What are Split Case Horizontal Pumps?

If you were to take an informal survey of the pump types in use today, you would probably find that many of them are split case horizontal pumps. These industrial workhorses, while not as flexible as many other designs, have been known to continue to work year after year, even decades, without failure. Let's look at the split case horizontal pumps and what makes them special.

What Are Split Case Horizontal Pumps?

Split case horizontal pumps are designed to move a large volume of liquid with a limited amount of particulates at low to medium pressure. While they are more expensive than many pump types, they are also known to be inflexible and not very adaptable.

But split case horizontal pumps work well for the applications they are designed for, and they usually continue to work for many years without failure. This is why they are known as the workhorses of many industrial and municipal applications.

How They Work

As their name suggests, split case horizontal pumps are designed with casings that come apart. The design allows for the top part of the case to removed without disturbing the driver or associated piping. This allows for quick and easy inspection and repair of the rotor as needed.

Split case horizontal pumps are usually axially-split. That is, the flange where the case splits is in the plane as the pump axis. There are radially-split pumps, but they are generally used in high-pressure, high-temperature applications and are not as common.

Thanks to their design, split case horizontal pumps usually have a smaller footprint than a frame mounted pump of the same rating. They also typically have a higher efficiency than a similar frame mounted pump.

The design of the split case horizontal pump is what makes it stand out from others. They have a between-the-bearing design, which means that the impeller is supported by bearings on both sides. This allows for more significant support of the impeller and will enable it to turn more efficiently under stress.

Also, split case horizontal pumps are one of the only common pump designs to incorporate a double-suction impeller. Since this design draws water in from both sides of the impeller (unlike standard single-suction designs that pull from only one side), it dramatically reduces the load requirements on the bearings. This translates to longer lasting bearings and a more efficient operation.

Design Limitations

While split case horizontal pumps are known to be the industry workhorse and tend to remain in service for many years, they are not without their design limitations. Since the casing comes apart as it does around the components, there is not a confined gasket design. Because of this, there are limits to the pressure that the pump can handle.

Split case horizontal pumps are sensitive to horizontal elbows (and other piping constrictions) on the suction side. Such usage can induce asymmetrical pressure on the impeller, leading to a failed bearing or seal failure. Pipe strain can also be an issue with this pump type.

Since the casing halves do not have the same mass, they will expand and contract at different rates when the operating temperature changes. This uneven expansion can impact bearing and seal life. For this reason, most manufacturers limit their use to 400 degrees F.

Applications

Split case horizontal pumps are found in use in many different applications and often have been there for quite some time. Many municipal water systems will use this pump design since they are well suited for fixed, high-volume, low-pressure applications.

Cooling towers and cooling systems, which depend on the exchange of high volumes of water at low to mid pressure, will use split case horizontal pumps in their operation. You will also find them in use for heating plants, or anywhere that water is used as a heat exchange mechanism.

Because of their durability and ease of maintenance, many industrial processes will incorporate split case horizontal pumps in their operating design. Irrigation applications will also put them to use, distributing water as needed to crops and turfs.

Split case horizontal pumps are the industry workhorse when it comes to transferring liquids at high-volume and low to mid-pressure. Mader Electric, Inc. specializes in the installation and repair of split case horizontal pumps, as well as pump training. Contact us to see how we can help with your pumping needs.