Hydronic Systems: Pumps and Pumping Systems

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Key Questions

The following key questions are answered in this module:

What are some common types of hydronic systems?
Hydronic systems include heating water systems, chilled water-cooling systems as well as some process and domestic water distribution systems.

What are hydronics?
Hydronics are a means of heating and cooling using a fluid as the heat transfer medium.

What are the primary parts of a centrifugal pump?
The primary parts of a centrifugal pump are the impeller, volute, mechanical seal, drive assembly, and coupling.

What is the impeller?
The impeller is the rotating component within the pump that transfers the energy from the drive to the water being pumped.

What are couplings?
Couplings are mechanical devices used to connect rotating shafts and absorb minor misalignments between them.

Sample Video Transcript

Below is a transcript of the video sample provided for this module:

Opposite the volute and down the shaft we have the drive assembly. The drive assembly will require a shaft to transfer the power, bearings to support the shaft, and a coupling to the motor itself. Where the elements are located depends on whether they are close-coupled or split-coupled. Split-coupled pumps are more expensive and very common in base-mounted pumps. The pump has its own bearing assembly and the motor and pump shafts are coupled. The coupling joins the two shafts, but it also acts as a decoupler and potentially, a sacrificial element between the motor and pump bearing assemblies if the motor or pump were to lock up. In close-coupled pumps, the pump impeller, mechanical seal, and shaft sleeve are all mounted on the motor shaft. Because the pump does not have a bearing assembly, the motor bearings must handle all the torsional load. This limits the size and power of motor that can be used. Close-coupled pumps are compact, simple, and cheap, and are used in light duty applications. Couplings are mechanical devices used to connect rotating shafts and absorb minor misalignments between them. Couplings can be rigid or flexible depending on the alignment accuracies of the system and torque requirements. There are many types of couplings, and we will touch on those most commonly used with hydronic pumps. Jaw coupling, also referred to as a spider coupling, consist of pairs of multi-jawed hubs that mate with flexible elastomeric spiders. The elastomeric spiders give these couplings some damping capacity and often the spiders are available with different properties to accommodate various conditions. While a jaw coupling utilizes elastomeric components, most often when someone refers to an elastomeric coupling, they are referring to an older design that has been used for decades. In fact, this type of elastomeric coupling is the most common coupling used. Elastomeric couplings consist of two metal hubs that attach to both the motor and pump shaft. Between them there is a hard rubber insert. There's no maintenance necessary with this coupling, as it does not need lubrication.