Technical FAQs1. Why do you see blast-furnace cement specified, and what is the difference between blast-furnace cement and Portland cement and sulphate-resisting cement? Why is sulphate-resisting cement used in ductile iron pipe? Answer 2. Why do European manufacturers use EPDM gaskets and American manufacturers normally use SBR (plain rubber) gaskets? Answer 3. What benefit does zinc coating really provide? Answer 4. Besides metric versus inch O.D. sizes and thicknesses, what are the main differences between the ISO and AWWA manufacturing specifications for ductile iron pipe and fittings? Answer 5. Should cracking or looseness of the cement lining be a concern? How is the cement lining repaired in the field? Answer 6. What are the laying lengths, overall lengths, minimum lengths, and socket depths for pipe and fittings? Answer 7. What are welded-on outlets, and in what situations should welded-on outlets not be used? Answer 8. What lining should be used for certain conditions? Answer 9. How do contractors transition from PVC, PCCP, steel, or old gray cast iron pipe, etc. to current ductile iron pipe, particularly when slightly different outside diameters are involved? Answer 10. Are thrust blocks better than restrained joints? Or, when do I need restrained joint pipe, and when is Fastite® pipe satisfactory? Or, what restrained joint length is needed for specific situations? Answer 11. Which bells, spigots, and gaskets are compatible with TYTON® products? Answer 12. What does gauging mean? Or, what is the difference between GAFST, GAMJ, GADR, and no gauge? Or, what does gauge full-length mean? Are there certain sizes (or size ranges) for each? When does a gauge need to be specified? Is "calibrated" the same as "gauged"? Answer 13. What is the cause/effect of rust on the bell and spigot ends of pipe? Should this cause concern? Answer 14. How does a customer handle the re-rounding of pipe if necessary? Answer 15. What are the differences between a wall, thrust, puddle flange, waterstop, weep, seep (ring), welded-on, or water collar? Answer 16. What joint should be used in a bridge-crossing application? Answer 17. What are the major differences between polyethylene and polyurethane linings? Answer 18. Can ductile iron pipe be used for pressure requirements greater than what is shown in the Pipe Manual? If you can't answer this question without more information, what information do you need? Answer 19. What exterior corrosion protection besides polyethylene encasement is available? Answer If you don't see your question listed here, send it to us via the "Submit a Technical Question" page. * * * * * * * * * 1Q. Why do you see blast-furnace cement specified, and what is the difference between blast-furnace cement and Portland cement and sulphate-resisting cement? Why is sulphate-resisting cement used in ductile iron pipe?1A. Some manufacturers have ready access to blast-furnace cement, which is made from waste material from the metals industry. It is reported to have good durability and is generally less expensive (particularly in areas where it is readily available as a waste product) than Portland cement. Sulphate (or "sulfate") resisting (or "resistant") cements, per ASTM C150 Type 5 or BS 4027, are specially formulated cements with very low tricalcium aluminate (C3A) for better quality/sulfate resistance than ordinary Portland cement. Sulfates are present in some soil environments and in some fresh and salt waters that may contact pipe linings. Sulfate resisting cements are very good quality cements for general purpose use and are more resistant to attack when exposed to sulfate-containing waters than ordinary Portland cement. 2Q. Why do European manufacturers use EPDM gaskets and American manufacturers normally use SBR (plain rubber) gaskets? 2A. European manufacturers are generally standardized on EPDM, and American manufacturers and Standards are generally standardized on SBR gaskets for most normal water and wastewater applications. Both are durable, synthetic rubber formulations with excellent decades-long performance records all around the world. 3Q. What benefit does zinc coating really provide? 3A. Zinc coatings are "sacrificial" coatings that may provide at least some limited corrosion protection in some buried soil environments. This reportedly works by the zinc reacting with the corrosive environment and forming a further protective layer of rather low solubility zinc compounds in some cases. There is no ANSI/AWWA standard for zinc coating protection for ductile iron pipe and fittings. However, there is an ANSI/AWWA and ISO standard for loose polyethylene wrap corrosion protection for ductile iron pipelines buried in potentially corrosive soil environments. The polyethylene wrap system is a passive, non-sacrificial corrosion protection system. 4Q. Besides metric versus inch O.D. sizes and thicknesses, what are the main differences between the ISO and AWWA manufacturing specifications for ductile iron pipe and fittings? 4A. Each standard addresses pipe design, production and testing of pipe and fittings in different ways. Some of the differences include pipe class nomenclature (Pressure Class vs. "K" class); marking requirements are slightly different, as are the required physical properties of the ductile iron. Another difference between the ISO and AWWA ductile iron pipe standards is the procedure used to develop and issue the standards. Pipe Wall Thickness (Weight) Thickness tolerance = (1.3 + 0.001DN) This allows, in many cases, for a large minus tolerance in the net wall thickness, thereby, reducing safety factors and increasing pipe wall stresses. Hydro-Test Gasket Pipe Joints 5Q. Should cracking or looseness of the cement lining be a concern? How is the cement lining repaired in the field? 