ANSI SCTE 251 pdf free download
ANSI SCTE 251 pdf free download.Test Procedure for Determining the Thermal Oxidative Stability of Foamed Polyethylene.
6. General Two types of insulation test samples are described. Type II sample description is presented for information only. Type I samples are to be used: ●Type I- Insulation removed from cable (no copper present) (Recommended method).Use Type I samples to measure the intrinsic stability of the material and the efficacy of thermal stabilizers such as antiox idants. ●Type II- – Insulation on the wire (insulation and copper conductor). Use Type II samples to evaluate not only the thermal stability, but also the metal deactivation efficacy of the additives. Significance and Use: The OIT value measures the oxidative thermal stability of a material and is primarily dependent on: ●the intrinsic thermal stability of the material, ●the type and concentration of antiox idants and other thermal stabilizers present, ●the type and concentration of metal deactivators present, and the test temperature. Discussion- Other components in the foam material may cause secondary effects. The OIT value for insulation may be significantly altered by contamination or additives such as pigments, fillers, and processing aids as well as catalyst residues from the cable, wire, insulation, or resin manufacture. The OIT value may increase or decrease depending on whether these additives and residues act as oxidation inhibitors or promoters at the test temperature. At typical test temperatures (for example, ANSISCTE 74 requires 180°C), compounds present in the polyolefin material may decompose and change the polyolefin oxidation mechanism and thereby the OIT value. If the oxidation mechanism is so altered, then the OIT value may not correlate to aging at normal use temperatures. Before using the OIT value to predict field performance and lifetimes, additional studies may be required to establish a correlation between the OIT value measured at high temperature and the performance of the polyolefin under typical field conditions.Samples from a finished production cable- Remove the insulation from a 3-foot (91 cm) sample of completed cable by removing the jacket, braid, Trishield and Quadshield tapes (if any). Split the dielectric and shielding tape lengthwise, and carefully remove it from the center conductor. Carefully remove the shielding tape from the dielectric with a razor blade capable of highly accurate cutting. Consideration should be given to carefully removing the precoat from the dielectric with a razor blade capable of highly accurate cutting. Every effort should be made to prevent contamination of the insulation with oils from fingers, oils on the cutting blade or cutting surface. Samples- Cut 6 inches (15.2 cm) from the 3-foot sample and age for 14 days at 90 °C士90°C士2°Cina circulating air oven. Take three samples from the remaining dielectric material, one from each end and one from the middle. For the aged sample, the test specimen shall be taken from within 1/4 inch of the end of the aged sample. Sample Cleaning- Wipe the insulated wire sample with a clean cotton cloth or paper towel to remove any contaminants. Do not use solvents to clean the insulated wire. Sample Type- Determine the OIT value for an insulation using a: Type I sample- -Insulation stripped from the copper or copper clad steel wire.
ANSI SCTE 251 pdf download.
