Compared with the canned pump, the mechanical seal pump has the following advantages: the cost of the mechanical seal pump is about 60% of the cost of the same parameter canned pump, because it can use a detachable and ordinary drive motor. The mechanical seal pump can equipped with electric motor, steam motor. The motor is not in contact with the liquid to be transported. It is usually easier to repair or replace in case of failure. The efficiency of the mechanical seal pump is 15-20% higher than that of the canned pump. In addition, the starting performance is higher than for canned motors; mechanically sealed pumps can be used with any suitable type of oil lubricated bearings, including rolling bearings, and can be placed outside the range of liquid being delivered.
Of course, mechanical seal pumps also have many shortcomings, among which: mechanical seal pumps are still theoretically a type of restricted leak pump, commonly used chemical pumps. In order to ensure the absolute absence of leakage of the above-mentioned several types of liquids to be transported, in addition to the need to use multi-stage seals to reduce the load on the single-stage seals, some auxiliary systems and automatic devices are required to apply lubrication, cooling and failure to the seals. Protection, thus complicating its structure and increasing the size of the unit. The tightness of the mechanical seal pump is achieved by the fit between the moving ring and the stationary ring sealing surface. Because this fit is affected by many internal and external factors, failure is inevitable, thus fundamentally affecting the reliability and service life of its work. Although the cost of mechanical seals is not large, repairs and replacements do not require significant costs, but their economics are reduced due to their poor reliability.
A magnetic pump is a power pump that uses a stationary isolator to form a closed system of the pump chamber instead of a rotary seal. The energy of the prime mover drives the inner magnetic steel component mounted on the pump rotor and rotates it by the magnetic moment generated by the magnetic steel on the outer magnetic steel component.
Compared with mechanical seal pumps and canned pumps, magnetic pumps have the following main features: manufacturing costs are slightly higher than mechanical seal pumps (for general construction) and comparable to shielded electric pumps; mechanically sealed pumps with higher energy consumption than good performance However, the maintenance cost is low, which makes it roughly equivalent to the mechanical seal pump in total; the mechanical design is simpler and more convenient than the mechanical seal pump and the shielded electric pump; the standard motor can be used, the structure is compact, and the external dimensions of the unit are not increased; For high temperature and explosive conditions, it has high reliability and maintainability. The main disadvantage of the magnetic pump is that the transmission efficiency of the motor is reduced due to the presence of the spacer in the magnetic coupling. In the case of a good design of the isolation sleeve, the efficiency is about 92%-95%, which is about 5 times lower than the efficiency of the mechanical seal pump; when the high pressure liquid is delivered, the static seal of the isolation sleeve is prone to leakage. At the same time, the deformation caused by the isolator under high pressure will further aggravate the damage of the seal. Shielded electric pumps are often referred to as shielded pumps, and can also be referred to as non-filled pumps with shielded motors. Structurally, it is a pump that uses a special combination of a shielded motor and a drive pump. Although it can be divided into dry and wet, pneumatic or liquid-filled according to the internal structural characteristics of the motor, they have in common that there is no overhanging portion of the rotating shaft.
