Cast iron pipe

Last updated

Cast iron pipe is pipe made predominantly from gray cast iron. It was historically used as a pressure pipe for transmission of water, gas and sewage, and as a water drainage pipe during the 17th, 18th, 19th and 20th centuries.

Contents

In many modern applications, cast iron pipe has been replaced by ductile iron pipe, but this newer product is still often loosely referred to by the older historical name.

History

Typical leaded bell-and-spigot joint used for cast iron pipe Leaded Bell-and-Spigot Joint.pdf
Typical leaded bell-and-spigot joint used for cast iron pipe

The oldest cast iron water pipes date from the 17th century and were installed to distribute water throughout the gardens of the Chateau de Versailles. These amount to some 35 km of pipe, typically 1 m lengths with flanged joints. The extreme age of these pipes make them of considerable historical value. Despite extensive refurbishment in 2008 by Saint-Gobain PAM, 80% remain original.

Cast iron proved to be a beneficial material for the manufacture of water pipes and was used as a replacement for the original elm pipelines utilized earlier. These water pipelines were composed of individually cast pipe sections, often termed sticks, jointed together by a variety of joint mechanisms. Flanged joints consisted of flat machined surfaces that were tightly bolted together with a gasket between them to prevent leakage. This type of pipe joint is still in use today, typically for above-ground pipelines in water treatment and manufacturing plants.

Cast iron pipe was frequently used uncoated, although later coatings and linings reduced corrosion and improved hydraulics. In cast iron pipe, the graphite forms flakes during the casting process, when examined under a microscope. Cast iron pipe was superseded by ductile iron pipe, which is a direct development, with most existing manufacturing plants transitioning to the new material during the 1970s and 1980s. Ductile iron pipe is different than cast iron, because the introduction of magnesium during the casting process causes the graphite to form spheres (graphite nodules) rather than flakes. While this allows the material to remain castable, the end product is much tougher than cast iron, and allows elastic behavior at lower stress levels. [1] Little cast iron pipe is currently manufactured, since ductile iron pipe is widely accepted as a superior product. Many public utilities, municipalities, and private industries still have functional cast iron pipe in service to this day.

Joints

In a bell and spigot joint [2] one end of the pipe stick is flared, termed the bell or socket, to enable the opposite end of the next stick, the spigot end, to be inserted to create a joint. The gaps in these joints were stuffed with oakum or yarn to retain molten-lead, which solidified into a waterproof joint. This was a labor-intensive operation, and the quality of the seal was dependent on the skill of the laborer.

Mechanical joints were made by bolting a movable follower ring on the spigot close to the corresponding bell, which compressed a gasket in between. Many water pipes today use mechanical joints, since they are easily made and do not require special skills to install. This type of joint also allows some deflection to occur without sacrificing joint integrity, so that minor alignment adjustments can be made during installation, and the joints retain their integrity when subjected to limited subsidence. Typical joint deflections at mechanical joints today range anywhere from 3 to 5 degrees.

Ball-and-socket joints introduced more "rounded" sockets, allowing a relatively large amount of deflection at each joint. This type of joint, still in use today, was considered a special-purpose joint, and has been used primarily in both submerged and mountainous terrain. This type of joint can typically allow around 15 degrees of deflection at each joint, making 'snaking' of the pipe possible. [3] The advantage of this joint type was that it was quicker than bell and spigot joints, and did not require special skills or tools to install.

Push-on joints, developed in the mid 1950s, allowed a quicker and relatively non-skilled method of jointing pipe. This joint consisted of a bell with a recessed groove which held a rubberized gasket. A lubricated beveled spigot section can be pushed into this joint with care, as not to roll the rubberized gasket, and once installed became watertight. This type of jointing system is popular today with ductile iron and polyvinyl chloride (PVC) pipes.

