Circulation pump - one of the main components of the heating system and hot water . Designed to ensure the forced movement of fluid in a closed loop (circulation), as well as recycling. When calculating the performance of a pump operating in a circulation system, only friction losses in the pipeline should be considered. The height of the system (building) does not matter, since the fluid that is pumped into the supply pipe also pushes water in the opposite direction. Therefore, you can use a relatively small pump power to circulate the working fluid.
Classification
There are many different classifications of circulation pumps. Here are some of them:
"With a wet rotor" and "with a dry rotor"
"Wet" circulation pumps have a rotor with an impeller located in the fluid they pump. The rotor is separated from the stator by a glass, which, as a rule, is made of stainless steel. The rotor shaft can be made from metal or ceramic. The pumped liquid performs two functions: it lubricates parts and cools the engine. The efficiency of the pump "wet rotor" is about 50%. The new generation of wet-rotor pumps is designed according to a modular principle. Blocks are grouped according to pump dimensions and required flow. Thus, it is easier and carrying out repairs by replacing certain parts. The impeller of such pumps combines the advantages of axial and radial wheels. A shaft with bearings and a rotor form a single block in the “cartouche”. An important quality of this design is its ability to remove the air itself during start-up.
For pumping large volumes in large installations, pumps with dry rotors are used. These pumps got their name due to the fact that the motors of these pumps do not come into contact with the pumped water. A characteristic difference is the presence of a seal between the pump part and the electric motor. The seal is a “mechanical seal”. A thin film of water forms between the sliding surfaces, since the water in the heating circuit is under increased pressure compared to the surrounding atmosphere. This water film seals the pump when the surfaces rotate relative to each other. Rings are usually made of agglomerated coal. For work in difficult conditions, they can be made of ceramic or stainless steel. Such units usually have higher power and performance, but emit noise during operation, so their use is limited to installation in isolated rooms or buildings. [1] Two types of dry rotor pumps are structurally distinguished. These are centrifugal pumps with a flanged motor and large centrifugal pumps with a motor and coupling connection. If the suction and discharge nozzles are located on the same axis and have the same conditional passages, then such pumps are called direct-flow pumps. Such pumps can be installed directly in the pipeline. Either the pipeline must be fixed with the help of the console, or the pump is installed on the foundation or on its own console. With a direct-flow design, the position of the motor and shaft do not affect the operation of the pump. Large centrifugal pumps with a motor and a coupling connection can be mounted on a common support frame. In this case, we are talking about cantilever pumps on a foundation frame that comply with DIN 24255. Depending on the pumped medium, it is possible to use a pump with a sliding mechanical seal or with a gland. Vertically located discharge nozzle determines the conditional passage of the pump. A suction nozzle, located horizontally, has, as a rule, a larger diameter.
Note
- How to select a circulating pump for the heating system . The appeal date is February 13, 2019.