What method of restraint is best?
There are various methods available for restraining Ductile Iron Pipe joints, and a common question our customers ask us is, “Which method of restraint is best – locking gaskets or boltless restrained joints?”
Both methods work very well, but the “best” method of restraint for your project can vary depending on the type of installation, the pressure the line will operate under, and the size (diameter) of the ductile iron pipe that is being used.
In this article, we will compare two common restraint options supplied by McWane Ductile - Sure Stop 350® Gaskets and TR Flex® pipe.
To help guide us through this discussion, we will look at a list of questions to consider when choosing the proper restraint. But first, let’s start with a simple explanation of each type.
What is a Sure Stop 350® Gasket?
Sure Stop 350® gaskets are restrained joint gaskets typically made of SBR rubber and locking segments of stainless steel teeth that can be used in Tyton Joint® pipe for a quick installation option when joint restraint is required.
These gaskets can also be offered in other elastomers such as Neoprene or EPDM, too.
What is TR Flex Pipe?
TR Flex pipe is an integrally cast restrained joint system that encompasses a factory installed welded bead that works in conjunction with the locking segments to restrain the joint.
The TR Flex® system also includes a large selection of TR Flex® fittings.
What sizes are available with each type?
Sure Stop 350® gaskets are available in sizes 3” through 24”.
TR-Flex® is available in sizes 4” through 36”.
Where can I use these products?
The Sure Stop 350® gasket is a great solution for long runs of buried pipe where joint restraint is required and offers an easy solution for restraining field cut pipe. The Sure Stop 350® is also acceptable as a joint restraint for Tyton® push-on joint fittings that require restraint as well.
TR Flex® pipe can be used for direct bury projects, horizontal directional drilling, bridge crossings, pipe in casing, pipe bursting, above ground applications (pipe on supports), seismic areas, subaqueous installations and unstable soil conditions.
For more information on the usage applications for TR Flex® pipe, please refer to our blog "What is TR Flex® Pipe and How is it Assembled?"
Deflection consideration
When choosing the best option for your direct bury application, the amount of deflection that can be achieved form each joint can be important and may help reduce the number of bends you have to install. The deflection limits for each are as follows:
Sure Stop 350® maximum deflection
- 3” through 12” can achieve 5 degrees of maximum allowable deflection
- 14” through 18” can achieve 4 degrees of maximum allowable deflection
- 20” through 24” can achieve 2 ½ degrees of maximum allowable deflection
TR Flex® maximum deflection:
- 4” through 12” can achieve 5 degrees of maximum allowable deflection
- 14” through 16” can achieve 3 ¼ degrees of maximum allowable deflection
- 18” can achieve 3 degrees of maximum allowable deflection
- 20” can achieve 2 ½ degrees of maximum allowable deflection
- 24” can achieve 2 ¼ degrees of maximum allowable deflection
- 30” can achieve 1 ¾ degrees of maximum allowable deflection
- 36” can achieve 1 ½ degrees of maximum allowable deflection
Note: The owner or engineer may have specific job requirements that limit the available deflection of the joint. Make sure to consult the project requirements prior to material selection and installation.
Sure Stop 350® Features and Benefits
- Provides boltless restraint with a working pressure of 350 psi in accordance with ANSI/AWWA C111/A21.11
- Quick installation taking no longer than a standard Tyton Joint® gasket
- Prevents joints from separation due to thrust forces
- Allows up to 5 degrees of deflection depending on the pipe diameter
TR Flex® Features and Benefits
- Provides 350 psi working pressure in 4” through 24” and 250 psi in 30” through 36”
- Restrained joint connections with easy assembly and disassembly if needed
- Large variety of TR Flex® fittings to fit almost any application
- Available with arc applied zinc coating per ISO 8179
- Allows up to 5 degrees of deflection depending on the pipe diameter.
The correct restraint choice for your project
Once you know the size of the pipe, the type of installation, the desired deflection and if there may be a need for future disassembly of the pipe you are set to pick the correct joint restraint for your system.
For example, if you are installing 24” ductile iron pipe in a HDD application your recommended restraint would be TR Flex®.
If you are installing 24” ductile iron pipe in a buried application and would like to achieve up to 2 ½ degrees of deflection you may want to use Sure Stop 350® gaskets to achieve your desired result.
Hopefully, the above information has been helpful in determining what restraint method may be a better fit for your given project needs. If you have any additional concerns, don’t hesitate to contact your local McWane Ductile Sales Representative with any design considerations for your project. And as always, the McWane Pocket Engineer with its various calculators including one for Thrust Restraint can be found at www.mcwaneductile.com.
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