Polyethene Fittings for use with Polyethylene Pipes for the Supply of Gaseous Fuels - Specification, Part 1: Fittings for Socket Fusion using Heated Tools
2012 Edition

According to Clause 8.2.1 of IS 15927 Part 1:2012, the standard covers nominal diameters of 16, 20, 25, 32, 40, 50, 63, 75, 90, 110, and 125 mm. These sizes represent the fitting's nominal diameter (DN) and are categorized by fusion types (Type A and B) based on pipe surface conditions and dimensions defined in IS 14885. Each fitting is identified by its material grade, nominal diameter, and SDR value, for instance, 'PE 80 DN90 SDR 11' implies a PE 80 grade fitting with 90 mm nominal diameter and SDR 11.

The polyethylene compounds used for fittings must adhere to IS 14885, particularly the material grades detailed in Table 1. The permitted grades typically include PE 80 and PE 100. Additives are allowed only if essential for manufacturing and end-use, uniformly dispersed, and without adverse effects on fusion jointing. The materials must be free from visible moisture and comply with fusibility standards to ensure proper compatibility and performance.

Markings on fittings must be permanent, easily readable without magnification, and applied in a manner that does not induce cracks or diminish the fitting's strength, as per Clause 12.2.1. For fittings with diameters up to 90 mm, the character height should be at least 3 mm, and for sizes above 90 mm, at least 5 mm. Markings typically include the manufacturer's identification, nominal diameter, SDR rating, manufacturing date or batch number, and material type. Optional BIS standard marks may also be included to facilitate traceability and regulatory compliance.

Fittings must be evaluated using pipes conforming to IS 14885 and prepared following Annex A of IS 15927 Part 1. Key tests include determination of volatile matter content (3 samples, Annex H of IS 14885), hydrostatic resistance testing at 80°C for 1000 hours (3 samples, Annex A of IS 14885), and assessment of gas constituent effects on hydrostatic strength (3 samples, Clause 5.5 of IS 14885). Testing is conducted at Maximum Allowable Operating Pressure (MAOP) with a minimum C factor of 2.9, using socket fusion assemblies conditioned at 27 ± 2°C for 8 hours. Only similar polyethylene materials can be fusion joined, employing suitable tooling to achieve homogeneous joints.

The standard recommends electrically heated tools equipped with removable heating bushes and spigots, sized appropriately for each pipe dimension. Contact surfaces of these heating elements should have a non-stick coating to prevent material adhesion. Additional tools include pipe cutters or saws with cutting guides for precise pipe end preparation. The procedure involves conditioning pipes and fittings at 27 ± 2°C for at least 8 hours, matching pipe end and fitting socket dimensions to heating tools, simultaneous heating until fusion temperature is reached, and immediate joining by pushing the heated pipe end into the fitting socket to form a homogeneous fusion joint. Compatibility of materials (PE with PE) and adherence to minimum pipe wall thickness are critical for joint integrity.