HDPE (high density polyethylene) welding parameters should be adjusted according to different SDR (Standard Dimension Ratio, standard size ratio) values. SDR is the ratio of outer diameter to wall thickness of the pipe (SDR=DN / en), which directly affects the pressure bearing capacity and welding process of the pipeline. The following are descriptions of different SDR standards and butt welding precautions:

1. Definition and common standards of the SDR

Formula: SDR = outer diameter (DN) / wall thickness (en)

Example: SDR11 means that the outer diameter is 11 times the wall thickness.

Common SDR values:

SDR7.4, SDR9, SDR11 (high pressure tube with large wall thickness)

SDR13.6, SDR17, SDR21 (medium and low pressure pipe, with small wall thickness)

SDR26, SDR33 (low pressure or drain pipe, thinest wall thickness)

2. Effect of SDR on welding

(1) Heating time and temperature

High SDR (thin-walled tubes, such as the SDR17):

The wall thickness is thin, and the heating time should be shortened to avoid overheating and deformation of the material.

Usually use a lower heating plate temperature (200 to 210 °C).

Low-level SDR (thick-walled tubes, such as the SDR11):

Large wall thickness, so an extended heating time is required to ensure sufficient melting.

The heating plate temperature can be slightly higher (210~220°C).

(2) Welding pressure

High SDR: The welding pressure should be reduced to avoid the pipe wall collapse caused by extrusion.

Low SDR: A higher pressure is required to ensure adequate bonding of the melting surface.

(3) Cooling time

Thick wall pipe (low SDR): the cooling time should be extended to prevent weld cracking caused by internal stress.

3. Adjust the parameters of the welding machine for reference

4. Precautions

End surface flatness: the wall thickness of different SDR pipes varies greatly, so the cutting end surface is absolutely flat.

Clamping force matching: thick wall pipe needs higher clamping force to prevent sliding, thin wall pipe needs to prevent deformation.

Material consistency: Two segments welded shall be the same SDR and material grade (e. g. PE100).

Ambient temperature: extended heating and cooling time at low temperature.

5. Relevant standard reference

ISO 21307: Specification for butt-butt welding process of polyethylene pipe.

EN 12201 / ISO 4427: PE pressure piping system standard, with SDR series requirements.

ASTM F2620: HDPE butt-welding operation guide.

If you encounter HDPE BUTT FUSION WELDING MACHINE pipes of different standards when using HDPE, don't worry, you can easily find the solution by reading the following information.