Strength of Fusion Joint

The first question everyone asks is: How is a fusion joint as strong as the pipe?

HDPE fails in tension, not compression.  MaxDR is engineered and produced to maintain the HDPE Core Pipe in Compression such that the HDPE Fusion Joint cannot tear apart at the molecular level because there are no tensile stresses to exceed the design strength.  MaxDR pipe is designed with multiple features to ensure the strength of the fusion joint substantially exceeds any stresses that could be experienced.  By understanding the mechanical properties of HDPE and composite wraps, we have engineered and tested to prove our design basis.  Following is a summary of why the fusion joint of MaxDR pipe will operate at the highest levels of integrity:

• Due to our proprietary composite design and manufacturing process, MaxDR pipe has independently verified operating pressures of 350, 550 to 750 psi based on 4 to 1 Design Factors following ISO 14,692 -2, Method 1 – Quick Burst Qualification. This means that MaxDR 750 psi operating pressure pipe bursts in the body of the pipe at 3,000 psi.
• MaxDR pipe employs a proprietary wrapping process to reinforce fusion joints at butt ends combined with the thick-wall core-pipe long-term hydrostatic strength to exceed operating pressure design by nearly 400%, keeping the joints fully compressively constrained and eliminating any potential for bulging or expansion that would create tension on the fused HDPE material in the fused joint. Envision a collar on downhole steel casing or tubing, except our collar does not extend across the fusion itself.
• Composite fibers wrapped at unique helix-angles create slight elongation of the pipe, such that in a constrained environment (i.e. buried), there is a compression force across the fusion-joint when the pipe is pressurized. This compression further enhances the strength of the joint.  Put your two fists, knuckles to knuckles and push together. This is similar to the force that is exhibited at the butt-fusion joint.
• The encapsulation and restraint from the fiberglass wrap and elongation from the proper helix angle keeps a fusion butt joint fully constrained with a compressive axial stress across the fusion interface during fluid flow operation.

Bottom-line, MaxDR pipe fusion joints are locked in compression such that a properly fused joint does not fail under 4x its operating pressure rating.