Failure Analysis of Insulator Iron Cap in Low Stress State
- PDF / 3,353,670 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 46 Downloads / 181 Views
TECHNICAL ARTICLE—PEER-REVIEWED
Failure Analysis of Insulator Iron Cap in Low Stress State Xing Chen . Shuaijiang Yan . Chengsong Zhang . Guodong Cui . Chuan Yang
Submitted: 13 October 2017 / in revised form: 6 March 2018 ASM International 2018
Abstract The safe and stable operations of insulator components create an important issue, with massive constructions of high-voltage direct current (HVDC) projects. However, the service life of the insulator iron cap directly depends on the production process. Therefore, it is necessary to examine the quality of the products and clarify the causes of failure. Under equivalent conditions, the insulator iron cap, made of nodular graphite cast iron, failed when the load value reached 1929 kN by calculation, rather than 278 kN in this loading test. In this investigation, some of the defects were due to improper heat treatment process. When present, these defects eventually lead to fracture. The results of the research for the process design of insulator iron cap are available.
stalinite (or ceramics), as well as pin [2–4]. High tensile strength is required due to its working conditions [5–7]. If the parts of insulator have manufacturing defects which affect the tensile strength of materials, it could cause significant loss of property or personnel in engineering applications [8]. Therefore, it is necessary to ensure the quality of the insulator iron cap through adopting a reasonable process. In this case, an insulator was examined during a loading test [9], and an insulator cap, made of nodular graphite cast iron (QT450), fractured when the load reached 278 kN, far below the operating requirement. A schematic diagram and photographs of the insulator cap testing are shown in Fig. 1. The production process is as follows:
Keywords Insulator iron cap HVDC Failure QT450 Defect
1. 2. 3.
Introduction Electric energy has contributed greatly to the development of the modern economy. However, the safety of highvoltage transmission from remote areas to cities has been a topic of great concern [1]. An insulator is a significant component, widely used in the high-tension transmission field and it plays a vital role in supporting and fastening an energized conductor. It primarily consists of an iron cap,
X. Chen S. Yan C. Zhang (&) G. Cui C. Yang School of Material Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China e-mail: [email protected]
4.
Fabricating of dry-core and casting blank; Cleaning of sand, sprue and burr; Casting in model, pickling with hydrochloric acid, galvanizing and detecting flows; Pouring silicate cement into insulator cap and protecting in water at 70 C.
According to the production process above, the microdefects generated are likely to be related to the casting, pickling and galvanizing. During casting [10], some microdefects are inevitable, such as gas porosity. In addition, these imperfections could link to each other to form crack sources under the load [11]. In order to obtain a better galvanizing effect,
Data Loading...
