Hydraulic & Fluid Seals

Rod Seals

For linear and reciprocating dynamic sealing applications

Rod seals installation example
Example of rod seal installation
Rod seals example

The rod seal is designed to ensure that pressurized fluid does not leak out of the system as the rod cycles back and forth (dynamic pressure sealing). The rod seal is the most critical seal on any type of fluid power equipment. A leaking rod seal not only reduces equipment performance, but also causes environmental issues.

American High Performance Seals manufactures a comprehensive range of rod seal designs including lip seals, PTFE cap seals, compact squeeze seals and application–specific designed seals made from high-performance elastomers and engineering plastic materials to offer maximum durability and sealing performance.

Rod Seal Design Considerations:

• Pressure Rating…

• Pressure Rating

Pressure Rating

The maximum pressure rating of seals is greatly influenced by many factors:

– Extrusion gaps, clearances:
The extrusion gap is defined as the maximum radial clearance on one side between the seal housing opposite of pressure and the sealing surface. The extrusion gap is the most pressure-limiting factor to any seal. Larger extrusion gaps will always reduce a seal’s pressure capability.

– Wear rings:
The use of wear rings always leads to larger extrusion gaps compared to a close-tolerance sliding bearing design without wear rings. The above-metal exposed portion of the wear ring and tolerances are the dominating factors for the need for larger clearances between the two sealing surfaces.

– Seal material:
Typically, a harder seal material will increase the extrusion resistance and pressure rating of a seal compared to a softer seal material. The typical hardness range for dynamic elastomeric hydraulic seals is 85-95 Shore A (similar to car tires). AHPSeals offers a variety of high-performance sealing materials in different hardness to meet the most challenging high-pressure sealing applications.

– Back-up rings:
The proper design of a seal with a back-up ring will increase the pressure rating of a seal as long as the back-up ring is made of material with a higher modulus than the seal (typically noted as a harder material). AHPSeals offers specific rod and piston seals with integrated back-up rings to increase pressure capability.

– Temperature:
Higher operating temperatures will soften the seal and back-up ring material reducing its pressure capability. This affects most traditional seal materials when operating above 70% of their specified maximum operating temperature. Some of our high-performance sealing materials are designed to operate at 90% of their specified temperature without significant loss in hardness. Conversely, lower operating temperatures can increase the extrusion resistance of seal materials.


• Non-symmetrical Rod Seal Design…

• Non-symmetrical Rod Seal Design

Non-symmetrical Rod Seal Design- Features and Benefits

– Non-symmetrical Rod Seals are seals where the shape of the inside diameter lip differs from the outside diameter (see Fig. 1, inside lip shorter than outside lip).

– Non-symmetrical rod seals provided by AHPSeals are not centered in the gland groove (Fig. 2) and provide sealing contact with the gland across the entire surface of the static outside seal diameter (Fig. 2a) for improved static and low pressure sealing.

– Non-symmetrical rod seals are more stable and provide better sealing performance than symmetrical seals like U-cups or polypak type seals do.

Our rod seals are non-symmetrical lip or squeeze type rod seal designs in which the diameter of the seal is oversized (Fig.2), and are available for both uni-directional and bi-directional applications. This seal design creates a hoop pressure and ensures a high static sealing contact force over the entire surface of the outside diameter of the seal (Fig.2a), providing significantly higher stability of the seal during operating cycles and eliminating rocking and pumping effects, thereby improving sealing performance. Instability of a seal can create leakage and seal damage.

non-symmetrical-rod


• Lip vs. Squeeze Type Seals…

• Lip vs. Squeeze Type Seals

Lip vs. Squeeze Type Seals

The basic design of a rod seal significantly affects the overall function of the seal, especially at low pressures. One of the most challenging applications is linear dynamic sealing at low pressure while providing low breakaway and running friction. AHPSeals provides a series of low-friction rod seals for these challenging applications.

– Lip seals are without any energizing rubber elements. Therefore, they provide a more flexible dynamic seal lip and are generally characterized by lower friction on the unpressurized return stroke, resulting in reduced wear, longer seal life and moderate low-pressure sealing capabilities.

– Squeeze seals typically incorporate an energizing rubber element and are generally characterized by good low-pressure sealing, high friction, higher wear and therefore reduced seal life.

imps-4-single-acting-piston-seal-1


• Seal Lip Geometry…

• Seal Lip Geometry

Seal Lip Geometry

– Beveled seal lip or chamfered seal lip is the most aggressive seal lip design. Most of our rod seals feature this lip design as it provides the best fluid film breaking ability, which provides the best sealing performance. Sealing lips for all AHPSeals’ rod seals are precision machined for a sharp sealing edge that cannot be achieved by a net-molding process (Fig. 3).

