The impeller is the key component of the centrifugal pump, which is composed of several curved blades. The function of the impeller is to move the prime mover. The mechanical energy of the machine is directly transmitted to the liquid to improve the static pressure energy and dynamic pressure energy of the liquid (mainly improve the static pressure energy). The impeller is an energy supply device.
According to its mechanical structure, it can be divided into closed impeller, semi-closed impeller, and open impeller. The impellers should be used for conveying clean water, because of their high efficiency, the general centrifugal pump mostly adopts a multi-stage centrifugal pump; Semi-closed impeller is suitable for conveying materials that are easy to precipitate or slightly contain particles, and its efficiency is lower than that of closed impeller; The open impeller is suitable for conveying materials containing more suspended solids. Its efficiency is low and the pressure of conveying liquid is not high. According to its liquid absorption mode, it can be divided into the single suction type and double suction type. The single suction type has a simple structure, and the liquid is inhaled only from one side;
The double suction structure is more complex, and the liquid is sucked from both sides, which has a large liquid absorption capacity.
According to the blade shape, it can be divided into the backward-curved blade, radial blade, and forward-curved blade, because the backward-curved blade can obtain higher performance and static pressure energy, so centrifugal pumps mostly use backward curved blades. The pump impeller is driven to rotate by the motor; so that the medium (water) is subjected to centrifugal force or lifting force; so that the medium has mechanical energy (kinetic energy)
Titanium is a metal with a strong passivation tendency. It can quickly form a stable oxidizing protective film in air and oxidizing or neutral aqueous solution. Even if the film is damaged for some reason, it can recover quickly and automatically. Therefore, titanium has excellent corrosion resistance in oxidizing and neutral media.
Due to the great passivation performance of titanium, in many cases, when contacting dissimilar metals, it may not accelerate the corrosion of dissimilar metals but may accelerate the corrosion of dissimilar metals. For example, in low concentration nonoxidizing acid, if Pb, Sn, Cu, or Monel alloy is contacted with titanium to form a galvanic couple, the corrosion of these materials is accelerated, while titanium is not affected. In hydrochloric acid, when titanium comes into contact with low carbon steel, the newly generated hydrogen on the surface of titanium destroys the oxide film of titanium, which not only causes the hydrogen embrittlement of titanium but also accelerates the corrosion of titanium, which may be due to the high activity of titanium to hydrogen.
The iron content in titanium has an impact on the corrosion resistance in some media. In addition to the reasons for raw materials, the reason for the increase of iron is often that the contaminated iron infiltrates into the weld bead during welding, resulting in the increase of local iron content in the weld bead. At this time, the corrosion has the nature of non-uniformity. When using iron parts to support titanium equipment, iron contamination on the iron titanium contact surface is almost inevitable, and the corrosion is accelerated in the iron contamination area, especially in the presence of hydrogen. When the titanium oxide film on the contaminated surface is mechanically damaged, hydrogen will penetrate into the metal. According to temperature, pressure, and other conditions, hydrogen will diffuse accordingly, which makes titanium produce different degrees of hydrogen embrittlement. Therefore, the use of titanium in medium temperature, medium pressure, and hydrogen-containing systems should avoid surface iron pollution.
