In the processing of the vacuum equipment, it is necessary to follow the processing technology (especially the welding process) to carry out leak detection on the semi-finished parts in time. For parts that cannot be touched, leak-detected, or repaired after manufacturing, the quality of the welds must be strictly checked for leaks, and unqualified parts should be re-welded, repaired, and leak-detected in time, and the next process can only be carried out after meeting the requirements. Especially for the assembly, welding, and processing of large containers, leak detection in the intermediate process is very critical. If necessary, special leak detection tools (such as leak detection boxes, blind plates, etc.) should be designed and manufactured. For a vacuum chamber with a double-walled water-cooled chamber, it is best to first assemble and weld the inner chamber wall and check for leaks and then assemble and weld the outer chamber wall after confirming that there are no leaks. In the same way, for the case where there is an insulation layer on the outside of the chamber wall and other structures that are not easily disassembled, strict leak detection must be performed on the chamber wall before the outer structure can be covered.
All vacuum fittings and components (including vacuum chamber flanges and chamber walls) shall adopt the process of processing the flange surface after welding. Flanges without post-welding processing may meet the sealing requirements during the installation and commissioning stage, but during the use of the equipment, factors such as heat and vibration may induce the release of welding stress, resulting in the deformation of the flange and degradation of sealing performance.
In the process of processing and manufacturing, strictly implementing vacuum operation sanitation and operation specifications is also very helpful for improving the airtightness of vacuum equipment and systems. After the welding groove is ground and formed, it needs to be degreased, cleaned, and protected in time, which will help improve the air tightness of the weld. The dynamic and static sealing surfaces of parts that have been processed should have protective measures to prevent bumps and scratches during storage, handling, and assembly. When using vulnerable parts such as welded bellows, metal, ceramic or glass seals, glass devices, etc., more careful work should be done, especially to avoid leaks caused by damage after passing the pre-leakage inspection.
The installation and commissioning stage is the main body of vacuum equipment or system leak detection. If the airtightness of the weld seam of the equipment has been guaranteed through the leak detection in the processing stage, then in the process of equipment installation and commissioning, checking and ensuring the tightness of the connection parts is the focus of the leak detection work. Including key suspicious parts such as various pipelines, flange connections between components, and dynamic seals. If leak detection is performed on the weld seam and the joint at the same time, the workload and difficulty of leak detection will increase. For large and complex vacuum equipment, it is best to use segmental leak detection. Each time a component is installed, leak detection is performed on its connection parts and welds, and the next component is installed after meeting the requirements. Because after all the components are fully assembled, there are not only too many suspected parts, but also multiple leaks may leak at the same time, which brings great difficulties to the overall leak detection. The leak detection steps during the installation and commissioning of vacuum equipment are as follows:
Precautions during the use of vacuum equipment
During the operation stage of vacuum equipment, the airtightness of the equipment often decreases and the overall leak rate increases, which is the main reason for affecting the normal operation of vacuum equipment. The reasons for this phenomenon include: mechanical vibration causes the connection part to loosen; the sealing ring of the frequently disassembled part may be damaged or installed incorrectly; deformation and fatigue damage due to cold and thermal shock; Corrosion and damage; some leaks that were originally blocked by water, oil or other dirt are re-released; and stress concentration causes cracks, etc.
To use vacuum equipment correctly, leak detection should be included in the daily maintenance and management of vacuum equipment, such as regular static boost detection experiments. If the operator finds that the airtightness of the equipment has decreased, it should be solved in time, analyze the cause of the leakage according to the use of the equipment and the fault phenomenon, and take appropriate leak detection methods to detect the location of the leak and repair it in time. Don't wait until the equipment has multiple leaks and can no longer work normally before going for leak detection and maintenance.
In addition, preparing sufficient sealing spare parts at ordinary times and replacing vulnerable parts regularly (not after problems occur) are also the main measures to do a good job in vacuum leak detection and ensure the normal operation of equipment.