Lantern ring, packing gland, stuffing box… could you identify these parts on a centrifugal pump and correctly define their purpose? Centrifugal pumps contain many parts with names foreign to anyone who is just getting started with fluid processing systems. I took a trip out to the Crane Engineering Service Center to get the scoop on the parts you need to know about for packing in centrifugal pumps.
Base Ring (Stuffing Box Bushing)
When packing a pump, the base ring or stuffing box bushing is the first piece installed in the bottom of the stuffing box. The purpose of this bushing is to prevent packing from extruding through the bottom of the stuffing box.
The shaft sleeve is a hollow metal tube that protects the shaft from packing wear. In packing applications, it is typically hard metal coated for longer life.
Packing comes in many different sizes and types. Packing selection is determined by the application. Different packing exists for abrasive, high temperature, sanitary, and corrosive applications. Packing generally has a low upfront cost, but can become more expensive over time as it requires more maintenance and allows for more product loss than mechanical seals. We have another blog post that explains the basic differences between packing and mechanical seals as well. Either way, multiple rings of packing are installed in the stuffing box with a lantern ring oriented in different locations. Consult the O&M manual for proper orientation.
Also reffered to as “seal cage” or “water seal rings”, lantern rings are used when outside lubrication is necessary. They are typically made of PTFE or bronze material, and are usually split. The lantern ring has multiple holes around the sides to aid in lubrication. Packing requires lubrication to keep it cool and to flush corrosive chemicals and abrasive particles. It’s often necessary to flush the lantern ring from an external source, especially if the pumped product is contaminated or very abrasive.
This piece is installed last, after the packing has alraedy been installed in the stuffing box. The packing gland helps to hold the packing inside the stuffing box. It's very important to NOT overtighten this piece! Oftentimes, operators overtighten the packing gland in attempt to keep the packing from leaking. However, packing is designed to allow some leakage to keep the seal area properly lubricated. Read more about this in our blog post that explains why your pump might be drawing too much power.
A packing gland that is too tight can also cause the pump to draw more power. When packing is compressed, it squeezes tightly around the shaft sleeve causing additional drag on the shaft.
Knowing the names of different centrifugal pump parts, and their functions, is critical to proper pump maintenance and operation. Take the time to educate yourself and your team on all components to lessen maintenance downtime and keep pumps running efficiently.
Trouble with pump packing? Ask us about it! We gladly provide technical assistance to businesses and municipalities in Wisconsin and upper Michigan.