水成膜泡沫灭火剂标准GB17427—1998的研究

Discussion on the standard of aqueous film-forming foam extinguishing agent GB 17427—1998

结合作者对水成膜泡沫灭火剂(AFFF)的研究结果,讨论了AFFF国家标准GB17427—1998的一些值得商榷之处。对GB17427—1998中的AFFF定义、“扩散系数”和“扩散能力”、老化试验、pH值与泡沫水溶液的腐蚀性以及表面张力和界面张力的测定等进行了详细讨论,并提出了相应的修改建议。建议修改AFFF的定义、“扩散系数”和“扩散能力”等术语。将铺展系数的测定改为测定能迅速铺展的泡沫水溶液在油面的铺展量。建议修改老化试验及泡沫水溶液腐蚀性的判断标准,用更准确的方法测定泡沫液的表面张力和油水界面张力。希望本文的一些讨论能对我国AFFF标准的进一步完善有所帮助。

The present paper is aimed at bringing forward the authors＇ suggestions on the improvement on the standard of aqueous film-forming foam fire-extinguishing agents （AFFF）, GB 17427- 1998. We have found that some items in the standard might be incorrect and even somewhat mistaken, including the definition of AFFF, the diffusing coefficient and diffusing power, the ageing test. So are description of the relationship between pH and corrosivity of AFFF, ts of the surface as well as the interfacial tensions. It is just for these reasons that the first suggestion of ours is to revise the definition of AFFF into the ＂foam extinguishing agent forming aqueous film on the surface of hydrocarbon oil.＂ And, the items of ＂diffuse coefficient＂ and ＂diffuse ability＂ should be modified into ＂spread coefficient＂ and ＂spread ability,＂ respectively. Although the measurement of spread coefficient can be used to judge whether or not AFFF solution has spread on the hydrocarbon oil, it can not be used to evaluate its spread speed and spread amount. Therefore, we suggest measuring the spread ability instead of spread coefficient. In addition, the ageing test described in GB 17427-1998 may not be effective enough to evaluate the stability of AFFF, therefore either fire-extinguishing test or measurements of spread and foaming abilities should be performed after aging test. Besides, pH 6.0 - 9.5 can nei- ther be regarded as the criteria to judge whether the AFFF solution is corrosive or not to metal equipments because some species such as salts and acid can corrode metal equipment even if at pH 6.0 -9.5. Furthermore, since AFFF solution has usually very low surface tension and oil/water interface tension, the ring method described in GB 17427-1998 for measuring the surface tension of AFFF solution and the interface tension of liquid hydrocarben/AFFF solution are likely to induce more or less noticeable error. Therefore, we suggest adopting more suitable methods to do such measurements. In particular, spinning drop method is suggested for measuring the interface tension. Seeing what is mentioned above, the above suggestions can be expected to be helpful for further revision of the AFFF standard.