According to the hazard identification theory, run risks of solid rocket motor waterjet clearing system were identified from three different angles and potential causes of run risks were investigated; based on analysis of accidents that may occur in the running of solid rocket motor waterjet clearing system, fault tree analysis of propellant combustion/explosion and AP wastewater spill was carried out, minimal cut sets (path sets) and structural importance of each basic event were obtained, and furthermore corresponding recommendations in the accident prevention of solid rocket motor waterjet clearing system running were given accordingly.
The content of AP and Al in waste propellant and waste water produced by high pressure waterjet clearing HTPB propellant were determined according to some relative standard methods. The results show that the content of AP in the waste propellant with diameter less than 3mm drops from 69.5% to 35.28%, while the loss of Al and adhesives is slight; in the waste propellant with diameter larger than 3mm, the component content is close to normal charge with the increase in radial depth; the content of AP and Al in the waste water are 8368mg/L and 0.157mg/L respectively. Based on above results, the proper treatments of the wastes were chosen: the waste propellant can be used as auxiliary fuel for boilers after leaching AP out with the waste water; the waste water should be treated with biological methods to remove ammonia nitrogen and perchlorate in it.
Basing on the complexity and uncertainty of many risk factors which were presented in the solid rocket motor waterjet clearing system, according to operating procedures of the waterjet clearing system, the analytic hierarchy process was adopted to establish its safety evaluation index system, and then the gray comprehensive evaluation was used to evaluate the solid rocket motor waterjet clearing system security. The evaluation results indicate that the solid rocket motor waterjet clearing system's comprehensive evaluation value is 3.1126 and at a higher risk situation, thus there is need to strengthen the prevention and control of the risk factors in it; the comprehensive evaluation value of the waterjet clearing platform is 3.2417, which is higher than the overall comprehensive evaluation value, therefore it should be paid attention to in risk prevention and control; the evaluation result is in good agreement with the actual situation.
Security is the first requirement of obsolete solid rocket motor pretreatment. In response to this requirement, quantitative safety assessment of four units in the pretreatment of obsolete solid rocket motor was carried out by using ICI Mond Index; risk rating of each unit was obtained and weak links in the pretreatment security were analyzed; and then appropriate safety measures were proposed, providing scientific guidance for the safety of obsolete solid rocket motor pretreatment.
In order to ensure safety and efficiency in high pressure waterjet clearing HTPB propellant, the lower limit of outlet pressure was determined as 60MPa according to the compressive strength of HTPB propellant and the upper limit of outlet pressure was determined as 100MPa through ignition mode analysis and temperature rise experiment. Based on the corresponding empirical formula, the optimal target distance under different outlet pressure was calculated. Through the small size propellant clearing experiments, the main process parameters in high pressure waterjet clearing HTPB propellant were optimized. The optimal processing conditions of safe clearing are 100MPa for outlet pressure, 30mm for target distance, 0.25mm for nozzle diameter, 15minutes for single clearing time and thus the corresponding mass loss and clearing efficiency are 263.3g and 17.55g/min respectively.
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