Parker Gask-O-Seals®

• Parker Gask-O-Seal® Catalog

Gask-O-Seals® are metal, plastic, or composite retainers with a machined groove in the retainer plate into which a custom engineered rubber element is molded. The elastomer seal may be mechanically and/or chemically bonded to create a dependable, responsive seal for flat or curved surfaces. Gask-O-Seals are typically used in applications requiring extreme reliability, longevity, and durability.

• Sealing element molded precisely in place with controlled void-volume ratio and squeeze for optimum sealing
• Limited area of seal exposed to fluid/ chemical attack
• Multiple-port and complex shapes sealing capability
• Reduced number of sealing parts and installation time
• Visually detectable after assembly, eliminating the possibility of errors and omissions
• No retorquing required, metal-to-metal contact ensures positive closure and optimum bolt loading
• Segmented seal designs available for extremely large sizes and simplified packaging and shipping
• Reusability is possible, consistent with the overall condition of the seal after service
• Eliminates the need for machined grooves

The Parker Gask-O-Seal®, now more than 55 years old, enjoys a leading role as a world-class sealing concept. Profoundly simple, yet enviably reliable, a uniquely designed elastomeric element is molded directly into groove(s) to produce an integrated sealing solution for a virtually endless array of challenging static face type applications. Under pressure of assembly, the rubber compound is deformed from a round configuration to a square or oblong shape as shown in the figure. By predetermining and manufacturing the proper ratio between the volume of the molded-in voids and the volume of the crown, controlled confinement is obtained. The Gask-O-Seal is designed so that the elastomer is deformed against the faying surfaces, affecting the seal by the inherent “memory” or resiliency of the elastomer as it tries to return to its original molded shape. There are many features and benefits that come with Gask-O-Seal design in static face seal applications.

Gask-O-Seal® Fequently Asked Questions

Do the seal beads have to be in alignment from side-to-side, OR can they be offset?
They can be offset and the seal grooves do not need to match top and bottom sides.

What compounds are you able to bond and mold in a Gask-O-Seal® (GOS) or Integral Seal™ configuration?
Just about all elastomers provided by Parker’s O-ring and Engineered Seal (OES) Division can be bonded and molded.

What is the minimum land area required for a GOS?
The .250 includes .125 groove and .0625 shutoff area on either side of the groove.

How many styles of GOS are there and their purposes?
Mark I: bi-directional sealing, Mark II: double-seal bead for higher pressure sealing in both direction, Mark VII: unidirectional sealing for high pressure applications.

What material behavior model / models do you recommend for FEA simulation of gasket compression?
There are many options, but Parker primarily uses hyperelastic models.

What is the functionality of the cushion in a Mark I GOS?
The cushion serves no sealing purpose; however when compressed against the mating surface, the cushion limits the area of sealing surface area which is exposed to fluid attack. The cushion is also a necessity for the rubber molding process. It is very difficult to shut the mold off at the bottom of the void, so the existence of a cushion next to the void allows for the mold shut-off at the top of the groove.

How tall should the GOS bead be?
The seal bead height is a function of the assembly’s total flatness and the contact sealing pressure required for the applicationdepends on the specific material).

Gask-O-Seal Design Considerations

Once the operating parameters and leak rate criteria have been established and the appropriate sealing materials selected, the actual design for the GaskO-Seal can be started. This section provides basic guidelines for designing the seal.

