Ductile iron pipe

Dimensions				12.2
Ductile iron pipe is sized according to a dimensionless				15.0
term known as the Pipe Size or Nominal Diameter				Joints
(known by its French abbreviation, DN). This is				Individual lengths of ductile iron pipe are joined either
roughly equivalent to the pipe's internal diameter in				by flanges, couplings, or some form of spigot and
inches or millimeters. However, it is the external				socket arrangement.
diameter of the pipe that is kept constant between				Flanges
changes in wall thickness, in order to maintain				Flanges are flat rings around the end of pipes, which
compatibility in joints and fittings, and consequently				mate with an equivalent flange from another pipe,
the internal diameter does vary, sometimes				the two being held together by bolts usually passed
significantly, from its nominal size. Nominal pipe sizes				through holes drilled through the flanges. A
vary from 3 inches up to 64 inches, in increments of				deformable gasket, usually elastomeric, placed
at least 1 inch, in the USA.				between raised faces on the mating flanges provides
Pipe dimensions are standardised to the mutually				the seal. Flanges are designed to a large number of
incompatible AWWA C151 (U.S. Customary Units) in				specifications that differ due to dimensional variations
the USA, ISO 2531 / EN 545/598 (metric) in Europe,				in pipes sizes, and pressure requirements, but also
and AS/NZS 2280 (metric) in Australia and New				due to independent standards development. In the
Zealand. Although both metric, European and				U.S. flanges are 'threaded' and can be 'welded' onto
Australian are not compatible and pipes of identical				the pipe. In the European market flanges are often
nominal diameters have quite different dimensions.				welded on to the pipe. Flanges are available in a
North America				standard 125 lb. bolt pattern as well as a 250 lb. bolt
Pipe dimensions according to the American AWWA				pattern (steel bolt pattern). Both are usually rated at
C-151				250 PSI. A flanged joint is rigid and can bear both
Pipe Size				tension and compression as well as a limited degree
Outside Diameter (in)				of shear and bending. It is also dismantlable once
3				constructed. Flanged joints cannot, however, be
3.96				reliably used for buried pipe due to the possibility of
4				soil movement placing very large bending loads on
4.80				the joint.
6				Current flange standards used in the water industry
6.90				are ANSI B16.1 in the USA, EN 1092 in Europe, and
8				AS/NZS 4087 in Australia and New Zealand.
9.05				Spigot and Socket
10				Spigot and sockets involve a normal pipe end, the
11.10				spigot, being inserted into the socket or 'bell' of
12				another pipe or fitting with a seal being made
13.20				between the two within the socket. Normal spigot
14				and socket joints do not allow direct metal to metal
15.30				contact with all forces being transmitted through the
16				elastomeric seal. They can consequently flex and
17.40				allow some degree of rotation, allowing pipes to shift
18				and relieve stresses imposed by soil movement. The
19.50				corollary is that unrestrained spigot and socket joints
20				transmit essentially no compression or tension along
21.60				the axis of the pipe and little shear. Any bends, tees
24				or valves therefore require either a restrained joint
25.80				or, more commonly, thrust blocks, which transmit the
30				forces as compression into the surrounding soil.
32.00				A large number of different socket and seals exist.
Europe				The most modern is the 'push-joint' or 'slip-joint',
European pipe is standardized to ISO 2531 and its				whereby the socket and rubber seal is designed to
descendent specifications EN 545 (potable water) and				allow the pipe spigot to be, after lubrication, simply
EN 598 (sewage). European pipes are sized to				pushed into the socket. Push joints remain proprietary
approximately match the internal diameter of the				designs. The most common are the Tyton joint,
pipe, following internal lining, to the nominal diameter.				developed by U.S. Pipe, the Fastite, by the American
ISO 2531 maintains dimensional compatibility with older				Cast Iron Pipe Co., and the Rapid, by Saint-Gobain
German cast iron pipes. Older British pipes, however,				PAM, which is marketed outside the U.S. Restrained
which used the incompatible imperial standard, BS 78,				joint systems are available too. Each of the four U.S.
