Overview of the V-Ring / V Seal
The V Seal (also known as a V Ring) finds extensive applications in diverse settings, primarily serving rotating shafts. Operating independently, they effectively shield various bearing types from contaminants, ensuring reliable retention of lubricants. Additionally, they frequently function as secondary seals, providing extra protection to primary seals in environments with high levels of contamination.
Installed on shafts, V-rings feature a thin, tapered lip that seals against a counterface perpendicular to the shaft. With an interference fit on the shaft, they rotate with it, serving as effective flingers. V-rings exhibit a remarkable ability to tolerate angular misalignment between the shaft and counterface. Even in scenarios where the shaft is out-of-round or rotates eccentrically, V-rings deliver dependable sealing. The allowable displacement of the V-ring relative to its counterface determines the permissible axial displacement of the shaft.
Constructed entirely from elastomers without fabric or metal reinforcement, V-rings are user-friendly and easy to install. Their flexibility allows for stretching and, depending on size, effortless placement over components such as flanges, pulleys, or even housings. This feature proves invaluable, particularly when replacing a seal.
In simple terms, a V-Ring is a durable rubber seal designed for shafts, serving to prevent the intrusion of dirt, moisture, and undesired elements into oil seals, housing, or specified areas. Simultaneously, it retains lubricants by stretching tightly over the shaft, with its flexible lip lightly sealing against the counterface at a right angle to the shaft.
Operating effectively independently, the V-Ring showcases optimal performance when used in conjunction with rotary shaft seals, contributing to the prolonged lifespan of bearings, oil seals, and shafts. Gamma Seals offer similar functionality to V-Rings but come with the added safeguard of a protective metal case.
Features of the V Seal
A V-ring comprises a seal body, a flexible conical-shaped sealing lip, and an integral, resilient “hinge”. Once stretched, it is directly installed on the shaft, where the inherent tension of the seal body holds it in place. This allows it to rotate with the shaft, creating an axial seal against a stationary counterface.
The counterface may take various forms, including the end face of a bearing, a washer, stamping, bearing housing, or even the metal case of a radial shaft seal.
The flexible sealing lip applies a contact pressure against the counterface, which is relatively low but sufficient for maintaining the sealing function. In low-speed applications, the light contact pressure even permits the seal to run dry, resulting in minimal torque drag or heat build-up. The contact pressure varies based on the fitted width.
The flexibility of the lip and hinge ensures effective sealing, even in applications with significant end play and shaft misalignment.
Due to centrifugal force, the contact pressure of the lip decreases as speed increases. This minimises friction losses and heat, enhancing wear resistance and extending the service life. Power loss peaks at a shaft speed of approximately 12 m/s (2,360 ft/min) and gradually reduces up to 20 m/s (3,900 ft/min), where it eventually decreases to zero. At this point, the V-ring transforms into a gap-type seal and deflector.
V-rings are typically crafted from nitrile rubber, known for its commendable chemical resistance, wear resistance, and suitability for applications with normal operating temperatures. For environments with elevated temperatures or exposure to aggressive media, V-rings made of fluoro rubber are available.
At temperatures exceeding 300 °C (570 °F), all fluoro elastomers and PTFE compounds emit hazardous fumes. This may occur, for instance, during the use of a welding torch to remove a bearing. While fumes are only generated at such high temperatures, seals become unsafe to handle even after cooling down. When handling PTFE or fluoro elastomer seals subjected to these high temperatures, observe the following safety precautions:
- Always wear protective goggles and gloves.
- Dispose of seal remnants in an airtight plastic container labeled “Material will etch.”
- Adhere to safety precautions outlined in the material safety data available upon request.
- In case of skin contact, wash with soap and ample water. Rinse eyes thoroughly with water if these materials come into contact. Consult a doctor promptly, even if fumes have been inhaled.
M Barnwell Services presents five standard V-ring designs:
– Common V-ring type with a standard cross-section and straight back sideface.
– Typically employed to safeguard bearing arrangements in gearboxes, electric motors, and drives.
– Features a standard low cross-section, tapered back face, and wide body for a secure hold on the shaft.
– Commonly used in agricultural and automotive applications.
– Compact axial cross-section design.
– Applied in confined spaces as a replacement for labyrinth seals.
– Secondary seals for heavy-duty applications, protecting the primary seal from water and solid contaminants.