1. Edge Distance - Using standard metals and manufacturing techniques, the desired seal groove to edge distance is .060" minimum. The seal groove to hole distance can be as small as .050" minimum, providing the parts are not blanked. Blanked parts in low carbon steel require an edge distance at least as great as the thickness of the part. This is necessary because of the “roll” that occurs on the edges of blanked parts in this material.
2. Groove Design - It is good practice to use larger groove widths and higher crown heights for larger parts and higher pressures. It is recommended that customer’s contact the Composite Sealing Systems Division’s engineering department if the available land area is minimal. If adequate land area is available, .100" width is recommended.
3. Metal Thickness - Whenever possible, the metal thickness should be specified as a standard gauge callout with an accompanying standard stock thickness; i.e., Steel 11 gauge (.120" stock). This allows Parker to use materials that are readily available from suppliers and are most economical in producing the finished Gask-O-Seal. Metals with a thickness of less than .090" should be discussed with the Composite Sealing Systems Division’s engineering department.
4. Dimensional Tolerances - In developing the overall design and establishing tolerances, the noncritical features, such as outline or outside dimensions, should have wide tolerances to reduce manufacturing costs. Bolt holes should have sufficient clearance around the bolts to permit reasonable locating tolerances. However, when the seal groove is located in relation to the bolt holes, the holes should be located within O.014 on small parts (<10 inches). Broader location tolerances can be used if the groove width can be increased to allow for the resulting misalignment.
5. Bolting - In order to achieve optimum sealing, it is essential to provide sufficient flange preload and proper bolt size and spacing to create a metal to metal contact between the Gask-O-Seal retainer and the mating parts. Under all service conditions, such as out-of-flat, system pressure, and rubber strength, the separation between flanges should not exceed .003" in order to prevent extrusion and damage to the elastomer. The force required to compress the seal is generally between 30 and 150 pounds per linear inch of seal, depending on the rubber durometer, material, and the configuration used for larger gaps, contact the Composite Sealing Systems Division’s engineering department
6. Surface Roughness - Surface roughness of the Gask-O-Seal retainer itself is not critical to sealing. When a sheet metal retainer is used, the “as received” condition of the metal is satisfactory. On machined surfaces, Parker will maintain a roughness value of 125 micro-inch Ra or better. Callouts for finishes of the Gask-O-Seal retainer with roughness less than 125 Ra can add unnecessarily to the part cost. For mating surfaces that the Gask-O-Seal is to seal against, a 125 Ra or better will provide good sealing surfaces for almost all applications. The only noteable exceptions are seals for gaseous media where diffusion type leakage must be kept to a minimum. For these installations, the mating surface should have a finish of 32 Ra or better.
7. Flatness and Parallelism - In most cases, no particular attention needs to be given to flatness and parallelism requirements. Occasionally a Gask-O-Seal is used between two halves of a device that must be accurately aligned such as a gear box housing. For this, the mating surfaces must be parallel within close tolerances. If the Gask-O-Seal is molded directly into one of these rigid parts, which would often be a casting, a flatness requirement is generally acceptable.
8. Types of Bond - There are two types of bonding to retain sealing element in groove(s); mechanical and chemical.
   • Mechanical Bonding - In a double sided retainer with back-to-back grooves, it is convenient to provide cross holes in the web portion at planned intervals. During the molding process, the rubber compound flows through these holes, mechanically locking and holding the seal elements in place
   • Chemical Bonding - A chemical bonding agent is applied to the groove(s) prior to molding. During the molding process, the rubber compound interacts with this bonding agent, a process called co-vulcanization, to chemically bond the seal element in place
9. Finite Element Analysis (FEA) - The study of elastomer stress and its relationship to seal effectiveness has been dramatically enhanced with the advent of finite element analysis. FEA is a numerical modeling technique used to predict a deformation and stress concentration of a given seal cross section. Parameters such as cross section geometry and material property data are factored into the modeling equation to produce a stress concentration model of the seal. FEA is effective as a predictor of seal performance only when it is used in conjunction with historical seal and material data and specific performance testing. Please consult the division if FEA is being considered as a tool for seal design.
10. Assembly - The retainer permits extremely fast and sure installation. In fact, where volume dictates, the placement of the seal can be fully automated on a completely foolproof basis.
    • Bolt retention: The rubber can be molded on the bolt holes for positive pre-assembly gripping and transporting. Retainer fits conveniently over bolts to hold the seal in place during assembly
    • Fast assembly
    • Visually detectable after assembly

Gask-O-Seal Configurations

Gask-O-Seal Design	Configuration	Features
Single-Port or Multi-Port Seal		There is virtually no limit to the number of ports, compartments or chambers that can be sealed with a single plate-like package to facilitate simple and foolproof installation. This greatly reduces assembly time and missing seals. Prerequisites include sufficient flange hardware, strength and adequate bolting pattern and force to assure joint integrity during pressurization.
Tandem or Redundancy Seal		For “zero leakage” applications, a secondary companion groove and seal element parallel to the primary seal can be added. Note the leak-rate monitoring groove that can be provided between the two seals. The land width must be widened to accommodate dual seals.
Contoured or Non-Planar Surface Seal		The Gask-O-Seal can be molded into contoured, curved, non planar surfaces, even sharply bent corners, in some cases. This makes them ideal for sealing such applications as aircraft and missile nose cones, access doors, nacelles, industrial tanks, and similar curved structures. Curved Gask-O-Seals can be molded directly into structural components.
Branched Seal		Allows many barriers in one unit, saves space and weight, and accomplishes a variety of sealing missions with a manifold plate where it can handle differential pressures and different fluids for isolated ports and communication holes in either direction. This seal also greatly reduces assembly time.
Segmented Seals		Used for applications requiring very large Gask-O-Seals (>60 inches in major dimension). This configuration helps reduce manufacturing and assembly costs. It has been used in critical aerospace applications where the sizes of seals can become extreme. It simplifies handling, packaging, and shipping. Segmented seals can also be designed with a redundant seal for more security
Multiple Materials		Some applications require multiple materials for proper sealing. This may be due to chemical compatibility, permeation, or multiple ports with different fluids. Being able to incorporate different seal materials into the same retainer allows for optimization of the seal design vs. compromising with a single material selection. This feature should be discussed in detail with Composite Sealing Systems Division’s engineering department.

About Integral Seal

The Integral Seal is so named because it effectively integrates a stamped or machined metal or molded plastic retainer with a moldedin-place rubber sealing element to create an extremely versatile sealing device.

