Frequently Asked Questions (FAQs)
Frequently Asked Questions (FAQs)
FAQs // Frequently Asked Questions (FAQs)
If possible, the pipe can be inserted to make–up the joint, after assembly the jack can be removed. If the pipe will be inserted into a Mechanical Joint bell, the gland can be slid over the end to hold the pipe round while the joint is made. TYTON JOINT® and TR FLEX® bells are designed to round the pipe as long as the pipe will start into the throat of the bell. Once the pipe is pushed past the gasket it will seal.
Click here for Field Guides for Gauging and Re-Rounding
This information can be found in U.S. Pipe’s guide Safe Packaging and Shipping and also the Installation Guide for Ductile Iron Pipe, published by the Ductile Iron Pipe Research Association (DIPRA). Copies can be obtained from your local U.S. Pipe Sales Representative.
No. The asphaltic coating is applied to the outside of Ductile Iron pipe in accordance with ANSI/AWWA C151/A21.51 to minimize atmospheric oxidation for aesthetic reasons. If soils are determined to be corrosive when tested in accordance with Appendix A of ANSI/AWWA C105/A21.5, DIPRA and its member companies recommend that polyethylene encasement in accordance with the AWWA C105 standard be installed for corrosion protection.
The ANSI/AWWA C150/A21.50 procedure used for calculating truck loads on buried Ductile Iron pipe, which is based on the teachings of Spangler and others, employs the same methods used in ANSI A21.1, the older design standard for Cast Iron pipe. The approach for calculating truck loading is adequate at any depth of cover. However, depths of cover less than 2.5 feet are generally not recommended under roads and highways due to the possibility of high dynamic loading. When 2.5 feet or more of cover cannot be provided, the procedure in ANSI/AWWA C150/A21.50 can still be applied. However, if impact factors higher than 1.5, which is incorporated in the standard, are anticipated, then such impact factors should be employed. Further, in those shallow covers, maintenance of the road surface over the pipe may be more of a concern than serviceability of the pipe.
The procedure for installing gaskets is simple. However, a large part of the reliability of the seal depends on cleanliness of the joint at the time of installation. Considering the variety of conditions that may be encountered in transit or at the jobsite, it would not be possible to ensure joint cleanliness if the gaskets were pre-installed by the manufacturer. Pre-installation would also expose gaskets unnecessarily to ultraviolet exposure and even vandalism.
For mechanical joints, the gland should be slipped some distance back from the plain end of the pipe with the lip of the gland facing the bell. The inside diameter of the mechanical joint gasket is smaller than the outside diameter of the pipe. Brush the plain end of the pipe and the gasket with an approved pipe lubricant as supplied by the manufacturer. The gasket must then be stretched over the plain end of the pipe with the thinner side of the wedge facing the bell. The lubricant allows the gasket to slide more easily into the bell and become equalized as the gland compresses it to achieve a reliable seal.
The TYTON JOINT® and FIELD LOK 350® gaskets have a stiff rim called the heel bonded to a circular cross section called the bulb. After correct installation, the heel will fit into the first groove just inside the bell. The bulb will enter the bell first and will be compressed between the inside of the bell at the gasket seat and the outside of the pipe to achieve a seal. The gasket diameter is larger than the bell opening, so a technique must be followed to allow the gasket to be properly fitted inside the bell.
For smaller pipe, up to about 20”, draw a loop of the gasket towards its center forming somewhat of a heart shape. While holding the loop with one hand, start fitting the gasket heel into the groove of the bell with the other. Gradually release the loop while pressing the gasket evenly into position around the inside circumference of the bell. It may be necessary to firmly seat the loop with the heel of the hand to ensure it is fully seated.
As pipe size increases, it will be necessary to use an increasing number of loops to facilitate gasket installation. In the largest sizes, it is not uncommon to have as many as eight loops, evenly spaced around the gasket. Regardless of pipe size, if the gasket has been properly installed, the leading edge of the rubber should be slightly below the smallest part of the bell opening all around the inside circumference. If any part of the gasket is sticking up, it must be worked until fully seated, or the gasket must be removed and re-installed.
Once the gasket is properly seated, continue with the assembly procedure to make up the joint.
Yes. The HDSS® joint is easily disassembled by following the assembly instruction found in our HDSS® Pipe and Fittings brochure. The FIELD LOK 350® gasket requires a disassembly kit that can be purchased through your U.S. Pipe Representative.
Click to see the 4″-24″ Field Lok Disassembly
Gripper rings can be used to complete closures and are not recommended for use in the pulling/pull back process.
No. It’s always a good practice to use the lubricant furnished by the manufacturer. Our lubricant is formulated to be nontoxic, does not support bacterial growth, has no deteriorating effects on the gasket material, and is water soluble so it readily flushes away prior to acceptance testing of the pipeline. It doesn’t impart any taste or odor to the water in the pipeline, and meets the requirements of AWWA/ANSI C111/A21.11.
