New Pipeline Construction Product Allows for Simple Installation of Standard PVC Pipe in Houston HDD Project

By Dennis Shumard, P.E., MASCE, and Pat Moravits, BRH-Garver Construction | March 2014, Vol. 69 No. 3

“When pipe joint failures occur, in most instances the pipe was inserted well beyond the manufacturer’s recommended mark. This is referred to as ‘“Over-Belled”’ pipe.” (Folkman 2010)

“Numerous pipeline failure analyses have been traced back to excessive stresses on the bell as a result of over-insertion.” (Rahman 2005)

“In the Root Cause Analysis ‘“Over insertion of the joint”’ was listed first as the cause of failure.” (Dueck 2010)

“Gasketed joints must be able to accommodate the changes in length.” (Rahman 2005) This accommodation is accomplished in a properly installed joint via the resulting gap between the end of the spigot and the back of the bell as shown in Figure 1. (EBAA Iron Sales 2011) This gap is a characteristic of conventional PVC pipe bells and a stop line that is provided on every spigot as an installation aid to properly locate the spigot relative to the bell of the joined pipes.

Over-insertion prevents a joint from absorbing changes in length or joint deflection. Failure to address over-insertion can result in the build-up in stresses in the pipe bell that can, over time, exceed the strength capability of the pipe material and result in a failure of the pipe.

Figure 1: Gap in a properly assembled pipe joint.

The Mega-Stop bell protection device is designed specifically to address this issue. The simple device is shown in Figure 2 and is comprised of two basic components. The first is a stop ring that is fixed on the spigot to provide the means for physically preventing pushing the spigot of a pipe joint too far into the bell. The second is an expansion retention spring (ERS) that provides a “cushion” between the stop ring and the lip of the bell to ensure the proper placement of the spigot inside the bell. The ERS, therefore, maintains the ability of the assembled PVC pipe joint to expand and contract in response to temperature changes, soil movement, and joint deflection. This feature is beneficial for both trenchless and open cut installations.

The product can be installed in typical open-cut applications at every joint as well. Doing so ensures that every joint will be installed correctly, can be inspected easily, and will provide assurance of long-term performance. Likewise it has proven valuable in casing/HDD applications where pushing conventional pipe would result in over-inserted joints.

Figure 2: Installed Mega-Stop at a pipe joint identifying components.

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