– Knife-edge and straight seal lip designs offer good scraping properties but reduced sealing performance and are used for sealing applications with high fluid contamination (Fig. 4 and 5).

– Rounded seal lip is the least aggressive sealing lip and is typically used in pneumatic applications to maintain a microscopically thin oil or grease film on the bore to keep the piston wear ring and seal lubricated (Fig. 6).

lip_geometry_rod


• Single- or Double-acting Rod Seals…

• Single- or Double-acting Rod Seals

Single- or Double-acting Rod Seals

Single-acting or Uni-directional – capable of sealing dynamic pressure from one side. (most common)

imhr-3

Double-acting or Bi-directional – capable of sealing dynamic pressure from both sides

imhr-4

 


• High-Performance Rod Sealing Systems…

• High-Performance Rod Sealing Systems

High-Performance Rod Sealing Systems

Particular attention should be paid to selecting the best rod seal for your application. It is important to properly pair the rod seal and the wiper for the best sealing performance. If a less aggressive rod seal is paired with an aggressive wiper, the wiper can scrape off the microscopically thin film of oil that remains on the rod in microscopic surface imperfections during the return stroke, resulting in system leakage. The thickness of the oil film depends upon the surface finish, rod seal and surface speed of the rod. For more information go to High-Performance Sealing Systems for linear, dynamic sealing applications.



Application-specific and proprietary seal designs are available. Please contact engineering to get the best seal for your rod sealing applications.


High-Pressure Rod Seals up to 5,000psi (350bar)*

Typical Application

Linear, reciprocating dynamic sealing applications

Operating Range

Pressure:  up to 5,000psi (350bar)*. For pressure above 3,800psi (260bar), please contact engineering for clearances. Pressure ratings can be increased by reducing clearances.

Surface Speed: up to 13ft/s (4m/s)*

Temperature: -40°F to 400°F (-40°C to 210°C) depending on material

Materials: high-performance polyurethanes, NBR (Nitrile), FKM, Viton®, HNBR, EPDM, Silicone, low- and -high temperature materials, PTFE, Teflon®, FDA-compliant seal material grades and proprietary specialized Duralast™, Duraloy™, and Permachem™ compounds.

Availability: More Info…

Most standard or non-standard and application-specific designed piston seals, in inch or metric sizes, are available with a 2-4 day turnaround.

Single-acting or Uni-directional High-Pressure Rod Seals – capable of sealing pressure from one side

Double-acting or Bi-directional High-Pressure Rod Seals – capable of sealing pressure from both sides


Contact us to request more information or call 1-800-283-7140 for immediate answers to your question.


Ultra-High Pressure Rod Seals up to 10,000psi (700bar)*

Typical Application

Heavy duty, linear and reciprocating dynamic sealing applications. Capable of handling high pressure spikes, larger running clearances and extrusion gaps.

Operating Range

Pressure: up to 10,000psi (700bar)*, special designs up to 28,500psi (2,000bar)*. For pressures exceeding 5,000psi (350bar), please contact engineering for clearances. Pressure ratings can be increased by reducing clearances.

Surface Speed: up to 1.6ft/s (0.5m/s)*

Temperature: -40°F to 400°F (-40°C to 210°C) depending on material

Materials: high-performance polyurethanes, PTFE, Teflon®, engineered thermoplastics, NBR, Nitrile, FKM, Viton®, H-NBR, EPDM, FDA-compliant food grade, low- and high-temperature grades, including proprietary Duralast™, Duraloy™, and Permachem™ compounds.

Availability: More Info…

Most standard or non-standard and application-specific designed piston seals, in inch or metric sizes, are available with a 2-4 day turnaround.

Single-acting or Uni-directional Ultra-High Pressure Rod Seals – capable of sealing pressure from one side

Double-acting or Bi-directional Ultra High-Pressure Rod Seals – capable of sealing pressure from both sides


Contact us to request more information or call 1-800-283-7140 for immediate answers to your questions.


Long-Life High-Pressure Rod Seals up to 5,000psi (350bar)*

Typical Application

Linear, reciprocating dynamic sealing applications for extended seal life

Operating Range

Pressure: up to 5,000psi (350bar)*. For pressure above 3,800psi (260bar), please contact engineering for clearances. Pressure ratings can be increased by reducing clearances.