Because it is water soluble, it’s sometimes difficult to maintain lubrication on wet surfaces such as a wet trench or stream crossing. In these conditions, it’s advisable to apply the lubricant liberally – as much as three times as much as would normally be used.
We do not recommend the use of spray-on lubricants.
U.S. Pipe does not recommend the use of a FIELD LOK® Gaskets with a TYTON® Plugs. Due to the fact that you cannot get the gasket out unless you cut the pipe bell off because of the flange on the end of the plug. If the plug is pushed in too deep then the set screw holes can be in the gasket bulb causing it to leak. Since the installation was performed with a FIELD LOK Gasket, you cannot pull it out and the fitting or pipe bell would have to be scrapped.
Ductile Iron push-on and mechanical joints are covered in ANSI/AWWA C111/A21.11 “Rubber-Gasket Joints for Ductile-Iron Pressure Pipe and Fittings.” Section 4.2.2 of that standard states: “The mechanical and push-on joints shall have the same pressure rating as the pipe or fitting of which they are a part.” In other words, if the pipe is rated for 150 psi working pressure plus 100 psi surge (250 psi), so is the joint. If the pipe is rated for 350 psi working pressure plus 100 psi surge (450 psi), so is the joint.
This is not to say that Ductile Iron pipe and push-on and mechanical joints cannot be rated above 350 psi working pressure plus 100 psi surge (450 psi). Footnotes under Table 7 in ANSI/AWWA C151/A21.51 “Ductile-Iron Pipe, Centrifugally Cast, for Water” state: “Ductile Iron pipe for working pressures higher than 350 psi is available.” There are numerous Ductile Iron pipelines operating at working pressures well in excess of 350 psi throughout the United States. Additionally, Ductile Iron’s push-on joints have been proven effective in actual tests and/or service with at least 1,000 psi internal pressure, 430 psi external pressure, and 14 psi negative air pressure with no leakage or infiltration.
AWWA/ANSI C110/A21.10: Ductile Iron and Gray Iron Fittings, 3 in. through 48 in. For Water and Other Liquids
AWWA/ANSI C153/A21.53: Ductile Iron Compact Fittings, 3 in. through 24 in. and 54 in. through 64 in. for Water Service
AWWA/ANSI C111/A21.11: Rubber-Gasket Joints for Ductile-Iron Pressure Pipe and Fittings
AWWA/ANSI C104/A21.4: Cement-Mortar Lining for Ductile-Iron Pipe and Fittings for Water
AWWA/ANSI C116/A21.16: Protective Fusion Bonded Epoxy Coatings for the Interior and Exterior Surfaces of Ductile-Iron and Gray-Iron Fittings for Water Supply Service
AWWA/ANSI C105/A21.5: Polyethylene Encasement for Ductile-Iron Pipe Systems
AWWA/ANSI C600: Installation of Ductile-Iron Water Mains and their Appurtenances
ANSI/AWWA C600 “Installation of Ductile-Iron Water Mains and Their Appurtenances” requires that newly installed Ductile Iron water mains be hydrostatically tested at not less than 1.25 times the working pressure at the highest point along the test section and not less than 1.5 times the working pressure at the lowest point of testing.
After the air has been expelled and the valve or valves segregating the part of the system under test have been closed, pressure is then normally applied with a hand pump, gasoline-powered pump, or fire department pumping equipment for large lines. After the main has been brought up to test pressure, it is held at least two hours and the make-up water measured with a displacement meter or by pumping the water from a vessel of known volume. The make-up water is called the “testing allowance,” and the allowable amount is a function of length of pipe tested, nominal diameter of the pipe, and the average test pressure. The hydrostatic pressure test helps to identify damaged or defective pipe, fittings, joints, valves, or hydrants, and also the security of the thrust restraint system.
The “testing allowance” is not a “leakage allowance.” Properly installed Ductile Iron pipelines with properly assembled joints are bottle-tight and do not leak. The “testing allowance” is, however, a practical measure used to maintain the pressure, which might actually drop because of factors other than leakage, including trapped air, absorption of water by the cement lining, extension of restrained joints and other small pipe-soil movements, temperature variations during testing, etc.
