“GB/T 40079-2021”标准解读及阀门逸散性试验方法分析

Interpretation of“GB/T 40079-2021”standard and analysis of valve fugitive emissions testing method

为了加强GB/T 40079-2021《阀门逸散性试验分类和鉴定程序》的行业推广和科学实施,提高全行业对阀门逸散性试验的理论认识和实操水平,分析了标准所推荐逸散性试验的3种典型方法及其影响因素,其中包裹法操作便捷,运行经济性较好,检测精度高,可定量检测泄漏率,便于在一般工业现场推广,重点对其进行了研究。以“气体动力学”的基本原理为基础,揭示了包裹法的理论依据,检测包内气体流速一般不大于0.32 m/s,与当地音速之比远小于0.3,根据空气动力学的一般约定,可以忽略密度变化,推导了理论计算公式;检测用氦气浓度直接影响检测精度,对包裹法定量检测的关键理论公式进行了完善性补充,解决了测试介质的浓度影响问题,并对此进行了试验验证和分析,试验结果与理论推测基本一致,修正后的公式在氦气浓度不低于80%时基本可以保持较高的检测精度,且具有明显的经济性优势。

In order to strengthen the industry popularization and scientific implementation of the new version of the national standard“GB/T 40079-2021 Valve Emission Test Classification and Identification Procedures”,and to improve the theoretical understanding and practical level of the whole industry for valve fugitiveness tests,this paper analyzes three typical methods and their influencing factors of fugitive test recommended by the standard.Among them,the bagging method is easy to operate,economical in operation,has high detection accuracy,can quantitatively detect the leakage rate,and is convenient for popularization in general industrial sites.Therefore,we researched it.Based on the basic principle of“gas dynamics”,the article reveals the theoretical basis of the bagging method and points out that the gas velocity in the detection bag is generally about 0.32 m/s,and the ratio to the local sound speed is far less than 0.3.It is generally agreed that the density change can be ignored according to aerodynamics.Based on this,the theoretical calculation formula is deduced.At the same time,it is pointed out that the concentration of helium gas used for detection directly affects the detection accuracy.The key theoretical formula has been supplemented to solve the problem of the concentration effect of the test medium,and carried out test verification and analysis on this.The test results are basically consistent with the theoretical speculation.The modified formula can basically maintain a high detection accuracy when the helium concentration is not less than 80%,and has obvious economic advantages.