What Is a Cast Iron Pipe?

Cast Iron Pipe, a pipe cast from cast iron Cast iron pipe is used for water supply, drainage and gas pipelines. It includes cast iron straight pipes and fittings. Low labor intensity. According to different casting methods, it is divided into continuous cast iron pipe and centrifugal cast iron pipe, of which centrifugal cast iron pipe is divided into two types of sand and metal. Divided into gray cast iron pipe and ductile iron pipe according to different materials. According to different interface types, it is divided into flexible interface, flange interface, self-anchored interface, rigid interface and so on. Among them, the flexible cast iron pipe is sealed with a rubber ring; the flange interface cast iron pipe is fixed with a flange, and the inner flange is sealed with a rubber flange gasket; the rigid interface is generally a cast iron pipe with a larger socket. Basically eliminated.

According to its manufacturing method, it can be divided into: sand type centrifugal socket straight pipe, continuous cast iron straight pipe and sand type iron pipe.

According to the material used, it can be divided into: gray iron pipe, ductile iron pipe and high silicon iron pipe.

1. Water supply cast iron pipe:

Water-supply cast iron pipes use cast iron with a size of 18 or more. After adding nodulizing agent, the pipes are made by centrifugal nodular cast iron machines and centrifuged at high speed. The effect is good, the installation is simple, and it is mainly used for municipal water supply, gas and oil transportation. It is the first choice for water supply pipes and has a high cost performance.

2. Sand type centrifugal cast iron straight pipe:

Sand type centrifugal cast iron straight pipe is made of gray cast iron, which is suitable for conveying pressure fluid such as water and gas.

3. Continuous cast iron straight pipe:

Continuous cast iron straight pipe is the continuous cast gray cast iron pipe, which is suitable for the transportation of pressure fluid such as water and gas.

4. Drainage cast iron pipe:

Ordinary drainage cast iron sockets and fittings. Flexible anti-seismic drainage cast iron straight pipe. This cast iron pipe is sealed with rubber rings and bolted. It has good flexibility and flexibility under internal water pressure. It can adapt to large axial displacement and lateral deflection, and is suitable for indoor drainage pipes of high-rise buildings, especially suitable for seismic areas. From the interface form, it can be divided into: W-type flexible cast iron drainage pipe, B-type flexible cast iron drainage pipe, A-type flexible cast iron drainage pipe.

Continuous gray cast iron pipe

The connection between the tube and the socket adopts the socket or flange type interface; according to the function, it can be divided into two types: flexible interface and rigid interface. The flexible interface is sealed with a rubber ring, which allows a limited number of corners and displacements, so it has good shock resistance and tightness. It is simpler and faster to install than a rigid interface, and it requires less labor according to different casting methods.

GB / T 13295-2013 "Ductile iron pipes, fittings and accessories for water and gas pipelines"

GB / T 17457-2009 "General requirements for centrifugal lining of nodular cast iron pipe cement mortar"

GB / T 17458-1998 "Inspection of freshly mixed mortar of nodular cast iron pipe cement mortar centrifugal lining"

GB / T 17459-1998 "Asphalt coating of ductile iron pipe"

GB / T 17456 -2009 "Surface-painted zinc for ductile iron pipes"

GB / T 17219-2001 "Safety Evaluation Standards for Drinking Water Transmission and Distribution Equipment and Protective Materials"

GB / T 12772-2008 Flexible joint cast iron pipes, fittings and accessories for drainage

Engineering Standard

GB50242-2002 "Code for Construction Water Quality Acceptance of Buildings and Heating Engineering"

Related standard diagram

10S505 "Flexible Interface Water Pipe Support Pier"

China's ductile iron pipe production enterprises are mainly concentrated in Liaoning, Shandong, Hebei, East China and other regions, but there are very few tube production enterprises in South China, Southwest, and Northwest China. At present, with the development of China's economy and the implementation of the western development strategy, the South-to-North Water Transfer Project, the West-to-East Gas Pipeline Project, and the transformation of old urban pipe networks are increasing day by day.

After adding nodulizing agent to cast iron with size 18 or higher, it is made by high-speed centrifugal casting using a centrifugal nodular cast iron machine.

Ductile iron pipe is a type of cast iron pipe. In terms of quality, the spheroidization level of the cast iron pipe is controlled to be 1-3 (spheroidization rate> 80%), so the material itself is mechanical

Ductile iron pipe finished product warehouse

Can be better improved, with the nature of iron, the properties of steel. The annealed ductile iron pipe has a metallographic structure of ferrite plus a small amount of pearlite, good mechanical properties, excellent corrosion resistance, good ductility, good sealing effect, easy installation, and is mainly used for water supply and gas transportation in municipal and industrial and mining enterprises , Oil transportation, etc.