The ANSI/AWWA C100 series are applicable to Ductile Iron pipe and fittings. Below is a list of the Standards by title:
A21.4 ANSI Standard for Cement-Mortar Lining for Ductile-Iron Pipe and Fittings for Water
| C104 | |
| C105 | A21.5 ANSI Standard for Polyethylene Encasement for Ductile-Iron Pipe Systems |
| C110 | A21.10 ANSI Standard For Ductile-Iron or Gray-Iron Fittings, 3 In. Through 48 In. (76 mm Through 1,219 mm) for Water |
| C111 | A21.11 ANSI Standard to Rubber-Gasket Joints for Ductile-Iron Pressure Pipe and Fittings |
| C115 | A21.15 ANSI Standard for Flanged Ductile-Iron Pipe with Ductile-Iron or Gray-Iron Threaded Flanges |
| C116 | A21.16 ANSI Standard for Protective Fusion-Bonded Epoxy Coatings for the Interior and exterior Surfaces of Ductile-Iron and Gray-Iron Fittings for Water Supply Service |
| C150 | A21.50 ANSI Standard for Thickness Design of Ductile-Iron Pipe |
| C151 | A21.51 ANSI Standard for Ductile-Iron, Centrifugally Cast, for Water |
| C153 | A21.53 ANSI Standard for Ductile-Iron Compact Fittings, 3 In. Through 24 In. (76 mm Through 610 mm) and 54 In. Through 64 In. (1,400 mm Through 1,600 mm), for Water Service |
| In addition to the 100 series, the following also apply: | |
| C600 | Installation of Ductile-Iron Water Mains and Their Appurtenances |
| C606 | Grooved and Shouldered Joints |
| C651 | Disinfecting Water Mains |
Further information may be found in the AWWA Manual M41, Ductile Iron Pipe and Fittings.
These Standards and Manuals are available from the American Water Works Association, 6666 West Quincy Avenue, Denver, Colorado 80235, Telephone (800) 926-7337, Fax (303) 347-0804, or via e-mail at info@awwa.asn.au.
Yes, you can. Ductile Iron pipe and fittings can be direct tapped for air release valves, sampling ports, service connections, etc. You do want to ensure that there is adequate thread engagement to provide both strength and a leak-free seal. Testing has shown that, with the use of a good thread sealant, as little as one full thread engagement will provide a leak-free tap. Following the conservative nature of our industry, we recommend that you choose at least two full threads of engagement.
The limiting factor in achieving adequate thread engagement for a given metal thickness is the relative curvature of the parent body as the size of the tap increases. There are tables in AWWA/ANSI C151/A21.51 which show the maximum size of tap that can be used on a given size of pipe, and thickness to achieve 2, 3, or 4 thread engagement.
Also, you can order fittings with a boss cast at the location of the desired tap. The flat surface of the boss, along with the increased metal thickness, provides for multiple thread engagement of tap sizes larger than could be accommodated on the curved surface of the fitting.
Some Ductile Iron users specify that pipe be installed with the bell end facing the direction of flow. This theory emanates from the pre-pressure joint era, when common joint sealing materials were cement mortar and jute, asphalt and jute, just asphalt, and various other materials. The theory is predicated on the liquid flowing into the next pipe length prior to leaving the existing length.
Since the introduction of the TYTON JOINT® Pipe in 1956, it has been subjected to various tests. From this testing it has been determined the properly assembled joint will withstand a 14 psi vacuum, a 1,000 psi internal pressure, and a 430 psi external pressure without leakage. Given these results, it is obvious flow direction within the pipeline is not an installation factor.
Ductile Iron pipe is centrifugally cast by pouring molten iron against the inside wall of an externally cooled rotating metal mold. The DeLavaud casting process incorporates a metal mold which has a peen pattern on its inside diameter. This peen pattern is transferred to the pipe during the casting process. There are several reasons why the mold has this peen pattern in 4- 42” sizes. The peen pattern helps dispense thermal shock and helps the mold pick up the molten iron by increasing surface friction between the mold and the iron as the mold is rotated. Additionally, before casting each piece of pipe, an inoculating dry spray is distributed on the inside of the mold. The peen pattern on the mold acts as an anchor pattern that holds and evenly distributes the inoculant. This inoculant increases nodule count, helps refine the grain and nodular size, minimizes carbides, and makes the pipe more easily annealed. The inoculant also acts to deoxidize the iron, thereby preventing the formation of pin holes.
48-64” pipe do not have a peen pattern. The process is a chill-free wet spray casting process. A refractory slurry is sprayed on the inside of the mold followed by the inoculating dry spray. Because of the slurry, no peen pattern is required to hold and evenly distribute the inoculant.
A key to the reliability of the seal is the cleanliness of the joint at the time of assembly. Larger sized buckets of lubricant are more likely to become contaminated at the jobsite and less likely to be discarded when they are. TYTON JOINT® lubricant is available in pints, quarts, and gallons. The smaller containers are less likely to be contaminated with dirt, pebbles, or other foreign matter, which, if trapped between the pipe and gasket, could result in a joint leak.
Understand that if the earthquake is sufficiently large, Mother Nature will always win. However, studies performed after several recent major earthquakes (Kobe, Japan – magnitude 6.9 – 1995, Northridge, CA – magnitude 6.7 – 1994, and Loma Prieta, CA – magnitude 7.0 – 1989) show that ductile iron piping systems suffered significantly less damage than other piping materials.
TR-XTREME®, is our restrained joint pipe that is used for seismic applications, and have often been used to cross fault lines to increase the survivability of the pipeline. When used for this purpose, the TR-XTREME is installed only partially extended. TR-XTREME® pipe is designed for areas of seismic activity. TR-XTREME is the first and only domestic earthquake resistant ductile iron pipe that provides expansion/contraction and deflection within a single restrained bell joint connection.
