The pump still leaks even after it’s installed – what could be the reason?

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The pump still leaks even after it’s installed – what could be the reason? Leakage at the flange connection: The reason for leakage at the flange connection is basically due to excessive tension exerted by the tightening screws. Solution: Tighten the screws diagonally; do not tighten them all at once. The gasket used for sealing between the two flanges should ideally be of the same size as the flanges themselves. The motor is running but no water is being pumped out. Check the direction of motor rotation – the direction might be incorrect, or there could be a leak at the inlet area. Solution: Check whether the motor is rotating in the correct direction and whether there is any air leakage at the inlet. Leakage from the mechanical seal, caused by pumping without water and resulting in empty rotation, leads to the destruction of the mechanical seal. Possible reasons for this issue with a new pump: running the pump without water causes damage to the shaft seal. For old pumps, the following possibilities exist: 1. Wear of the moving and stationary surfaces of the mechanical seal, or excessive tightness during installation. Examine the surfaces of the stationary and rotating rings of the mechanical seal; if there is severe burning, the surfaces will be blackened with deep marks, and the sealing rubber will become hard (WeChat official account: Pump Butler), losing its elasticity. This phenomenon is caused by over-tightening during installation. It’s installed too loosely. By examining the moving and stationary rings of the mechanical seal, a thin layer of scale can be seen on their surfaces; this scale can be wiped off, and the surfaces show little signs of wear. This condition is caused by the spring losing its elasticity or by improper assembly, or it may result from axial movement of the motor. The water quality is poor and contains particles. Due to poor water quality, the presence of small particles and a high concentration of hydrochlorides in the medium, abrasive wear occurs on the surfaces of mechanical seals, resulting in grooves, ring-shaped scratches, and other defects. Operation under water shortage causes dry grinding damage. This phenomenon is commonly seen in installations with bottom-valve types, where there is negative pressure at the inlet, air in the water inlet pipe, and air inside the pump chamber. When the pump starts operating, the friction between the seal components generates high temperatures due to their rapid rotation, and cooling is not possible. Upon inspection of the seal, the spring tension is normal; however, the friction surfaces are burned and blackened, and the rubber has hardened and cracked. Cavitation. Cavitation mainly occurs in hot water pumps. Since the medium is hot water, the high water temperature generates steam; this steam enters the upper parts of the pump chamber, and it is not possible to remove this steam, which leads to operation with insufficient water, failure of the mechanical seal due to dry grinding, as well as cavitation. The automatic exhaust valve needs to be replaced, along with the mechanical seal. Assembly problem. When installing the pump cover, it may not be aligned properly, resulting in the shaft not being perpendicular to the pump cover and thus preventing the moving and stationary surfaces from fitting together. As a result, wear occurs on one side after short periods of operation, leading to leakage. It is also possible that the rubber components may be damaged, or the surfaces of the stationary and rotating rings may get scratched during installation. 2. Failure of the mechanical seal adhesive. Reasons for the failure of the mechanical seal adhesive: aging and deformation of rubber components, primarily occurring in hot water pumps. The signs of failure in mechanical seal gaskets are excessively high water temperature and the medium dissolving the rubber. Visually, the surface of the rubber parts appears loose and rough, losing its elasticity, which leads to the failure of the rubber. 3. The main cause of the problem in the pump cover’s static ring chamber is the large machining tolerances of the internal holes in this chamber, as well as its rough surface. The observed phenomena include axial water spraying, a gap between the stationary ring and the inner hole, or roughness of the inner hole, as well as rotation of the stationary ring and rubber wear. 4. Poor machining accuracy, small size, roughness of the motor shaft journals, and corrosion of these journals. The machining dimensions of the motor shaft journals (at the location where the moving ring is situated) are small; in addition, corrosive media can damage the pump. Moreover, when the pump is not in use for an extended period of time, water acting as a medium leads to differences in electrode potential between the steel shaft and the cast impeller serta pump cover, resulting in a galvanic reaction that causes corrosion of the shaft journals. The observable phenomenon is a pitted corroded surface. -END-