STANDARDS & TESTING | MACHINERY
Setting high standards in pipe and profile extrusion
Standards for products such as pipes and profiles help set a quality benchmark, while testing regimes help to ensure that these guidelines are being followed
Setting appropriate standards is an important way of ensuring that extruded plastic products – espe- cially critical ones such as pipes – adhere to agreed guidelines. With this in mind, US-based Plastics Pipe Institute (PPI) recently published a series of new documents with guidance on conduits and pipe testing. The most recent covers ovality in high-density polyethylene (HDPE) conduit, including cable in conduit. The document, TN-61 – Coilable HDPE Conduit Ovality and Coil-set – is available on PPI’s website. It explains what can cause ovality and coil-set in HDPE conduit products and describes how installers can correct or reduce it during installation. The primary factor in ovality is the diameter of the
conduit, and the secondary factor is the bend radius of the coiled conduit. Others include time stored in the coiled configuration, and ambient temperature and temperature cycles while in storage. “Users and installers must be aware that a
certain amount of ovality is normal in a flexible product like HDPE conduit,” said Patrick Vibien, director of engineering for PPI’s Power & Commu- nications Division (PCD). “This flexibility is one of a major advantage of HDPE conduit, allowing nominal sizes from 0.5 to 6in to be coiled onto reels or supplied as coils.” However, he said that excess ovality could
restrict the installation of cables into installed conduit. For this reason, the document lists several techniques for mitigating ovality, and describes how to re-round conduit during installation using proven techniques, to prevent ovality from causing problems in the field.
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Cable replacement
PPI has also published advice on adding or replac- ing cables in HDPE conduit. The document, TN59, explains options for sub-dividing larger conduit. “It compares each technology’s installation techniques, advantages, and protection capabili- ties, along with cable installation considerations,” said Lance MacNevin, director of engineering for PPI’s power and communications division. “It is intended to assist specifiers, contractors, and others with useful selection criteria when determin- ing which technology to employ, especially when considering the need to add additional fibre into conduit in the future.” HDPE innerduct or micro duct, and fabric dividers – sometimes referred to as fabric innerduct – are three options for sub-dividing an installed empty or occupied conduit for current and future installation of additional fibre optic cables. Both HDPE conduits and fabric dividers can be installed into empty or occupied conduits. Occupied
Main image: New advice from PPI explains how to correct or reduce ovality during installation of HDPE conduit
April 2020 | PIPE & PROFILE EXTRUSION 23
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