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HomeNewsPPH pipe fitting welding instructions (Part 2)

PPH pipe fitting welding instructions (Part 2)

2020-02-08
Welding procedure
1. welding preparation
1.1: Prepare the welding equipment according to the construction site layout plan for PPH Pipe Fitting welding.
1.2: take flange connection as the priority principle for PPH and PVDF Pipe Fitting, reasonably divide the prefabricated dividing points according to the requirements, and make corresponding technical disclosure at the same time.
1.3: corresponding dust-proof and isolation measures shall be taken for clean PVDF piping requirements
1.4: secondary detailed design of drawings and establishment of spatial view.
1.5: connect the electrical system and hydraulic system of the equipment, and adjust the equipment according to the requirements of the equipment manual.
1.6: prepare the hot melt welding operation instruction of PVDF fittings according to the technical documents and relevant standards and specifications provided by the PPH and PVDF material manufacturer
2. Pipe cutting
2.1: mark on PPH Pipe with marker according to the required length of empty view of design drawing.
2.2: the pipe shall be cut with approved cutting tools, toothless saw, curve saw or manual saw.
2.3: after the pipeline is cut, the flatness of the end face of the pipeline shall be checked with a square, and the allowable deviation shall be controlled within 5mm.
2.4: for the qualified pipelines, the length of the secondary end face cutting shall be marked along the circumference of the pipeline with a water-based pen.
3. Fixture installation
3.1: after a section of the pipeline is adjusted and leveled, it shall be fixed on the fixed end of the welding frame with clamps. When the effective length of the pipe section exceeds 1500mm, V-shaped auxiliary bracket as shown in the figure below shall be installed for support.
3.2: temporarily fix another section on the movable end of the welding frame. When the effective length of the pipeline exceeds 2000mm, the tugboat V-shaped auxiliary bracket shall be placed reasonably and the pipeline shall be placed on it.
3.3: adjust the two PPH pipes to be butt welded to make their axes concentric and coincide as much as possible, and check the flatness of the pipes with a level ruler.
3.4: the cut PPH pipeline shall be temporarily fixed with the fixing fixture of welding equipment, and the fixing fixture bolts shall be tightened after checking and adjusting its ovality.
4: Cutting of end face
4.1: adjust the hand wheel or other operating mechanism on the welding equipment to make the pipe clamp run along the track of the welding equipment rack to the position about 80-100mm from the end face of the connected pipe.
4.2: place the end cutting tool on the guide rail of the welding frame, and operate the hand wheel or other operating mechanism again to make the clamp fixed to the pipe slide tightly, and start the cutting tool to cut the end face of the pipe.
4.3: the length of pipe end cutting should be controlled within the range of 1mm ~ 2mm.
4.4: in the process of cutting, it should be noted that the shape of the waste shavings of PPH pipes peeled from both sides of the cutter is continuous roll shape, the width of the shavings is the same as the thickness of the pipe wall, and the cutting can be stopped slowly when the length exceeds the outer diameter circumference of the pipe.
4.5: operate the hand wheel of welding machine or other operating mechanism to make the pipe clamp run along the direction of the rack guide rail, completely separate from the cutting state and check the cutting section.
5: Check the clearance and concentricity of the end surface pre bonded pipe
5.1: operate the pipe clamp to pre bond the end face of the pipe section to be welded.
5.2: use a feeler gauge to check the bonding clearance of the end face of the pipe. The deviation must be controlled at 1% of the outer diameter of the pipe and the end face clearance should be less than 0.5mm.
5.3: check the flatness of both sides of the two sections of pipeline after pre bonding with a horizontal ruler, so as to determine the concentricity of the two sections of pipeline. The maximum allowable displacement of concentricity is 0.1s (s is the wall thickness of the pipe), and the maximum displacement is not more than 1mm.
5.4: for socket type hot-melt welded PPH pipes, the fitting clearance between socket and spigot shall not exceed 1mm, and the deviation of ovality shall meet the requirements.
5.5: for socket connected PPH pipes, the corresponding depth shall be marked on the spigot with a water-based marking pen.
