Overview of cast iron pipes for water supply

The cast iron pipe has been widely used for many years in the laying of the sewer system. Over time, heavy metal began to be replaced by plastic products. Since the nineteenth century, cast iron pipes have been actively used in the construction of plumbing systems in large cities. For example, in Peterhof, water is still supplied to the fountains through a cast-iron water supply system. And there is no need to change it in the near future.

Steel or cast iron

Long-term operation of the water supply system is not relevant in urban areas. The changing face of the city, in which something is constantly being demolished or rebuilt, requires a completely different approach to the implementation of the water supply part of the urban infrastructure. The optimal service life of the water supply system is 40-50 years. Further exploitation is unprofitable, because urban development requires a different, more rational pipe layout.

Cast-iron highways began to give way to steel ones. The latter are economically viable, the method of their installation is much easier. This applies to the technology of connecting the elements of the water supply network to each other, where simple electric welding is used, and not chasing, which is used to seal cast iron.

However, there are cast iron pipes on the market, since there are still requirements for water supply networks that only this material meets.

State standard

GOST for cast iron pipes for water supply was introduced during the Soviet Union in 1977. The standard has changed occasionally, with the last amendments being made in 2011. Changes made in 1995 became the basis of the standard, therefore the modern GOST has the number 9583-95.

Dimensional parameters

The length of the products is a fairly wide range, in which the minimum value is 2 m, the maximum is 10 m. In this case, the length multiplicity is 1 m. Manufacturers also offer non-standard pipes, the length of which varies in the range of 2.5-10.5 m.

Diameter (bore) and wall thickness are directly dependent on each other. But in the GOST it is indicated that pipes made of cast iron for water supply can be divided into three classes, which are based on the thickness of the wall: "LA", "A" and "B".

In the table of diameters, all ratios are well shown:

Depending on the indicated parameters, the weight of the tubular product changes. The minimum value is 11.3 kg of one running meter, which corresponds to the "aircraft" class with a diameter of 65 mm and a wall thickness of 6.7 mm. The maximum value is 627 kg / running meter, which corresponds to a class “B” pipe with a diameter of 1000 mm and a wall thickness of 27 mm.

Requirements

The GOST clearly stipulates what requirements are imposed on the size of cast-iron pipes for water supply. They mainly relate to technological tolerances, that is, deviations from the nominal dimensions:

• length deviation to the smaller or larger side - 20 mm;
• wall thickness - 0.5-1;
• outer diameter up to 300 mm - 4.5;
• above 300 mm - 5;
• inner diameter - 1-1.5.

Ovality of the pipe is not considered a defect. The main thing is that the deviations do not exceed the guest standards. The weight of cast iron products should not exceed 5% of the norm.

At the production site, all batches of cast iron pipes undergo a mandatory pressure test. Testing is performed with water, which is pumped under pressure into the test piece. The nominal pressure is determined by the product class:

• pipes with a straight-through diameter up to 300 mm are tested by pressure: for class "LA" - 25 kgf / cm², for "A" - 35, for "B" - 40;
• diameter from 300 to 600 mm: class "LA" - 20, "A" - 30, "B" - 35;
• more than 600 mm: "LA" - 20, "A" - 25, "B" - 30.

Usually, in the water supply system, water moves under a pressure of 3-4 kgf / cm². So the tested pressure is enough to speak of a large strength reserve.

Both ends of the pipe are cut perpendicular to the axis of the product. Deviations are allowed, but not more than 0.5 °. The transition plane from the socket to the pipe can be produced in two versions: in the form of a slope or in the form of a ledge.

The standard requirement is to cover cast iron pipes from the outside and from the inside with a protective coating that should not reduce the quality of the pumped water. In this case, the applied coating should not cause a decrease in the sealing of the joints. Manufacturers are ready to supply pipes made of cast iron without protective material, if such are the requirements of customers.

Rules and nuances of installation

Cast iron water and sewer pipes are connected by a bell-shaped method. Products are manufactured with two different ends. When connecting pipes, the small end is inserted into the large one. But with such a connection, it is impossible to achieve maximum tightness of the joint. In addition, the water inside the water supply network moves under pressure.

The main method of sealing is embossing with a bobbin. It is an organic fiber treated with technical oil. The fibers are twisted and placed in the opening between the inner plane of the socket wall and the outer plane of the pipe. After that, a seal is made with the help of chasing, on which they beat with a hammer from above.

It is not enough to lay and seal the cable. It is important to protect the oiled tourniquet from bacterial attack, as well as moisture changes and mechanical stress. Therefore, the joint is additionally filled with various durable materials. Here are some options:

• Cement of the M400 brand. It is diluted with water in a ratio of 1: 9. The mixture is filled in the inner space of the socket and coined until it is completely filled. After that, the junction is closed with a wet rag for a day.
• Expanding cement. According to the recipe, it is diluted with water and poured into the junction. There is no need to mint the material.
• A mixture of cement and asbestos in a 1: 2 ratio. The dry mixture is diluted with water and minted in the same way as in the first case.
• Molten sulfur and kaolin. The latter in the total volume is 10-15%. The mixture is a liquid substance, therefore it can only be used in vertically installed risers.
• Lead. It is used in molten form.
• Lead in the form of a rod. It is laid on top of the bobbin and raked so that it completely covers the entire plane.

It is possible to repair pipes only if the defects are minor. If the flaws are large, clamps made of steel or cast iron pipes are applied on top.

The cost of cast iron water pipes

The price of cast iron pipes for water supply depends on the diameter, wall thickness, the presence or absence of a protective coating. A few examples:

• a ductile iron pipe with a diameter of 100 mm, covered with a protective varnish costs 6200 rubles;
• 300 mm with protective varnish - 20,000 rubles;
• 1000 mm - 270,000 rubles.

Manufacturers offer cast iron pipes with a galvanized surface. They have improved performance, but the price is slightly higher.