As a companion piece to the Iron Strong Blog entry, What Type of Ductile Iron Pipe Joint Is Right for You? by Scott Rhorick, this article takes a deeper dive into the specifics of installing restrained joint Ductile iron pipe (DI pipe) through a steel casing pipe. While many options are available industry-wide, this article concentrates on using TR Flex® or Sure Stop Gaskets in cased installations.
TR Flex Pipe in Casings
TR Flex is the most widely accepted and installed integrally cast restraint joint system in the Ductile iron pipe industry and perfectly suited for use inside casing pipe. McWane Ductile manufactures TR Flex pipe in sizes 4-inch through 36-inch. Some of the benefits of TR Flex include:
- TR Flex is easily assembled, flexible, and watertight to and beyond its 350-psi rating.
- TR Flex uses a Tyton joint gasket for a watertight seal along with a factory-adapted spigot and bell to provide positive longitudinal joint restraint while also permitting considerable expansion/contraction and in-service deflection within each joint when needed.
- Each joint itself can expand/contract from 0.36-inches to 0.72-inches and deflect from 1.5 to 5.0 degrees in any direction depending upon diameter. Hence, the “flex-ible” in TR Flex.
- Because the TR Flex joint, pipe and/or fittings, is a boltless restraint joint system, it eliminates the need for any bolts, clamps, rods, or retaining glands.
- This system also removes the worry of proper assembly and tightening of mechanical restraining devices and bolts. However, if desired, mechanical joint fittings can be used with TR Flex pipe by simply cutting any pipe barrel of a TR Flex pipe and using wedge-actioner retainer glands to secure the Ductile iron fitting into the restrained pipeline segment.
Anyone who has ever been involved with installing DI pipe in casing pipe knows the importance of making sure the joints are watertight and will not pull apart. Repairing a leak inside a casing pipe can be time-consuming, challenging, and costly.
A Few Installations Tips:
- Keep the Tyton gaskets warm and flexible during cold weather to ease installation.
- After carefully placing the rubber gasket into its bell recess, apply plenty of lube to the gasket Inside Diameter and the spigot end of pipe.
- Maintain straight alignment when installing spigot into the bell. If casing spacers are being used, wood blocks under the spigot end could help maintain proper alignment.
- Chain-downs or other bracing behind the bell prevents the joint being assembled from traveling into the casing until desired following assembly.
- Once the TR Flex joint is completely assembled, extend the joint to take out the slack inside the joint. If not manually extended, the joints will all extend themselves once the internal pressure exceeds 50-psi for any pipe diameter, so leave both ends free to move until this occurs.
- While pushing is most often the primary driving force for placing the pipeline through the casing as it builds, it is highly recommended to tug the leading spigot concurrently to keep the pipeline reasonably straight, joints extended, and minimize the potential for damaging the casing spacers. A puller head or other mechanism on the lead spigot connected by wire-rope or chain to a backhoe or similar mobile equipment beyond the exit end of the casing accomplishes this easily.
- PRO TIP: a small remote-control vehicle can deliver a nylon rope through the casing, to which the pull-chain can then be attached to and dragged from the exit end through the casing to the feed-end by the contractor.
- A final note about TR Flex pipe is that if the joint needs to be disassembled for any reason, it can be easily taken apart compared to other joints.
Sure Stop 350 Gaskets in Casing Pipe
A second method of restraining Ductile iron pipe in casings would be to install with Sure Stop 350 gaskets in Tyton® Joint pipe. Sure Stop 350 gaskets have specially designed stainless-steel teeth vulcanized into the gasket body, which during joint assembly grip the spigot end and restrain the pipe. The gaskets are available in sizes 3-inch through 24-inch and have a rating of 350 psi.
While the safe end pull of this type of restraint is not equal to that of the integrally cast TR Flex pipe joint, it is more than sufficient to handle most casing applications between 500 and 750 feet in length, depending upon the diameter and pipe wall class chosen. Contact your McWane Ductile Sales Representative for a consult with our engineering staff for casings outside than range.
This method also does away with the need for bolts, rods, clamps, or retainer glands, which could lead to leaks inside the casing if not properly installed and tightened. As mentioned previously, joint repairs inside of casings are expensive and time-consuming.
General Pro Tips When Using Sure Stop 350 Gaskets:
- They are often referred to as "one-shot" gaskets, in that once the pipe barrel engages the embedded teeth of the gasket, there is no "backing out" or easy disassembly. The harder you try to pull the joint apart the more they grip. Take the extra 10 seconds and make sure the gasket channel is clean and the gasket is seated correctly. The front edge of any gasket should NEVER sit above the front lip of the pipe bell face.
- Use more lube on the gasket than you do on standard Tyton gaskets. This can minimize the accidental engagement of a steel tooth with the pipe barrel during the spigot's initial set onto the bell entry.
- Push the joint home FIRM, STRAIGHT, and STEADY. "Wiggling" the joint home with a push-bar or backhoe bucket is highly discouraged. Sure Stop 350 gaskets will "push home harder," do not be alarmed by that.
Installation Tips When Using Sure Stop 350 Gaskets Inside Casings:
- Same as with the standard Tyton gaskets described in the earlier bullet list above, PLUS:
- Sure Stop 350 gaskets have little to zero expansion capability within the joint itself yet it remains crucial, for the integrity of the casing spacers and to prevent over-deflecting the joints during the pipelines travel through the casing, that a pulling force from the lead spigot (exit end of the casing) is applied during concurrently to any pushing force provided at the feed end of the casing.
- The only true caveat to using restraining gaskets such as Sure Stop 350 is that they are not recommended for installations that will experience regular or repeatable vibrations, such as traffic or other influences on a bridge or railroad adjacent. While this is more of a theoretical restriction than actual experienced, it is always better to err on the side of caution.
While engineers and contractors most-prefer TR Flex joints for casing installations of Ductile iron pipe, Sure Stop 350 gaskets have served numerous cased installations around the United States and many other countries. Each installation requires just a little bit of thought and planning to avoid adversity during construction or long-term in-service action.
Need Assistance with Your Waterworks Project?
If you have any questions regarding Ductile iron pipe installations, be sure to reach out to your local McWane Ductile representative. We have team members who've managed small and large water utility systems, served in engineering consulting firms, and bring decades of experience in solving field issues involving pipeline construction and operation. From design to submittal, to installation, we strive to provide education and assistance to water professionals throughout the water and wastewater industry.