COMMON FAILURES AND TREATMENT METHODS OF MECHANICAL SEALS IN SEWAGE TREATMENT EQUIPMENT

There are a large number of people in cities, and a lot of sewage for production. And production will be generated. These sewage must be treated and discharged into the natural world. If the sewage is not treated properly, it will cause environmental pollution, or affect people's normal water use, or damage the ecology, or even cause irreversible damage to the earth. Therefore, sewage treatment is an important issue that we must deal with well. However, in sewage treatment equipment, it is often difficult to achieve effective treatment of sewage due to improper mechanical seals, and an effective treatment method must be proposed. The mechanical seal of the sewage treatment equipment not only has good effect and stable work, but also has low friction power consumption. It can also realize sewage treatment under high temperature and high pressure. The effect is self-evident. However, mechanical seals often fail and need to be addressed in a timely manner.

Common faults

The two sealed end faces leaked from each other. After the unit was running, due to the increase in pressure, many sewage or related chemicals splashed radially. Leakage occurred at the position where the body of the sewage treatment equipment was pressed against the static ring base or the gland was screwed. Leakage occurred at the fitting position of the mechanical seal moving ring sleeve and journal.

Failure cause analysis

There are many unknown particles in the sewage, because these particles remain in the sealed fluid film, which will eventually lead to voids and affect the sealability. Because the sewage is highly corrosive, the equipment will be corroded over time. The main factors are as follows:

1. Excessive solid particles in sewage. When the equipment is treating sewage, first adjust the acid and alkali of the sewage into a neutral solution. The general method adopted is to put quicklime into an acidic solution. When quicklime meets water, it will produce alkaline substances. These substances react with acidic substances to form calcium. Many acid acids of calcium are solid particles. After the sedimentation, the sewage is put into the equipment for treatment. After the sedimentation of the sewage, there will inevitably be particles. These small particles will enter the treatment equipment with the sewage and run the equipment. At times, it is adsorbed on the equipment, which ultimately affects the sealing effect.

2. The coupling is in the wrong position. This situation is mainly for technical reasons. When the equipment is installed, the coupling between the motor and the equipment's main shaft is not set on a balance line. This may be a technical problem or a fault in the production of equipment parts, or an inspection occurred. Missing.

3. The rubber seal has failed. The auxiliary sealing material used for mechanical seals is usually a polytetrafluoroethylene 0 ring. Because the sewage contains a large amount of corrosive solutions, it will cause the rubber ring to expand and deform, corrode, and oxidize. When the rubber ring adheres to the metal, it is elastic. Performance is impaired, reducing strength. Because of corrosion and adhesion, the 0-shaped section in the rectangular groove of the journal becomes a rectangular section, and the area is reduced, thereby forming a leak. Part of the reason is that the area of the rubber is reduced due to the strong deformation of the rubber during use.

4. The bearing deforms itself. Because it has been immersed in sewage for a long time, pitting and grooves will occur on the surface of the bearing, which will cause leakage points in the bearing connection. The thinner shaft will be bent and deformed under the action of the groove, and may even be broken. Sewage leaks.

5. Mechanical seal spring or bellows failed. The working environment of many sewage treatment equipment is harsh, because of the presence of sludge or solid particles in the sewage, the cylindrical mechanical seal spiral compression spring is blocked by sludge or other solid debris and loses the compensation ring. Axial thrust. After the sewage is corroded, the diameter of the spring will become thinner, resulting in a great decrease in strength, the axial thrust of the compensation ring will be insufficient, and even the spring will break, causing the compensation ring to detach from it. If a metal bellows is used, cracks or fractures often occur in the trough. Some mechanical seal equipment compensating ring springs use a stainless steel shaft snap ring. Under the strong corrosiveness of sewage, the shaft snap ring is corroded, and the spring loses the axial thrust on the compensating ring, making the mechanical seal invalid.

Method of Handling Failure

Check carefully before component installation

Repairing and maintenance of sewage treatment equipment is usually done well, and related parts and components that have been dismantled must be strictly inspected in accordance with technical indicators for quality inspection. Mainly to see if there is a problem with the surface of the spindle journal. If it cannot be repaired, you need to replace it with a new one. Discard any severely worn couplings. Observe whether the rotation of the bearing has high accuracy and flexibility, and it must be discarded resolutely for axial and radial movement. Check the effective thickness of the mechanical seal friction pair. If the abrasion is serious, replace it with a new one, if the end face is deformed, whether the flatness and roughness meet the technical requirements, or re-grind or replace it with a new one. All compensating springs, O-rings and other accessories should be thoroughly inspected.

Correct installation and usage

Observe the stability of the installation foundation of the motor and the body, whether there is local settlement or damage, and whether the embedded bolts of the foundation are loose. Otherwise, the carcass should be used for repair or re-pouring in time. For equipment using couplings, the accuracy of the centerline position of the two shafts should be controlled during installation. Generally, dial gauges and feeler gauges are used to adjust the outer circle deviation of the two shaft couplings and the gap between the two end faces to the specified technical parameters. "Second settling tank" is set on the structure of the pool body and the silt at the bottom of the pool is regularly removed. In view of the impact of excess solid particles in sewage on equipment and pipelines, we have considered the structure of each sewage pumping station pool structure, and try to make solid sediments in the sewage settle in a "sink tank" to minimize the outlet pool. The solid content in the sewage of the body (second settling tank) can effectively reduce the incidence of frictional failure of mechanical seals. Depending on the degree of sludge deposition in each pond, timely organize forces to remove thick silt at the bottom of the pond. Then carry out environmental protection treatment to reduce the solid impurity content in sewage and effectively reduce the failure rate of sewage treatment equipment. We can manually treat the sewage before it enters the equipment. First, the acidity and alkalinity of the sewage are reconciled, the acidic sewage is treated with calcium oxide, the alkaline sewage is neutralized with an acidic solution, and the solid particles are filtered out after filtering. The filtered sewage is precipitated by centrifugation to remove those small particles and prevent the pipeline from being blocked when entering the pipeline. Then proceed with other methods.

Precautions for maintenance of sewage treatment equipment

The maintenance of sewage treatment equipment is a necessary method to avoid the occurrence of sewage leakage. However, many issues should be noticed while maintaining the equipment, which are highlighted here. During maintenance, first carry out a comprehensive inspection of the mechanical seal to check whether there is any damage to the seal. If there is damage, immediately reseal it. Then check whether any parts are damaged or fail, and perform necessary repair and replacement according to the degree of damage, and replace those failed parts. When disassembling the device, pay attention to the joint method of the device, and disassemble in order. Do not forcibly remove this part in order to repair a certain aspect, which will cause damage to other parts. Sewage leaks frequently occur between maintenance periods. Care should be taken to reduce maintenance intervals. If leakage occurs frequently in a part of sewage treatment equipment, attention should be paid to whether the sealing effect here meets the requirements and whether the mechanical parts meet the working conditions. For the place where the sewage is leaked periodically, the sealing strength of the part should be strengthened.