When buying a centrifugal pump, we always look for pumps with high efficiency, minimal maintenance and good reliability. One must always consider all these factors, however, one thing that people forget to look at is the selecting the right impeller style for your centrifugal pump. Earlier, impellers generally were divided into two categories open and closed. But these days, there is also a third type available. It is called a semi open impeller. Here are a few differences between the open and closed impeller:
- The open impeller has a series of vanes attached to a central unit. This is done for the mounting on the shaft. However, this design is more sensitive to wear and tear of the blades. The closed impeller has a side wall on the either sides (top and bottom) of the vanes.
- Closed impellers are the most commonly used impellers in the industry since they can deal with volatile and explosive fluids.
- The closed impeller is initially really efficient, but with time, loses its efficiency as the clearance of the wear ring increases, whereas the efficiency of an open impeller can be maintained through clearance adjustment.
- The pump had to be disassembled when it has a closed impeller to check the status of the wear rings. In an open impeller, no pump disassembling is necessary.
- An open impeller is less likely to get clogged and even if it does, it is easier to clean whereas in a closed impeller, if stringy material or solids are pumped, the impeller can clog and it becomes really difficult to clean them.
- The internal parts of a closed impeller are hidden hence it is difficult to cast and inspect for flaws whereas in an open impeller, all the parts are visible. It thus becomes easy to inspect for damage.
- The design of a closed impeller is more complicated and expensive since the additional wear rings are needed while the open impeller is less costly to build.
- You cannot easily modify a closed impeller so as to improve its performance. While the vanes can be easily cut to improve the capacity in an open impeller.
- In a closed impeller, speed choices are limited. But you have a wide range of specific speed, choice is an open impeller.
As we just saw, there are very specific benefits and pitfalls in both the types of impellers. But it depends on the kind of application you are buying the pump for. Would you think about buying a car that has a poor mileage? No, right? Similarly, when buying a pump if you keep the above mentioned points in mind, you can surely make the best decision without any regrets in the future.