Technique For Risk Assessment And Failure Data Analysis And Application On Acrylonitrile Unit

While the rapid development of industry has brought great benefits to mankind, it also leads to a lot of great disasters and accidents. So, effective risk assessment technologies are required to identify potential risks of units or process, and, control measures are needed to reduce or remove them, which is quite necessary to make units or systems operate reliably and stably.At present, risk assessment technologies of units or processes applied in chemical industry primarily include HAZOP (Hazard and Operability Analysis), LOPA (Layers of Protection analysis), and so on. However, general risk assessment is less helpful for decision-making on essential safety update of units than hardware risk analysis. Besides, SIS (Safety Instrumented System) and function safety assessment play an increasingly important role in risk control of chemical industry process. But actual failure data required by SIL (Safety Integrity Level) verification of SIS is in lack, which makes accurate design and update of SIS difficult. So, in order to solve the aforementioned problems in the two aspects in chemical industry process:risk identification and risk control, primary work performed in this paper is as follows:1. In order to carry out potential hardware assessment on chemical industry devices, two improvements on traditional FMEA were proposed to enhance availability. First, according to different failure causes of chemical industry devices, hardware failure was divided into body failure and shock failure, and summarized failure types of all the main equipments in the FMEA appointed level. Second, according to actual condition of the enterprise and related communities, judgement criterions of S (severity),O (Occurrence), D (Detection) were proposed. Then, improved FMEA (Failure Modes and Effect Analysis) was performed on 25 units of acrylonitrile process in some certain enterprise, which produced 25 pieces of FMEA reports, identified 189 important hardware failure modes and 54 failure modes of high risk.2. In order to solve the problems existing in the application of traditional Risk Priority Number algorithm, Improved FMEA-RPN based on the method of Analytic Hierarchy Process (AHP) was proposed, called Relative Risk Priority Number algorithm (RRPN), which can not only discriminate the relative importance among S, O, D, but also identify maintenance models:breakdown maintenance model, low/high frequency periodic review model, regular restore model. Last, improved FMEA and RPN were applied on air compressor, and appropriate maintenance suggestion was presented.3. In order to solve the problem that SIL verification lacks failure data of equipment in specific environment, an actual product failure data analysis method based on the method of subjective estimation, Pearson chi-square, and FMEDA (Failure Modes, Effects and Diagnostic Analysis) was proposed. Besides, pneumatic diaphragm control valve was selected as the example. And FMEDA report, failure rate, safe/dangerous failure rate and safety failure fraction (SFF) were given.4. In order to compare the gained data with industry data bases, FTA (Fault Tree Analysis) was applied on the interlock loops upon high exit temperature and low exit temperature of acrylonitrile reactor to perform the SIL calculation. Finally, conclusions were given based on the analysis.