In the event that the pin does not rise, the supervisor or operator must investigate the following to determine if the joint is satisfactory by confirming all the following features are within specification: • Dimensional check and compliance of the pipe or spigot OD and ovality. • The pipe dimension within the fusion zone should be compliant with the standard definitions. • That the input power supply to the ElectroFusion control unit is stable without disruption, and no error messages are reported on the display panel. • That the heat fusion parameters are correct. • The pipe to fitting alignment is correct with no visible plastic extruded out from the fitting. It is possible that a good weld has been performed even if the MI did not rise. If the parameters above have been checked and no problem could be detected the weld need not be rejected. Cooling time The defined cooling time mentioned on the product barcode is an integral part of the ElectroFusion process and should be adhered to - it is a critical part of the welding process, and is often overlooked and misunderstood. In order to help understand the importance of this stage we shall look at the full fusion cycle and follow its phases:
Intermingling of PE chains from pipe and fitting as heating commences
The Polyethylene on the fitting side begins to melt and its volume increases. The melt begins to flow and fill the gap between the fitting and the pipe, and once the pipe surface comes in contact with the hot flowing melt it starts to melt as well and a “melt pool” starts to build up between fitting and pipe as the current continues to be applied.
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