5A. Some cracking and looseness of cement-mortar linings is inevitable. These conditions are normal results of drying, shrinkage during curing and storage, handling stresses and impacts, and cyclic thermal effects. The existence of mortar cracks or looseness, however, is normally not a serviceability concern in that exposure to water or even 100 percent humidity conditions will cause the durable, cement-rich linings ACIPCO furnishes to swell back out in firm contact with the pipe or fitting wall. In a process called "autogenous healing," the sides of cracks will, in effect, mend together in long exposure to service conditions. If significant portions of the linings have been knocked out of the pipe or fittings, they should be repaired in accordance with ISO 4179 or ACIPCO literature in accordance with this standard.This procedure employs hand placement or troweling of a simply prepared mortar mix followed by a short cure. A brochure is available from ACIPCO explaining all of these lining issues in detail. Contact Us 6Q. What are the laying lengths, overall lengths, minimum lengths, and socket depths for pipe and fittings? 6A. The laying lengths of most flanged fittings are generally standardized and illustrated in the ACIPCO International Pipe Manual (as well as on this Web site) and ISO 2531 as applicable. The laying lengths and socket depths of pipes and fittings with one or more of the various designs of available sockets are less standardized and may be subject to more variation depending on manufacturer. The best available information relative to the expected lengths of the various socketed pipes and fittings is shown in ACIPCO and vendor literature or as specifically requested by the customer. A sales order for what is referred to as "nominal laying length" ductile iron pipes are usually 6.1m, but 10 percent of that order can be furnished with shorter laying lengths, per ISO 2531. It must be understood that many items sold by ACIPCO are produced by vendor companies to their specific designs at the time, and thus we do not have control over and not necessarily knowledge of their dimensions. It is important to realize that the "overall length" of pipes and fittings with one or more (spigot insertion) sockets is greater than the "laying length" of the item by the amount of the respective spigot insertion(s). Wall castings or wall pipe fabrications with sockets are sometimes specified with a given overall length, as this length often must fit "flush" between concrete wall forms before the wall is poured, encasing the pipe. 7Q. What are welded-on outlets, and in what situations should welded-on outlets not be used? 7A. A welded-on outlet is a piece of ductile iron pipe welded at some angle to another piece of ductile iron pipe, normally in the configuration of a tee or a blow-off. ACIPCO regularly furnishes pipe with welded-on outlets for proven effectiveness and simplicity in layout and installation. Outlets can be readily located at variable positions along the pipeline, and rotation of the pipe can often position the outlet at any desired angle. Welded outlets should not be used if there is a potential for relative movement or impact, and/or subsequent beam loading, etc., which may damage the connecting pipes. An example would be buried flange outlets or other relatively rigid joint outlets, particularly with relatively rigid-joined (such as with Megalugs or mechanical adapters) valves, fittings, or piping connected to them. For any questions regarding the use and application of welded-on outlets, contact ACIPCO. 8Q. What lining should be used for certain conditions? 8A. Lining uses are discussed to some extent in the ACIPCO International Pipe Manual and also in standards. In addition, DIPRA publishes an available lining recommendation guide, which is referenced and annotated to answer this question showing some ACIPCO lining offerings in some categories mentioned:
9A. Transitions from different types/diameters of pipe are normally accomplished with special transition couplings, gaskets, and/or glands. ACIPCO normally recommends that the customer talk to a third party supplier, such as Dresser, Smith-Blair, Romac, JCM, Hydro Conduit, etc. for transition couplings. 10Q. Are thrust blocks better than restrained joints? Or, when do I need restrained joint pipe, and when is Fastite® pipe satisfactory? Or, what restrained joint length is needed for specific situations? 10A. Thrust blocks and restrained joints are alternative or supplementary methods of providing thrust restraint. One is not necessarily better than the other. The methods for sizing thrust blocks and for calculating lengths of restraint can be found in the DIPRA brochure "Thrust Restraint Design for Ductile Iron Pipe." There is also a program that can be downloaded from DIPRAs website, http://www.dipra.org, which will calculate the restrained joint length needed based on the specific parameters of the job. A very conservative design sometimes employed by designers and particularly helpful for extra security/flexibility in seismic areas employs both an adequate length of restrained joints for carrying the full thrust load and, in addition, full-sized thrust blocks. ACIPCO does not object to such conservative design when applied fairly. 11Q. Which bells, spigots, and gaskets are compatible with TYTON® products? 