TR-XTREME joints provide 2.9″ of extension capability to accommodate ground settlement and soil liquefaction during earthquakes while providing joint flexibility up to 5° for 6″, 8″, 12″, and 16″ diameters. TR-XTREME is also available in 20″ and 24″ diameters, and 20″ provides up to 4° deflection, and 24″ provides up to 3° deflection respectively.
Click here to learn more about TR-XTREME Restrained Joint Pipe
No. Usually, a pipeline flowing constantly maintains a fairly even temperature. HDSS® Pipe should always be extended at installation to engage the locking segments which provide joint restraint. When the joint is properly extended, there is sufficient clearance between the face of the pipe plain end and the back of the adjoining bell to accommodate slight changes in length due to thermal effects.
If a Telescoping Sleeve is installed above ground, internal pressure will usually extend the sleeve to its maximum length. In the case of a bridge crossing where the ends of the pipeline are usually fixed, the increase in length often causes the pipeline to snake. A zigzag pipeline is not only aesthetically not pleasing, it can also result in over-deflection at the joints.
The exception to this recommendation is where a pipeline is to cross a lengthy bridge that has been constructed in sections such that the roadbed has expansion joints between sections. Provided the individual pipe on each section are given adequate vertical and lateral support, it may be desirable to add a Telescoping Sleeve at each bridge expansion joint so that the pipeline can accommodate significant movement to the roadbed.
Click here for our information on Long Span & Bridge Crossing Pipe
Cast iron is a generic name for any high carbon molten iron poured as a casting. When used to refer to pipe, cast iron (sometimes called gray iron) is a specific type in which the free graphite (Carbon) is in the shape of flakes. Cast Iron pipe were introduced into the United States in 1817.
Ductile Iron is a specific type of cast iron in which the free graphite is in the shape of nodules or spheroids. (Other names for ductile iron are nodular iron or spheroidal graphite iron.) Ductile Iron Pipe were introduced to the market in 1955.
Although nearly identical chemically, the two irons are quite different metallurgically. The now obsolete standard for Cast Iron Pipe (ANSI/AWWA A21.6/C106) required an iron strength of 18/40 (18,000 psi Bursting Tensile Resistance and 40,000 psi Ring Modulus of Rupture.) Although tensile testing was not a requirement of this standard, a tensile test of gray cast iron pipe would give a test result of approximately 20,000 psi Ultimate Tensile Strength, with no measurable Yield Strength or Elongation.
The current standard for Ductile Iron Pipe (ANSI/AWWA A21.51/C151) requires a minimum grade of 60-42-10 (60,000 psi Ultimate Tensile Strength, 42,000 psi Yield Strength, and 10% Elongation.) In addition, Ductile Iron Pipe manufactured under this standard are required to meet a minimum of 7 ft lbs impact resistance by the Charpy test. (Compare Gray Iron Pipe with an impact resistance of approximately 2 ft lbs or less.)
The difference in the physical properties of these two materials is attributable almost entirely to the difference in the shape of the free graphite. The shape of the graphite is determined at the instant of solidification and is made nodular by the addition of magnesium to the molten iron bath. Although Cast Iron was the best engineering material available for pipe production for nearly five hundred years, the development of Ductile Iron Pipe provides a far superior product.
While other manufacturers are licensed to manufacture the TYTON JOINT® through 24″ diameter, only TYTON JOINTS® conforming to current joint configurations which allow 5 degree joint deflection are applicable with FIELD LOK 350® gaskets.
FIELD LOK 350® gaskets cannot be used for bridge crossings. The FIELD LOK 350® gasket is a friction restrained joint and due to the fact that bridges are subject to vibration from vehicles traveling over the bridge, there is a possibility that the gasket could work itself lose. U.S. Pipe’s recommendation for bridge crossings is HDSS® pipe.
Click here for our PDF on Long Span & Bridge Crossing Pipe
Click here for Technical Resource Video – Bridge Crossing Planning & Installation
The FIELD LOK 350® gasket and HDSS® joint are both boltless restraints. This saves time by not having to tighten any nuts & bolts as well as preventing possible leaks where a bolt wasn’t tightened.
U.S. Pipe’s primary method of thrust restraint are restrained joints.
A column of liquid moving through a pipeline has momentum or force that tends to separate the joints at changes in direction (bends and tees), stops (plugs, caps, or closed valves), and changes in size (reducers). Some means must be used to prevent joint separation to maintain the integrity of the pipeline. Three such means are thrust blocks, tie rods, and restrained joints.
Thrust blocks are usually poured-in-place concrete. They must be engineered with full knowledge of the pipeline operating characteristics and of soil type and bearing strength. They must bear against virgin soil, because thrust forces in the pipeline are transmitted through the thrust block to the soil. Depending on these conditions, thrust blocks can be quite massive. The use of thrust blocks can delay completion of the project to allow the concrete to cure adequately before applying test pressure to the pipeline. If future construction disturbs the thrust block or the surrounding soil, joint restraint and the integrity of the pipeline can be jeopardized.
