TECHNICAL MANUAL - Sharq.biz

welding pressureThe welding pressure required by the polyethylene must be like that the surfacesat contact is equal to:(0,15 ± 0,02) N/mm 2This pressure is calculated through the proper formula, knowing the totalpressure section of the oleodinamic cylinders of the welding buttfusion machine.In general, the values are reported on proper tables supplied by the manufactureraccording to the weldable diameters and thicknesses. The drag pressure P t mustbe always added to these values.The pressure, monitored by the pressure gauge, is adjusted using the specificdevice.drag pressureThe drag pressure P t is the minimum pressure value necessary in order to winthe friction of the movable jaws of the welding machine (loaded with the pipe/fitting), which depends on the weight of the gear and of the pipes/fittings to bewelded, from the oil temperature in the hydraulic circuit and the jaws clampingforce. Its value has always to be traced experimentally every time we proceedwith a welding process and then added to the pre-heating (P 1 ) and welding (P 5 )pressures given in the tables. Never exceed to this value.24