require adapter pieces when connecting to newly				manufacturers has their own proprietary restrained
installed pipe. Coincidentally, the British harmonization				joint system that generally involves a "boltless
with European pipe standards occurred at				system". Clow Water Systems has the Super-Lock
approximately the same time as its transition to				joint, Pacific States Cast Iron Pipe Co. has the
ductile iron, so almost all cast iron pipe is imperial, and				Thrust-Lock system, Griffin Pipe Products has the
all ductile pipe, metric.				Snap-Lock joint, U.S. Pipe has the TR-Flex joint, and
DN				American Cast Iron Pipe has the Flex-Ring joint. Also
Outside Diameter (mm)				available are locking gasket systems. Available for the
Wall thickness (mm)				standard 'push-joint' systems are the Sure Stop
Class 40				gasket by McWane, Field Lok by U.S. Pipe, and Fast
K9				Grip by American Cast Iron Pipe Co. These locking
K10				gasket systems work on the "Chinese Box" principle
40				where you can push the pipe together, but will be
56				unable to pull it apart (without using a special tool or
4.8				blow torch on the gasket).
6.0				Manufacture
6.0				Ductile iron pipe is produced by a technique known as
50				centrifugal casting, originally developed by Dimitr
66				Sensaud deLavaud for cast iron pipe in 1918. The
4.8				molten ductile iron is poured into a rapidly spinning
6.0				water-cooled mold. Centrifugal force results in an
6.0				even spread of iron around the circumference.
60				Internal Coatings
77				Ductile iron pipe is somewhat resistant to internal
4.8				corrosion in potable water and less aggressive forms
6.0				of sewage. However, even where pipe material loss
6.0				and consequently pipe wall reduction is slow, the
65				deposition of corrosion products on the internal pipe
82				wall can dramatically reduce the effective internal
4.8				diameter and effectively choke flow, increasing
6.0				pumping costs and lowering system pressure, long
6.0				before the pipe itself is at risk of failure. A variety of
80				linings are available to reduce or eliminate corrosion,
98				including cement mortar, polyurethane and
4.8				polyethylene. Of these, cement mortar lining is by far
6.0				the most common.
6.0				Cement Mortar Linings
100				The predominant form of lining for water applications
118				is cement mortar centrifugallly applied during
4.8				manufacturing. The cement mortar comprises a
6.0				mixture of cement and sand to a ratio of between
6.0				1:2 and 1:3.5. For potable water, portland cement is
125				used, for sewage it is common to use sulfate
144				resisting or high alumina cement.
4.8				Cement mortar linings have been found to
6.0				dramatically reduce internal corrosion. A DIPRA
6.0				survey has demonstrated that the Hazen-Williams
150				factor of cement lining remains between 130 and 151
170				with only slight reduction with age.
5.0				External Coatings
6.0				Unprotected ductile iron, similarly to cast iron, is
6.5				intrinsically resistant to corrosion in most, although not
200				all, soils. Nonetheless, due to frequent lack of
222				information on soil aggressiveness, and to extend the
5.4				installed life of buried pipe, ductile iron pipe is
6.3				commonly protected by one or more external
7.0				coatings. In the U.S. and Australia, loose polyethylene
250				sleeving is preferred. In Europe, standards
274				recommend a more sophisticated system of directly
5.8				bonded zinc coatings overlaid by a finishing layer be
6.8				used in conjunction with polyethylene sleeving.
7.5				Polyethylene Sleevings
300				Polyethylene sleeving was first developed by CIPRA
326				(since 1979, DIPRA) in the U.S. in 1951 for use in
6.2				highly corrosive soil in Birmingham, Alabama. It was
7.2				employed more widely in the U.S. in the late 1950s
8.0				and first employed in the U.K. in 1965 and Australia in
350				the mid 1960's.