A certain amount of spherical graphite is distributed on the ferrite and pearlite substrates. The ratio of ferrite and pearlite in the matrix structure is different according to the nominal diameter and the requirements for elongation. Generally not more than 20%, the general control of large diameter is about 25%.

Minimum tensile strength: 420 / Mpa

Minimum yield strength: When the nominal diameter is DN100 1000 and the elongation after breaking is 12%, the allowable yield strength is 270MPa;

Or when the nominal diameter DN> DN1000 and the elongation after fracture 10%, the allowable yield strength 270MPa; in other cases the yield strength 300MPa.

Standard: GB / T13295-2013, ISO2531-2009

Caliber: DN80-DN2600

In 1947, the British H. Morrogh discovered that when cerium was added to the hypereutectic gray cast iron so that the content was more than 0.02wt%, the graphite was spherical. In 1948, the United States APGanganebin et al. Pointed out that when magnesium was added to cast iron and then fertilized with ferrosilicon, spherical graphite was obtained when the residual magnesium content was greater than 0.04 wt%. Since then, large-scale industrial production of ductile iron has begun. The history of the use of ductile iron pipes can be traced back to the water line of about 21.14Km from the Seine to Versailles in the suburbs of Paris in 1668. 300 years have passed. Except for the repair and replacement of some pipes and joints, the body is still in use.

Status and Prospects of Ductile Iron Pipes in China

China's ductile iron pipe industry started in the early 1990s, and developed rapidly with the strong support of the China Urban Water Supply Association. After nearly 20 years of practical use, its safety and practicability have been generally recognized by the water supply industry. The annual output has reached 2.2 million tons, which is 11 times that of 1990. As China is a country with insufficient water resources, there are more than 600 cities with water shortages and more than 200 cities with severe water shortages. The water supply and water saving business is still in the ascendant. Ductile iron pipes have broad development prospects.

1.Trench excavation

The bottom width of the groove should be calculated as follows: B = D1 + 2 (b1 + b2)

Where: Bexcavation width at the bottom of the pipeline trench (mm) D1outer edge width of the pipeline structure (mm) b1width of the working surface on one side of the pipeline (mm) b2support width on one side of the pipeline (mm)

Groove support

The design is based on factors such as trench soil, groundwater, slotted section, and load conditions. It is required to be firm and reliable, to prevent landslides, and support not to hinder the downpipe and stabilize the pipe.

3. T-junction pipes should be provided with pieres at vertical or horizontal turns. The size of the pier should be determined by calculation based on factors such as pipe diameter, corner, and working pressure.

4. When transporting drinking water, the pipeline should not pass through the area polluted by poisons. If it must be passed, protective measures should be taken.

5. Ductile iron pipelines with socket connections must be calculated to set up pier, see National Building Standard Design Atlas 03SS505 "Flexible Interface Water Supply Pipe Pier".

6. The outer anti-corrosion coating of ductile cast iron pipe should be selected according to the soil conditions of the pipe to be coated with galvanized and epoxy asphalt coating or higher requirements.

7. After the pipeline is installed and the pressure test is qualified, it should be washed with low chloride ion water and sterilized with 0.03% potassium permanganate solution.

Flexible cast iron pipe

From the composition of the piping system, cast iron drainage pipes can be divided into three categories: straight pipes, pipe fittings and auxiliary parts.

From the interface form, it can be divided into:

It is suitable for socket-type and indoor and outdoor pipe diameters of DN50mm ~ DN300mm and internal pressure not greater than 0.3MPa for new, expanded and reconstructed civil and industrial buildings.

At present, there are many domestic manufacturers of flexible cast iron drainage pipes, and the quality and performance of W-type cast iron pipe manufacturers are uneven. Choosing the right manufacturer in accordance with the specifications is always a guarantee for the smooth progress of construction, and it is also one of the foundations for easy maintenance during the warranty period after completion of construction.

1 underground, then ground;

2 first large tube, then small tube;

3 Supervisor first, then branch.

1. The W-shaped pipe adopts flat mouth connection, which has high requirements on the quality of the pipe, and has higher requirements on the outer diameter ellipse, wall thickness and physical properties of the rubber ring of the drainage cast iron pipe.

2. The installation and construction of the W-shaped pipe should be strictly performed in accordance with the operating procedures. Especially in the installation of straight pipes, a riser card should be used to fix the riser on the load-bearing wall of the building at each pipe joint; a hanger should be installed at each joint of the transverse pipe ^[1] .