PTFE Lantern Ring

Lantern Ring

Standard PTFE Lantern Ring / Universal Seal Cage

PTFE Lantern rings， also well know by Universal Seal Cage are usually in the center of every compression packing set in a centrifugal pump. They are simple components, but get something wrong when selecting, installing or operating them, and big problems may occur in the stuffing box. A lantern ring is placed between packing rings in each packing set and extends the life of the packing, stuffing box and shaft. Ultimately, lantern rings increase the life span of the pump system.

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About Lantern Ring

Ensuring stuffing box reliability and controlling the environment mitigate many issues in the ‘space’ where it happens.

PTFE Lantern rings serve three purposes: protection, cooling and lubrication. They
protect the stuffing box and the installed packing by providing an access point
for flush water. If process fluids or other contaminants enter the stuffing box and are not removed by flush water, several problems occur, including:
• damaged or destroyed packing
• shaft or sleeve damage
• stuffing box wear

A lantern ring also gives the stuffing box an outlet to assist with cooling. It allows the system to avoid being completely closed off and assists in mitigating overheating. The final lantern ring purpose is lubrication. Compression packing causes friction along the shaft and stuffing box walls or casing.
Fluid entering through the lantern ring lubricates the packing. The liquid reduces friction, limits the wear of the machine’s parts and decreases heat within the system.

Size of Lantern Ring / H * W (mm)

LENGTH 1200MM

7,6x11,4	9,0x 13,2	9,0x19	9,4x13,2	10,5x 14,3
10,5x22	11,1x15,6	12,1x17	12,1x25,4	12,6x17
13,5x19,2	14,2x19,2	15,2x20,6	15,2x31	17x22,1
18,1x22,1	18,1x38	19 x23,8	20,8x25,2	23,5x28,2

Remark: Considering the inch size, there may be some error between the actual delivery size and the data in this table, which will not affect installation and use.

Lantern Ring Structural Style

Materials for Lantern Rings

Selecting the correct material for the application is critical. Lantern ring selection should be given equal consideration because they are equally as important as packing. PTFE and PEEK, general material for Lantern Ring.

PTFE & PEEK Strengths & Weaknesses

PTFE Strengths	PTFE Weaknesses
Broad chemical resistance	Creep and cold flow
Nonflammable	Relatively soft
Low-temperature flexibility	Low thermal dissipation
Low coefficient of friction	Poor dimensional stability
High-temperature stability	High material shrinkage
Easy to process	Low rigidity
High-frequency resistance	Low electrical conductivity

PEEK Strengths	PEEK Weaknesses
Tensile strength, elongation and wear properties	Not suitable for applications involving nitric or sulfuric acid
Chemical resistance	More costly
Withstands long exposure to high pressure, water and steam	Difficult to process
Low flammability
Resistant to gamma radiation
Continuous use up to 500F

How Is a Lantern Ring Installed?

Most packing sets have five packing rings. The lantern ring can be inserted after the second or third packing ring is installed. This all depends on where the flush port of the stuffing box is located. To ensure that the lantern ring is installed correctly, insert a small object through the flush port and feel the lantern ring.

Once this is done and all the packing rings and packing follower are installed, end users should install the proper flush setup and start flushing the stuffing box. For many reasons, starting the flush before operating the pump is important. One reason is to ensure that flush water is moving through the lantern ring and into the stuffing box correctly.

Care must be taken to ensure the lantern ring’s fit around the shaft is correct. Most lantern rings have a larger fit on the inside diameter and a tighter fit on the outside diameter, so frictional heat is not an issue.

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