Mechanical seal for kettle Manufacturer, causes of leakage and solutions

Mechanical seal refers to a device composed of at least one pair of end faces perpendicular to the rotation axis, under the action of fluid pressure and the elastic force (or magnetic force) of the compensation organization, and with the cooperation of the auxiliary seal, to maintain sticking and relative sliding, thus preventing fluid leakage.

Introduce the cause of mechanical seal leakage and the treatment method of water pump leakage: whether it is self-priming pump, centrifugal pump, QW submersible sewage pump and other mechanical seals are the key cause of industrial water pump leakage.

Mechanical seal is also called end face seal. It has a pair of end faces perpendicular to the rotation axis. Under the effect of fluid pressure and external elastic force of compensation machinery, the end faces rely on the cooperation of auxiliary seals to maintain contact with the other end and slide relatively, so as to prevent fluid leakage.

01 Common leakage phenomenon The proportion of mechanical seal leakage accounts for more than 50% of all industrial water pump leakage. The operation of mechanical seal directly affects the normal operation of water pump. The summary and analysis are as follows: 02 Causes of excitation penetration (I) Pressure leakage 1 Obstacle 1: Cause of mechanical seal leakage caused by high pressure and pressure wave: the specific pressure of the spring and the total specific pressure are designed to be too large. When the pressure in the seal cavity exceeds 3MPa, the specific pressure of the seal face will be too large, which will make it difficult to form a liquid film. The wear of the seal face is important, and the heat will increase, forming the thermal deformation of the seal face.

Treatment method: when the mechanical seal is equipped, the spring shrinkage must be carried out according to the regulations. It is not allowed to be too large or too small. The mechanical seal under high pressure should adopt countermeasures. In order to make the end face stress correct and reduce deformation, materials with high compressive strength such as cemented carbide and ceramics can be selected, and the smooth countermeasures of cooling can be strengthened.

2. Obstacle 2: The reason for the leakage of mechanical seal formed by vacuum operation: during the starting and stopping of the pump, due to the congestion of the pump inlet and the gas contained in the pumping medium, negative pressure may appear in the seal chamber. If negative pressure is not allowed in the seal chamber, it will lead to dry conflict of the seal end face, and gas (water) leakage will occur in the built-in mechanical seal.

Treatment method: double end mechanical seal is used to improve the smooth condition and improve the sealing function.

（2） Leakage caused by medium 1 Obstacle 1: The auxiliary seals of the static ring and the dynamic ring are inelastic, and some of them may still rot, resulting in a large amount of leakage of the mechanical seal and even grinding of the shaft.

Cause: High temperature and weak acid and alkali in sewage corrode the static ring and auxiliary rubber seals of the dynamic ring, resulting in excessive mechanical leakage. The raw material of the dynamic and static ring rubber seals is nitrile 40, which is not resistant to high temperature and acid and alkali. When the sewage is acidic and alkaline, it is easy to corrode.

Treatment method: For corrosive media, the rubber parts shall be fluororubber with high temperature resistance, weak acid resistance and weak alkali resistance.

2. Obstacle 2: The reason for mechanical seal leakage caused by vacuum solid particle impurities: solid particles entering the seal end face will scratch or accelerate the wear of the seal end face, and the stacking speed of scale and oil stains on the shaft (sleeve) surface exceeds the wear speed of the collision pair, which makes the moving ring unable to compensate for the wear displacement. The operating life of the hard to hard collision pair is longer than that of the hard to graphite collision pair, Because solid particles will be embedded in the sealing surface of the graphite sealing ring.

Treatment method: mechanical seal of tungsten carbide to tungsten carbide conflict pair shall be selected at the position where solid particles can easily enter.

03 Mechanical seal leakage caused by other problems There are still some problems in the mechanical seal such as incorrect design, selection and installation.

(1) The spring shrinkage must be carried out according to the regulations. It is not allowed to be too large or too small. The deviation is ± 2mm. If the shrinkage is too large, the end face specific pressure will be increased. If the conflict heat is too much, the thermal deformation of the sealing face will be formed and the end face wear will be accelerated. If the shrinkage is too small, the end face specific pressure of the dynamic and static rings will be insufficient, and the sealing will not be allowed.

(2) The end face of the shaft (or shaft sleeve) for installing the dynamic ring seal ring and the end face of the sealing gland (or housing) for installing the static ring seal ring shall be chamfered and polished to avoid damaging the dynamic and static ring seal ring when it is equipped.

Mechanical seal itself is a sophisticated part with high requirements for design, machining and equipment quality. When using mechanical seals, various factors of using mechanical seals should be analyzed, so that the technology of applying mechanical seals to various pumps should address the requirements of using media and have sufficient smooth conditions, so as to ensure the long-term and reliable operation of seals.