Manufacture

Horizontally cast

The first cast iron pipe was produced in horizontal moulds, the core of the mould would be supported on small iron rods which would become part of the pipe. Horizontal casting resulted in an uneven distribution of metal around the pipe circumference. Typically slag would collect at the crown of the pipe creating a much weaker section.

Vertically cast

In 1845, the first pipe was cast vertically in a pit and by the end of the century, all pipe was manufactured by this method. Using this method the slag would all collect at the top of the casting and could be removed by simply cutting off the end of the pipe. Pipes cast using this method often suffered from off centre bores caused by the core of the mould being placed off centre, resulting in one side of the pipe being thicker than the other.

Centrifugally cast

Subsequent to its invention by Dimitri Sensaud deLavaud, a French-Brazilian, in 1918, much cast iron pipe manufacturing shifted to the dramatically different technique of centrifugal casting. Modern ductile iron pipe production continues to use this general method of casting.

Historically, two different types of molds have been used in centrifugal casting of cast iron pipe: metal molds and sand molds. With metal molds, molten iron was introduced into the mold to uniformly distribute metal over the interior of the mold surface by the centrifugal force generated. The outside mold was typically protected from damage by a controlled water bath or water spray system. When the pipe was cool enough to be handled and hold its shape, the mold was stopped and the pipe removed. Pipe formed in metal molds were typically annealed after casting to eliminate any stresses in the pipe, and were then cleaned, inspected, tested, gauged (for dimensions), coated internally and/or externally, and stored for use. Standards for cast-iron pipe centrifugally cast in metal molds for water were established and published by the American Water Works Association. [4]

When cast with sand molds, two types of manufacturing processes were used. In the first method, a metal pattern was typically positioned in a metal flask and molding sand was rammed into the annular space between the flask and pattern. The pattern was then removed for casting of the pipe using molten grey iron. The second method did not entail a metal pattern, but entailed the forming of the mold centrifugally by lining the heated flask with a measured amount of thermosetting resin and sand. Either way, the casting machine was stopped after the pipe had solidified and the flask was removed. Cast iron pipe formed using this procedure was typically oven-cooled under controlled time and temperature conditions. As with metal molds, pipe was typically annealed to eliminate any stresses in the pipe, and were then cleaned, inspected, tested, gauged (for dimensions), coated internally and/or externally, and stored for use. [5] Standards for cast-iron pipe centrifugally cast in sand molds for water were established and published by the American Water Works Association. [6]

Internal corrosion

Corrosion of cast-iron-pipe can occur on both the internal and external surfaces. In electro-chemical corrosion, internal anodes develop where bare iron is exposed to aggressive waters, promoting iron to move into solution. The iron combines with various components in the water, forming a tubercle on the pipe interior. This process of tuberculation can eventually cause significant restrictions in cross-sectional area within the pipe. Since the tubercles are irregularly shaped, buildup of bacterial growths on the surface are likely. As more iron moves into solution, the result is a loss of pipe structure over time potentially affecting pipe integrity. In storm and sanitary sewer systems, the creation of acidic gases (such as hydrogen sulfide) by microbial action can further corrode internal pipe walls but is most pronounced on the inside ‘ceiling’ of the pipe.

Starting in 1922, internal cement linings were introduced to act as a barrier to minimize internal corrosion. In 1929, the American Standard Association (ASA) Sectional Committee issued a tentative standard for cement-mortar linings, which was published in 1932. In 1939, American Standard A21.4 was published, which defined a Type I cement coating on the inside of waterline pipe to be used. When the standard was updated in 1953, the Type I cement was replaced with Type II, since it was believed that Type II was a more closely controlled product. The standard was further revised in 1964, which included the use of either Type I or Type II cement, and making two different mortar thicknesses available. [7]

Standardization

The first standardization of cast iron water pipes in Britain occurred in 1917 with the publishing of BS 78. This standard specified a dimensionless nominal size, which approximately corresponded with the internal diameter in inches of the pipe, and four pressure classes, Class A, Class B, Class C and Class D, each with a specified wall thickness and outer diameter. It is noted that the outer diameter is identical between classes with the exception of sizes 12 to 27, where Classes A and B share one diameter and Classes C and D have another, larger diameter.