Surface Speed: up to 1.6ft/s (0.5m/s)*

Temperature: -40°F to 400°F (-40°C to 210°C) depending on material

Materials: high-performance polyurethanes, NBR (Nitrile), FKM, Viton®, HNBR, EPDM, Silicone, low- and high-temperature, FDA-compliant seal material grades and proprietary specialized Duralast™, Duraloy™,

Availability: More Info…

Most standard or non-standard and application-specific designed piston seals, in inch or metric sizes, are available with a 2-4 day turnaround.

Single-acting or Uni-directional Long-Life High-Pressure Rod Seals – capable of sealing pressure from one side


Contact us to request more information or call 1-800-283-7140 for immediate answers to your questions.


Long-Life Ultra-High Pressure Rod Seals up to 10,000psi (700bar)*

Typical Application

Linear, reciprocating dynamic sealing applications for extended seal life

Operating Range

Pressure: up to 5,000psi (350bar)*. For pressure above 3,800psi (260bar), please contact engineering for clearances. Pressure ratings can be increased by reducing clearances.

Surface Speed: up to 1.6ft/s (0.5m/s)*
Temperature: -40°F to 400°F (-40°C to 210°C) depending on material

Materials: high-performance polyurethanes, NBR (Nitrile), FKM, Viton®, HNBR, EPDM, Silicone, low- and high-temperature, FDA-compliant seal material grades and proprietary specialized Duralast™, Duraloy™, and Permachem™ materials.

Availability: More Info…

Most standard or non-standard and application-specific designed piston seals, in inch or metric sizes, are available with a 2-4 day turnaround.

Single-acting or Uni-directional Long-Life High-Pressure Rod Seals – capable of sealing pressure from one side


Contact us to request more information or call 1-800-283-7140 for immediate answers to your questions.


Low-Friction Rod Seals up to 5,000psi (350bar)*

Typical Application

Linear, reciprocating dynamic sealing applications for reduced friction

Operating Range

Pressure: up to 5,000psi (350bar)*. For pressure above 3,800psi (260bar), please contact engineering for clearances. Pressure ratings can be increased by reducing clearances.

Surface Speed: up to 6.5ft/s (2m/s)*
Temperature: -95°F to 400°F (-70°C to 210°C) depending on material

Materials: PTFE, Teflon®, high-performance polyurethanes, NBR (Nitrile), FKM, Viton®, HNBR, EPDM, Silicone, low- and high-temperature, FDA-compliant seal material grades and proprietary specialized Duralast™, Duraloy™, and Permachem™ materials.

Availability: More Info…

Most standard or non-standard and application-specific designed piston seals, in inch or metric sizes, are available with a 2-4 day turnaround.

Single-acting or Uni-directional Low-Friction Rod Seals capable of sealing pressure from one side

Double-acting or Bi-directional Low-Friction Rod Seals – capable of sealing pressure from both sides


Contact us to request more information or call 1-800-283-7140 for immediate answers to your questions.


Applications & Industries 

AHPSeals’ seals are currently in successful service in the following industries:

  • Abrasive Substance Pumps and Valves
  • Adhesives Dispensing Valves and Cylinders
  • Automotive Plants
  • Can and Package Filling Machines
  • Chemical Pumps
  • Chemical Pumps and Valves
  • Construction Equipment
  • Cryogenic Liquid Control Components
  • Domestic Goods Production
  • Drilling Equipment
  • Food Processing
  • Government, Military and Defense
  • Heavy Mobile Equipment
  • Hydraulics
  • Liquid Handling Swivel Joints
  • Marine
  • Mining
  • Oil-Field Exploration and Production
  • Paint and Solvent Manufacture and Application
  • Pharmaceutical Production
  • Pharmaceuticals
  • Presses
  • Rubber and Plastics
  • Space Exploration
  • Steel Works
  • Tire Production
  • Vacuum Service
  • Many other Applications

*Maximum values depend on seal material, seal configuration, media, temperatures, pressures, surface speed, dynamic running surface finish and working environment.  Data provided are guidelines for ideal operating conditions.  Seals cannot be operated at their upper pressure and speed ratings at the same time.  For maximum seal life expectancy, do not operate your seal beyond 75% of any of its operating limits. Please consult engineering or call 1-800-283-7140 for advice.


American High Performance Seals assumes no obligation or liability for any advice furnished, or results obtained with respect to these products. All such advice is given and accepted at the buyer’s risk.

This information, based on our experience, is offered as part of our service to customers. It is intended for use by persons having technical skill, at their own discretion and risk. We do not guarantee favorable results, and we assume no liability in connection with its use.


Any purchases resulting from information provided by American High Performance Seals, Inc., including proposals, recommendations and quotes, are subject to “AHPSEALS TERMS AND CONDITIONS OF SALE.