Bonding Method of 1. UPVC/CPVC Pipe

UPVC/CPVC piping system is bonded with special adhesive, the specific steps are as follows:

 

 

1. Pipe cutting

The pipe can be cut with a chainsaw, pipe scissors or plastic pipe cutter. When cutting, ensure that the nozzle is vertical and flat, so that the pipe has a larger bonding surface when bonding.

 

2. Grinding

Remove burrs and filings inside and outside the tube cut with a fillet, file, or sandpaper so that the tube and fittings are bonded together.

 

3. Marking

Before connection, the socket depth shall be marked outside each pipe to prevent water leakage at the connection due to failure to insert the pipe into the bottom of the fitting during connection.

 

4. Apply adhesive

The adhesive surface of the pipe and the fitting shall be penetrated and softened with detergent to increase the dissolving effect of solvent viscose. Use a special brush to evenly apply the solvent on the outer surface of the pipe socket and the inner surface of the pipe socket.

 

Standard dosage of solvent

Nominal Outside Diameter （mm）	20	25	32	40	50	63	75	90	110	125	140	160
Cement Volume（g/piece）	0.40	0.58	0.88	1.31	1.94	2.97	4.10	5.73	8.43	10.75	13.37	17.28

 

5-Connections

After applying the adhesive, insert the pipe into the fitting immediately and rotate it by 1/4 turn. The pipe must be inserted into the bottom of the fitting. During the combination, it should be fixed for 10-15 seconds to ensure the initial combination (the combination of the pipe fittings above 6 ″ requires the cooperation of 2 people). The glue overflow around the joint point of the pipe and the pipe fitting should be obvious. If the glue overflow around the socket is discontinuous, it means that the glue applied is insufficient, if excessive overflow, wipe off with a cloth, glue can not be less smeared or smeared too much.

 

Precautions for Hydrostatic Testing of 2. UPVC/CPVC Piping System

 

1. The pressure test can only be carried out after 48 hours of installation for the bonded pipeline. The strength and pressure test of the pipeline can only be carried out after the trench backfilling meets the requirements.

2. The support of the tee and elbow on the pressure test pipe section, especially the pipe plug at the end of the pipe, should have sufficient stability. If the thrust block of concrete structure is used, there should be sufficient solidification time before the test to make it reach the specified compressive strength.

3. Block the end of the pressure test pipeline, slowly inject water, and discharge the gas in the pipeline at the same time.

4. After being filled with water, carry out watertight inspection.

5. Manual pump or electric pump should be used to pressurize slowly, and the boosting time shall not be less than 10min.

6. After rising to the specified test pressure, stop pressurizing, stabilize the pressure for 1h, and observe whether there is water leakage at the joint. If depressurization occurs, the pressure shall be supplemented to the specified test pressure value, and the pressure drop within 15 min does not exceed 0.05MPa, which is qualified.

 

3. PPR/PPH/PVDF pipe bonding method

 

1. Process requirements for hot melt socket welding

 

 

① Pipe cutting

Cut off the pipe according to the design requirements of the pipe. When cutting, ensure that the nozzle is vertical and flat, clean and free of oil. Use a file or sandpaper to remove the burrs and filings inside and outside the pipe incision.

 

② Marking

Before connection, the socket depth shall be marked outside each pipe to prevent water leakage at the connection place if the pipe is not inserted into the bottom of the fitting during connection.

 

③ Heating

The pipe end shall be introduced into the heating sleeve without rotation and inserted to the marked connection depth. At the same time, the pipe shall be pushed to the heating head without rotation and reach the specified depth mark.

 

④ Connection

The heating time must be in accordance with the following table. After the specified heating time is reached, the pipes and fittings must be immediately removed from the heating sleeve and heating head at the same time, and inserted into the marked depth in a straight line and evenly without rotation, so as to form a uniform flange at the joint. Within the specified processing time, the newly welded joint is allowed to be corrected immediately, but rotation is strictly prohibited. The pipes and fittings shall be fixed so that they are not subject to torsion, bending and tension.

