Extrusion & Post
3 Aufrufe
Insufficient long-term hydrostatic strength of heat-resistant polyethylene PPR pipes
Problembeschreibung
PPR/PP-R pipes rupture in long-term hydrostatic tests (1000h, 8760h) and cannot meet ISO 15874 requirements.
Insufficient long-term strength affects pipe service life and design safety factor.
Ursachenanalyse
(1) Raw material molecular weight too low or molecular weight distribution unreasonable
(2) Extrusion temperature improper, material partially degraded
(3) Pipe wall thickness insufficient or uneven
(4) Improper cooling rate, unsuitable crystallinity
(5) Welded joint as weak point with insufficient strength
Lösung
(1) Select special grades meeting PPR pipe standards (MFR 0.2-0.5g/10min)
(2) Strictly control extrusion temperature at 200-220°C to avoid material degradation
(3) Ensure pipe wall thickness meets SDR value requirements and is uniform
(4) Optimize cooling conditions to ensure reasonable crystallinity (50-60%)
(5) Strengthen welded joint quality control and inspection
Wichtigste Erkenntnis
Insufficient long-term hydrostatic strength is caused by material selection and processing quality, and needs to be comprehensively controlled from raw materials, process and welding.
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