Non-Contact Gap Seal Introduction
1. Material Characteristics
(1) Temperature Range
Applicable temperature range: -40°C to 60°C (-40°F to 140°F).
(2) Rate Limit
Well rate is limited to 80 m/sec.
(3) Chemical Resistance
It is resistant to a variety of chemicals, including common organic solvents, alcohols, esters, ketones, aliphatic and aromatic hydrocarbons, greases, and oils. Alkaline solutions will not damage the material even at high temperatures. Furthermore, this material has extremely low water absorption, with a maximum of only 0.8%. However, gap seals made of polyoxymethylene resin cannot be used to seal oxidants, organic or inorganic acids (pH < 4).
2. Working Principle
(1) Structural Composition
The GMN gap seal consists of two plastic components mounted on a conical housing, forming a serrated gap. During installation, the crests and troughs of the inner and outer ring profiles (machined by the same tool) merge upon engagement. The seal is delivered as an indivisible unit.
(2) Labyrinth Seal Principle
The labyrinth seal is designed based on an internal labyrinth geometry. This labyrinth structure causes contaminants to change direction before entering the bearing. The conical enveloping labyrinth design uses centrifugal force to accelerate the radial movement of contaminants, causing them to be ejected from the seal gap. For contaminants to penetrate the seal, they must creep from the larger labyrinth diameter facing the contaminant to the smaller diameter on the "dry" side of the seal to overcome centrifugal force. Particles that penetrate the conical labyrinth in the first step are expelled under centrifugal force and guided back to the side of the seal facing the contaminant. (3) Limitations Gap seals cannot handle high liquid levels, nor can they completely balance the pressure gradient between the inside and outside of the seal. They can only reduce or throttle pressure, not achieve a true seal.
3. Application Advantages and Precautions
(1) Dustproof Applications For dustproof applications, grease can be added to the gap seal before installation to improve sealing efficiency in dusty environments. During rotation, a certain amount of grease will be removed from the seal.
(2) Installation Points When installing the gap seal, pay attention to the orientation; the larger labyrinth diameter should face the contaminant.
(3) Clearance Parameters The axial and radial clearances of the seal are approximately the same, both around 0.5 mm, and they influence each other.
(4) Speed Limitations GMN gap seals are press-fitted onto the shaft. Under centrifugal force, the inner ring may lift off the shaft. Speed limits vary depending on size.
4. Methods to Improve Sealing Efficiency
(1) Preventing Direct Splashing of Contaminants
If contaminants may splash directly into the sealing gap, a disc can be installed in front of the seal, ensuring sufficient space between the seal and the disc to prevent liquid backflow into the sealing gap.
(2) Handling Large Amounts of Splashing Liquid
When large amounts of splashing liquid are present, sufficient free space should be provided in front of the seal to allow the splashing liquid to drip or flow freely. Additionally, a "Sa" type rotating shaft and a "Si" type rotating housing can be used.
(3) Achieving Dual Sealing Function
To simultaneously prevent contaminants and lubricants from entering the equipment, two seals can be used back-to-back (i.e., the smaller labyrinth diameters of the two seals are opposite each other).
Post time: May-15-2026
