Why Furnace Muffles Fail: Using the Wrong Materials

Furnace muffles are designed to maximize your furnace up-time and lower your costs. As a maintenance manager or process engineer, you’re looking for optimum performance and a long lifespan. Prematurely pulling a muffle out of service for any reason causes disruption and lost revenue for your company.

While there are several reasons why furnace muffles fail, in this post we’ll dive into the reasons related to materials selection.

Why the correct material is important

Every furnace is different; no two manufacturing operations have the exact same goals. Some manufacturers seek a design that will better resist creep at higher temperatures. Others opt for a muffle strengthened to prevent the bottom from humping.

Conversations about materials selection will overlap with conversations about the design of your muffle. However, we strongly believe that choosing the right materials is one of the biggest factors in extending the life of your muffle.

Whether the material is stainless steel, nickel base alloys, carbon steel or other bi-metal composites, it’s important that you select the best option and design it correctly for your application.

Factors to consider when selecting your furnace muffle material

Understand why it failed

First and foremost, you need to understand how and why your current muffle is failing. One option is to evaluate the material of a failed muffle in order to understand what might have gone wrong. This process might get as detailed as having the material grain analyzed under a microscope. This process will help determine if the proper material has been selected or if another material would be better served for the application.

Make sure you partner with a trusted vendor who knows what to look for. Remember that items such as materials discoloration, floor humping, a collapsed roof and dew point issues are some of the early indicators of failure. These items can be addressed as you work through design modification and materials selection.

Consider your furnace temperature

Operating temperatures can vary greatly, which means the optimal materials will vary from furnace to furnace. For example, we partnered with a customer who was consistently seeing their muffle fail in less than one year when they operated their sintering furnace at 2100° Fahrenheit.

We suggested several recommendations (which they implemented) and changed the material of construction to better able to resist creep at higher temperatures. As a result, the new muffle exceeded the lifespan of the original.

Consider fabrication capabilities

Working with specialized materials for high-temperature environments requires the use of different rolling, forming and welding techniques. Remember that not all shops provide these services at the same level.

A muffle that’s cheaper and manufactured faster can be indicative of a poorly designed product with less-than-ideal materials. A properly welded muffle made to your exact specification might take a little more time to build, but that contributes to a high quality, more durable muffle.

Next steps in your muffle replacement

As a consumable product that needs maintenance and eventual replacement, you want to make sure your next muffle investment is a wise one. We recommend working through design modifications as early as possible, which leaves time for a conversation about what materials are best for your application.

Alloy Engineering offers muffles in a variety of application-specific configurations. To learn more, contact us here or call us at 440.243.6800.