation of the equipment.
II. Regular maintenance
1. Monthly maintenance
Safety device inspection
Check whether the safety valve can be opened and closed normally, and whether its starting pressure and return pressure are within the specified range. The function of the safety valve can be verified by manual testing (where permitted).
Check whether the appearance of the bursting disc is damaged, such as scratches, deformation, etc. The bursting disc is a one-time safety device. If the bursting disc is found to be damaged or has reached its service life, it should be replaced in time.
Verify the accuracy of the pressure gauge and thermometer to ensure that their readings are reliable. If the error of the pressure gauge or thermometer is found to be beyond the allowable range, it should be calibrated or replaced.
Lubrication maintenance (if applicable)
For pressure vessels with movable parts (such as the valve stem of some valves), check the oil level and oil quality of the lubricating oil. If the oil level is too low, add an appropriate amount of lubricating oil; if the oil quality deteriorates, such as containing impurities or has deteriorated, the lubricating oil should be replaced in time.
2. Quarterly maintenance
Internal inspection (partial containers)
For pressure vessels that can be internally inspected, an internal inspection is performed once a quarter. Tools such as endoscopes can be used to check the corrosion and wear of the internal surface of the container, and check whether the internal components (such as agitators, etc.) are loose, deformed or damaged.
Clean the dirt, impurities, etc. inside the container to prevent them from corroding the container or affecting the normal operation of the internal components.
Electrical system inspection (electric container)
For electrically controlled pressure vessels, check the insulation resistance of the electrical system, whether the wire connection is firm, and whether the electrical components such as contactors are working properly. Too low insulation resistance may cause leakage accidents, and loose wire connections may cause electrical failures, affecting the normal operation of the container.
3. Annual maintenance
Nondestructive testing
Perform a comprehensive nondestructive testing once a year, such as using radiographic testing (RT), ultrasonic testing (UT), magnetic particle testing (MT) or penetrant testing (PT) to test key parts of the container such as the cylinder, head, and weld. Check whether there are internal defects, such as cracks, pores, etc., so as to timely discover potential safety hazards.
According to the results of nondestructive testing, evaluate the defects found, and take corresponding repair measures for repairable defects, such as repair welding (for cases that meet the repair welding conditions); for defects that cannot be repaired or seriously affect the safety of the container, consider scrapping.
Wall thickness measurement
Use tools such as ultrasonic thickness gauges to measure the wall thickness of the container, and compare the measurement results with the original wall thickness or the minimum allowable wall thickness. If it is found that the wall thickness is thinned beyond the specified range, analyze the reasons, such as corrosion, wear, etc., and take corresponding measures according to the situation, such as strengthening monitoring, repair or scrapping.
Overall performance test
Perform pressure resistance test and sealing test to test the strength and sealing of the container. The pressure test generally adopts hydraulic test (such as water pressure test) or air pressure test (under specific conditions), and the test pressure should be higher than the design pressure of the container; the sealing test can adopt methods such as airtight test to ensure that the container will not leak under normal working pressure.
3. Maintenance in special situations
1. Maintenance after abnormal events
If the container has experienced abnormal events such as overpressure, leakage, abnormal vibration, etc., a comprehensive inspection and maintenance should be carried out immediately.
After the overpressure event, check whether the container has permanent deformation, whether the safety valve is working normally, whether the sealing part is leaking, etc. Overpressure may cause damage to the structure of the container, such as bulging of the cylinder or deformation of the head, and the safety of the container needs to be carefully evaluated.
For leakage events, in addition to finding and repairing the leakage point, it is also necessary to check the impact of the leakage on the surrounding equipment and environment, such as whether it causes corrosion or pollution. For abnormal vibration events, the cause of the vibration should be checked. It may be caused by imbalance of internal components, excessive stress of pipelines, or instability of external support structures, and targeted treatment is required.
2. Maintenance after long-term disuse
When the container is reactivated after a long period of disuse (such as more than 3 months), a comprehensive inspection and maintenance should be carried out.
Check the appearance of the container for new corrosion, deformation or damage, clean the inside of the container, and check whether the internal parts are rusty or damaged.
Before reactivation, perform pressure test and sealing test to ensure that the container can operate safely and normally.
IV. Other matters needing attention
1. Qualification of maintenance personnel
Personnel who perform pressure vessel maintenance must undergo professional training, have the corresponding knowledge and skills, and hold relevant qualification certificates, such as non-destructive testing personnel qualification certificates, welder certificates, etc. Especially when performing key maintenance operations (such as welding repairs, non-destructive testing, etc.), ensure that the qualifications of the operators meet the requirements.
2. Maintenance records
Record the details of each maintenance, including maintenance date, maintenance content, problems found, measures taken, and equipment status after maintenance. Maintenance records are important data on the maintenance history of containers, which help analyze the operating status and failure trends of containers, and are also necessary documents to meet safety supervision requirements.
3. Spare parts management
Reasonably manage the spare parts required for pressure vessel maintenance to ensure the quality of spare parts. For some wearing parts (such as sealing gaskets, safety valves, etc.), a certain amount of inventory should be maintained so that they can be replaced in time when needed to reduce equipment downtime.