378				Polyethylene sleeving comprises a loose sleeve of
7.0				polyethylene sheet that completely wraps the pipe,
7.7				including the bells of any joints. Sleeving inhibits
8.5				corrosion by a number of mechanisms. It physically
400				separates the pipe from soil particles, preventing
429				direct galvanic corrosion. By providing an impermeable
7.8				barrier to ground water, the sleeve also inhibits the
8.1				diffusion of oxygen to the ductile iron surface and
9.0				limits the availability of electrolytes that would
450				accelerate corrosion. It provides a homogeneous
480				environment along the pipe surface so that corrosion
8.6				occurs evenly over the pipe. Finally, the sleeve
9.5				restricts the availability of nutrients which could
500				support sulfate-reducing bacteria, inhibiting
532				microbially-induced corrosion. Sleeving is not designed
9.0				to be completely water-tight but rather to greatly
10.0				restrict the movement of water to and from the
600				pipe surface. Water present beneath the sleeve and
635				in contact with the pipe surface is rapidly
9.9				deoxygenated and depleted of nutrients and forms a
11.0				stable environment in which limited further corrosion
700				occurs. An improperly installed sleeve that continues
738				to allow the free flow of ground water is not
10.8				effective in inhibiting corrosion.
12.0				Polyethylene sleeves are available in a number of
800				materials. The most common contemporary
842				compositions are linear low-density polyethylene film
11.7				which requires an 8 mil or 200 m thickness and
13.0				high-density cross-laminated polyethylene film which
900				requires only a 4 mil or 100 m thickness. The latter
945				may or may not be reinforced with a scrim layer.
12.6				Polyethylene sleeving does have limitations. In
14.0				European practice, its use in the absence of additional
1000				zinc and epoxy protective coatings is discouraged
1048				where natural soil resistivity is below 750 ohm/cm,
13.5				where resistivity is below 1500 ohm/cm and the soil
15.0				is frequently water logged, where there are additional
1100				artificial soil contaminants or where there are stray
1152				currents. Due to the vulnerability of polyethylene to
14.4				UV degradation, sleeving, or sleeved pipe should also
16.0				not be stored in sunlight, although carbon pigments
1200				included in the sleeving can provide some limited
1255				protection.
15.3				Polyethylene sleeving is standardised according to
17.0				ISO 8180 internationally, AWWA C105 in the U.S., BS
1400				6076 in the U.K. and AS 3680 and AS 3681 in
1462				Australia.
17.1				Zinc Coatings
19.0				In Europe, ductile iron pipe is typically manufactured
1500				with a zinc coating overlaid by an either bituminous or
1565				polymer, normally epoxy, finishing layer. EN 545/598
18.0				mandates a minimum zinc content of 135 g/m2 (with
20.0				local minima of 110 g/m2 at 99.99% purity), and a
1600				minimum average finishing layer thickness of 70 m
1668				(with local minima of 50 m) although some
18.9				manufacturers, notably Saint-Gobain PAM considerably
21.0				exceed these thicknesses.
1800				No current AWWA standards are available for
1875				bonded coatings (zinc, coal tar epoxy, tape-wrap
20.7				systems as seen on steel pipe) for ductile iron pipe,
23.0				DIPRA does not endorse bonded coatings and
2000				AWWA M41 generally views them unfavourably,
2082				recommending they be used only in conjunction with
22.5				cathodic protection .
25.0				Bituminous Coatings
Australia				As noted, zinc coatings are generally not employed in
Australian and New Zealand pipes are sized to an				the U.S. and Australia. In order to protect ductile iron
independent specification, AS/NZS 2280, that while				pipe prior to installation, pipe is instead supplied with a
adopting the nomenclature of European standards, is				temporary 1 mil or 25 m thick bituminous coating.
not compatible. Australia adopted at an early point				This coating is not intended to provide protection
the imperial British cast iron pipe standard BS 78, and				once the pipe is installed.
when this was retired on British adoption of ISO				Producers
2531, rather than similarly harmonizing with Europe,				U.S.
