Several common causes of water pump leakage and Solutions!

Mechanical seal is the main cause of water pump leakage, but the mechanical seal itself is a kind of high precision component, which has high requirements for design, machining and assembly quality. In the use of mechanical seals, the various factors that use mechanical seals should be analyzed so that the mechanical seals are applicable to the technical requirements of various pumps and the requirements for the use of medium and sufficient lubrication conditions to ensure the long-term and reliable operation of the seals.


Mechanical seal is also called end face seal. It has a pair of end faces perpendicular to the axis of rotation. Under the action of fluid pressure and compensating mechanical force, the end face depends on the auxiliary seal to keep fit with the other end and slide relatively, so as to prevent the leakage of the fluid.


One, common leakage phenomenon


The proportion of mechanical seal leakage accounts for more than 50% of all maintenance pumps. The operation of mechanical seals directly affects the normal operation of pumps.


1. periodic leakage


(1) the axial movement of the pump rotor is large, and the interference between the auxiliary seal and the shaft is large. The moving ring can not move flexibly on the shaft. After the pump is turned over, the displacement of the moving and static ring is not compensated.


Countermeasures: the axial channeling of the shaft should be less than 0.1mm in the assembly of the mechanical seal, and the interference of the auxiliary seal and the shaft should be moderate. At the same time, the radial seal can be ensured to move flexibly on the shaft after the ring assembly is assembled (the dynamic ring pressure is freely bouncing back to the spring).


(2) the amount of lubricating oil on the sealing surface is insufficient to cause dry friction or napping seal ends.


Countermeasures: the height of the lubricating oil surface in the oil chamber should be higher than that of the static and dynamic sealing surface.


(3) the periodic vibration of the rotor. The reason is that there is no balance between the stator and the upper and lower ends of the impeller and the main shaft, the cavitation or the bearing damage (wear), which can shorten the sealing life and produce the leakage.


Countermeasure: The above problems can be corrected according to maintenance standards.


Grinding shaft phenomenon caused by sealing leakage of 2. small submersible pump


(1) the failure of the small pump machine under 715kW often produces the grinding shaft, and the position of the grinding shaft is mainly as follows: the auxiliary ring of the ring, the position of the static ring and the phenomenon of the grinding axle of a few springs.


(2) the main reasons of the grinding shaft are: (1) BIA type double end mechanical seal. The back pressure state is a bad working state. The particles and impurities in the medium can easily enter the sealing surface to make the seal fail. The main parts of the grinding shaft are rubber bellows, and because the close cover of the upper end is in a bad lubrication state, the friction torque between the static and static rings is greater than the transfer torque between the rubber bellows and the shaft, and the relative rotation occurs. 3. Due to the weak acid and weak alkali corrosion in the moving and static ring, the rubber parts are inelastic. Some have rotted and lost their proper functions, resulting in the phenomenon of grinding shaft.


(3) in order to solve the above problems, the following measures are taken: 1. Ensure the cleanliness of the lower cover and oil chamber, and prohibit the assembly of the unclean lubricating oil. 2. The oil line in the oil sealing chamber should be higher than the static ring cover. According to different media, choose different structural seals. For the high lift pump, the mechanical seal structure should be redesigned. For the corrosive medium rubber, the fluorine rubber with weak acid and weak base should be selected. The sealing ring should be added with the anti - turn pin.


Two. Leakage due to pressure


(1) the mechanical seal leakage caused by high pressure and pressure wave is too large to be designed by spring specific pressure and total specific pressure and the pressure of the seal cavity is more than 3MPa, which makes the seal face larger than the pressure, and the liquid film is difficult to form, the seal face is worn seriously and the heat is increased, resulting in the heat change of the seal face.


Countermeasures: when the assembly machine is sealed, the quantity of the spring compression must be carried out according to the regulations. It is not allowed to have too big or too small phenomenon, and the mechanical seal under high pressure should take measures. In order to make the end face stress reasonable and reduce the deformation as much as possible, the materials such as hard alloy, ceramics and other materials with high pressure resistance can be adopted, and the lubrication measures of cooling are strengthened, and the transmission mode, such as key and pin, can be selected.


(2) in the process of vacuum state operation, the mechanical seal leakage pump may cause the negative pressure in the seal cavity due to the blockage of the pump inlet and the gas in the pumping medium. If the sealing cavity is negative pressure, the seal face will cause dry friction, and the internal sealing mechanical seal will produce air leakage (water) phenomenon, vacuum seal and positive pressure. The difference between seals is the directional difference of sealing objects, and the mechanical seals also have their adaptability in a certain direction.


Countermeasure: double face mechanical seal is adopted, which helps to improve lubrication conditions and improve sealing performance.


Three. Leakage caused by medium


(1) after most of the mechanical seal of the submersible pump is disassembled, the auxiliary seals of the static ring and the movable ring are inelastic and some have rotted, resulting in a large amount of leakage and even the phenomenon of grinding shaft. Because of the corrosion of the weak acid and weak alkali in the high temperature and the sewage to the rubber sealing parts of the static ring and the movable ring, the mechanical leakage is too large. The rubber seal ring material of the dynamic and static ring is butyl (harmonious) - 40, not resistant to high temperature and acid and alkali, when the sewage is acidic alkaline, it is perishable.


Countermeasures: for corrosive media, rubber parts should be fluorinated rubber with high temperature resistance, weak acid resistance and weak base.


(2) mechanical seal leakage caused by solid particle impurities, if solid particles enter the seal face, it will scratch or speed up the wear of the seal face. The accumulation speed of the scale and oil pollution on the surface of the shaft exceeds the wear speed of the friction pair, causing the moving ring to not compensate for the wear displacement, and the hard working life of the hard pair is better than the hard pair Shi Momo. The pair is long because the solid particles are embedded in the graphite seal ring.