Welding polyethylene pipes: a comparison of methods + installation instructions

To assemble the wiring from polyethylene (PE) pipes, certain skills are needed in their welding and connection with fittings. For this work, equipment used for the installation of polypropylene pipelines is also suitable.

Welding of polyethylene pipes is carried out by special devices and requires certain knowledge, which we will talk about in this article. We will consider in detail the features of preparing equipment for the welding process, we will give recommendations for the implementation of a high-quality weld. We also consider various options for welding pipes made of polyethylene.

Preparation of equipment for welding

For each type of welding, different equipment is used. It makes no sense to buy it for a one-time assembly of communications by the butt and electric-welded method, because the cost of the kit is several thousand dollars. It is better to use the services of third-party companies or rent equipment.

Used welding equipment

Socket soldering equipment costs between $ 100-200, so the question of purchasing welding machine everyone decides on their own.

The standard set of devices for butt welding of polyethylene pipes includes:

1. Centralizer. This is a bed with 4 metal clamps for pipes, two of which are movable, and two are rigidly fixed to the base.
2. Trimming. It is a separate disk device for precise mechanical trimming of the ends of welded pipes. The device is attached to the guides of the welding machine.
3. Heating mirror. It is a rounded plate coated with Teflon, to which the joints of pipes for melting PE are pressed. Has a built-in thermometer.
4. Hydraulic or mechanical drive. A device for regulating the compression force of pipes when they are heated and subsequently connected.
5. Reduction liners. This is a set of interchangeable half rings for fixing pipes of various diameters.
6. Control block. Included in equipment kits with automation of the welding process.

In fact, a set of equipment is an independent device that performs certain functions at various stages of the welding process. They can be either designed for purely manual welding, or for connecting pipes in a fully automatic mode.

For the installation of electrofusion joints, an appropriate welding machine with an integrated barcode scanner is used. No additional devices are required for this process.

Butt welding is an advantage for pipes with a diameter of more than 50 mm, therefore, the equipment for it has a considerable size

For socket welding, it will be necessary to purchase such a kit:

• electric welding machine;
• pipe shears;
• stand;
• calibrator and chamfer;
• nozzles for heating the connected elements.

In addition to the specified equipment, for the installation of pipes, general business tools may also be needed: an adjustable wrench, a tape measure, a marker and others.

Preparation for the welding process

An important factor in the high-quality welding of pipelines from HDPE is their preliminary preparation. The necessary manipulations to form a good weld will be presented in the form of instructions.

Immediately before heating the soldered parts, you need:

1. Ensure that the material and marking of the soldered parts are identical.
2. To clear and degrease joints of the connected products.
3. Center the pipes and fix them firmly.
4. Trim the slices until a continuous tape is formed in two pipe circumferences.

After all, it is necessary to clean the edges of the connected parts from chips.

Electric trimmer significantly speeds up the installation process, especially for large volumes of work, but its cost is too high for a single job

After carefully preparing the polyethylene pipes and fittings for welding, you can be sure that a high-quality seam is half guaranteed.

Welding methods for PE pipes

Industrial low-pressure polyethylene (HDPE) is a thermoplastic material whose properties do not change during heating-cooling cycles. Therefore, it is perfectly suitable for the installation of domestic and industrial pipelines.

The connection of individual PND pipes and fittings to each other occurs using detachable threaded connections or the following welding methods:

• bell-shaped;
• electrofusion;
• butt.

Pipes with a wall thickness of up to 4.5 mm (diameter up to 50-110 mm) are soldered in the first two ways, and for thicker-walled pipes, a fittingless butt welding method is used.

HDPE is sensitive to elevated temperatures, therefore it is used only for water supply with a working temperature of up to + 40 ° C or its short-term increase to + 60 ° C

Option # 1 - butt welding mode

During butt welding, it is important to control critical parameters: tool and plastic temperature, clamping force and duration of operations. In the absence of sensors of these values, it is unlikely to be able to stably obtain a high-quality seam.

It is better to consider step-by-step instructions for butt welding of polyethylene pipes with the example of semi-automatic equipment with a hydraulic drive.

Butt welding is performed if the wall thickness of the polyethylene pipe does not exceed 5 mm and its diameter does not exceed 50 cm. The technology includes a number of standard steps:

Step # 1 - heating the joints

After processing the ends of the pipes, the welding mirror is heated to a temperature of 200-230 degrees and placed in the middle of the centralizer. Then, using a hydraulic drive, the edges of the HDPE pipes are pressed tightly against it with a force of 4-6 kg / cm2.

After approaching the size of the burr to the minimum allowable values, the force is reduced to 0.2-0.5 kg / cm2 and the plastic is continued to be heated for the entire standard time. Welding is permissible at temperatures from 15 frost to 45 heat, but in cold conditions, the heating time can be increased.

