Connection of HDPE pipes with a metal pipe: features, practical recommendations and reviews

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

When various kinds of water and heat supply systems are being equipped, it becomes necessary to connect metal pipes with plastic ones. To solve this problem, you can use one of many options, but the main ones involve the use of flanges and the threaded interface method.

Main types of connections and their characteristics

If you decide to connect HDPE pipes to metal pipes, then it is important to familiarize yourself with the basic technologies for the work. When threading metal pipes with HDPE of small diameter up to 40 mm, it is best to use fittings that have a thread for a metal pipe. At the same time, couplings are often used for these purposes. However, they are not used to connect HDPE pipes to metal. But for the articulation of polypropylene elements with each other, they are the best fit. To do this, purchase a smooth connecting element. In order to obtain a reliable sealjoints, you should use flax fiber, which is pre-processed in drying oil. This is true when assembling steel pipes. If we are talking about a flange connection, where pipes of a larger diameter are used, then elements with a diameter of up to 600 mm can be mated. In this case, twisting is carried out manually. Below we will consider the connections of polypropylene pipes according to the method of using threads. Whereas the flange joint is best used in conjunction with polypropylene and polyethylene pipes. But it is worth noting that these compounds can be used for both types of products.

Applications of threaded fittings

In order to install polypropylene pipes, which have metal parts in the form of filters, pipes, meters and mixers, you can use fittings with a thread of the desired diameter. This element will be located on one side, while on the other there should be a coupling for soldering a plastic pipe. Thread for fittings can be external or internal. The connection of HDPE pipes with fittings is carried out according to the following method. First you need to unscrew the metal pipe coupling in the place where it should be connected to the plastic element. Otherwise, a part of the steel pipe can be cut off, while the resulting edge must be treated with oil or grease, forming a new thread with the appropriate tool. At the next stage, the thread is wiped, fum tape or tow is wound on it, the surface is lubricated with silicone. Vitkovshould not be more than two, the edge of the tape when clamping should be directed along the thread. Without using a wrench, screw the press fitting to prevent cracking. If, after starting the system, water began to flow, then tighten the fitting.

Work methodology

When a HDPE pipe connection is made, the steel element can be mated with a fitting. Polypropylene elements will allow you to form different bends and turns in the system. The configuration of the fitting can also be changed, for this it is necessary to warm it up with a building hair dryer, however, the temperature should not exceed 140 °. Polypropylene will ignite if the temperature is above 350 °, which is why you should not allow the possibility of overheating. Polypropylene products expand and contract when exposed to temperature, so when using them for arranging a heating system or supplying hot water, it is necessary to install pipes under a layer of plaster. In this case, the gap in the strobes should be approximately one centimeter, while tubular insulation should be located around the tees and bends.

Flange applications

Connection of HDPE, PVC pipes with metal can be carried out by means of flanges. In this case, it will be possible to obtain a detachable connection, for which flange bushings are used. They are welded to the ends of the products. Otherwise, overhead flanges, which are made of metal, can be used. If inin the process of work, you will use a HDPE pipe, the methods of connecting this element with metal pipes may involve the use of flanges. This technology is applicable if the pipe has steel components (valves, pumps can be included in this category). Among other things, a detachable connection is relevant when there is a need to disassemble the pipeline during operation. Such a need arises during repair and cleaning. Flange connection is advisable to use for pipes of large diameter. On sale you can find the so-called free-type flanges, they are based on collars and are most common when working with plastic pipes. Loose flanges can match the dimensions of the metal parts of pipelines.

For reference

When HDPE pipes are connected to metal ones using flanges, it should be noted that the latter should be free of burrs and sharp elements. If present, polyethylene products may be damaged.

Recommendation from a pipe flange specialist

Loose flanges have been described above, which are most often used for heavy and medium-sized polyethylene products, the diameter of which does not exceed 150 mm. Among other things, such connecting elements can also be used for light pipes, while their diameter should not exceed 300 mm. In order to achieve an increase in the strength of the connection, you can use a directcollar with a conical transition. Loose flanges can be used to connect pipes with diameters greater than 200 mm. The wedge connection, which is characteristic of curly flanges, can be used for pipes of any diameter.

Recommendations for working with flanges

When HDPE pipes are connected to metal ones using flanges, the pipe is cut off at the junction, while the cut should be as even as possible. A metal flange is put on the pipe, then a rubber gasket. It should not be allowed to protrude beyond the pipe cut, but the maximum value of the overlap is 10 mm. The flange should be pushed onto the gasket, and then connected with bolts. The bolts should be tightened evenly, the force is applied only until you feel resistance. When working, you must be guided by the specification that is attached to the component parts.

Features of connecting HDPE pipes

The connection of HDPE pipes is also carried out in everyday life quite often. To create a detachable connection, you can use flanges, which are the most common type of fastening. This is due to the fact that in the process of work there is no need to use welding. It will be most convenient to use water pipes, the diameters of which start from the mark of 50 mm. If we are talking about a smaller diameter, then fittings or special clamps should be used, which are sometimes replaced by clamps. Flanges can be used to connect copper, cast iron ormetal pipes with polyethylene. In order to connect HDPE pipes with compression fittings, it is necessary to correctly prepare the pipeline. To do this, the plastic element is cut at a right angle. At the next stage, work must be carried out according to the technology described above, however, in this case, two pipes will turn out to be plastic.

Features of connecting pipes from different materials

If you decide to connect a HDPE pipe to a metal pipe, then it is highly discouraged to save money by trying to seal a plastic pipe with cement joints or embossing technology. In the latter case, the plasticity of polyvinyl chloride or polyethylene will fail, since it will be impossible to achieve a tight connection. In addition, the pipelines are deformed. In other cases, one should remember the coefficient of thermal expansion of plastic. If hot water is drained several times, the connection will simply loosen and lose its original tightness. If there is a need to connect a HDPE pipe to a metal pipe, but it was not possible to find a sealant for sale, then the problem can be solved by using microporous rubber. From an old car carpet, you need to cut a long narrow tape, which can be wrapped around the joint, tamping the material inside with a blunt wide screwdriver.