8 Gasket Myths – Debunked

March 13, 2018

Clearing Common Gasket Misconceptions: A Technical Guide


Gasket performance, material selection, installation procedures, and troubleshooting are common topics of discussion across various industries. However, persistent misconceptions continue to influence how gaskets are chosen and installed. This article addresses these myths and offers clarity on key factors to ensure optimal gasket performance.

1. Thicker Gasket Material is Better

A frequent assumption is that thicker gaskets are superior, particularly when compensating for flange misalignments or gaps. However, thicker gaskets are more prone to creep and relaxation, which can reduce sealing efficiency over time. Gasket creep increases proportionally with material thickness, often leading to higher leakage rates and compromised torque retention. Thinner gaskets, in contrast, exhibit better torque retention, higher blow-out resistance, and reduced leakage. When facing misaligned flanges, it’s advisable to correct the alignment rather than defaulting to thicker gasket material.

2. Gasket Colors Indicate Identical Materials

A common misconception is that the color of a gasket signifies its material properties. For instance, individuals might say, “I’ve always used a blue gasket, so I need a blue gasket.” However, color alone is not a reliable indicator of a gasket’s material or performance characteristics. Different manufacturers may color their entire product line uniformly, leading to confusion. To ensure the right gasket selection, focus on key application factors such as pressure, temperature, and media rather than relying on color.

3. All Gasket Materials Share the Same Torque Values

Contrary to popular belief, torque values are not universal across all gasket materials. Torque specifications vary depending on factors like bolt material, percent of bolt yield, K-Factor, and the maximum compression a material can endure. For most soft gaskets, the maximum compression is typically around 15,000 psi. For semi-metallic gaskets, such as spiral wound gaskets (SWGs) and kammprofiles, maximum compression can reach between 20,000 and 30,000 psi. Using incorrect torque values can lead to crushing or damaging the gasket, potentially causing failure.

4. Retightening Leaking Gaskets is a Quick Fix

Retightening a leaking gasket, especially in high-temperature applications, is not recommended. For soft gasket materials, applying additional torque after the gasket has been subjected to heat can cause cracking or complete failure. Over-tightening can exacerbate leaks or even lead to blow-outs. When a gasket begins to leak, the best course of action is to replace it rather than attempting to retighten it.

5. All Gaskets are Manufactured and Perform the Same

Not all gaskets are created equal. Manufacturing methods such as calendaring, skiving, and beater addition impart unique properties to gasket materials, affecting their performance. While gasket technical data sheets provide baseline characteristics for comparison, they do not reflect real-world performance. Standards such as ASTM F104 offer a more reliable basis for comparing materials, but specialized tests, like the Fluid Sealing Association (FSA) steam test, provide more accurate performance data for specific applications. Understanding these nuances is key to selecting the right gasket material for your application.

6. Using Grease or Lubricant Helps Gasket Installation

Although it may seem practical to use grease or lubricant to hold a gasket in place during installation, doing so can lead to detrimental outcomes. Lubricants can chemically degrade the gasket material and reduce friction on the sealing surface, increasing the risk of the gasket being pushed out by system pressure. The goal during installation is to achieve sufficient compression so that the flange serrations “bite” into the gasket, enhancing resistance to system pressure. Grease undermines this goal and should be avoided.

7. Softer Materials Seal Better

While softer gasket materials can conform to uneven or worn flanges, this does not necessarily make them better for all applications. Softer materials are more prone to creep, which can compromise long-term sealing performance. For high-temperature and high-pressure applications, harder materials and attention to surface finish are critical to achieving a reliable seal. Always evaluate material firmness relative to the application’s operating conditions.

8. Gasket Installation Procedures Do Not Affect Sealing Performance

Proper installation is the single most important factor affecting gasket performance. Following an approved installation method, such as the Legacy Method or those outlined in ASME PCC-1, Appendix F, ensures that flange surfaces are aligned and evenly loaded. This reduces the risk of crushing or unevenly loading the gasket, which can lead to leaks or gasket failure. Consistent and correct torque application during installation is essential for optimizing gasket performance and ensuring long-term sealing reliability.


 
Figure 1. Legacy Method Bolt Tightening Pattern

By addressing these misconceptions, we hope to provide clarity and improve both gasket selection and installation practices. Understanding the factors that influence gasket performance will help you achieve better results and avoid common pitfalls.