The clamping pressure is controlled by a pressure gauge integrated in the hydraulic mechanism. If it is absent, the necessary force is determined visually by the type of burrs formed

Step # 2 - pipe connection

After the necessary heating and melting of the PND at the joints, the pipes are hydraulically driven, the mirror is removed and the welded surfaces are pressed against each other again with a force of 1-3 kg / cm2. The size of the burr is visually monitored, and therefore the pressure may vary.

Excessive force during the fusion of the ends of the pipes harms no less than its insufficiency. This leads to the formation of a large inner roller, which will create vortex flows and reduce water pressure.

Step # 3 - cooling and inspection

The pipes continue to be pressed against each other until the connection is completely cooled.After removing the force from the hydraulic drive, the pipes are removed from the clamps of the centralizer, and the condition of the weld and burr is evaluated. If their parameters are normal, then the pipe is ready for operation.

Option # 2 - socket welding of HDPE pipes

After preliminary trimming and preparing HDPE pipes and parts, you can start their socket welding. The process will be reviewed as a step-by-step instruction.

Step # 1: preparing a soldering iron

The optimum temperature for welding polyethylene pipes ranges from 210 ° C, so only soldering irons with adjustable heating are suitable. Before connecting to the network, it is necessary to wind special double-sided nozzles (sleeve and mandrel) on the iron and put the soldering iron on the cross-shaped stand.

The greater the power of the soldering iron, the greater the number of PND pipes it can connect per unit of time. For homework, an 800-watt appliance will be enough

When the set temperature is reached, a signal (usually green) lamp will light on it.

Step # 2: heating the parts

It is safer to wear gloves when working with hot pipes. To heat the parts, it is necessary to simultaneously pull one connected part onto the mandrel, and then insert the second into a metal sleeve.

Attach and disconnect the PND parts with a soldering iron is necessary directly without rotational movements. A similar rule applies when connecting heated products.

To maintain the depth of the connection, you can pre-mark with a marker the corresponding mark on the pipe, and then navigate it when docking the heated products.

The data given in the table are approximate, and you should rely only on the information specified in the instructions for the welding machine

Above is a table with approximate time frames for heating, docking and cooling pipes, as well as the depth of insertion into the socket. At minus temperatures, the heating time of the material can be increased by 1-2 seconds.

Step # 4: connecting the parts

After warming up, the product must be simultaneously disconnected from the nozzles and with a strong direct movement enter the pipe into the socket to the marked line. It is impossible to twist the parts relative to each other. 5-10 seconds after joining, any movement can lead to a sharp decrease in the strength of the joint.

When connecting heated parts, their axes should be located as parallel as possible, since after 20-25 seconds it will be impossible to correct the curvature

After cooling, it is advisable to inspect the formed inner seam for the presence of sagging blocking the lumen of the pipe. If it is narrowed, it is better to re-solder the connection to prevent pressure drop in the system.

Option # 3 - electrofusion welding of polyethylene

Welding polyethylene pipes using an electrofusion coupling is the easiest and fastest way. Plastic fittings have a built-in metal spiral, which independently heats the connected surfaces and melts PE.

With this method, you have to additionally spend money on electric couplings, the cost of which starts with 3-4 dollars per piece. Therefore, such welding is used only in those places where butt and socket methods are not available. The advantage of the electrofusion method is the ability to connect pipes with a thickness of 4.5 mm or less.

The main stages of welding:

1. Cleaning and machining the fitting and pipe ends.
2. Centering and inserting the pipe into the electrofusion coupling.
3. Connecting the fitting to the electrical contacts of a special welding machine, heating the connection.

The last stage is a power outage and a cooling pipe.

The electrofusion butt joint is more durable than the pipe itself. In tensile tests, the pipe itself ruptures, and not the weld seam

There is a barcode on the electrical couplings with encoded parameters for the heating time, current and voltage.It is read by the scanner of the welding machine, which then carries out the soldering process in automatic mode. Products are tightly and securely welded over a large area.

Correct Butt Welds

The correct execution of all welding instructions can be assessed by the final appearance of the polyethylene compound. In the case of the formation of the wrong seam and a high risk of leakage during further operation, it is better to cut the connection around the edges and weld a new one.

In a correctly executed seam, the size of the burr roller should correspond to the standard values.

Regulatory parameters are calculated based on laboratory tests. Their observance guarantees high reliability of the joint and a long service life of the pipeline

There are additional requirements for the parameters of the rollers:

1. Symmetry and uniformity around the entire circumference of the joint.
2. The displacement of the walls of the pipes in the radial plane should not be more than 10% of their thickness.
3. The color of the rollers should be identical to the color of the pipe.
4. The hollow between the grates should not go deeper than the level of the outer surface of the pipes.

And of course, the presence of cracks and pores is completely eliminated.

