APPLIED SEALS DESIGN CENTER

LAB OVEN

Conformance to specification is vital to seal performance. ASNA implements its Lab Oven tests to provide a controlled environment in which to ensure that each product meets critical tolerances, including ASTM D395.

For example, as part of a typical ASTM D395 test, seals are compressed to 75% of their original height and baked at 200C for 72 hours. The seal is then removed from the oven and its height is measured again to calculate its compression set. The results provide a definitive indication of how each seal will perform at specific temperatures and compression.

Many seals are designed for compression sets of 5% to 30%. Seals with high compression set values will suffer permanent deformation under load and result in seal failure. Lab Oven testing delivers empirical data that guides the proper selection of seals based on real world applications.

HEIGHT GAUGE

Seals that exhibit a strict adherence to dimensional tolerance limits are essential to sealing integrity. When a seal is fabricated above its tolerance limit, overfilling within the gland may cause seal extrusion once installed and premature failure as a result. When a seal is fabricated below its tolerance limit, the sealing process may be compromised and leakage results. In either case, verification of tolerance limits assures sealing integrity.

OPTICAL COMPARITOR

The dimensional precision of a seal's cross-section to its corresponding gland's cross-section is vital to optimal sealing performance. The Optical Comparator provides up to 40x magnification of seal and gland profiles through the use of a measuring compound that is injected into the gland. The measuring compound hardens, is removed from the gland, and its molded impression is observed and accurately measured using the Comparator.

Understanding gland shapes and dimensions is particularly important when developing a custom seal. Correctly determining gland characteristics including squeeze and gland fill safeguard against seal movement once a seal is installed into the gland.

TEST DESCRIPTION AND DESIRED OUTCOME

Seal hardness characteristics dramatically affect sealing soundness. The hardness of a seal is dependent on filler types, base polymers and fabrication processes. Understanding which characteristics are best for a given application impact the efficacy of sealing for that application.

Harder seals are typical in dynamic applications, such as a body seal in a control valve, where minimal seal movement within the gland is essential. In applications where leakages such as permeation and blow by are less tolerable, softer seals are usually specified. Applied Seals products are controlled to within +5 and -5 Shore A hardness

OPTICAL MICROSCOPE

Sealing failures result from a variety of complications including twisting, discoloration, incorrect compression set and spiral failure, all of which can be observed and resolved. Determining the root cause of a failure is the first step in specifying the correct seal for an application.

The optical microscope is particularly useful in evaluating the premise of a sealing failure and for the specification of a better optimized sealing solution.

FEA

Seal optimization is the result of a balance between seal performance characteristics and seal life. Load simulation tests predict seal behavior under typical operating conditions and by providing data on maximum internal stresses as shown in the FEA. With this information on hand, designers can optimize seal designs for maximum and predictable sealing results.