2.2 Maintenance in operation
In order to prolong the service life of the ball valve, reduce losses caused by failures, and bring greater economic benefits, it is also necessary to do a good job in maintenance during operation. Its maintenance mainly includes the following aspects: First, a scientific and reasonable inspection plan must be formulated according to the actual situation of natural gas transportation. Valves must be inspected regularly for sealing, corrosion and damage. Once a problem is found, it should be dealt with immediately to shorten the maintenance time. Second, according to the frequency of valve movement, the grease should be injected, and it is consistent with the frequency of valve movement. The injection volume is one-eighth of the entire sealing system to prevent dust and impurities from entering the cavity and causing damage to valves. Third, for valves with low activity frequency, manual operation is required, and then grease should be injected to reduce internal mechanical friction and better protect the valve. Fourth, for the valves in operation, maintenance should be carried out regularly, mainly including the cleaning of dust and impurities, and the removal of moisture in the cavity in order to prevent rusting and freezing and affect normal use. Fifth, the gear transmission mechanism inside the ball valve should also be greased every year, and problems should be checked and dealt with. Sixth, the rust on the outside of the ball valve should also be cleaned regularly to prevent the internal mechanical operation from being affected.
3. Troubleshooting for ball valves in pipelines transporting natural gas
3.1 Internal leakages of ball valves
An internal leakage of a ball valve is one of the common failures of ball valves in pipelines transporting natural gas, and it has a relatively great impact on the entire transportation process. The reasons for the internal leakage of the ball valve mainly include two aspects, that is, improper construction and improper maintenance in the later stage.
Internal leakages caused by improper construction
In order to prolong the service life of the ball valve, reduce losses caused by failures, and bring greater economic benefits, it is also necessary to do a good job in maintenance during operation. Its maintenance mainly includes the following aspects: First, a scientific and reasonable inspection plan must be formulated according to the actual situation of natural gas transportation. Valves must be inspected regularly for sealing, corrosion and damage. Once a problem is found, it should be dealt with immediately to shorten the maintenance time. Second, according to the frequency of valve movement, the grease should be injected, and it is consistent with the frequency of valve movement. The injection volume is one-eighth of the entire sealing system to prevent dust and impurities from entering the cavity and causing damage to valves. Third, for valves with low activity frequency, manual operation is required, and then grease should be injected to reduce internal mechanical friction and better protect the valve. Fourth, for the valves in operation, maintenance should be carried out regularly, mainly including the cleaning of dust and impurities, and the removal of moisture in the cavity in order to prevent rusting and freezing and affect normal use. Fifth, the gear transmission mechanism inside the ball valve should also be greased every year, and problems should be checked and dealt with. Sixth, the rust on the outside of the ball valve should also be cleaned regularly to prevent the internal mechanical operation from being affected.
3. Troubleshooting for ball valves in pipelines transporting natural gas
3.1 Internal leakages of ball valves
An internal leakage of a ball valve is one of the common failures of ball valves in pipelines transporting natural gas, and it has a relatively great impact on the entire transportation process. The reasons for the internal leakage of the ball valve mainly include two aspects, that is, improper construction and improper maintenance in the later stage.
Internal leakages caused by improper construction
- In the construction of the valve, a large amount of mechanical equipment will be used for transportation and hoisting. Damage to the valve happens and causes internal leakages due to improper mechanical operation.
- Before the valve is installed, the drying and anti-corrosion treatment is not carried out, resulting in failures caused by sealing and internal leakages.
- After being transported to the construction site, there is a lack of reasonable supervision and protection, which cause dust, impurities and moisture to enter the inner cavity, resulting in failures caused by sealing and internal leakages.
- Grease is not injected during installation. This causes impurities to enter the interior of the rear cavity and damage the valve at the high-temperature welding.
- The impurities and garbage on the construction site are not cleaned up in time, which will damage the sealing surface of the valve and cause damage to a large area during installation.