Tie rods usually involve some sort of fabricated steel harness on either side of the joint held together by tie-rods. This type of joint restraint is generally labor intensive. A tie-rod type of joint restraint must be adequately protected against weakening by corrosion, or else the joint restraint and integrity of the pipeline can be jeopardized.
Restrained joints are designed to hold the joint together against a rated pressure while the pipeline transfers the thrust force to the surrounding soil envelope. In order to calculate the footage of restrained pipeline necessary for the thrust force to be fully dissipated to the soil, it is necessary to know pipe diameter, maximum anticipated internal pressure, depth of cover, soil type, and trench construction type, as well as the configuration (e.g., bend angle) requiring restraint. The calculated restrained footage must be installed on each side of the fitting. Since polyethylene encasement for external corrosion protection reduces the friction between the pipeline and the surrounding soil, the calculated restrained footage is usually multiplied by a factor of 1.5 for pipelines where polyethylene encasement is to be installed.
Mechanical joint retainer glands, both common and proprietary design, are available for use where such devices must be used (e.g., a special valve or meter). However, U.S. Pipe does not recommend their use. Restrained push-on joints manufactured by U.S. Pipe are less susceptible to external corrosion, offer appreciably more deflection, and are much less labor-intensive to install.
Deflection of the pipe should occur after the plain end has compressed the gasket but prior to the plain end being homed into the bell. See FIELD LOK 350® animation for complete details of assembly.
Click here for: 4″-24″ Field Lok Installation
Pulling back on the FIELD LOK 350® gasket causes the stainless steel locking segments to engage the pipe, activating the restraint mechanism. Pulling back on the HDSS® pipe puts the joint in tension as well as taking up the “slop” in the joint. If this is not done, the line will “grow” when pressure is introduced to it which could cause problems.
There are many variables that determine the length of pull using horizontal directional drilling. The type of soil, size of equipment, amount, concentration and viscosity of the bentonite in the drilling mud are just a few of the variables that can determine the length of the pull. The longest pull to date was 2120 feet of 12” TR FLEX® pipe.
Soil conditions can vary widely and change dramatically within the length of the intended pull, it is for this reason that consideration be given to take soil samples at regular intervals along the intended bore-path at the depth of the bore. This information would enable the drilling operator to adjust the bentonite mixture, viscosity and add any other stabilizing additives as per the bentonite manufactures recommendations.
Double poly-wrap is recommended either with the first layer being the low-density poly with high-density over the outside or double wrapped with low-density.
Spiral winding is easier to do in a muddy trench and also does not allow the drilling mud to build-up underneath the poly-wrap causing it to balloon. All over-lapped edges of the poly-wrap should be taped except for the over-lapped poly along the length of the barrel, where the spiral winding is sufficient.
Because buried Ductile Iron pipelines are electrically discontinuous and are essentially grounded for their entire length, overhead AC power lines normally don’t impose corrosion or safety concerns.
A consequence of AC power lines and buried pipelines sharing rights-of-way is that AC voltages and currents can be induced by magnetic induction on the pipelines. The magnitude of the induced voltage and current on the pipeline is a function of a number of variables, including the length of pipeline paralleling the AC power line, the longitudinal resistance of the pipeline, and the resistance of the pipeline coating.
Ductile Iron pipe is manufactured in nominal 18- and 20-foot lengths and employs a rubber-gasketed jointing system. These rubber-gasketed joints offer electrical resistance that can vary from a fraction of an ohm to several ohms but nevertheless is sufficient for Ductile Iron pipelines to be considered electrically discontinuous. In effect, the rubber-gasketed joints normally segment the pipe, restricting its electrically continuous length, and prevent magnetic induction from being a problem. Also, in most cases, Ductile Iron pipelines are installed bare with only a standard 1-mil asphaltic coating and therefore are effectively grounded for their entire length, which further prevents magnetic induction on the pipeline.
During construction of Ductile Iron pipelines in the vicinity of overhead AC power lines, certain safety precautions should be followed, e.g., “limit of approach” regulations governing construction equipment, grounding straps, chains attached to rubber-tired vehicles to provide a ground, grounding mats, etc., especially if safety concerns are heightened due to the use of joint bonding and dielectric coatings.
Repair is achieved by first cutting out the defective or damaged lining to the metal so that the edges of the lining not removed are reasonably perpendicular to the pipe wall or slightly undercut. A stiff mortar is then prepared, containing not less than one part of cement to two parts of sand, by volume. This mortar is applied to the cutout area and troweled smooth with adjoining lining. To provide for proper curing of patches by preventing too rapid of a moisture loss from the mortar, the patched area is normally seal-coated immediately after any surface water evaporates, or alternatively the area is kept moist (e.g. with wet rags or burlap over the area or with the ends of the pipe or fitting taped over with plastic film, etc.). Of course, in potable water-related applications, no patch or curing components should be used in the repair that would negatively affect health or water quality.
