Heating RPAP5 pipeline installation (welding) process

RPAP5 is a new type of heating pipe. Because the installer first contacted the pipe and did not understand its performance, the welded pipeline had multiple pressure tests and multiple leaks.

Installers generally report that the pipe has poor meltability.

In response to the poor fusion of the RPAP5 pipeline reported by the construction unit, the joint fusion destructive test was carried out in the laboratory: the pipeline blasted at 7.48MPa, and its blasting pressure was far

It is much higher than the design working pressure of 1.25MPa, and the hot-melt joints are intact, which proves that the material has a very good meltability.

1. Analysis of the cause of water leakage in the welded joint

1. There are the following main defects in the section observation of the joint:

a. The joint is not welded to the deepest part

b. The inner wall of the pipe is not fused

2. Reason analysis:

2.1 Hydropower installers used PE and PPR pipes for hot-melt connections. They have not touched the RPAP5 double-sided pad fusion connection. According to the previous operating procedures, the phenomenon of fusion is prone to not in place.

2.2 The fusion temperature of RPAP5 pipe should be controlled at 220～230℃. The fuser provided by the supplier is temperature adjustable, and the fuse temperature range is wide, either the material is not melted or

Heating it into a molten state will seriously affect the quality of the welding.

2.3 After the mold is welded with a certain number of joints, the surface has adhesion phenomenon. The operator does not clean the mold in time, and slag inclusions appear at the joints, which affects the quality of the joints.

2.4 When leaving the factory, the process of coiling, straightening and cutting on site can easily cause the ovality of the pipe to exceed the standard. The non-circular inner diameter is the main reason for partial unfusion during welding.

2. Development of welding process

1. Preparation of welding equipment:

2. Welding:

The first step: cut the pipe, cut the pipe with a pipe cutter (or pipe quick cut), cut the end of the pipe as flat as possible when cutting, otherwise it will affect the welding effect

The second step: round, use chamfering or plasticizer to round, but no need to chamfer.

The third step: spray release agent before heating.

The fourth step: heating, when the green light of the fuser lights up, the fuse connection can be started. The pipe fittings should be inserted into the die at the same time, and the pipes and pipe fittings need to be inserted into the deepest part of the hot melt die slowly (and never shake left and right).

After a small amount of molten material overflows from the overflow hole at the bottom of the die, quickly withdraw the pipes and fittings from the dual hot melt die. The heating time should be 5-8 seconds, and the winter construction time can be appropriately extended.

Step 5: Welding, take out the pipe fittings from the die in the fuser at the same time, and immediately insert the pipes into the pipe fittings smoothly without rotation to reach the specified maximum depth (check the second through the observation hole)

The connection time cannot exceed 4 seconds until the overflow hole extrudes the plastic. At this time, there is a uniform flange at the joint, that is, the welding is completed. At this time, it must be left to cool for a while to achieve complete welding.

Step 6: Cooling. After welding, the cooling time should not be less than 2 minutes. Before cooling sufficiently, twisting, bending and stretching should be avoided.

3. Matters needing attention:

It is necessary to ensure sufficient heating time during welding, and the shorter the conversion time, the better.

The socket must be in place when welding, and it is strictly prohibited to rotate or bend after socket.

After the double hot melt is completed, if there is any accumulated material remaining on the die, it must be cleaned up in time. Since the hot melt die is coated with a special Teflon, please do not use sharp metal objects to clean it.

If the accumulated material cannot be cleaned out or the coating film of the hot melt die is damaged, the die must be replaced.

  3. RPAP5 pipeline installation improvement measures

1. According to 'Code for Construction Quality Acceptance of Building Water Supply and Drainage and Heating Engineering' GB50242-2002, Article 8.2.15 'Plastic pipes and composite pipes shall be directly bent and turned by pipes except where right-angle elbows must be used.'

8.5.1 'The buried part of the coil pipe laid under the ground should not have joints' to conduct cold bending and pressure test of RPAP5 pipeline: