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Leakage problems of mechanical seals and repair countermeasures
- Sep 11, 2018 -

Mechanical seal skill is based on a pair of possible pairs of opposite sliding ends perpendicular to the shaft, which are able to stick together under fluid pressure and other forces of compensation tissue, together with auxiliary sealing equipment to achieve the function of stop leakage.Mechanical seal makes the touch surface of static ring and moving ring fit together permanently.Passing through the static and moving rings the appropriate specific pressure and always in between a layer of liquid membrane to achieve the intention of sealing.

The main components for mechanical seal are static and dynamic seal components.There are O type, U type, X type and other types of sealing ring that play a role in mechanical sealing.The compensation parts include spring, pushing ring, etc.Driving parts include driving screws and driving pins, etc.The fastening part includes many parts, such as push ring, spring seat, gland and set screw.

What equipment does mechanical seal mostly use for?Mechanical seals are usually used for centrifugal pumps, centrifuges, compressors, reactors and other equipment.It has good sealing function, less leakage, longer service life, lower energy consumption, and does not require frequent repair.Mechanical seal is also very good in habit ability. Under normal conditions, it can be used to automatic production, high temperature, pressure and other harsh environment and strict requirements for sealing.

Seal leak question

Common leakage conditions of mechanical seals are as follows:

1. Leakage caused by damage to the flatness of the sealing surface

Most of the damage to the sealing surface is the uneven sliding and face interception.The factors of the outbreak may be due to the deformation of the seal heading of the pump's seal box and mixer, or the uneven bolt fastening, etc., leading to the deformation of the sealing surface of the static ring, and finally the leakage scene.It is also possible that the shape of the sealing surface is altered due to changes in the temperature of the sliding parts during hot installation and the existence of thermal expansion differences.Leakage can also be caused by damage to the seal.

2. Leakage due to the smooth damage of the sealing surface

The smoothness of the end face seal is also very important, in addition to the end face liquid membrane seal role, together with the smooth role to end the normal work.Once the liquid film at the end surface is damaged, it will form dry conflicts and the sealing surface will become increasingly worn and rough in a flash, and even some hard data will break out cracks and other serious scenes.When the temperature of the sliding conflict surface rises suddenly and the heat accumulation cannot be removed immediately, the evaporation of the sealing fluid and the disappearance of the light synovial membrane will lead to the outbreak of dry conflict.Dry conflicts can easily damage the sealing surface and bury many risks of leakage.

3.Leakage due to action damage

The dynamic and static rings of mechanical seals always rotate along with the shaft, and they always repeat the same movement frequently. This repetitive movement not only changes the seal face, but also adds the axial movement of the equipment, gradually reducing the precision of mechanical seals.Over such a long period of time, the various parts of the equipment would be damaged or even deformed, and thus lose their mobility, resulting in leakage of the seal.

What affects mechanical seal performance?The accumulation of the primary slurry will make the spring action blocked, slide parts out of control, and the sealing surface will be worn.When the sliding sealing surface is worn, hardened and aged, the shaft and sleeve will be damaged, and the spring seat will be worn or even twisted.

4.Leakage resulting from a combination of elements

The occurrence of leakage is sometimes caused by the superposition of multiple factors, such as dry conflict, poor sliding, sliding ring deformation and planar deformation, etc., which can easily lead to leakage.Many of these factors are caused by excessive fatigue, uneven compression and fluid film damage.Thus accurate equipment and adherence to mechanical seal cleanliness is very important, coupled with outstanding cooling effect, which can be very good at eliminating hazards.

Countermeasures of leakage repair

1. The countermeasure of poor action

Use the o-ring with good abrasion resistance and good rubber elasticity first. This ring can stick to its inherent shape and size when minor damage occurs.The o-ring usually used for sealing is mostly rubber, probably teflon.Teflon is mainly corrosive and can be used as corrugated gasket or V tube.If at high temperature or low temperature, the bellows of stainless steel and other raw materials are usually selected as the sealing ring. If mechanical sealing of rotary type is required, the o-ring shall be selected for sliding sealing.

We can consider the use of stop-type mechanical seals with a long life, the static ring device on one side of the shaft, and the moving ring device on the other side of the housing, so that mechanical deformation will not affect the equipment outbreak, together with the planar structure has an excellent role of persistence.In this way, the spring of the equipment does not touch the sealing fluid, and the motion is greatly improved, which provides great convenience in removing the slurry and maintaining the flatness and machine precision of the seal.

The effect of mechanical seal is also very large due to the heat, which will result in data degeneration and part deformation, resulting in the change of load capacity, thus greatly reducing the operation function of seal and burning condition.The treatment method is subject to the size of the heat and depends on the situation, including natural cooling, internal circulation cooling, external scouring cooling and internal circulation cooling, etc. Moreover, the temperature of the sealing is controlled to make the sealing effect reach the best.

2. Countermeasures for sliding surfaces

In the maintenance and repair of the equipment, carefully check the equipment for wear and sliding image to ensure the accuracy of static ring appearance.Together, choosing a stop-type mechanical seal can handle the wear problem extremely well.Another way to handle the thermal deformation of the seal is to change the holding mode of the o-ring or graphite ring of the sealing ring from sliding mode to pricking mode.

3. Countermeasures to avoid dry sliding

If dry sliding, which is caused by lack of cooling during sliding heating, results in damage to the sliding surface, we can select the sealing fluid and cooling water and temperature control units that are increasingly well equipped, together with the need to make a circuit of the supply lines to avoid blockages.When selecting mechanical seals, the best choice of mechanical seals with good pulp resistance is to stop mechanical seals, which can avoid dry conflict.Otherwise, it is very important to strengthen the handling of rotating machinery, check the pressure of mechanical seals and other various parameters and conditions on time, and deal with relevant questions timely.