Yes, Ductile Iron products can be successfully Glass lined. Glass lined pipe and fittings have been specified and utilized as a deterrent to interior build-up and clogging of problematic sludge and scum piping systems in wastewater and sewage treatment facilities for over 40 years. Not only is the excellent non-stick characteristic effective in combating the build-up of grease, sludge, and scum, but has been found to be the only deterrent to Struvite and Vivionite build-up as well.
See more here: Glass Lining (Porcelain Enamel)
Direct service taps may be made right through the polyethylene encasement. The preferred method is to apply two of three wraps of adhesive tape completely around the wrapped pipe to cover the area where the tapping machine and chain will be mounted. The corporation stop is installed directly through the tape and wrap. Although this method is effective in eliminating damage to the polyethylene during the tapping operation, the entire circumferential area should be inspected for damage and repaired if needed.
To install the gasket correctly in the groove in the bell, it must be uniformly distributed around the interior of the bell circumference. To do this, the gasket must be looped as it is initially placed in the bell. As a general rule:
4″ through 12″ gaskets generally require one loop. In cooler weather it may be easier to install the 10″ and 12″ gaskets using two loops placed at the twelve and six o’clock positions.
14″ through 20″ gaskets generally require two loops but three may be necessary, placed at the twelve and six o’clock positions.
24″ through 36″ gaskets generally require four loops, spaced approximately 90° apart. Put the bottom loop in first to prevent debris from being introduced into the joint.
42″ and 48″ gaskets generally require six loops, spaced equally around the circumference of the bell. Put the bottom loop in first to prevent debris from being introduced into the joint.
54″ through 64″ gaskets generally require eight loops, spaced equally around the circumference of the bell. Put the bottom loop in first to prevent debris from being introduced into the joint.
In cooler weather, it is usually a good idea to warm the gaskets before trying to install them or store them in a warm environment.
Never lubricate the gasket or gasket groove prior to installation of gasket into the bell.
Potable Water
This is by far the most common application for Ductile Iron Pipe. Because of its reliability and durability, it is the ideal choice for the transmission and distribution of potable water. The value of potable water is rapidly increasing. Water lost between the treatment plant and the customer’s meter is revenue lost. From the aspect of protecting the public health, it is vitally important to protect water quality from treatment to point of use. With the exception of some special linings for sewer service, virtually all of the products marketed by U.S. Pipe & Foundry are approved by the National Sanitation Foundation (NSF) for the conveyance of potable water.
Fire Protection
Historically, the primary purpose for developing a system to distribute water was for fighting fire. The concern for the protection of lives and property was paramount, even above that of providing water for drinking and sanitation. A fire protection system must be absolutely reliable and fully functional at all times. Factory Mutual is an insurance organization with a focus on risk management and the prevention of property loss. In that role, they are particularly interested in fire protection systems, most of which are 12″ and smaller. Most of the products 12″ and smaller marketed by U.S. Pipe and Foundry are approved by Factory Mutual for use in fire protection systems.
The National Fire Protection Association is a national organization that promulgates codes and standards dedicated to fire safety and prevention. It is common for one such body to recognize and accept standards written by another organization, and to incorporate them into their own. Many of the NFPA Standards for fire protection systems incorporate the same American Water Works Association Standards to which U.S. Pipe and Foundry manufactures its products.
Wastewater
Ductile Iron pipe and fittings are ideally suited for wastewater systems. Wastewater pipelines fall into two categories: gravity sewers and force mains. A leaking sewer line can spread contaminated wastewater to the groundwater system. Infiltration and inflow (I&I) can overburden the wastewater treatment plant, since every gallon flowing to the plant must be treated. Severe I&I also leads to extremely excessive treatment costs. It is important to specify and install a durable piping material with reliable joints. U.S. Pipe’s TYTON JOINT® and TR FLEX® Pipe joints are bottle-tight, preventing both I&I and exfiltration.
In a gravity sewer system, wastewater flows downhill through the force of gravity. Gravity systems generally do not flow full, which can lead to septic sewage transformations that can lead to hydrogen sulfide gas being converted to concentrated sulfuric acid, which is very aggressive toward cement mortar linings and Ductile Iron. In a properly designed and constructed gravity sewer system, there will be adequate slope to provide a self-cleaning velocity (generally accepted as 2 ft/sec.). Under these conditions, a standard cement mortar lining will provide adequate corrosion protection for the pipeline. For less than optimum conditions, PROTECTO 401™, a ceramic epoxy lining, is recommended.
Gravity sewers must often be installed at great depths in order to achieve adequate slope. The inherent strength of Ductile Iron enables it to withstand the external loads imposed by the earth at greater depths. As the gravity sewer increases in depth, it will reach a practical limit. At this point in the project, wastewater is collected at a pumping station. The discharge line from the pump station is then a force main, since the wastewater is pumped under pressure.
