Electrostatic Discharge

Polyethylene plastic used in manufacturing gas pipe has many advantages over steel and other materials. However, one disadvantage is the potentially dangerous buildup caused by gas flowing through this non-conductive material.

The possibility of static electric discharge during squeeze-off of PE gas pipe is now recognized and addressed by gas utilities and pipe manufacturers. During the normal flow of natural gas in PE pipe, electric charges move in the direction of the gas. When squeeze-off occurs, turbulence and gas velocity increase at the squeeze point, which causes the charges to become heavily concentrated at that same point. As the charge increases in density on the inside wall surface, the force between the charges inside the pipe and the opposing charges outside the pipe increase. When the force exceeds the dielectric strength of the pipe, the charges move through the pipe and creates a pin hole opening in the pipe wall. If the squeeze tool is properly grounded, the discharge will move through the squeeze tool to the earth.

This phenomenon is aggravated by:
1. Sufficient gas flow to cause extensive turbulence, such as the reduced area of pipe during squeeze-off.
2. Rust or foreign particles present in the gas.