How to determine the heating time and cooling time of HDPE socket fittings

HDPE socket welding is a commonly used hot-melt connection method. A special heating tool is used to heat and soften the joint surface of the pipe fitting and the pipe, and then the joint is quickly plugged in and kept cooling to form a firm integrated connection. The core parameters of the welding process include: heating plate temperature, heating time, plugging time, cooling time, etc., among which the heating time and cooling time directly affect the quality of the joint, structural integrity and long-term reliability.

Definition and influencing factors of heating time
Heating time refers to the time required for the pipe and the pipe fitting to contact the heating plate and maintain a constant temperature until their surface melts. The determination of this time requires consideration of multiple technical factors:
Wall thickness of pipes and fittings (SDR grade)
Material grade (PE80 or PE100)
Surface temperature of heating plate
Ambient temperature and wind speed (especially significant in outdoor construction)
Stability of contact between the heating surface of the equipment and the pipe fitting
Insufficient heating time, insufficient softening of the melt surface, insufficient fusion strength of the joint, and easy formation of cold welding or delamination. If the heating time is too long, it may cause degradation of HDPE material, collapse of the melt surface, and loss of roundness of the interface, thereby affecting the plug-in fit and sealing effect.
Recommended heating time parameters for HDPE socket welding
According to industry standards such as "ISO 4427-3", "DVS 2207-1", and "CJJ/T 123-2018", the typical heating time is recommended as follows (taking the heating plate temperature of 260±10℃ as an example):

The heating time needs to be adjusted based on the standard and in combination with the actual situation. For example, in a cold or windy construction environment, it is recommended to extend the heating time by 10%-20%; in a high temperature environment in summer, it can be appropriately shortened.

Definition and control principles of cooling time
Cooling time refers to the time required for the joint to remain stationary in a natural state after the socket welding is completed, until the temperature drops below the thermal deformation temperature of the HDPE material, and the weld solidifies and crystallizes. It is forbidden to apply external force or move the joint during the cooling process to avoid dislocation of the welding surface or loose structure.
The length of the cooling time mainly depends on the following factors:
Interface size (diameter and wall thickness)
Thermal capacity of the joint and ambient temperature
Thermal conductivity and specific heat capacity of the material
Air cooling or static method
The cooling time is too short, the joint is not completely fixed, and it is easy to have problems such as cold cracking, shrinkage holes, and poor sealing. Although the cooling time is too long, it will not affect the structure, but it will reduce the construction efficiency.

Recommended cooling time parameters for HDPE socket welding
Based on industry measured data and construction experience, the recommended cooling time is as follows:

When constructing in winter or cold areas, it can be appropriately extended by 10%-30%. It is strictly forbidden to move or test the joint before the end of the cooling time.

On-site confirmation method of heating and cooling time
Surface melting ring observation method: After heating, a uniform and round melting ring should be formed at the junction of the pipe fitting and the pipe, indicating that the heating time is sufficient.
Touch test method (non-standard recommendation, only applicable to experience judgment): After welding is completed, touch the outer edge of the melting ring with your hand. When there is no obvious adhesion, it means that the cooling is completed.
Actual measurement recording method: Use a stopwatch or intelligent welding equipment to record the heating and cooling process of each joint to ensure that the parameters are traceable.
Temperature gun monitoring method: Before the end of cooling, the surface temperature of the joint can be measured with an infrared temperature gun. When the temperature drops below 60°C, it can be determined that the cooling is complete.

The role of equipment in heating and cooling
The heating tools used for HDPE socket welding should have the following functions:
The heating plate has strong constant temperature control ability, and the temperature difference is controlled within ±5℃
The surface coating has anti-sticking and high temperature resistance functions to prevent carbonization residues from contaminating the pipe fittings
The heating plate is equipped with a time reminder device to remind the operator of the heating and cooling time
The welding auxiliary device can stably fix the pipe to prevent displacement during the plug-in process
The selection of qualified equipment can not only improve welding efficiency, but also stably control the heating and cooling time, and improve the overall project quality.

Time adjustment suggestions for different application scenarios
Indoor construction: The temperature and humidity are stable, and can be executed completely according to the standard recommended time.
Plateau or cold areas: The ambient temperature is low, the heat dissipation is fast, and the heating and cooling time needs to be extended by more than 10%.
Direct sunlight or hot climate: The pipe is preheated, and the heating time needs to be shortened by 2-5 seconds to prevent over-melting.
Continuous welding operation: It is necessary to ensure that the surface temperature of the equipment is uniform to prevent local overheating from causing uneven heating.