Australia opted for a 'soft' conversion from imperial				In the United States ductile iron pipe is manufactured
units to metric, published as AS/NSZ 2280, with the				by McWane Inc.(consisting of four foundries -
physical outer diameters remaining unchanged,				McWane Cast Iron Pipe Co., Clow Water Systems
allowing continuity of manufacture and backwards				Company,Atlantic States Cast Iron Pipe Co. &
compatibility. A result is that the inner diameters of				Pacific States Cast Iron Pipe Co.), Griffin Pipe
lined pipe differ widely from the nominal diameter and				Products, U.S. Pipe & Foundry, and American
hydraulic calculations do require some knowledge of				Cast Iron Pipe Co. The primary headquarters for
the pipe standard.				three of these four companies are based in
Nominal Size (DN)				Birmingham, AL.
Outside Diameter (mm)				Europe
Nominal Wall Thickness (mm)				Saint-Gobain PAM, a subsidiary of Saint-Gobain and
PN 20				the world's largest ductile iron pipe manufacturer, is
PN 35				predominant in Europe. Saint-Gobain PAM formed in
Flange Class				1970 following the merger of Saint-Gobain and the
100				company Pont--Mousson (PAM). Saint-Gobain PAM's
122				ductile iron pipe factory in the town of
5.0				Pont--Mousson remains the world's largest.
7.0				Australia
150				In Australia, Tyco Flow Control Pacific, a subsidiary of
177				Tyco International, is by a wide margin the largest
5.0				Australian manufacturer of DICL, after having
8.0				purchased Tubemakers Water and its single Yennora
200				Manufacturing Facility in Sydney's west, from BHP in
232				1999.
5.0				Industry Associations
8.0				In the United States ductile iron pipe is often
225				promoted to municipalities and consulting engineers by
259				DIPRA, which is the Ductile Iron Pipe Research
5.0				Association. Their focus is to promote the benefits
5.2				of using ductile iron pipe on utility projects (water
9.0				& sewer) over alternate products like PVC,
250				PCCP, and HDPE.
286				Environmental
5.0				Ductile iron pipe in the developed world is normally
5.6				manufactured exclusively from scrap steel. Ductile
9.0				iron pipe itself can be recycled. In the U.S. with the
300				growing 'Green' movement ductile iron pipe is in a
345				natural position to regain market share lost to its
5.0				largest competitor, the PVC industry, over the past
6.3				40 years. PVC pipe has negative environmental issues
10.0				ranging from carcinogens produced at resin plants to
375				the burning of it releasing dioxins into the atmosphere
426				to its carbon footprint.
5.1				Colloquialisms
7.3				As a commonly used construction material ductile iron
10.0				pipe has assumed various colloquial shortened names.
450				In America it is commonly referred to as 'ductile', in
507				the UK, by the initials, 'DI', and in Australia as the
5.6				acronym, DICL (Ductile Iron - Cement Lined),
8.3				pronounced 'dickle'.
11.0				Notes
500				^ a b c Moser, A. P. and Folkman, Steven L. (2008)
560				Buried Pipe Design (3rd edition) McGraw-Hill, New
6.0				York, p. 336-337, ISBN 978-0-07-147689-8
9.0				^ a b IGN 4-50-03 - Operating Guidelines for the Use
12.0				of Site-Applied, Factory Applied and Reinforced
600				Factory Applied Polyethylene Sleeving on Ductile Iron
667				Pipeline Systems
6.8				^ AWWA Manual M41 - Ductile-Iron Pipe and Fittings
10.3				External links
13.0				Official Web Site of Clow Water Systems Co.
750				Official Web Site of the Ductile Iron Pipe Research
826				Association
7.9				Official Web Site of McWane Inc.

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Ductile iron pipe