 

Nominal pipe (mm)	Hot melt depth (mm)	Heating time (s)	Welding time (s)	Cooling time (min)
20	14.0	5	4	2
25	15.0	7	4	2
32	16.5	8	6	4
40	18.0	12	6	4
50	20.0	18	6	4
63	24.0	24	8	6
75	26.0	30	8	8
90	29.0	40	8	8
110	32.5	50	10	8

If the ambient temperature is lower than 5 ℃, the heating time is extended by 50%

 

2. Requirements for hot-melt butt welding process

 

① Five stages of hot-melt butt welding

Preheating stage-endothermic stage-conversion stage-welding stage-cooling stage.

 

② Preparation before welding. The following preparations shall be carried out before welding:

a) The influence of bad weather shall be prevented in the welding area;

B) Ensure that the tools and workpieces used are clean and the welding area is free of oil;

c) Clean the oil circuit joint and correctly connect all parts of the welding machine; measure the power supply voltage to confirm that the voltage meets the requirements of the hot-melt butt welding machine;

d) Set the heat absorption, cooling time and heating part temperature correctly according to the welding process. The hot plate of the first weld joint shall be preheated at the welding temperature for 10min.

 

③ Clamping pipes/fittings

Clamp two components to be welded on the hot-melt butt welding machine, flatten the pipe (pipe fitting) to be welded with the bracket, adjust the concentricity, adjust the two pipes (pipe fittings) to make them on the same axis, check the alignment, and the dislocation of the bonding surface shall not exceed the allowable size, I .e. 0.1 * the thickness of the pipe or the outer wall of the panel.

 

④ Milling welding surface

After milling, check the maximum gap width between the welding surfaces and meet the requirements of Tables 1 and 2 below:

 

Table 1 Maximum gap width between welded surfaces of PP pipes, fittings and panels after milling

Nominal outer diameter of pipe (dn)	Gap width	Panel width (B)
dn≤ 355	0.5
400<dn≤ 630	1.0	≤ 1500
630<dn≤ 800	1.3	1500<B≤ 2000
800<dn≤ 1000	1.5	2000<B≤ 2300
dn＞630	2.0	2300<B≤ 3000

Unit: mm

 

Table 2 Maximum gap width between welded surfaces of PVDF pipes, fittings and panels after milling

Nominal outer diameter of pipe (dn)	Gap width	Panel width (B)
dn≤ 355	0.5
400＜dn＜630	1.0	≤ 1500
400＜dn＜630	1.3	1500<B≤ 2000
400＜dn＜630	1.5	2000<B≤ 2300
400＜dn＜630	2.0	2300<B≤ 3000

Unit: mm

 

⑤ The centering pipe or pipe fitting reaches coaxiality

Check the end face of the pipe or fitting for uneven milling, voids or other defects, and if it meets the requirements, check that the end face is properly aligned.

 

⑥ Measurement and inspection of drag pressure

The closed rack is evenly and slowly pressurized. When the rack starts to move, the recorded pressure value is the drag pressure (pt). The drag pressure is not fixed, and each welding must be measured. The gap between the butt end faces must be less than 0.3mm; the misalignment of the welded parts must be less than 10% of the thickness of the welded parts.

 

⑦ Flat end face heat absorption

When the temperature of the heating component reaches the set temperature, the heating component is placed on the hot-melt butt welding machine. After the pressure is maintained to complete the specified flanging forming time or reach the specified flanging size, the pressure is adjusted to the hot-melt butt heat absorption pressure and the heat absorption time is maintained to reach the required time period without interrupting the contact of the pipe or pipe with the heating tool. Total welding pressure (p1)= drag pressure (pt) joint pressure (p2), the height of the entire circumference of the heating tool on both sides shall reach the specified value, and the pressure shall be reduced until the drag pressure (pt) starts to absorb heat. It is necessary to ensure that the heating tool is closely attached to the welding end face without any gap.