Nominal sizeClass
A & BABC & DCD
Outer diameter
[in (mm)]
Wall thickness
[in (mm)]
Internal diameter
[in (mm)]
Wall thickness
[in (mm)]
Internal diameter
[in (mm)]
Outer diameter
[in (mm)]
Wall thickness
[in (mm)]
Internal diameter
[in (mm)]
Wall thickness
[in (mm)]
Internal diameter
[in (mm)]
33.76 (95.504)0.38 (9.652)3.00 (76.200)0.38 (9.652)3.00 (76.200)3.76 (95.504)0.38 (9.652)3.00 (76.200)0.40 (10.160)2.96 (75.184)
44.80 (121.920)0.39 (9.906)4.02 (102.108)0.39 (9.906)4.02 (102.108)4.80 (121.920)0.40 (10.160)4.00 (101.600)0.46 (11.684)3.88 (98.552)
55.90 (149.860)0.41 (10.414)5.08 (129.032)0.41 (10.414)5.08 (129.032)5.90 (149.860)0.45 (11.430)5.00 (127.000)0.52 (13.208)4.86 (123.444)
66.98 (177.292)0.43 (10.922)6.12 (155.448)0.43 (10.922)6.12 (155.448)6.98 (177.292)0.49 (12.446)6.00 (152.400)0.57 (14.478)5.84 (148.336)
78.06 (204.724)0.45 (11.430)7.16 (181.864)0.45 (11.430)7.16 (181.864)8.06 (204.724)0.53 (13.462)7.00 (177.800)0.61 (15.494)6.84 (173.736)
89.14 (232.156)0.47 (11.938)8.20 (208.280)0.47 (11.938)8.20 (208.280)9.14 (232.156)0.57 (14.478)8.00 (203.200)0.65 (16.510)7.84 (199.136)
910.20 (259.080)0.48 (12.192)9.22 (234.188)0.49 (12.446)9.22 (234.188)10.20 (259.080)0.60 (15.240)9.00 (228.600)0.69 (17.526)8.82 (224.028)
1011.26 (286.004)0.52 (13.208)10.22 (259.588)0.52 (13.208)10.22 (259.588)11.26 (286.004)0.63 (16.002)10.00 (254.000)0.73 (18.542)9.80 (248.920)
1213.14 (333.756)0.55 (13.970)12.04 (305.816)0.57 (14.478)12.00 (304.800)13.60 (345.440)0.69 (17.526)12.22 (310.388)0.80 (20.320)12.00 (304.800)
1415.22 (386.588)0.57 (14.478)14.08 (357.632)0.61 (15.494)14.00 (355.600)15.72 (399.288)0.75 (19.050)14.22 (361.188)0.86 (21.844)14.00 (355.600)
1516.26 (413.004)0.59 (14.986)15.08 (383.032)0.63 (16.002)15.00 (381.000)16.78 (426.212)0.77 (19.558)15.24 (387.096)0.89 (22.606)15.00 (381.000)
1617.30 (439.420)0.60 (15.240)16.10 (408.940)0.65 (16.510)16.00 (406.400)17.84 (453.136)0.80 (20.320)16.24 (412.496)0.92 (23.368)16.00 (406.400)
1819.38 (492.252)0.63 (16.002)18.12 (460.248)0.69 (17.526)18.00 (457.200)19.96 (506.984)0.85 (21.590)18.26 (463.804)0.98 (24.892)18.00 (457.200)
2021.46 (545.084)0.65 (16.510)20.16 (512.064)0.73 (18.542)20.00 (508.000)22.06 (560.324)0.89 (22.606)20.28 (515.112)1.03 (26.162)20.00 (508.000)
2122.50 (571.500)0.67 (17.018)21.16 (537.464)0.75 (19.050)21.00 (533.400)23.12 (587.248)0.92 (23.368)21.28 (540.512)1.03 (26.162)21.00 (533.400)
2425.60 (650.240)0.71 (18.034)24.18 (614.172)0.80 (20.320)24.00 (609.600)26.26 (667.004)0.98 (24.892)24.30 (617.220)1.13 (28.702)24.00 (609.600)
2728.70 (728.980)0.75 (19.050)27.20 (690.880)0.85 (21.590)27.00 (685.800)29.40 (746.760)1.04 (26.416)27.32 (693.928)1.20 (30.480)27.00 (685.800)
3032.52 (826.008)0.79 (20.066)30.94 (785.876)0.89 (22.606)30.74 (780.796)32.52 (826.008)1.09 (27.686)30.34 (770.636)1.26 (32.004)30.00 (762.000)
3335.66 (905.764)0.83 (21.082)34.00 (863.600)0.94 (23.876)33.78 (858.012)35.66 (905.764)1.15 (29.210)33.36 (847.344)1.33 (33.782)33.00 (838.200)
3638.76 (984.504)0.87 (22.098)37.02 (940.308)0.98 (24.892)36.80 (934.720)38.76 (984.504)1.20 (30.480)36.36 (923.544)1.38 (35.052)36.00 (914.400)
4042.92 (1,090.168)0.92 (23.368)41.08 (1,043.432)1.03 (26.162)40.86 (1,037.844)42.92 (1,090.168)1.26 (32.004)40.40 (1,026.160)1.46 (37.084)40.00 (1,016.000)
4245.00 (1,143.000)0.95 (24.130)43.10 (1,094.740)1.06 (26.924)42.88 (1,089.152)45.00 (1,143.000)1.30 (33.020)42.40 (1,076.960)1.50 (38.100)42.00 (1,066.800)
4548.10 (1,221.740)0.99 (25.146)46.12 (1,171.448)1.09 (27.686)45.92 (1,166.368)48.10 (1,221.740)1.35 (34.290)45.40 (1,153.160)1.55 (39.370)45.00 (1,143.000)
4851.20 (1,300.480)1.03 (26.162)49.14 (1,248.156)1.13 (28.702)48.94 (1,243.076)51.20 (1,300.480)1.38 (35.052)48.44 (1,230.376)1.68 (42.672)47.84 (1,215.136)

