Pipe Joining

 

Heat fusion is the process in which two sections of plastic pipe trimmed and cleaned, aligned, heated to the melting point, brought together, and allowed to cool. Heat fusion results in a joint that is actually stronger than the pipe itself. For reliability, all underground piping must be thermally fused, rather than mechanically coupled.

Two fusion techniques are used for joining polyethylene pipe – socket fusion and butt fusion.

Equipment is available to make these heat fusion joints in the field. It's essential that foreign materials are prevented from entering the pipe.

Socket Fusion
Let's take a look at the seven steps in socket fusing a polyethylene pipe:

  1. Check the temperature of the fusion tool to make sure it is hot enough usually between 500 and 525°F.
  2. Prepare and clean the pipe ends.
  3. Apply a cold ring to the pipe using a depth gauge.
  4. Make a dry run of joining the pipes to check clearance and make sure the ends will fit smoothly.
  5. Use the fusion tool to heat the pipes for the correct amount of time based on the pipe's size.
  6. Join the pipes and hold them in position while they cool. This keeps stress off the new joint.
  7. Allow the joint to cure.

Butt Fusion
Now, let's take a look at the steps in butt fusing a polyethylene pipe:

  1. Check the temperature of the fusion tool to make sure it is hot enough usually 500°F±.
  2. Square the ends of the pipe.
  3. Check inside the pipe for trimmings.
  4. Check two pipe ends for proper alignment.
  5. Heat pipe ends - apply minimal pressure, allowing heat to flow into pipe, Pipe will melt against heater plate if excessive pressure is applied.
  6. Allow pipe to heat until rollback occurs of approximately the size of a toothpick or kitchen match.
  7. Bring pipe ends together to form double rollback.
  8. Allow to cool.
  9. Inspect for uniform double rollback, absence of gaps, and make sure there is no discoloration.