6: Hot melt bonding surface cleaning
6.1: for the qualified pipe section, operate the welding hand wheel or other operating mechanism to separate the pipe clamps from each other and clean them.
6.2: clean the hot-melt end face and both sides of the hot-melt zone of the pipeline by dipping the dust-free cloth with alcohol or acetone for several times, and check with the dust-free cloth after drying.
6.3: for the socket type hot-melt welded PPH pipes, the inner and outer surfaces of the socket and spigot pipes within the scope of hot-melt shall be cleaned with acetone or alcohol, and the marking lines at the spigot shall be protected during cleaning.
7: End hot melt
7.1: adjust the limit values of heating temperature and heating time on the hot-melt welding machine according to the specifications of materials, so as to make it meet the requirements of heating technical data provided by PPH pipe material manufacturer (see the table below)
7.2: place the heater on the rack, use a dust-free cloth dipped in alcohol or acetone to clean the heating surface of the heating plate, and then turn on the power supply of the heating plate to raise the temperature of the heating plate. When the temperature of the heating plate reaches the welding temperature, continue heating for about 10 minutes to make the temperature of the heating plate uniform.
7.3: place the heating plate on the track of the welding machine frame, start the hydraulic system of the welding machine, and make the end face of the PPH pipe to be heated close to the heater.
7.4: in the process of heating the end face of PPH pipeline, the hydraulic system of welding machine shall be kept at a certain working pressure to eliminate the residual non plane of the end face of PPH pipeline and make it fused evenly.
7.5: the working pressure of the hydraulic system during heating shall be reasonably selected according to the specification of the pipe (see table 5.2.6-1), but it must meet the requirements of the technical parameters of the PPH pipe manufacturer.
7.6: when the heating time reaches the specified time, operate the hydraulic system of the welding machine to make the pipe clamp at the movable end run reversely, make the heated pipe completely separate from the heating plate and make the hydraulic system stop working, at the same time, remove the heating plate quickly.
7.7: when removing the heating plate, the distance between the end face of the heated pipe section and both sides of the heating plate shall be controlled within 5mm.
7.8: for socket hot melting, the insertion depth of heating rod shall meet the requirements of socket depth. See the table below for the depth of hot melt, heating time, processing time and cooling time
8: Pipe welding
8.1: restart the hydraulic system of the welding machine, so that the end faces of the heated pipes can be squeezed and fused with each other under the action of external mechanical force, and the appearance of which is shown in the figure below
8.2: during extrusion and fusion, the flanging width of the end face of the pipe shall be observed. The flanging on both sides must be uniform and continuous (see the figure above). The flanging amount shall meet the requirements of the technical data provided by the material manufacturer.
8.3: the working pressure of the hydraulic system of the welding machine during hot-melt welding shall meet the requirements of the technical data provided by the PPH pipe manufacturer.
8.4: from the removal of the heating plate to the beginning of the hot-melt welding of the end faces of the two pipes, the switching time must be controlled within the time specified by the material manufacturer.
8.5: for the pipe connected by socket hot melting, the socket must be straight when inserting into the socket, and the insertion depth must reach the position of the mark line, so as to form a uniform convex edge at the joint (see the figure above)
9: Pipe cooling
9.1: after the flanging and width of the hot-melt weld meet the requirements, the work of the hydraulic system of the welding machine shall be stopped to keep the pipe clamp in the working position during welding, so that the hot-melt weld area starts to cool.
9.2: the cooling time of pipeline shall meet the requirements of technical data provided by PPH pipeline material manufacturer.
10: Appearance quality inspection of hot-melt weld
10.1: check whether the middle K value of the weld is greater than 0, i.e. the outer surface of the pipe must be lower than the lowest point in the middle of the weld (k > 0)
10.2: check whether the welded weld is clean.
10.3: check whether there are two weld beads after welding, and the deviation proportion of its width shall not exceed 50%.
10.4: check whether the weld is continuous and even.
10.5: check whether there are air holes in the weld after welding.
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