Fused Seams vs Traditional Sewn Seams

Fused seams and traditional sewn seams are two different methods of construction, each with its own set of characteristics and advantages. Let’s delve deeper into the differences between these two approaches:
1. Fused Seams
Fused seams are created through fusion welding, where heat is used to melt and fuse the materials together. This method results in a seam that offers comparable or slightly higher strength when compared to sewn seams. One of the key advantages of fused seams is their ability to create a near-bypass-free area. This means that the seam is more resistant to allowing substances or particles to pass through, enhancing the overall integrity and efficiency of the seam. Fused seams can be particularly beneficial in applications where maintaining a strict barrier is crucial.
2. Traditional Sewn Seams
Sewn seams are created using sewing needles with a diameter of approximately 0.0270 inches, and they rely on thread to hold the materials together. While sewn seams also provide a similar level of strength as fused seams, they do not completely prevent bypass. Bypass refers to the potential for substances to pass through the perforations or gaps created by the stitching. The choice of material plays a role in the effectiveness of sewn seams. For example, needle-punched felt tends to collapse around the thread, potentially creating perforations that allow for bypass. In contrast, woven textiles maintain their structure, resulting in perforations that can allow controlled bypass of varying dimensions.

The choice between fused seams and traditional sewn seams depends on the specific requirements of the application:

Both methods offer similar levels of strength, but the choice may depend on the materials being used and the intended load-bearing capacity of the seam.
Bypass Prevention
If preventing bypass is a critical factor, fused seams may be preferred due to their near-bypass-free nature.
Material Considerations
The behavior of the materials being used, such as collapse or maintenance of structure, can influence the decision between the two seam types.
Application Requirements
The specific needs of the application, such as environmental conditions, the type of substances being filtered, and the desired level of filtration efficiency, will play a significant role in determining the most suitable seam construction method.
In conclusion, the choice between fused seams and traditional sewn seams involves a careful evaluation of factors such as strength, bypass prevention, material characteristics, and application requirements. Understanding these distinctions will help in selecting the appropriate seam construction technique for various filtration and construction applications.
Case Study: Fused Seams vs. Sewn Seams for Filtration in the Pulp and Paper Industry
A Kraft Mill in the Pulp and Paper industry specializes in caustic recovery, a critical process involving the recycling of expensive and toxic chemicals used in the Kraft method. The mill employs pressure vessels or candle filters to facilitate filtration in their caustic recovery cycle.


The customer had been facing challenges with their filtration process using felt Polypropylene candle filters with sewn seams. The caustic recovery area presented a problem of bypass through the needle holes in the filters. Various attempts were made to address this issue, including using different stitching techniques and thread materials like PTFE and Polypropylene. However, these efforts were not successful in completely preventing seam leakage and bypass.


Upon thorough analysis of the filtration process and examination of failed candle filters, a solution was identified. It was proposed to replace the traditional sewn seams with fused vertical seams on the candle filters. Fusing the vertical seams involved thermally bonding the filter material to itself, creating a single “melted” or “fused” seam. This fused seam design not only eliminated the flow area where particulate bypass could occur but also offered increased strength compared to conventionally sewn seams.


After implementing the solution, the customer transitioned to using Polypropylene filters with fused vertical seams. The outcome was highly successful, with no reported failures or bypass issues at the vertical seam over the course of several years. This significant improvement led to the development of a new outage schedule, leveraging the enhanced lifecycle of the filter bags. As a result, the customer experienced reduced expenses related to filter bags and fewer unplanned outages, contributing to improved operational efficiency and cost savings.
In summary, the shift from sewn seams to fused vertical seams in the filtration process of the Kraft Mill’s caustic recovery area proved to be a successful solution. The fused seams effectively addressed the challenge of bypass and leakage, leading to prolonged filter bag lifecycles and minimized operational disruptions. This case study highlights how a thoughtful and innovative approach to seam construction can yield substantial benefits in specific industrial applications.