Internal leakages caused by improper maintenance in the later stage
- Managers don't think it's important to maintain valves in the later stage due to the weak ideological concept. There is neither a reasonable maintenance method and plan, nor a serious effort to carry out the work; improper operation often occurs, resulting in internal leakages of the valve.
- Higher-level operation managers pay too much attention to short-term economic benefits and ignore the investment of financial, human and material resources in later maintenance and management. As a result, maintenance costs are low; the professional ability of maintenance personnel is low, and maintenance equipment and technology are outdated, making it difficult to ensure efficient maintenance.
- Impurities and garbage generated in the construction process is not removed in time, which will scratch the valve and cause internal leakages.
- The cleaning and maintenance of the valve cannot be carried out regularly, resulting in increased friction inside the valve and easy to cause damage to sealing.
- Opening and closing of the valve is improper, which deviates from the actual requirements. Failures caused by friction can occur under repeated long-term operation.
- The grease used is of poor quality, so it is prone to hardening. The injection volume is not up to the standard, which will also cause the bolts to loosen and cause internal leakages.
In addition, the grease inside the valve that dries and loses its effect, and is not cleaned regularly eventually causes the elasticity of the valve seat to fail, causing internal leakages of the sealing. The solution is that first turn the valve to the fully open or fully closed position, and then check the discharge capacity of the discharged nozzle. If it can drain well, it means the sealing is intact. If it cannot drain well, there is an internal leakage. The effective treatment method is as follows: first, check the limit position of the valve, and then make appropriate adjustments. Second, inject the grease slowly and carefully observe. Third, inject the cleaning solution, and soak it for half an hour and then clean it to discharge the impurities in the valve cavity; then open and close the valve to check the operation.
3.2 Leakages of valve stems
Leakages of valve stems are caused by wear and aging caused after long-term operation. Therefore, it is possible to prevent leakages by injecting grease. When the valve stem no longer leaks, the grease injection should be stopped immediately, and then a compacted seal should be performed.
3.3 Abnormal operation
Troubleshooting for abnormal operation are as follows: First, when the ball valve is less active and lacks maintenance, the operation will be slightly laborious. At this time, it can be injected with a cleaning solution and soaked for about half an hour. Second, the abnormal operation can also occur due to external impurities, dust and moisture entering the inside of the pipeline, or grease piling up around the seat ring. The cleaning solution can also be injected at this time and then removed. Third, if the purity of natural gas is insufficient, a large amount of water will condense inside the valve, which will eventually cause rust and freezing, resulting in abnormal operation. At this time, it is necessary to carry out regular drying and anti-corrosion treatment, and timely maintenance.
Fourth, if the bolt of the valve stem is too tight, it will also cause abnormal operation. At this time, appropriate loosening should be carried out. Fifth, if the gear of the valve stem transmission device is severely worn or broken, it will not operate normally; the safety pin on the worm is broken or the bearing is damaged, or the lubrication is not good, it will also cause abnormal operation. At this time, regular maintenance is required. Once wear and tear are found, it must be replaced immediately. It is also necessary to inject grease to ensure that the transmission is always in a stable and safe operation state. Sixth, when the gas circuit and oil circuit of the valve are blocked, or the air source pressure is insufficient, the internal sealing device fails, and the air pressure difference is great; it will also cause abnormal operation. At this time, the air pressure gauge should be used for regular inspection and maintenance, and the air pressure inside the valve cavity should be vented to ensure its normal operation.
4. Conclusion
To sum up, the main failures of ball valves are internal leakages of ball valves, leakages of valve stems and abnormal operation, which directly affect the safety and stability of natural gas transportation. Therefore, in future pipeline construction, it is necessary to carefully carry out investigation and treatment for failures from the early construction and later maintenance in order to improve the quality and efficiency of the project, obtain more social and economic benefits, and realize the long-term development of pipelines transporting natural gas.
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