A sewer force main operates as a pressure line. It does not have to be installed to a precise grade. For maximum hydraulic efficiency it should flow full at all times. This generally requires air relief valves at all high spots in the pipeline. When the pipe is kept full, there is no opportunity for hydrogen sulfide gas to collect, which virtually eliminates the possibility of septic sewage transformations. A standard cement mortar lining is usually adequate to protect the pipeline. Other linings, such as PROTECTO 401™, are available if the designer so specifies.
Reclaimed Water
A reclaimed water pipeline conveys treated wastewater for beneficial re-use. Only products meeting the requirements for potable water should be specified for reclaimed water, since, ultimately, reclaimed water usually ends up in the potable water supply system.
Digester Gas – Not!
Ductile Iron pipe and fittings are not suitable for digester gas service; thus, U.S. Pipe will not knowingly supply products for such a project. At one time, the ANSI A21.52 and A21.14 standards governed the manufacture of Ductile Iron pipe and fittings (respectively) for gas service. These standards were withdrawn a number of years ago. Ductile Iron pipe for gas service was required to undergo special processing and testing. The equipment needed is no longer available at any U.S. Pipe facilities.
If external corrosion is a concern, the Ductile Iron Pipe Research Association (DIPRA) recommends the use of loose film polyethylene encasement, purchased and installed in accordance with AWWA C105. Polyethylene encasement is the most cost-effective means of mitigating external corrosion under the broadest range of possible conditions.
The subject of external corrosion on underground metallic pipelines has been written about extensively, with many “experts” extolling the absolute necessity for elaborate corrosion control systems. While the debate continues, two facts are often overlooked:
- Extensive soil surveys conducted by a multitude of agencies throughout the country indicate that only about 10% of the soils in the United States are aggressive toward ductile iron products.
- Loose film polyethylene encasement has over 45 years of service history protecting your investment in millions of feet of cast and ductile iron pipe.
Sometimes called “Polywrap,” loose film polyethylene is inexpensive, easy to install, does not degrade in service and therefore, requires no maintenance.
You may sometimes encounter corrosive conditions so severe that you should consider methods other than polyethylene encasement. When in doubt, ask your U.S. Pipe Sales Representative to arrange a free consultation with a DIPRA Regional Engineer. DIPRA Regional Engineers are NACE International-certified Corrosion Specialists, and will help you make the right decision for your specific project requirements.
| Internal Lining Systems | Holiday Test | Minimum Number of Coats | Minimum Thickness (MILS) | Average Thickness (MILS) |
| Unlined | – | 0 | – | – |
| Asphalt Lining 1 | – | 1 | 1 | 3 |
| Cement Lining with Sealcoat 1 | – | 1 | AWWA C104 | – |
| Cement Lining without Sealcoat 1 | – | 0 | – | – |
| Double Thick Cement Lining with Sealcoat 1 | – | 1 | AWWA C104 | – |
| Double Thick Cement Lining without Sealcoat 1 | – | 0 | – | – |
| Protecto 401 Ceramin Epoxy Lining 5 | 2500 volts | 1 | 35 | 40 |
| Induron® Red Oxide Epoxy Primer 1 | – | 2 | 8 | 10 |
| Tnemec® 140 – 1211 Red Oxide Primer 1 | – | 2 | 9 | 11 |
| Induron® Ruff Stuff 3300 Epoxy 6 | low volt wet sponge | 2 | 20 | 24 |
1 NSF approved for drinking water
2 Primer coat only applied at factory
3 Standard lining and coating for 4″ – 24″ fittings and valves
4 Conforming to AWWA C116
5 Sanitary sewer only
6 12″ and greater, pipe and fittings
Select the link below to see our UL Listings. For FM listings, email info@uspipe.com.
U.S. Pipe recommends that only flexible joints be buried i.e. Mechanical Joint, TYTON JOINT®, HDSS®, and HP LOK®.
Can a plain end pipe spigot be assembled into a restrained joint pipe bell such as HDSS® or HP LOK®?
Yes, any Ductile-Iron plain end pipe sized spigot (be it Ductile-Iron, Cast-Iron, Steel or PVC) having the same AWWA diameter tolerance of Ductile-Iron, will fit and seal in a HDSS® or HP LOK®.
Double thickness cement mortar lining in accordance with ANSI/AWWA C104/A21.4, Section 4.7.2., with seal coat in accordance with section 4.11. The cement in the cement mortar lining shall conform to ASTM C150, Type V. The internal joint areas coming in contact with the seawater, the “wetted areas”, should be coated with Induron PE-54 epoxy or they can be wrapped with Denso tape. Denso tape can be purchased through DENSO NORTH AMERICA, INC. in Houston, TX – Phone No. 281-821-3355 or www.densona.com.
Although there are differing opinions on this subject, a conservative maximum velocity for design purposes is 7 fps (feet per second).
The AWWA (American Water Works Association) standard for thickness design of ductile iron pipe is C150. The exercise for calculating the required thickness based on internal pressure includes a 100 psi allowance for surge pressure and a 2:1 safety factor. The surge pressure allowance is based on a 50 psi pressure rise for each foot of extinguished velocity, and the fact that most domestic water systems operate at approximately 2 fps.