BS 78 was finally superseded when the UK harmonised with incompatible European standards, however, the specified outer dimensions continue to remain in effect (albeit in metric form) as the standard pipe outer diameter for ductile iron pipe in Australia and New Zealand through the descendant specification, AS/NZS 2280.

Related Research Articles

<span class="mw-page-title-main">Plumbing</span> Systems for conveying fluids

Plumbing is any system that conveys fluids for a wide range of applications. Plumbing uses pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids. Heating and cooling (HVAC), waste removal, and potable water delivery are among the most common uses for plumbing, but it is not limited to these applications. The word derives from the Latin for lead, plumbum, as the first effective pipes used in the Roman era were lead pipes.

<span class="mw-page-title-main">Metal casting</span> Pouring liquid metal into a mold

In metalworking and jewelry making, casting is a process in which a liquid metal is delivered into a mold that contains a negative impression of the intended shape. The metal is poured into the mold through a hollow channel called a sprue. The metal and mold are then cooled, and the metal part is extracted. Casting is most often used for making complex shapes that would be difficult or uneconomical to make by other methods.

A gate valve, also known as a sluice valve, is a valve that opens by lifting a barrier (gate) out of the path of the fluid. Gate valves require very little space along the pipe axis and hardly restrict the flow of fluid when the gate is fully opened. The gate faces can be parallel but are most commonly wedge-shaped.

