Please advise on the differences between vortex pumps and canned motor pumps

A vortex pump is a type of vane pump; it was first manufactured by the German companies Siemens and Henschel. Its main components include an impeller (a disk with radial vanes on its outer edge), a pump casing, and an annular flow channel formed by the pump cover, the pump casing, and the impeller. The liquid enters the flow channel through the suction pipe, gains energy from the rotating impeller, and is then delivered to the discharge pipe, thus completing the pump’s operating cycle. The working principle, layout, and performance curves of vortex pumps differ from those of conventional pumps such as centrifugal pumps, axial flow pumps, and mixed-flow pumps. They are pumps designed for low flow rates and high head pressures, with their specific speed Ns typically being less than 40. For vortex pumps, the minimum flow rate can be as low as 0.05 L/s or even lower ； The flow rate can reach 12 L/s, allowing it to replace centrifugal pumps in certain applications. When the specific speed Ns exceeds 40, it is generally used less often because its performance is far inferior to that of centrifugal pumps. Features of vortex pumps: The small size and light weight of vortex pumps give them significant advantages when used in ship equipment. It has self-priming capability or can achieve self-priming with the help of a simple device. It has a steep head curve, and therefore is insensitive to pressure fluctuations in the system. Certain vortex pumps can achieve the transportation of gas-liquid mixtures. This is of great significance for pumping volatile liquids containing gases and high-temperature liquids with very high vaporization pressures. Vortex pumps have a simple structure, and their casting and machining processes are easy to implement; moreover, certain components of vortex pumps can be made from non-metallic materials such as plastic or nylon molded impellers. Disadvantages of vortex pumps: 1. Their efficiency is relatively low, not exceeding 55% in the best cases; most vortex pumps have an efficiency of 20-40%, which hinders their development for use in high-power applications. 2. The cavitation performance of vortex pumps is poor. 3. Vortex pumps cannot be used to pump media with high viscosity. As the viscosity of the liquid increases, the pump’s head and efficiency drop sharply (WeChat official account: Pump Butler); therefore, the viscosity of the fluid should be kept below 114 centipoise. 4. The stringent requirements regarding the radial and axial clearances between the impeller and the pump casing of vortex pumps pose certain difficulties to the machining and assembly processes. 5. The medium to be pumped is limited to pure liquids only. When a liquid contains solid particles, wear causes an increase in the axial and radial clearances, which reduces the pump’s performance or even prevents the vortex pump from functioning.

A rotary vane pump can be considered a type of centrifugal pump; it meets the requirements of specific operating conditions through the conversion of mechanical energy into kinetic energy and then into pressure energy. Unlike conventional centrifugal pumps, its operating principle involves the synchronous rotation of the pump body with the medium, which reduces frictional losses, followed by the conversion of energy into pressure through a collector tube； The pump structure is of the cantilever type; there are various opinions regarding the type of bearings used. Its conveying capacity is increased by means of speed enhancement. Due to its special structure, changes in flow rate have virtually no effect on the stability of the rotary shell pump, which is an excellent feature for many pumping applications where regulation is complex ； It has clear advantages in applications involving low flow rates, high head, and clean fluids. Its rotational speed is lower than that of high-speed pumps, there is no pulsation, and its structure is simple; a single impeller is sufficient to achieve a transfer distance of several dozen to several hundred meters ； Due to electrical considerations, various design institutes and engineering companies give priority to the standard frequency; in fact, operating at a variable frequency is what maximizes its advantages ； However, there are also limitations: for example, the capacity to handle high-pressure inflows is insufficient, the cavitation performance is slightly worse than that of ordinary centrifugal pumps (not by much), and the requirements for the fluid are relatively high (casing pumps are generally not suitable for fluids containing particles or suspensions); moreover, the time required to start the pump may be longer ； As a pump designer, I still recommend rotary shell pumps for applications in the petrochemical industry, with pure media and conditions where vaporization is not likely to occur. For owners, these pumps have a simple structure, which reduces costs related to spare parts and after-sales maintenance. For domestic pump manufacturers, new pump types provide more options for design and selection. As for manufacturers themselves, there are technical barriers in place, resulting in higher profit margins compared to ordinary centrifugal pumps