Ductile Iron pipe may be rated as high as 350 psi service. A pipeline operating at 7 fps velocity could account for a 350 psi pressure surge (7fps X 50 psi/fps). Adding a potential surge pressure equal to the pressure rating of the pipe encroaches significantly on the safety factor. Exceeding 7 fps velocity could produce potentially damaging surge pressure.
The “service allowance” used in the design of Ductile Iron pipe is a holdover from the old Gray Iron pipe days. During that early period, it was called a “corrosion allowance” to offset any initial corrosion or minor surface imperfections that might occur.
With the advent of Ductile Iron pipe and polyethylene encasement for corrosion control, the corrosion allowance was retained for similar general conservatism but renamed as a service allowance.
The addition of a 0.08-inch service allowance, which is unique to Ductile Iron pipe, ensures that the actual wall thickness will always exceed the design thickness, thereby providing an additional margin of safety and dependability.
The external trench load in ANSI/AWWA C150/A21.50 consists of earth load plus truck load. The earth load on pipe increases as the depth of cover increases; the truck load increases as the depth of cover decreases. Therefore, the maximum depth of cover normally is limited by the earth load and the minimum depth of cover is limited by the truck load. For lower pressure classes of pipe in sizes 14 inches and larger installed in a Type 1 trench, this band of allowable depth of cover is limited, or even non-existent. Also, for higher pressure classes of pipe in sizes 14 inches and greater, it would normally be more economical to specify a better trench and a lower pressure class of pipe than a higher pressure class of pipe and a Type 1 trench. Improved bedding is desirable, particularly in larger pipe sizes, to improve uniformity of axial support under the haunches.
Yes. Both ANSI/AWWA C150/A21.50 and ANSI/AWWA C151/A21.51 state that Ductile Iron pipe is available for water working pressure greater than 350 psi. These standards also list Pressure Class and Special Thickness Class Ductile Iron pipe. The Pressure Class designations (150 psi to 350 psi) in the standards are based on a 2.0 safety factor times the sum of working pressure and 100 psi allowance of surge. This establishes a net thickness to which a service allowance of 0.08-inch and a casting tolerance (which is dependent on the diameter of the pipe) is added. Based on the same design criteria, 6-inch Special Thickness Class 56 Ductile Iron pipe would be rated at 1,726 psi internal working pressure. Special Thickness Classes of Ductile Iron pipe are normally specified only because of high external loads due to deep bury, high dynamic loading, etc.; however, Special Thickness Class Ductile Iron pipe has also been specified and installed in systems with working pressures greater than 1,000 psi. For information and limitations, contact the manufacturers of Ductile Iron pipe.
Appendix A of ANSI/AWWA C151/A21.51, Ductile Iron Pipe, Centrifugally Cast, for Water, contains the minimum metal wall thickness required for 2, 3, and 4 threads for different diameter threaded outlets and different diameter pipe. Information is given for both threads conforming to Standard ANSI/ASME B1.20.1 (a.k.a. National Pipe Thread (NPT), Iron Pipe Thread (IP), or Standard Taper Pipe Thread) and AWWA C800 (a.k.a. Mueller Thread, cc thread, Corp Stop Thread). To assure adequate metal thickness for a particular pipe diameter and Pressure or Thickness Class, it is necessary to subtract the casting tolerance found in the Table in Section 4.4.2 from the Nominal Metal Wall thickness found in Table 1 of ANSI/AWWA C151/A21.51.
Concerning the security of a two engaged threads engagement, the Ductile Iron Pipe Research Association (DIPRA) conducted a study of ¾-inch and 1-inch corporation stops direct tapped into 6″ Pressure Class 350 pipe. The tests were conducted on pipe sections with less than nominal metal wall thickness. After multiple corporation stops were installed in each piece of pipe under city line pressure, the installations were observed for leakage through the threads. The water pressure was then raised to 1,000 psi in an effort to fail the 6″ pipe and threaded connection. Leakage was not observed at the threaded connection. These tests were conducted with and without 3-mil thread sealing tape applied to the threads of the corporation stop. The installed corporation stops were then subjected to pull-out and cantilever load tests. In the pull-out tests, the corporation stop failed at loads in excess of 6,500 pounds of force. The pipe threads were undamaged in each of the three tests. In the cantilever load tests, the corporation stops failed at bending moments in excess of 385 foot-pounds of force. Again the threads in the ductile iron pipe wall were undamaged.
It can be clearly seen that work crews can direct tap service connections into Pressure Class Ductile Iron pipe under pressure, effecting structurally secure, watertight seals. It is recommended that two layers of 3-mil thread sealant tape be applied to the corporation stop threads to achieve a watertight service connection using a minimal tightening torque.
The results of this study have been published by the Ductile Iron Pipe Research Association under the title Direct Tapping of 6-inch Pressure Class 350 Ductile Iron Pipe and is available through the Web Site http://www.dipra.org.
