Case histories

Plastic corrosion-resistant pumps

Figure 1
Figure 1 shows a case information regarding the nature of the liquid not communicated correctly. In particular, information regarding the concentration and temperature of the acid to be handled was incorrect. This resulted in the select of materials that reacted in unexpectedly when they came into contact with the chemical agent. The problem was overcome as soon as true information on the liquid was obtained.

Figure 2

Figure 2 instead shows the case of a vertical pump that worked submerged in sludge: to be avoided due to the consequential clogging problems.

Figure 3Another case of how the liquid can influence the proper functioning of the pump is shown in figure 3: in this case the problem is represented by the presence of foreign bodies in the fluid pumped. The presence of miscellaneous objects which accidentally ended up in the tanks (filaments, cables, pieces of packaging, machining scrap, bags, cigarette butts, etc?) can create problems such as clogging the suction line or the impeller blades.
Vertical pumps are normally provided with a grid on the suction inlet in order to prevent bodies large enough to damage the pump from entering. Horizontal pumps are subject to this type of problem, though only in certain cases. Nevertheless, in all cases it is recommended that a grid be used for the liquid at the inlet of the basin or the suction tank to prevent the presence of foreign bodies.

Figure 4In the photo 4 the effects of a thermal shock on the faces of a mechanical seal can be seen. If a mechanical seal works incorrectly with the fluid being pumped, which lubricates the seal and removes the heat generated from the friction between the seal faces, the temperature will rise considerable precisely in the area between the seal faces. If the cold liquid reaches the overheated rings, stresses will be generated within the rings that will cause them to disintegrate. To prevent such events, in this case it's important that the suction conditions always be under control.

Figure 5Image 5 shows the effects caused by the dry operation of a vertical pump. Vertical axis pumps with guide bushings are pumps designed to work with the constant presence of liquid. In fact the liquid being pumped is also used for flushing and cooling the shaft guide bushings. If the pump is forced to work without liquid, the temperature around the guide bushings will increase due to friction: this raise in temperature can lead to melting and the consequential damage to the bushing housing and the shaft.

Figure 6

Image 6 shows an example of liquid crystallization and its effects in a centrifugal pump.

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