11A. Because the standards require the spigot ODs to be within given tolerances, a Fastite plain-end will fit a Tyton bell and vice versa, though care must be taken transitioning in restrained joint areas (contact ACIPCO in such cases). Gaskets, in general, should not be interchanged. 12Q. What does gauging mean? Or, what is the difference between GAFST, GAMJ, GADR, and no gauge? Or, what does gauge full-length mean? Are there certain sizes (or size ranges) for each? When does a gauge need to be specified? Is "calibrated" the same as "gauged"? 12A. If a customer anticipates field cuts, they may need to order "gauged" (also called "gaged") pipe. This means that an inspector at ACIPCO's factory has measured this pipe in this extent with a "pi" tape placed circumferentially around the pipe. "Gauged full-length" means that the pipe barrel can be cut at any location from the spigot end up to within approximately 2 feet of where the back of the bell blends with the barrel, and thereafter the field-cut ends can be used with confidence in accordance with our written joining procedures. Gauged-full pipe will have a circumferential green stripe around the back of the bell. It is good engineering/construction practice, however, that before any field cuts are made, the barrel of the pipe be measured at the location of the desired cut to ensure the proper dimensions. Gauging (with the exception of factory gauged ends for mechanical joining) has no implications on ovality, and it is thus normal for some field-cut ends to exhibit more ovality than ends provided from the factory. 13Q. What is the cause/effect of rust on the bell and spigot ends of pipe? Should this cause concern? 13A. The cause of what is normally very superficial rust could be a scratch, some sort of breech, or pinhole in the coating or lining, moisture, etc. The ends of pipes are most likely to rub up against other objects and are typically coated with very thin, soft coatings such as asphaltic paint or rust veto for appropriate joining. Unless the corrosion or future exposure of the pipe is very severe (say caused by unusual exposure to very low pH acid, etc.), there should not be a cause for concern. 14Q. How does a customer handle the re-rounding of pipe if necessary? 14A. Occasionally, field rounding of pipe ends may be necessary to accomplish assembly, particularly when large diameter pipes are cut to be assembled into mechanical joints or couplings. Need for rounding in assembly of mechanical joints can be predetermined by a difficulty in sliding the gland or end ring over the end of the pipe. Rounding may be accomplished in the following manner using a mechanical jack and shaped blocks. (Note: This procedure may also be used with the assemblies involving push-on joint pipe, fittings, valves, etc.; however, rounding is less frequently necessary for assembly of push-on joints.)
15Q. What are the differences between a wall, thrust, puddle flange, waterstop, weep, seep (ring), welded-on, or water collar? 15A. This question is best answered by first explaining what is common to all of these terms. All of these terms normally relate to various descriptions of annular "collars," normally of ductile iron or steel, which are located or placed around the outside of centrifugally or static-cast ductile iron castings in the factory. These collars, and typically also some length of pipe or casting on either side of them, are subsequently encased in a field-poured or grouted concrete wall, floor section, or other structure. One of the purposes of these collars is often to provide a longer, more tortuous "water seep path" and thereby a better water barrier for the pipe penetration through the wall or floor. Another purpose of many of these collars is structural anchorage or support of the piping system relative to a concrete wall or other structure. It should, however, be noted that the effectiveness of any water barrier is also dependent on the length of encasement specified by the project engineer and also the quality/consolidation (lack of voids, honeycombing, etc.) of the concrete around the wall penetration. Also, the strength of the "anchorage" mentioned in the other purpose might be limited by the strength of the wall in which it is placed. All of the terms above, with the exception of "puddle flange," generally refer to collars that are permanently "fixed" in a specified position on the pipe or static-casting or sleeve at the factory. In general, collars employing less than 360 degree welding on at least one side have employed a 360 degree fillet/bead of sealant or "water-stopping" mastic on both sides of the collar and additionally have had lesser ability to withstand loads or thrusts than the fully welded collars. A "puddle flange" is a bolt-on flange in two or more parts that is infrequently supplied. This collar can be mechanically bolted in field-adaptable fashion around a pipe in the field. A somewhat compressible waterstopping material, clamped within and between the puddle flange sections as they are assembled onto the pipe, aid in the sealing function. A puddle flange is normally not intended to withstand thrust loads. While the strength of a thrust collar might not be needed in all cases, ACIPCO recommends (based on extensive analyses, testing, and experience) our standard, fully (360 degrees both sides) welded-on thrust collar fabricated pipes. These collars are reasonably economical and do not depend on a mastic to seal. When encased in a concrete wall or floor of sufficient strength they can withstand the rigors of adjoining joint assembly as well as subsequent full dead-end or bulkhead thrust loads due to full rated internal pressure. AMERICAN does not promote nor provide instructions for "field-welding" of thrust collars. However, some degree of field-adaptability might be furnished by using factory collars welded some distance "up the barrel" on candidate "gauge full-length" pipes, with these pipes furnished longer than expected so the plain end can be "cut to suit in field" (CTSIF). 