one. definition
Ductile iron pipe is mainly called centrifugal ductile iron pipe. It has the essence of iron, the performance of steel, excellent anti-corrosion performance, good ductility, good sealing effect and easy installation. It is mainly used for water supply, gas transmission and transportation of municipal and industrial and mining enterprises. Oil, etc. It is the first choice for water supply pipes and has a high cost performance. Compared with PE pipe, from the installation time, the spheroidal tube is easier and faster to install than the PE pipe, and the internal and external bearing pressure is better after installation; from the perspective of airtightness and corrosion resistance, the airtightness of the spheroidal pipe after installation is better. Corrosion resistance can be improved by various anti-corrosion methods; from the hydraulic performance point of view, the size of the spheroidal tube generally refers to the inner diameter, and the PE tube specification generally refers to the outer diameter. Because of the same specifications, the spheroidal tube can achieve greater runoff; In terms of comprehensive installation and maintenance cost, the spheroidal tube has a more superior cost performance. The main components of ductile iron pipes are carbon, silicon, manganese, sulfur, phosphorus and magnesium. Zinc spray on the inner wall, anticorrosive materials for cement mortar, etc. Advantage:
The tensile strength is high, which is three times that of the usually gray cast iron pipe; the resistance is good and the elongation is high, 5-15%. Impact resistant, sensation resistant, corrosion resistant, ductile iron pipe manufacturers are better than steel pipes. The price is higher, only slightly lower than the steel pipe.
Although its corrosion resistance is better than that of steel pipes, its pipe wall is thin, and it is buried in the soil. The speed of corrosion and perforation is much faster than that of gray cast iron pipe. If external corrosion protection is not enough, corrosion perforation will occur in almost 5-8 years. The corrosion rate of the pipe in the corrosive soil is 0.5-1.5mm/a, so the external corrosion of the spheroidal tube must be done according to the demand, and this is not easy to ensure in the production, construction and installation, and the accident is hidden.
The lining is usually coated with cement mortar. In some cases, the cement mortar fabric will affect the water quality. The experiment indicates that if the mortar is corroded by water capable of dissolving lime, the mortar will be lost, the mortar will be damaged, and the water will be alkalized. The pH value is increased, the chlorine consumption is increased, and the effect of water disinfection is affected. And because the function of cement and cast iron is different, under the conditions of external impact, internal pressure, temperature change, etc., the cement mortar fabric is more likely to crack, causing moisture to enter, or even fall off, forming a water resistance increase, affecting water quality.
Second, the anti-corrosion treatment of ductile iron pipe
Asphalt paint coating
Asphalt paint coating is a pipe used to transport gas. Preheating the pipe before painting can improve the adhesion of the asphalt paint and accelerate drying
2 cement mortar lining
Special coating This internal anti-corrosion measure is suitable for pipes that transport sewage, which can improve the corrosion resistance of the lining.
3. Epoxy coal tar pitch coating
Epoxy coal tar pitch coating is suitable for both gas pipelines and sewage pipelines. It is a two-component coating with high adhesion and a very smooth surface
4. Epoxy ceramic lining
Epoxy ceramic lining is suitable for sewage pipes and gas pipes, but due to the difficulty in manufacturing process and high cost, it has certain limitations in use. Epoxy ceramic lining is an excellent anti-corrosion coating with high adhesion and finish.
5. Aluminate cement coating and sulfate cement coating
These two special cement coatings are suitable for internal corrosion protection of ductile iron pipes for sewage pipelines.
Improve the ability to resist the erosion of acid and alkali components in sewage.
6. Polyurethane coating is a special coating, a high-grade coating
Second: the performance of anti-corrosion treatment of ductile iron pipe
A ductile iron pipe is a type of cast iron that is an alloy of iron, carbon and silicon. Graphite in ductile iron is stored in the form of spheres
In general, the size of graphite is 6-7, and the quality of the cast tube is required to be controlled to 1-3 grade (spheroidization rate ≥ 80%).
Therefore, the mechanical properties of the material itself are 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, and has good mechanical properties.
Third: standard and selection of ductile iron pipe
Product standard GB/T 13295-2003 Ductile iron pipe, fittings and accessories for water and gas pipeline GB/T 17457-1998 Ductile iron pipe cement mortar Centrifugal lining General requirements GB/T 17458-1998 Ductile iron pipe cement mortar centrifugation Ingredient test of lining fresh mortar GB/T 17459-1998 Ductile iron pipe asphalt coating GB/T 17456 Ductile iron pipe surface zinc spray GB/T 17219-1998
Safety evaluation criteria for drinking water distribution equipment and protective materials for drinking water
2.
Engineering Standard "Code for Acceptance of Construction Water Supply and Drainage and Heating Engineering Construction" GB50242-2002
3. Relevant standard figure 03SS505 "Flexible interface water supply pipe buttress"
Selection suggestion
1 The selection of ductile iron pipe should be based on the specific conditions of the laying site, and the interface form of the straight pipe and the fitting should be selected.
