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IRVING, TX — The Plastics Pipe Institute’s (PPI) Building & Construction Division's new technical document provides design and installation recommendations for transitioning from polypropylene pipe to other piping materials using flange adapters and connections. PPI TN-71, “Flanges and Flange Adapters for Polypropylene (PP-R & PP-RCT) Piping Systems”, is now available at the division’s website.
Polypropylene (PP-R and PP-RCT) pressure pipe and fittings are usually joined to each other by butt fusion, socket fusion, sidewall outlet fusion, or electrofusion methods. ASTM recently published the new ASTM F3722-24 “Standard Practice for Heat Fusion Joining of Polypropylene (PP) Pipe & Fittings” to give guidance on joining those types of fusion connections.
Flanged Assemblies
Flanged assemblies are commonly used for connections to fittings and valves from PP pipes to pipes of other materials (e.g., CPVC, HDPE, steel), or as end connections on fabricated pipe spools and assemblies.
According to Lance MacNevin, P. Eng., director of engineering for PPI's Building & Construction Division, “Flanged joints prevent leakage by compressing a deformable gasket material into irregularities in a less deformable material to seal possible leak paths. The mating faces of flanged joints are the surface areas that need to be sealed. The deformation characteristics of the material, which includes gasket hardness, compressive strength, and compression set, are the primary determinant of the amount of compression, expressed as force per unit area, or pressure, required to properly seal a flanged joint.”
PPI TN-71 step-by-step installation procedures for flanged connections include tightening sequences for bolts, bolt torques, retightening recommendations, and much more. Several illustrations show each component of a flange joint while also explaining the terminology used for these types of connections. It was published in October 2024 with the input of industry experts including PPI staff along with members who are manufacturers of PP-R and PP-RCT piping systems.
MacNevin continued, “The mating interfacial surface area of a metal-to-PP flange adapter may be significantly less than that between PP-to-PP flange adapters, since the bore (i.e., inside diameter) of the metal flange and pipe is typically larger than the bore of the PP flange adapter. Because of this, the required bolt and nut force of a PP-to-PP flanged joint may be greater than for PP-to-metal flanged joints.”
To Learn More
PPI TN-71 contains detailed information about selecting proper gaskets and bolts, calculating bolt torque, making flanged connections to join PP pipes to butterfly valves, and safe disassembly of flanged connections.
The new PPI TN-71 is available directly from PPI at: https://plasticpipe.org/common/Uploaded files/Technical/PPI TN-71.pdf .
Additional information about multiple types of plastic pressure piping systems is available from the PPI Building & Construction Division at www.plasticpipe.org/buildingconstruction.
Founded in 1950, PPI is the non-profit North American trade association representing the plastic pipe industry, including several manufacturers of PP pipes, fittings, and valves. PPI formed its Polypropylene Pressure Pipe Steering Committee in 2018 to develop industry publications, collaborate on standards, and create educational information about these systems.