Why Can’t Different Grades of PE Pipes Be Butt Fused Directly?

In HDPE pipeline construction, a common question is: can PE80 and PE100 be butt fused directly? The key factor is the Melt Flow Rate (MFR).

Under the same heating time, PE80 usually melts faster than PE100. If the MFR difference between the two exceeds 0.5 g/10min, butt fusion should be avoided, and electrofusion is the proper choice. The reason is that uneven melting causes the weld beads to form asymmetrically, creating residual stress inside the joint. While this may not show immediate problems, pipelines buried under traffic loads or high-pressure systems could face cracking or joint failure over time.

That’s why Welping recommends using electrofusion for different grades of PE pipes to ensure reliable welding and long-term pipeline safety.