2 It is recommended to use EPDM rubber ring for rubber ring.
3 Coating selection:
The appropriate coating is selected according to the internal and external conditions at the time of use. The existing inner coating is a new product of ductile iron pipe such as epoxy resin, ester inner and outer coating, PE film coating, etc., and the performance should be understood in detail when selecting.
Fourth: precautions when installing ductile iron pipe
1. During the transportation process, due to the problem of loading and unloading method, it may cause the pipe socket to be elliptical. The tube below DN400 will cut off the ellipse. If it is larger than 500mm, rebuild the garden with special tools, then carry out cement lining repair on site, cement mortar composition. (weight ratio) as follows: 2 parts of cement, 3 parts of sand, 2 parts of water, 1 part of additive, stir well, clean up the sand and debris before repairing, then soak the area around with water; Water accumulation, repair surface should be smoothed, plastic cloth covered with health;
2. The groove under the first branch pipe is positioned according to the center line of the pipe toward the water flow direction, and then each pipe is inserted into the front pipe socket according to the elevation.
The small tube observes whether the socket line is in place, and the large tube observes the interface gap in the tube, and the minimum gap should be no less than 3 to 5 mm.
From the second branch, a 2T-8T tensioning guide chain is placed on both sides of the axial direction of the pipe body to ensure uniform interface clearance.
It also solves the problem of the tube shifting down when the design has a slope. Straight line segments are not allowed to be installed at an angle from top to bottom, such as
When the terrain must be deflected, the angle of rotation below DN1400mm can be 1.5 degrees to 3 degrees, and the maximum angle of the tube above DN1600mm
Must not exceed 1.5 degrees;
3. The installed pipeline cannot be in a serpentine state. If the construction team is required to make adjustments, keep the pipeline in a straight line;
4, the apron is stored in a cool and closed place;
5. The gutter sand cushion should be flat, and no large local bulges are allowed. The installed pipe should be checked to see if the pipe is suspended.
phenomenon;
6. Check whether the pipe is displaced when backfilling, including up and down and left and right;
7. Requirements for backfill: The lifting distance per 200mm below the centerline of the pipeline should be compacted once, the soil compaction density is greater than 90%, and the height of each 500mm above the pipeline centerline should be compacted once, the soil compaction density is greater than 85%, when backfilling want
Responsible and supervised;
8. When there are special requirements, the interface part can be set aside, and the middle of the pipe body should be fully backfilled to avoid the tube floating and the overall test.
The tube body moves during the pressing process;
9. It is not necessary to specially select the backfill soil for the ductile iron pipe. But the part that is in direct contact with the pipe is preferably sand.
The good soil or sand in the sub- or trench is used for backfilling, which is more economical;
10. In the case of weak soil, it is best to backfill the center of the pipe diameter with sand, which also has a good effect. Special attention,
Do not sink the installed pipe;
11. The groundwater should be drained as much as possible to avoid the foundation being blistered, and the softening of the foundation caused by the foundation is extremely important for the construction of the southern region;
12. It should be noted that the sides of the pipe are uniformly filled with soil sand, and the bottom of the pipe should also be fully surrounded by soil sand;
13. If the newly connected pipe is not fully filled or backfilled, water in the ditch may cause it to float. The water in the ditch may be groundwater or rain.
Fifth: design requirements for ductile iron pipes
1. The buried depth of the pipeline should be determined according to factors such as the degree of freezing, the external load and the intersection of other pipelines. Under normal circumstances, the depth of burial can be 0.2 meters below the freezing line, and meet the following conditions: when the pipe diameter is greater than 100mm, the top of the pipe is buried
The depth is 1.20 meters.
2. The bottom width of the design groove is generally 0.5 m of the outer diameter of the pipe, and the slope of the excavation is determined according to the soil condition, and the groove cross-sectional view is drawn.
3. The ductile iron pipe is the same as other pipes, and the head loss along the uniform flow is also hf=λ/dv2/2g, the difference is only
"λ" (hydraulic friction coefficient), that is, the head loss can be calculated according to the local resistance loss of the original cast iron pipe.
Sixth: cleaning method of ductile iron pipe
First clean the adhesive on the apron, bend the apron into a plum-shaped or 8-shaped shape into the socket, and press it along the entire apron by hand, or use a rubber mallet to tamper with it. Make sure that all parts of the apron are not twisted and twisted, evenly stuck in the groove, and then evenly apply the lubricant to the inner surface of the apron installed on the socket. When applying the lubricant on the outer surface of the socket, the socket other than the socket should be inserted. Brush all the parts. Finally, the tube should be lowered to the bottom of the tank as required by the tube, usually by manual or mechanical down tube method.
Seventh: spheroidal graphite cast iron pipe installation method
Installation points:
1. Clean the nozzle: Remove all the debris in the socket and clean it.
2, cleaning the rubber ring, the upper rubber ring: wipe the adhesive on the rubber ring clean, bend the rubber ring into a "plum blossom" or "8" shape
Into the socket groove, and press it along the entire apron by hand, or use a rubber hammer to ensure that the various parts of the apron are not twisted,
Evenly stuck in the slot.
