Heat Fusion and Joining
Appendix A

Hydralic Fusion Machine Guage Pressure

The manufacturer of the fusion machine should be consulted for guidance in determining the proper conversion of PolyPipe^®’s recommended interfacial pressure to the gauge pressure. The effective hydraulic piston area must be available in order to calculate the required hydraulic gauge pressure. The calculation for hydraulic gauge pressure is as follows:

Where
PG = Hydraulic Gauge Pressure, psi
OD = Pipe outside diameter, inches
ID = Pipe inside diameter, inches
PI = Required interfacial pressure, psi
AP = Total hydraulic piston area, in2
DF = Hydraulic fusion pressure required to move the carriage holding the pipe (generally accepted minimum is 30 psi).

*The drag factor is an important parameter easily overlooked. If two long pieces of pipe are being fused, the drag factor can easily reach several hundred pounds per square inch (psi).

References

1. Plastics Pipe Institute Technical Report-33. Generic Butt Fusion Joining Procedure for Polyethylene Gas Pipe, 2001.
2. Plastics Pipe Institute Technical Report-41. Generic Saddle Fusion Joining Procedure for Polyethylene Gas Pipe, 2002.
3. Plastics Pipe Institute.Polyethylene Joining Procedures, March 1998.
4. ASTM D2657-97. Standard Practice for Heat Fusion Joining of Polyolefin Pipe and Fittings. Volume 8.04. American Society of Testing and Materials. Baltimore, 2002.
5. ASTM F1056-97. Standard Specification for Socket Fusion Tools for Use in Socket Fusion Joining Polyethylene Pipe or Tubing and Fittings. Volume 8.04. American Society of Testing and Materials. Baltimore, 2002.
6. Pipeline Safety Regulations. U.S. Department of Transportation. CFR 49. Washington, 2002.

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