The basic Diesel Exhaust Flex Assembly has been used for quite some time in exhaust applications, and the fundamentals have only slightly changed over the years. A Diesel Exhaust Flex Assembly is a great product and will definitely do the job effectively given the application allows for it. The function of these assemblies is to isolate vibration between the engine and piping, and allow misalignment of pipe, thus protecting the engine. Diesel Exhaust Flex Assemblies are a less expensive alternative to the more competent Bellows Exhaust Assembly though the Diesel Exhaust Flex Assembly does require longer lengths due to the shorter, wider and stiffer convolutions.
There is a significant difference between a Bellows Exhaust Assembly and a Diesel Exhaust Flex Assembly. One has an integral neck while the other does not. This simple difference has an enormous impact on the performance of the assembly due to the location of the attachment weld of the end fittings.
A Diesel Exhaust Flex Assembly does not have an integral neck and the fitting attachment weld is located on the radius of the convolution (See Fig. 1). This weakened, “Heat Affected”, weld area is made even weaker due to the prior cold metal forming process of the convolution. The combination of these two issues typically causes a Diesel Exhaust Flex Assembly to fail (separate) at the weld.
Unlike the Diesel Exhaust Flex Assembly the Bellows Exhaust Assembly does have an integral neck, and the fitting attachment weld is placed on the end of this neck, thus keeping it away from the convolution (See Fig. 2). This simple difference in the location of the weld creates a more durable weld and allows the assembly to outlast and outperform the economical Diesel Exhaust Flex Assembly.
Both of the above assemblies are critical in allowing the movements of pipe in exhaust applications. One may outperform the other over time, yet both are always available from DME.