Best Practices for Hydronic Systems Part 10: Installation Measures to Ensure Performance and Longevity of Inline Pumps

Location and installation of inline pumps requires planning. Otherwise, you could be setting the owner (or yourself) up for a lot of frustration. Here are some tips to ensure your inline pump is installed for easy access and long-lasting service.

Properly orient the pump. Always consult the Installation and Operation Manual (IOM) to find out whether the pump can be installed to discharge up or down, left or right, and what position the motor shaft should be in. Also, most pumps will have an arrow on the body to indicate the direction of flow. Some pumps, like the B&G Series PL, can be oriented in several different ways, while others cannot.

Smaller fractional horsepower circulator pumps often have to be installed with the motor shaft horizontal. This is achieved by simply rotating the motor ninety degrees to keep the conduit box on top. Typically, these small pumps are installed directly in line with the pipe and supported by the pipe. If the pump has a bearing assembly, it is fine to have the pipe support the pump. If you feel that additional support is needed, be sure to support from underneath the bearing assembly and not the motor. Otherwise, you will cause misalignment of the pump coupler and the pump will fail prematurely (Figure 1 and 2).

Figure 1

Figure 2

Larger closed-coupled inline pumps can be installed vertically or horizontally (up to 256 NEMA motor frame size).

Large split-coupled inline pumps are typically only installed vertically.

Locate the pump for ease of service. Larger pumps should be installed for ease of service and removal of the pump motor. There should be sufficient room around and above the pump to remove the motor so the seals, impeller and bushings can be accessed. A pump motor hoist beam can be installed for larger inline pumps (typically 10HP or greater) to help move the heavy motor for servicing. Don't install a larger pump where it can't be serviced from the floor, otherwise maintenance will be very difficult because motors on larger pumps can weigh hundreds of pounds.

Provide proper support for larger pumps. Because inline pumps are designed to be installed without a base, they must have ample support. Depending on the size of the pump, the pipe itself may provide enough support. However, some inline pumps will require the additional support of a pump base or pipe stand. (See Figure 3)

Figure 3

Extra care should be taken when installing inline pumps in seismic applications—that is geographical areas where there is a high instance of seismic activity. Inline pumps have a high center of gravity compared to base-mounted pumps due to the weight of the motor. This increases the risk for what is known as an overturning moment or OTM. OTM refers to the point at which a specific rotational force becomes great enough to cause an object to tip over or overturn. Inline pumps don’t “tip over” because they are connected to piping, however seismic forces magnify their rotational movement and can result in a twisting effect on the piping. This places unacceptable stress on the pump flange and bolts, therefore additional piping and equipment supports are usually needed in seismic applications.

Don’t forget to accessorize! The following pump accessories will ensure the care and longevity of the pump.

• Flex connectors compensate for minor pipe misalignment and reduce pipe vibration.

• Suction diffusers are needed when an elbow is required near the suction. Conveniently, they play the role of both a strainer and elbow. But most importantly they help stabilize the turbulence and swirling action created by the 90° turn. Otherwise, this swirling action in the flow can create an imbalance of forces on the impeller and shaft, and ultimately shorten the life of seals and other pump components.

• A single pressure gauge should be installed and connected to both the pump suction and discharge for convenient pressure readings. Make sure this is a compound gauge on open condenser water applications.

• A triple duty valve should be installed on the discharge side of the pump for balancing, backflow prevention, and isolation/shut-off.