<span class="mw-page-title-main">Sand casting</span> Metal casting process using sand as the mold material

Sand casting, also known as sand molded casting, is a metal casting process characterized by using sand — known as casting sand — as the mold material. The term "sand casting" can also refer to an object produced via the sand casting process. Sand castings are produced in specialized factories called foundries. In 2003, over 60% of all metal castings were produced via sand casting.

Molding sand, also known as foundry sand, is a sand that when moistened and compressed or oiled or heated tends to pack well and hold its shape. It is used in the process of sand casting for preparing the mold cavity.

Spin casting, also known as centrifugal rubber mold casting (CRMC), is a method of utilizing inertia to produce castings from a rubber mold. Typically, a disc-shaped mold is spun along its central axis at a set speed. The casting material, usually molten metal or liquid thermoset plastic, is then poured in through an opening at the top-center of the mold. The filled mold then continues to spin as the metal solidifies.

<span class="mw-page-title-main">Electrosteel Castings</span> Indian ductile iron pipe manufacturer

Electrosteel Castings Limited is an Indian company based in Kolkata. It is one of the largest manufacturers of ductile iron pipes in the Indian sub-continent, having a production capacity of 280,000 MT per annum. Electrosteel was the pioneer in setting up a Ductile Iron Spun Pipe Plant in India in 1994 and is among the five largest producers of Spun Iron pipes in the world.

<span class="mw-page-title-main">Pipe (fluid conveyance)</span> Tubular section or hollow cylinder

A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.

Victaulic is a developer and manufacturer of mechanical pipe joining systems, and the originator of the grooved pipe couplings joining system. The firm is a global company with 15 major manufacturing facilities, 28 branches, and over 3600 employees worldwide. Currently, its headquarters is located in Easton, Pennsylvania.

<span class="mw-page-title-main">Piping and plumbing fitting</span> Connecting pieces in pipe systems

A fitting or adapter is used in pipe systems to connect straight sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating fluid flow. These fittings are used in plumbing to manipulate the conveyance of water, gas, or liquid waste in domestic or commercial environments, within a system of pipes or tubes.

<span class="mw-page-title-main">Pattern (casting)</span>

In casting, a pattern is a replica of the object to be cast, used to form the sand mould cavity into which molten metal is poured during the casting process. Once the pattern has been used to form the sand mould cavity, the pattern is then removed, Molten metal is then poured into the sand mould cavity to produce the casting. The pattern is non consumable and can be reused to produce further sand moulds almost indefinitely.

Goldens' Foundry and Machine Co. is a privately held ductile iron and gray iron foundry with headquarters in Columbus, Georgia and additional facilities in Cordele, Georgia in the United States. It has operated continuously since 1882. Goldens' provides castings to a variety of industries, including agricultural, construction, power transmission, defense, and large vehicles.

<span class="mw-page-title-main">Cement-mortar lined ductile iron pipe</span>

Cement-mortar lined ductile iron pipe is a ductile iron pipe with cement lining on the inside surface, and is commonly used for water distribution.

Shell molding, also known as shell-mold casting, is an expendable mold casting process that uses resin covered sand to form the mold. As compared to sand casting, this process has better dimensional accuracy, a higher productivity rate, and lower labour requirements. It is used for small to medium parts that require high precision. Shell molding was developed as a manufacturing process during the mid-20th century in Germany. It was invented by German engineer Johannes Croning. Shell mold casting is a metal casting process similar to sand casting, in that molten metal is poured into an expendable mold. However, in shell mold casting, the mold is a thin-walled shell created from applying a sand-resin mixture around a pattern. The pattern, a metal piece in the shape of the desired part, is reused to form multiple shell molds. A reusable pattern allows for higher production rates, while the disposable molds enable complex geometries to be cast. Shell mold casting requires the use of a metal pattern, oven, sand-resin mixture, dump box, and molten metal.

