What Is Creep Relaxation, Why Do I Care?

This week, we’re going to talk about creep relaxation in gaskets and gasket material. This is something that will happen to some extent in most gasket materials. How much or how little of this you see depends on your gasket material selection and the application itself. It is important to have an understanding of creep relaxation and how it relates to a particular material.

Creep Relaxation

In basic terms, creep relaxation is the measurement of how much a particular gasket material spreads (thins) out when force is applied. As the gasket loses thickness, the bolts can relax, which leads to a loss of load. When the level of creep relaxation is too high for the application, that’s when you’re going to have problems maintaining the seal.

Thickness of your gasket material plays a big part in the amount of creep relaxation you see in the material. If you’ve read our previous blog post How Thick Does Your Gasket Need to Be? Here Are 4 Ways to Know For Sure., you’ll see that thicker is not always better. Generally, the thinnest gasket you can use is going to be the best option. The amount of creep relaxation seen in a material is going to be directly proportional to the thickness of the gasket. With that said, sometimes a thick gasket is necessary. If that is true for your application, then you should expect a certain level of creep to take place. Ideally, the bolts and joint will be loaded sufficiently to overcome the relaxation that is present and maintain the seal.

The majority of the creep relaxation seen in a material occurs early in use. Some suggest that material will continue to creep indefinitely, but the loss is negligible. If your application can withstand the creep that occurs within the first duty cycle, chances are it will maintain its seal.

Materials have different amounts of creep, depending on the temperatures and pressures used in the joint. Generally, denser materials will have less creep than softer materials. So, in stiff flanged joints with plenty of load, generally a denser material is a better choice.

Softer materials are more compressible and provide better conformance to flange surfaces. However, some types of softer materials due to their make-up, exhibit high creep/relaxation under load and temperature. This can be addressed by providing sufficient bolt load, to overcome any expected creep effect and maintain a long-term seal. Minimizing gasket thickness will also help in this area.

High temperature and high pressure also have an effect on the amount of creep you will see in the material. If you work in these types of applications, you will need to pay special attention to the specifications of the material you are selecting to work within the suggested temperature conditions. Taking material higher than its capability can lead to the breakdown of various components, additional creep and ultimately load loss on the fasteners.

Material Selection Matters

Being aware of the creep relaxation characteristics of a specific material is paramount to choosing the right material for your application. Don’t hesitate to talk to your trusted gasket material supplier for help in identifying the type of material that you may need for your application.

Until next time! If you are interested in subscribing to Sealed-In’s blog posts email sales@mtigasket.com

What Is Air Aging, and Why Do I Care?

This week, we’re going to talk about air aging as it relates to your gaskets and gasket material, and why it is important. Air aging is similar to ignition loss in the fact that there is interest in the weight loss of a material at elevated temperatures, but the similarities really stop there. So, what is air aging?

What Is Torque Retention, and Why Do I Care?

This week, we’re going to talk about torque retention (or torque loss, depending on your particular viewpoint) and how it affects your gasket performance. Torque retention is related to many of the topics previously discussed, but we thought we’d take a closer look at it specifically.

What Is Compressibility & Recovery, and Why Do I Care?

This week, we’re going to talk about compressibility and recovery. These are two of the most important properties in selecting a gasket material, and ones you definitely need to pay attention to. Having a material with the right compressibility and recovery for your application makes all the difference in the performance of the application.

What Is Bolt Load, and Why Do I Care?

This week, we’re going to talk about bolt load. You may also have heard the terms: torque load, flange load, or compressive force, which all refer to the same thing. Bolt load is something to keep in mind when you are designing your joint and selecting your gasket material. Without knowing or paying attention to it, you may be setting yourself up for an insufficient load situation…and a problem.

What Is Creep Relaxation, and Why Do I Care?

This week, we’re going to talk about creep relaxation in gaskets and gasket material. This is something that will happen to some extent in most gasket materials. How much or how little of this you see depends on your gasket material selection and the application itself. It is important to have an understanding of creep relaxation and how it relates to a particular material.