16Q. What joint should be used in a bridge-crossing application? 16A. Virtually all available joint types have been used successfully on bridge crossings at one time or another. However, bridge crossings, and particularly long bridge crossings, can involve very complicated design and installation considerations. Specifically, all effects of installation, pipe support, thrust restraint, lateral support or restraint near joints, joint "take-up," thermal expansion and contraction effects throughout the life of the pipeline, and the interaction of the pipeline and bridge structure (particularly at any bridge construction expansion joints, etc.), and also combination of these effects need to be considered. Some engineers specify restrained Flex-Ring and Lok-Ring joint pipes and also external anchorage for maximum security and control of movement in bridge crossing installations. Please see also Design on Aboveground Supports on the ACIPCO Web site and Long Span and Piping Supports on the AMERICAN web site. 17Q. What are the major differences between polyethylene and polyurethane linings? 17A. Polyethylene (the fluid contact material of PolybondPlus®) is a thermoplastic lining that is heat-fused inside the prepared ductile iron pipe surface at the factory. Polyurethane is a chemically cured or thermosetting lining that is normally sprayed inside the pipe with a fast-curing chemical mixture by a third party. The applicator then ships the lined pipe directly to the customer. Polyethylene and PolybondPlus® linings are thus generally manufactured with the extensive surface preparation, quality control, and warrantee of ACIPCO, whereas polyurethane linings (and exterior coatings, if required) are applied by others and any warrantee is thus by others. Polyethylene is generally a more inert or chemically resistant material than polyurethane, and our linings can be manufactured by ACIPCO to pass a properly performed, high-voltage holiday test at the ACIPCO factory. While one or more domestic ductile iron pipe manufacturers formerly promoted and furnish polyurethane linings, particularly for their sewer pipe offerings, we understand for some reason they no longer do so, and polyurethane linings are now less frequently specified for ductile iron pipe. For more advantages, particularly of ACIPCO PolybondPlus® linings, please refer to ACIPCO literature or contact ACIPCO. 18Q. Can ductile iron pipe be used for pressure requirements greater than what is shown in the Pipe Manual? If you can't answer this question without more information, what information do you need? 18A. It should be obvious from the routine very high-pressure hydrostatic proof-tests of our ductile iron pipe and joints, and also special tests such as those performed on many products in the presence of Underwriter's Laboratory and Factory Mutual, etc. inspectors, that our pipe is capable of safely withstanding far more internal pressure than the 20-40 bar maximum working pressure ratings ascribed to them. Per appendices in current European standard EN 545, ductile iron pipes may be satisfactory in some sizes for allowable operating pressures, excluding surge, of up to 64 bars (928 psi) and even greater design or one-time field test pressures. However, when greater working pressures are desired in a prospective application, all aspects of the specific design, installation, and testing must be considered by the project engineer and constructor (e.g. potential surge pressures, thrust restraint and movement/take-up, all fittings, valves, hydrants, meters, flanges, thrust collars, other specials or fabrications, line testing means and locations of permanent or temporary test bulkheads, etc.). Due to the greater potential, though, for customer problems in unfettered or uncontrolled very high pressure application of our products, all potential applications for working pressures greater than the standard ratings of our products should be routed through the ACIPCO Technical Division for potential consideration/suggestions. This may or may not result in approval of the project for quoting and manufacture, potential special requirements in factory manufacture and testing (resulting of course in at least some additional cost), and/or additional suggestions to the project engineer and/or constructor relative to aspects of the system design, installation, or testing. The inquirer for high-pressure applications should have at least the following information available for ACIPCO's consideration:
19Q. What exterior corrosion protection besides polyethylene encasement is available? 19A. There are two primary, though it should be noted "non-standard," alternatives to polyethylene encasement sometimes specified by Purchasers: bonded coatings and cathodic protection systems. If cathodic protection systems are required, they are normally applied in conjunction with special bonded coatings or polyethylene encasement. While not commenting on the efficacy or desirability of these non-standard systems that are also not normally recommended by ACIPCO, some of their features are as follows:
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