Eventos Anais de eventos
CONEM 2022
XI Congresso Nacional de Engenharia Mecânica - CONEM 2022
FAILURE ANALYSIS OF DOT-39 NON-REFILLABLE REFRIGERANT CYLINDERS
Submission Author:
Giovani Martins , SC
Co-Authors:
Giovani Martins, Leonel Beckedorff, kleber paiva, Jorge Luiz Oliveira
Presenter: Giovani Martins
doi://10.26678/ABCM.CONEM2022.CON22-0559
Abstract
DOT-39 refrigerant cylinders are low-pressure vessels, used in industrial, commercial and consumer markets as well as in medical applications. These vessels are non-reusable and equipped with a non-refillable one-way hermetic leak-stop valve to prevent refilling. Refilling is considered unsafe and illegal. However, the discarded refrigerant reservoir promotes heavy metal pollution. For the sake of sustainability and pollution prevention, DOT-39 cylinder reutilization demands appraisal. DOT-39 refrigerant cylinders have been evaluated from the fatigue perspective in a test bench. A hydraulic-pneumatic pump was employed to pressurize the cylinder samples with water. The samples were instrumented at the main weld zone (with rosette strain gauges at circumferential and longitudinal directions) and at the torospheric region (with three-axis strain gauges at 0º/45º/90º). Strain gauge measurements were used to determine local equivalent von Misses stresses. The fatigue life of DOT-39 samples was assessed with loads varying from ambient to service pressure (1.5 to 2.5 MPa), emulating their service conditions. Setup parameters were adjusted to promote a slow propagation failure due to crack propagation speed being disturbed by the rate of stress tensor change. The cyclic pressure loads lasted a total of 18 second. The experiments were carried out continuously until failure occurred. Eleven cyclic tests were carried out with the test pressure (Pt) below the upper typical operation pressure. Failure locations due to fatigue were found at welded regions, predominantly at the main weld zone, regardless of lower stress levels. Stress-life diagrams and experimental strength reduction factors at the critical welded locations were obtained based on ASME rules (Sec. VIII, Div. 2). At critical welded locations, fatigue strength reduction factors were determined: between 4 and 5 for the main weld zone at the cylinder center, between 2 and 3 at the valve and tube system and nearly 3 at the pressure relief dimple; DOT-39 cylinders can endure over 700 typical working cycles.
Keywords
Fatigue Life, DOT-39 refrigerant cylinders, welded regions, fatigue strength reduction factors