3. Apply lubricant to the outer surface of the socket and the apron: apply the lubricant evenly on the inner surface of the apron installed on the socket.
When applying lubricant to the outer surface of the socket, brush all the sockets other than the socket wire.
4. Lower tube: The tube should be lowered to the bottom of the tank according to the requirements of the tube, usually by manual lower tube method or mechanical lower tube method.
5. Install equipment: Install the prepared equipment in place. Be careful not to clean the parts when installing.
Pollution again.
6. Push the tube to insert it into the socket: During installation, it is more labor-saving and smooth to insert the socket into the socket. First will
Insert the socket into the socket and press the socket onto the rubber ring in the socket. Connect the wire rope and the chain and tighten the chain until the socket is inserted.
The sockets are all in place, and a gap of about 2 mm should be left between the socket and the socket, and the distance from the outer edge of the socket to the apron is guaranteed.
Consistent.
Seventh: application field of ductile iron pipe
1: Industrial field
Ductile iron pipes are designed to have a threefold safety factor, which not only guarantees the entire fire protection system, including valves and
The fire hydrant is a complete and consistent ductile iron product, and fully meets the requirements of the fire piping system.
2: Agricultural irrigation
For a long time, the requirements of agricultural irrigation for pipeline sealing performance are not as strict as drinking water. Now with the water resources
This concept is changing as it becomes increasingly scarce and costs increase. In order to ensure long-term impermeability for long-term, agricultural irrigation pipe network
Must be able to resist soil movement, the passage of agricultural machinery, water hammer (because of the start of the water pipe and the sudden stop of the water discharge)
And any other possible accidents (such as the impact of a hoe). Ductile iron pipe is adaptable, it is easy to expand, or revised
(At the same time do not destroy) the original pipeline. Ductile iron pipe systems have a high safety margin to meet the above conditions.
3: Small hydropower station
Current small or satellite hydropower generation is a newly developed but fast-growing area, usually
It is operated by local enterprises or private capital. In this field, ductile iron pipes have the ability to resist internal high water pressure.
There is also excellent resistance to external pressure on the soil, allowing pipes to be buried in deep pits and valleys.
4: water pipe
The first step in the water cycle is to draw water from underground aquifers, lakes and rivers. We rely on natural water, so we must also cherish it to make them suitable for drinking. From water withdrawal to storage, groundwater requires a series of treatments and tests prior to water distribution. Jinhui Casting Pipe provides a complete water transfer solution for the entire process of water withdrawal.
5: Municipal water
With the shortage of water resources, many cities are facing severe conditions in drinking water. Some central cities have now begun to use medium water, which is between tap water (water supply) and sewage discharged into the pipeline (sewage). Water can be used
Car wash, lawn, road cleaning, city fountains, cooling water in thermal power plants, etc.
6: Industry (paper, thermoelectric, textile, cement, steel, etc.)
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How to choose ductile iron pipe
Ductile iron pipe is mainly called centrifugal ductile iron pipe. It has the essence of iron, the performance of steel, excellent anti-corrosion performance, good ductility, good sealing effect and easy installation. It is mainly used for water supply, gas transmission and transportation of municipal and industrial and mining enterprises. Oil, etc. It is the first choice for water supply pipes and has a high cost performance. Compared with PE pipe, from the installation time, the spheroidal tube is easier and faster to install than the PE pipe, and the internal and external bearing pressure is better after installation; from the perspective of airtightness and corrosion resistance, the airtightness of the spheroidal pipe after installation is better. Corrosion resistance can be improved by various anti-corrosion methods; from the hydraulic performance point of view, the size of the spheroidal tube generally refers to the inner diameter, and the PE tube specification generally refers to the outer diameter. Because of the same specifications, the spheroidal tube can achieve greater runoff; In terms of comprehensive installation and maintenance cost, the spheroidal tube has a more superior cost performance. The main components of ductile iron pipes are carbon, silicon, manganese, sulfur, phosphorus and magnesium. Zinc spray on the inner wall, anticorrosive materials for cement mortar, etc.
We use the following ductile iron pipe as follows:
1. The selection of ductile iron pipe should be based on the specific conditions of the laying site, and the interface form of the straight pipe and the fitting should be selected.
2. It is recommended to use EPDM rubber ring for rubber ring.
3. Selection of coating: Select the appropriate coating according to the internal and external conditions at the time of use. The existing inner coating is a new product of ductile iron pipe such as epoxy resin, polyurethane inner and outer coating, PE film coating, etc., and the performance should be understood in detail when selecting.
Ductile iron pipe joint parts including which
Pipe fittings should first understand the way the pipes are connected, and the relevant parts of the pipes.
The purpose of the pipeline is generally water supply and drainage.
The joints of ductile iron pipes generally have three connections:
1 socket connection (also known as W type),
2 flange connection (also known as type A),
3 clamp connection
General three-way elbows Reducing pipe clamps (clamps), etc., drainage is also the floor sweeping port, riser inspection, etc.; water supply is also short pipe short tube B quick joints.
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Label: ductile iron pipe
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