Plastic/FRP Piping & The Proco Series 261R

The Proco Series 261R Wide-Arch Expansion Joint is specifically designed for use with plastic or FRP piping systems. A replacement for the standard spool-type expansion joints, the Proco 261R has exceptionally low spring rates compared to its conventional counterparts. With its low forces to compress, extend or laterally offset, the Proco Series 261R can be used on plastic or FRP pipes, pumps, valves or tanks without fear of the expansion joint being stronger than the pipe, pump, valve or tank flanges. 

Series 261R

Figure 1: Series 261R

When pairing the Series 261R with standard control units utilizing control/gusset plates, it is recommended to use a stiffener ring to reinforce the mating flange. Placing the stiffener ring on the back of the mating flange will reinforce the mating flange by more evenly distributing the pressure thrust loads experienced by the control units across the flange in lieu of a standard installation where the loads are localized at the points of contact between the control/gusset plate and flange. 

Series 261R with Control Units

Figure 2: Series 261R w/Control Units (Inboard & Outboard Nuts)

If stiffener rings are not used, then the allowable stress on the mating flanges need to be confirmed. Not utilizing stiffener rings while using control units adds local stresses on the points of contact between the mating flange and control plates that may surpass the allowable stress for the flange resulting in a possible failure of the flange. 

Series 261R stiffeners

Figure 3: General stress plot of mating flange without stiffener ring (Left), with stiffener ring (Right)

For more information regarding the Series  261R wide-arch, low spring rate expansion joints, please contact a Proco representative or download the brochure for more information.