The Integral Seal is custom designed, versatile and provides similar performance benefits seen with Parker’s Gask-O-Seal. The Integral Seal lends itself to space constrained applications where overall seal thickness may be of primary concern. Integral Seals can be manufactured in thickness as low as 0.012". The Integral Seals design also lends itself to high volume manufacturing methods making it a cost competitive option for high volume sealing applications. As shown below, the rubber sealing element is molded, and mechanically and/or chemically, bonded in place to the edge of the retainer.

Integral Seal Design Considerations

Once the seal type is determined the actual design for the Integral Seal can be started. There is a simple step by step method for designing an integral seal for your application. Here are the key points to consider:

1. Metal Thickness - Whenever possible, the metal thickness should be specified as a standard gauge callout with an accompanying standard stock thickness; i.e., Steel 11 gauge (.120" stock). This allows Parker to use materials that are readily available from suppliers and are most economical in producing the finished Integral Seal. Capabilities exist to go down to .012", however, metals with a thickness of less than .090" should be discussed with the Composite Sealing Systems Division’s engineering department.
2. Dimensional Tolerances - In developing the overall design and establishing tolerances, the noncritical features, such as outline or outside dimensions, should have wide tolerances to reduce manufacturing costs. Bolt holes should have sufficient clearance around the bolts to permit reasonable locating tolerances. However, when the seal groove is located in relation to the bolt holes, the holes should be located within O .014 on small parts (<10 inches).
3. Bolting - In order to achieve optimum sealing, it is essential to provide sufficient flange preload and proper bolt size and spacing to create a metal to metal contact between the Integral Seal retainer and the mating parts. Under all service conditions, such as out-of-flat, system pressure, and rubber strength, the separation between flanges should not exceed .003" in order to prevent extrusion and damage to the elastomer. The force required to compress the seal is generally between 30 and 150 pounds per linear inch of seal, depending on the rubber durometer, material, and the configuration used. For larger gaps contact the Composite Sealing Systems Division’s engineering department.
4. Surface Roughness - Surface roughness of the Integral Seal retainer itself is not critical to sealing. When a sheet metal retainer is used, the “as received” condition of the metal is satisfactory. On machined surfaces, Parker will maintain a roughness value of 125 micro-inch Ra or better. Callouts for finishes of the Integral Seal retainer with roughness less than 125 Ra can unnecessarily add to the part cost. For mating surfaces that the Integral Seal is to seal against, a 125 Ra or better will provide good sealing surfaces for almost all applications. The only noteable exceptions are seals for gaseous media where diffusion type leakage must be kept to a minimum. For these installations, the mating surface should have a finish of 32 Ra or better.
5. Flatness and Parallelism - In most cases, no particular attention needs to be given to flatness and parallelism requirements. Occasionally the Integral Seal is used between two halves of a device that must be accurately, aligned such as a gear box housing. For this, the mating surfaces must be parallel within close tolerances.
6. Flange Separation - When pressure is applied to a separable joint of any kind (e.g. flanges, lids, covers, etc.) there is a tendency for the mating surfaces to separate or “gap”. This gap can result in extrusion, wear and failure of the seal element. Ascertain whether the existing flanges or covers separate, gap, or bulge during pressurization and/or cycling. This will determine seal cross-section, crown height, style, and re-enforcement required once you know the magnitude.
7. Type of Bond - During the molding-in-place process, the carefully designed seal element is either chemically bonded to and/or mechanically interlocked with the edge of the metal (or plastic) retainer.
   • Chemical Bonding - For the sizes equal to or larger than 1" inside diameter, a chemically bonded retention of the rubber seal element is provided. This bonding takes place during the actual molding-in-place of the rubber via a process called co-vulcanization. This assures excellent adhesion of the seal element.
   • Mechanical Interlocking - A unique mechanical type retention of the molded-in-place rubber to the metal retainer is available. During the stamping operation, the inside of the retainer/washer is splined and then coined to provide a series of interlocking openings for the securing of the rubber as it vulcanizes in place.
8. Retrofit with Parker's Integral Seal - Integral Seals can be adapted to retrofit existing flange designs that already have an O-ring groove or counterbore for complete interchangeability. The retainer thickness can be reduced to as low as .012" to facilitate retrofitting in previously grooved flanged surfaces.
9. Finite Element Analysis (FEA) - The study of elastomer stress and its relationship to seal effectiveness has been dramatically enhanced with the advent of finite element analysis. FEA is a numerical modeling technique used to predict a deformation and stress concentration of a given seal cross section. Parameters such as cross section geometry and material property data are factored into the modeling equation to produce a stress concentration model of the seal. FEA is effective as a predictor of seal performance only when it is used in conjunction with historical seal and material data and specific performance testing. Please consult the division if FEA is being considered as a tool for seal design.
10. Assembly

    The retainer permits extremely fast and sure installation. In fact, where volume dictates, the placement of the seal can be fully automated on a completely foolproof basis.

    • Bolt retention: The rubber can be molded on the bolt holes for positive pre-assembly gripping and transporting. Retainer fits conveniently over bolts to hold the seal in place during assembly the seal cannot fallout.
    • Fast assembly
    • No blow out
    • Visually detectable after assembly
    • Resists extrusion under high pressure and flange separation