This article describes a process-based approach to optimizing material selection. How will the OEM designer select the best material solutions for their next gasket application within a reasonable development time?
Here are suggested goals to pursue:
- Achieve the optimal balance between material performance and cost
- Ease of manufacturability
- Keep options open with dual material specifications for:
- Future flexibility in case of market price changes
- Adjust to supplier mergers and acquisitions
There are thousands of materials that each serve small fragments of the total gasket solution spectrum, and each unique gasket material has a proprietary composite formula. For business reasons, each material-producing company is biased towards its own material portfolio over promoting competitors’ products.
An effective gasket material selection process quickly reduces the wide field of material candidates to a manageable few, by eliminating large groups of irrelevant materials.
The elimination process considers material performance criteria, not material recipes. Efficient system thinking about performance includes the entire assembly of the gasket, such as the two mating flanges and the fasteners which generate the compression forces.
We begin modeling the assembly in operation, and use 4 main steps when selecting a gasketing material:
- Identify Compression Forces: A gasket stops leaks that occur when the two mating flange surfaces, alone, fail to perfectly meet and a leak path results. To seal, flange pressure exerted against the gasket surface compresses the material to conform to these flange surface imperfections. It’s critical to match the compression force to the gasket material in order to seal but not crush it. It’s about finding a matching gasket material whose compression deflection profile, or spring rate, fits the assembly.
- Understand the Operating Temperature Range: Gasket materials are frequently polymer based. They exhibit elastic properties over a limited temp range. Outside this
range, the gasket material will lose its spring-like performance and will either soften or become brittle.
- Assess the Gasket’s Chemical Compatibility with the Sealed Media: Harsh chemicals degrade gasket performance over time. Materials lose elasticity when attacked by sealed liquids and gases. Standard material formulas cover a significant range of applications and occasionally, custom material formulation is required.
- Select Material Thickness: Maximum gasket lifespan occurs when material thickness is minimized. First, calculate the total surface imperfections in the two mating flanges, such as roughness and flatness irregularities. These irregularities are the sources of leaks, because the flanges fail to meet. A rule of thumb is that minimum gasket thickness is established when the compression from tightening the fasteners to seal is approximately 1/3 of the material’s uncompressed or original thickness. If a material is compressed beyond 1/3, there is high risk of permanent crushing, or compression set. If needed, certain specialized materials and composites exhibit excellent compression set resistance at greater compressions.
To add to this, additional considerations can help to eliminate irrelevant materials, which include:
Material Compliance to Standards
Minimum order quantity
Field support available
Tests used to validate system
R&D Initiatives of supplier
Functionality as a vibration damper, thermal or electrical conductor/EMI shield or thermal barrier
Supply chain stability
These engineering concepts, applied to your gasket development project, are used to reduce development costs of gasket systems below traditional iterative trial and error cycles. PGC supports rapid solution development using time-efficient modeling procedures, including:
- Flange Model Analysis (FMA)
- Solid Modeling/Finite Element Analysis (FEA).
PGC is known as a development partner to support your design projects, because we help analyze opportunities for optimal material selection and modeling high-performance gasket systems. For additional questions about current and future applications, visit our website at pgcsolutions.com
About PGC: PGC works with brand leading, global OEMs and design engineers looking for innovative solutions for complex applications. Unlike transactional parts suppliers, PGC enjoys preferred partner status with customers who look to us to help them differentiate their products using our proven 4D business process
(Discover, Diagnose, Develop, Deliver).
Written By: Steve Hanson, Co-CEO