Pe Pipe, Water Pipe Hot Melt Over Asymmetry How To Solve

Hot melt turn-over asymmetry is a common problem in the hot melt process of pe pipes, and the reasons are not complicated. In the process of hot melt, there are five stages: preheating the heating plate of the welding equipment, heating the polyethylene pipe, taking out the heating plate, welding and cooling. Temperature, pressure and time are important factors to control the quality of the hot melt connection of the pe pipe. The interaction between heating temperature and welding pressure and contact time has a particularly obvious impact on the performance of the joint, followed by the cooling time, and the length of the cooling time also has an impact on pe pipes and fittings.

Heating temperature and heating time mainly play a role in the heating stage, welding pressure mainly plays a role in the welding stage, these two stages will affect the asymmetry of pe pipe over, please see our analysis below;

Heating stage

1 Device Cause

The fault of the hot melt connection device causes the temperature inconsistency between the two sides of the heating plate after preheating. The surface temperature on both sides of the heating plate connecting the PE100 pipe must be 225 ± 10°. When the welding equipment is faulty, the temperature difference between the two sides of the heating plate is too large, resulting in different heat absorption of the polyethylene pipes on both sides of the joint, resulting in asymmetric edge rolling.

2 On-site Impurities

There are impurities on the heating plate or the polyethylene pipe end. Common impurities such as dust, soil, etc., impurities absorb heat to consume a part of the heat, or impurities form a layer of diaphragm to hinder the normal heat absorption of polyethylene pipe, this situation caused by the asymmetric difference between the two sides of the edge is small, but the bigger problem is that the presence of impurities in the welding joint will seriously affect the quality of welding.

3 Environmental Impact

The most influential factor is the wind, the flowing wind will take away part of the heat on the heating plate or polyethylene pipe, in the construction site, the wind side of the polyethylene pipe heat absorption is reduced, the lee side heat absorption is relatively normal, which leads to the less heat absorption on the side of the roll up will be less, resulting in the phenomenon of asymmetric rolling edge.

Welding phase

1 pe tube difference

The difference between polyethylene pipes on both sides of the interface can be subdivided into:

(1) The raw materials used in pe pipes are different;

(2) The wall thickness of pe tube is different, the flanging amount formed by the smaller wall thickness is large, and the flanging amount formed by the larger wall thickness is small;

(3) There is a large time difference in the production date;

(4) belongs to the same batch of pe pipes, but the storage conditions are different, the storage environment is poor, such as the end after the sun and rain, the amount of rolling up will be less than the side of the storage condition is good;

(5) The difference of melt mass flow plastic (MFR) is large, and the difference of melt mass flow rate should be less than 0.5g/10min(190t, 5kg) according to the specification.

2 wrong side measure

Due to the large ellipticity value of the polyethylene pipe end surface, or the operation is not standardized, resulting in a large amount of wrong edge, when the wrong edge is large, the top surface of the pipe at both ends is not on the same horizontal plane, in the case of the same amount of rolling, the raised end is relatively high, the concave end will be lower, so it will form an asymmetric rolling edge.

3 Clearance of interface end faces

The end face of the milled pe tube is not vertical, and the end clearance is too large, resulting in the local position can not absorb heat. When the matting is not vertical, some polyethylene pipes fail to contact the heating plate for adequate heat absorption, and can not form enough or curled edges in the extrusion stage, resulting in serious defects.

Suggestion

Reduce the pipe differences between pe pipes on both sides of the joint, try to use the same brand and the same batch of pipes for the same project, do a good job of pipe inspection measures, and carry out standardized testing of testing items such as ellipticity and wall thickness. Do a good job of pe pipe protection measures at the construction site, block both ends of the pipeline, to avoid sediment and other pollution inside the pipeline. Check the verticality of the end of the pe pipe after matting to ensure that the amount of misalignment on both sides of the joint meets the specifications. Check the temperature on both sides of the heating plate during welding, and the temperature on both sides of the heating plate should be consistent and meet the requirements of the specification. Before each of the first hot melt welding and the hot melt connection of different pipe diameters, the edge forming cleaning method is used to remove impurities from the heating plate. Regular maintenance of the welding machine.