 

⑧ Switching and docking

After completing the heat absorption period, pull the end face of the pipe or pipe fitting apart from the heating component. After removing the heating component in a controllable manner, quickly butt the end faces of the molten pipe or pipe fitting together, and quickly increase the pressure to the total welding pressure (p1) of the hot-melt butt joint at a constant speed. High-pressure collision is strictly prohibited.

During alignment, press the bonding surface to be welded on the hot soldering iron until the whole surface is completely in contact with the hot soldering iron, and the surface is parallel to the surface. The formation of the flanging can be observed for determination. When the height of the flanging around the entire circumference of the pipe or the entire top of the panel reaches the required value, it is aligned.

 

Joint cooling

The joint after hot-melt butt joint connection shall be fixed in the hot-melt butt joint mechanism, and the required cooling cycle shall be completed in accordance with the pressure retaining cooling regulations in the welding machine.

 

⑩ Disassemble pipes/fittings

At the end of the cooling time, the pressure is reduced to zero and the welded tubes/fittings are disassembled.

 

PP pipe and pipe fittings hot melt butt welding process reference

Nominal wall thickness/mm	Alignment	Heating	Conversion	Welding
	Temperature of heating components 210 ℃ ± 10 ℃
	After the alignment time ends Height of flanging on heating element (min) (alignment p = 0.01N/mm2)/mm	Heating time ≈ 10e 40s (Heating p ≤ 0.01N/ mm2)/s	Conversion time （max）/s	Welding pressure Formation time/s	Cooling time under welding pressure (min) 【p=(0.10 0.01)N/ mm2】/min
6.0～7.0	0.5	135～175	5～6	6～7	6 to 12
7.0～12.0	1.0	175～245	6～7	7～11	12～20
12.0～19.0	1.0	245～330	7 to 9	11～17	20～30
19.0～26.0	1.5	330～400	9～11	17～22	30～40
26.0～37.0	2.0	400～485	11～14	22～32	40～55
37.0～50.0	2.5	485～560	14～17	32～43	55～70

 

PVDF pipe and pipe fittings hot melt butt welding process reference

Nominal wall thickness/mm	Alignment	Heating	Conversion	Welding
	Temperature of heating components 210 ℃ ± 10 ℃
	After the alignment time ends Height of flanging on heating element (min) (alignment p = 0.01N/mm2)/mm	Heating time ≈ 10e 40s (Heating p ≤ 0.01N/ mm2)/s	Conversion time （max）/s	Welding pressure formation time/s	Cooling time under welding pressure (min) 【p=(0.10 0.01)N/ mm2 t≈1.2e 2min】/min
6.0～10.0	0.5～1.0	95～140	4	5 to 7	8.5～14
10.0～15.0	1.0～1.3	140～190	4	7 to 9	14～19
15.0～20.0	1.3～1.7	190～240	5	9～11	19～25
20.0～25.0	1.7～2.0	240～290	5	11～13	25～32

 

4. PPR/PPH Hydrostatic Test Precautions

 

● The hydrostatic test should be carried out in sections, and the total length of the test pipe section should not exceed 500m;

● Before the test, the pipeline shall be fixed, the joint shall be open, and the water distribution device shall not be connected;

● The pressure gauge is installed at the lowest point of the test pipe section, and the pressure accuracy is 0.01Mpa;

● Slowly fill water into the pipeline from the lowest part of the pipe section, fully eliminate the air in the pipeline, and carry out water tightness test;

● Slowly increase the pressure of the pipeline. Manual pump should be used for the pressure increase, and the pressure increase time should not be less than 10min;

● After the pressure is raised to the specified test pressure, the pressure is stabilized for 1 hour, and the pressure drop shall not exceed 0.06Mpa;

● Under the condition of 1.15 times the working pressure, the pressure shall be stabilized for 2 hours, and the pressure drop shall not exceed 0.03Mpa;

● During the test, there shall be no leakage at each connection;

● Allow two pressure supplements within 30 minutes and rise to the specified test pressure.