– Boasts the largest cross-section among V-ring designs, allowing substantial axial displacements.
– Available in the diameter range of 300 to 2,010 mm (11.811 to 79.134 in.).
– Heavy-duty, large-diameter V-ring suitable for applications with significant axial displacements.
– Can be axially and radially located on the shaft using a standard band clamp.
– Primarily designed to safeguard high-speed bearing arrangements in rolling mills, paper-making, and large machine applications.
– Similar to VR5/VRM but lacks the extension to the rear of the body section.
– Retains the saddle feature for axial and radial location on the shaft with a band clamp.
– Available on a made-to-order basis.
Special sizes, including split versions, can be customised upon request. Contact a member of our team for sizes outside the standard range.
Functions of the V Seal
V-rings are well-suited for both grease and oil-lubricated applications. When sealing grease-lubricated bearing arrangements and safeguarding against contaminants, it is recommended to position the V-ring outside the housing cover or housing wall. This configuration effectively excludes dust, water spray, and other contaminants. The V-ring can also serve as a grease valve, allowing used grease or excess new grease to escape between the counterface and the sealing lip. Use two opposing V-rings for installation in scenarios where both lubricant retention and contaminant exclusion are equally crucial.
For applications involving oil retention, V-rings should be axially located on the shaft on the lubricant side.
It is important to note that V-rings should not be submerged in the application medium.
Additionally, V-rings can serve as secondary seals, particularly in situations where protecting the sealing lip and counterface of the primary seal against contaminants or corrosion is necessary. They can also enhance the efficiency of labyrinth seals.
V-rings can accommodate misalignment between the shaft and housing, referring to deviations from perpendicularity between the shaft and the counterface of the housing.
For the very compact VR3/VL design, the permissible misalignment values are notably lower compared to the VR1/VA and VR2/VS designs.
V-rings in the VR4 design feature a large seal cross-section, allowing for more substantial misalignments.
Reduce the maximum value indicated in the diagram in applications where V-rings lack axial support on the shaft.
An accurately turned counterface is suitable for V-rings, with the appropriate surface roughness values varying based on the circumferential speed. M Barnwell Services recommends polishing all turned surfaces with an emery cloth to eliminate any sharp peaks resulting from the turning operation. To obtain an accurate reading of the surface, the surface finish should be measured at approximately 90 degrees to the path of the groove.
- No special treatment is necessary in the presence of grease, oil, or dry lubricants.
- Zinc-plate or passivate mild steel counterfaces exposed to water or corrosives.
- Chromium- or cadmium-plated shafts should undergo painting or treatment with an anti-corrosive spray.
Additional Counterface Information:
- Aluminum surfaces should be free of scratch marks, and surface hardness should exceed 100 HB in abrasive applications. Die-cast aluminum can be utilised in the as-cast condition.
- Steel and cast iron surfaces should be devoid of lead and sharp tool marks. Cold roll steel stampings can be used without machining.
- Plastic counterface materials are generally not acceptable due to poor heat dissipation.
- Avoid using stainless steel in dry-running applications unless the speed is below 1 m/s (200 ft/min).
To prevent damage to the V-ring during installation, it is essential to avoid sharp edges, nicks, and burrs on the shaft.
V-rings rotate along with the shaft and necessitate only a moderate surface roughness value. As a rule of thumb, this value should not exceed Ra 6.3 µm (252 µin.). In scenarios where the V-ring is exposed to fluids or fine, solid contaminants, a surface roughness value of maximum Ra 3.2 µm (128 µin.) is recommended.
During installation, a V-ring undergoes stretching and accommodates all shaft diameters within the specified ranges in the product tables.
V-rings can stretch and conveniently fit over other components, streamlining the installation process. When working with multiple V-rings, use a simple tool to push the seals to their intended position at a predetermined distance from the counterface. Moreover, V-rings can be cut and reconnected in the field.
The general guidelines for installation include:
- Clean the V-ring, counterface, and shaft thoroughly.
- Ensure the shaft is dry and devoid of grease or oil, especially when installing a V-ring without axial support.
- Apply a thin film of grease or silicone oil to lubricate the V-ring’s lip.
- In applications where minimising friction is crucial, coat the counterface with a low-friction agent. Avoid applying grease to the lip.
- Ensure the V-ring is uniformly stretched around the shaft during installation.