1. Normal weld. The rollers of the right seam have round sizes and shapes that do not go beyond the established standards. 2. A seam with a small burr. A small burr indicates an insufficient warm-up time or a slight compression of the pipes during upset

3. Rollers with oversized dimensions. An enlarged weld may be the result of excessive temperature of the heating equipment or its malfunction. 4. Radial displacement of the rollers. The radial displacement of the pipes sharply reduces the strength of the connection and can lead to its rupture already at the laying stage

The cause of the asymmetry of the rollers around the circumference may be poor preliminary milling or the location of the miter at an angle to the pipe.

Polyethylene Pipe Installation Instructions

To connect polyethylene pipes with water supply elements, the following connections can be used:

• one-piece;
• detachable.

One-piece joints are obtained by soldering pipes to each other or to special welded fittings. This method is cheap, but the resulting designs are often cumbersome. The use of one-piece connections is justified when installing underground stationary water pipes.

To assemble temporary systems from polyethylene pipes, as well as in the absence of welding equipment, threaded compression fittings can be used, the installation of which will be discussed later.

Pipe connection to compression fitting

Compression fittings are more expensive than welded models, but they are collapsible and easy to operate. Recommendations for their installation are discussed in the following step-by-step instructions.

Step One - Exterior Inspection and Trimming

The assembly of the system from a polyethylene pipe and a plastic compression fitting begins with their inspection for cracks and deep scratches. It is better to cut off the defective pipe section immediately.

You can cut a plastic pipe with a knife and a special pipe cutter. The result should be a perfectly perpendicular cut without hooks and waves. To remove uneven edges, you can purchase a manual trimmer.

There are many types of pipe cutters, but they all have a wide base, which ensures a strictly perpendicular position of the pipe relative to the cutting element

Step Two - Putting Fittings on the Pipe

First, a clamping nut is put on the hose, then a collet, then a clamping ring, and at the end a rubber gasket is pulled.

The complete set of the fitting may be different, so it is important to remember the sequence of its elements when untwisting, in order to properly wear them when assembling the connection

The end of the pipe is inserted all the way into the fitting body, and the elements worn on the hose are pushed to the thread.After that, the clamping nut tightly twists by hand. If you have a chain key, you can tighten the connection to them.

It is not worth rushing to tighten the clamping nut - it can skew. With a tight course, it is better to unwind the connection once more and repeat the assembly process.

After fitting, it is worth checking the tightness of the connection. In the event of a leak, you can easily twist the nut by adjusting the structural elements.

Insert of a saddle into a pipe

If you need to make a branch from a polyethylene pipe, it is not necessary to buy a tee. It will be enough to drill a hole in it and put a saddle. How to do this will be discussed in a step-by-step instruction.

Step One - Preparation

Initially, you need to inspect the connected products for scratches and cracks and wipe their surface with a damp cloth.

Step Two - Clamp Assembly

Put both parts of the clamp on the pipe, tighten its nuts with a wrench. The purpose of the procedure is to firmly fix the saddle.

There are saddles that can be installed under a running water supply. They have a built-in mechanism that drills a hole without depressurizing the structure.

Step Three - Drilling

Mark a point in the center of the saddle hole, and mark the strip at the edges of the fitting with a marker to remember its position. Unscrew the saddle and remove its parts. Drill a polyethylene pipe in the intended place using a drill of the required diameter.

There are drills in the shell that allow you to make holes in pipes and recesses without risking damage to the surrounding walls.

Step Four - Assembling the Saddle

Clean the inside of the PE pipe from the chips and remove any hooks from the edges of the drilled hole. According to the marks drawn earlier, attach the parts of the fitting to the pipe and tighten the fixing nuts tightly.

Simple nurses may not be equipped with a clamping mechanism for connecting the pipe. In this case, it is recommended to wrap the threads of the attached fitting or pipe with tape.

When screwing a pipe or fitting into a nurse, you can wrap several layers of fum tape.

Part of the saddle with the outlet may have a groove for the rubber sealing ring on the pipe side. Therefore, in the presence of a sealant, it is necessary to put it between the pipe and the fitting.

If you need to bend the pipe in a certain section of the pipeline, we recommend that you do this according to the instructions, given here.

Conclusions and useful video on the topic

The proposed videos will clearly demonstrate all types of HDPE pipe welding, as well as acquaint with the assembly process of the compression fitting and saddle.

Socket welding of polyethylene pipes:

Electrofusion welding process:

Butt welding of PND pipes by a semi-automatic apparatus with a hydraulic drive:

Installation on a compression fitting pipe:

Installing saddles on the HDPE pipe:

The independent installation of polyethylene water pipes requires some knowledge and skills, but it is quite feasible subject to the above rules. In the absence of special equipment, it is possible to assemble a water supply system without tools at all, using only compression fittings.

There are many mounting options, but you need to use one that will provide a result with a minimum of financial costs.

Determine the best way to weld polyethylene and want to clarify some points? Feel free to ask your questions to our experts - we will try to help you.

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