<span class="mw-page-title-main">Ductile iron pipe</span> Pipe made of ductile cast iron

Ductile iron pipe is pipe made of ductile cast iron commonly used for potable water transmission and distribution. This type of pipe is a direct development of earlier cast iron pipe, which it has superseded.

Electrotherm (India) Limited (Ltd.) is an Indian technology conglomerate. Its operations span across many different segments of the manufacturing and process industries, including steelmaking, foundry, heat treatment, the design and manufacturing of electric vehicles, and the energy industry. Ranging from more energy-efficient alternatives to renewable energy. It's also India's largest manufacturer of induction furnaces.

<span class="mw-page-title-main">Centrifugal casting (industrial)</span> Casting technique that is typically used to cast thin-walled cylinders

Centrifugal casting or rotocasting is a casting technique that is typically used to cast thin-walled cylinders. It is typically used to cast materials such as metals, glass, and concrete. A high quality is attainable by control of metallurgy and crystal structure. Unlike most other casting techniques, centrifugal casting is chiefly used to manufacture rotationally symmetric stock materials in standard sizes for further machining, rather than shaped parts tailored to a particular end-use.

<span class="mw-page-title-main">American Cast Iron Pipe Company</span>

American Cast Iron Pipe Company is a manufacturer of ductile iron pipe, spiral-welded steel pipe, fire hydrants, and valves for the waterworks industry, and electric-resistance-welded steel pipe for the oil and natural gas industry. Headquartered in Birmingham, Alabama, American's diversified product line also includes static castings and high performance fire pumps.

<span class="mw-page-title-main">Hobas</span>

HOBAS is a manufacturer of centrifugally cast glassfiber reinforced (GRP) pipe systems made of unsaturated polyester resin with diameters ranging from 150 mm to 3600 mm. The company was founded in Basel, Switzerland in 1957. In 1977 the Wietersdorfer Group acquired the license for the pipe production in Austria and became owner of HOBAS to 50% in 1987. HOBAS is fully owned by the Wietersdorfer Group since 2011.

Centrifugal casting, also commonly known as spin casting, is typically used for industrial manufacturing of cast parts. It was the work of A. G. Eckhardt in 1809 to develop a patent showing the basic principles involved with the process. Centrifugal casting is one of the few casting processes that can be used both to manufacture metals as well as plastic parts. Parts ranging from belt buckles, medallions, figurines, and souvenirs to "pot metal" gears and machine parts, bushings, and concrete expansion fasteners are usually manufactured using this process. Spin casting or centrifugal casting is considered to be a relatively inexpensive process ranging to a total cost of no more than a $20,000 investment requirement, in comparison to a process such as investment molding that costs a lot more. Centrifugal casting is a popular process for the petrochemical market, defense market, and virtually any other market who needs good quality products at a low manufacturing cost.

References

  1. Rajani, Makar, McDonald, Zhan, Kuraoka, Jen and Viens, "Investigation of Grey Cast Iron Water Mains to Develop a Methodology for Estimating Service Life", AWWA Research Foundation, 2000.
  2. bell and spigot joint ,
  3. "Introduction to Water Distribution, Principles and Practices of Water Supply Operations", American Water Works Association, Volume 3, 1986.
  4. "American Standard for Cast-Iron Pipe Centrifugally Cast in Metal Molds, for Water or Other Liquids", American Water Works Association, A21.6-1962 (AWWA C106-62), 1962.
  5. "Handbook of Cast Iron Pipe", Third Edition, Cast Iron Pipe Research Association, 1967.
  6. "American Standard for Cast-Iron Pipe Centrifugally Cast in Sand-Lined Molds, for Water or Other Liquids", American Water Works Association, A21.8-1962 (AWWA C108-62), 1962.
  7. Foreword from "American Standard for Cement-Mortar Lining for Cast-Iron Pipe and Fittings for Water", American Water Works Association, A21.4-1964 (AWWA C104-64), 1964.