Lantern Ring for Stuffing Box

Specialized in lantern rings with PTFE / Filled PTFE / PEEK / Stainless Steel & Bronze. Precision CNC machined for reliable sealing, flushing and cooling.

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Lantern Ring Dimensions

Standard & custom sizes – Integrated ring, dual‑ring, or strip design (up to 48″/1200mm). PTFE, PEEK, metal lantern rings are machined precisely according to stuffing box specifications. Porous design ensures unobstructed liquid flow.

INCH (Cross Section x OD)
1/4″ x 5/16″	1/4″ x 3/8″	1/4″ x 1/2″
5/16″ x 7/16″	5/16″ x 5/8″
3/8″ x 1/2″	3/8″ x 3/4″
7/16″ x 9/16″	7/16″ x 7/8″	7/16″ x 5/8″
1/2″ x 5/8″	1/2″ x 1″	1/2″ x 11/16″
9/16″ x 11/16″	9/16″ x 1″
5/8″ x 3/4″	5/8″ x 1″
3/4″ x 7/8″	3/4″ x 1″
7/8″ x 1″
1″ x 1″

METRIC (mm x mm)
7,6 x 11,4	9,0 x 13,2	9,0 x 19
9,4 x 13,2	10,5 x 14,3	10,5 x 22
11,1 x 15,6	12,1 x 17	12,1 x 25,4
12,6 x 17	13,5 x 19,2	14,2 x 19,2
15,2 x 20,6	15,2 x 31	17 x 22,1
18,1 x 22,1	18,1 x 38	19 x 23,8
20,8 x 25,2	23,5 x 28,2

Custom dimensions upon request – strip length up to 1200mm (48″).

Lantern Ring Purposes & Position

A lantern ring (also known as seal cage) is placed between packing rings in centrifugal pump stuffing boxes. It serves three critical purposes: Flushing, Cooling and Lubrication. By injecting clean fluid into the stuffing box, it protects packing from abrasive media, dissipates heat, and reduces friction on shaft sleeves.

Protection: Prevents solids from damaging packing and shaft.
Cooling: Removes heat generated by compression packing.
Lubrication: Reduces wear and extends pump life.

Stuffing Box Arrangement

Stuffing Box Lantern Ring position diagram

Fig: Typical stuffing box layout with lantern ring (D) centered between packing rings.

Lantern Ring Materials

PTFE, Filled PTFE, PEEK, Stainless Steel, Carbon Steel, Bronze – each material offers unique benefits for different media and temperatures.

PEEK Strengths	PEEK Weaknesses
High tensile strength & wear resistance	Not for nitric/sulfuric acid
Chemical & hydrolysis resistance	Higher cost vs PTFE
Continuous use up to 260°C (500°F)	Difficult processing
Low flammability & radiation resistant	——

PTFE Strengths	PTFE Weaknesses
Outstanding chemical resistance	Creep & cold flow tendency
Low coefficient of friction	Low thermal conductivity
High temp stability (-200°C to +260°C)	Poor dimensional stability
Easy to machine & nonflammable	Low rigidity / soft material

Metal Lantern Rings

Stainless Steel (304/316), Carbon Steel, Bronze – suitable for high-pressure or high-temperature services, slurry applications, and where extra rigidity is required.

Lantern Ring Installation Guide

Typically inserted after the 2nd or 3rd packing ring depending on flush port location. Use a small probe through flush port to confirm correct alignment. Proper flush water flow must be established before pump operation to prevent overheating.

Fit clearances: Lantern ring ID should allow free shaft movement; OD provides tighter seal against box bore. Porous strip design simplifies installation for large diameters.

Example A: Slurry/river water – spacer ring at bottom + lantern ring for barrier flush.
Example B: Crystallizing media – outer packing seal against flush medium.
Example C: Toxic/explosive media – inert gas flush via bottom lantern ring.
Example D: Expensive media – leakage extraction for reclamation.