GB/T 5275.6-2014 in English

《GB/T 5275.6-2014气体分析 动态体积法制备校准用混合气体 第6部分：临界锐孔》由TC206（全国气体标准化技术委员会）归口，主管部门为中国石油和化学工业联合会。
GB/T5275的本部分规定了通过临界锐孔系统用纯气或混合气连续制备两种或多种组分的校准混合气体的方法。通过选择适合的锐孔组合并配合纯气的使用,校准组分在校准混合气体中的体积分数可以以104 为系数变化。另外通过改变锐孔系统的初始压力可使校准组分的体积分数以102 为系数变化。临界锐孔法的不确定度主要取决于流量校准方法、温度变化以及出口压力。二元混合气体可得到的体积分数相对扩展不确定度(在包含因子k=2时)为3% 。
使用预混气体而不是纯气可制备体积分数低得多的混合气体(参见附录 A)。确定质量或体积分数的质量流量或体积流量,可通过计算得出,也可采用ISO6145-1给出的适当方法单独测量。
这种制备方法的优点是可连续制备大量混合气体,并且只要使用适当数量的锐孔,制备多组分混合气体就如制备二元混合气体一样容易。流量范围可从每分钟几毫升到每分钟10L。
本方法特别适用于在大气压力下制备混合气体,但也可在高于大气压的压力下制备混合气体。
使用本方法的实用提示参见附录 B。

Scope

This part of GB/T 5275 specifies the method for continuously preparing a calibration mixed gas of two or more components with pure gas or mixed gas through a critical orifice system. By selecting a suitable combination of orifices and using pure gas, the volume fraction of the calibration components in the calibration mixture can be changed by a factor of 10⁴. In addition, by changing the initial pressure of the orifice system, the volume fraction of the calibration components can be changed by a factor of 10². The uncertainty of the critical orifice method depends primarily on the flow calibration method, temperature variation, and outlet pressure. The relative expanded uncertainty (when the coverage factor k=2) of the available volume fraction of the binary gas mixture is 3%. Gas mixtures with much lower volume fractions can be prepared using premixed gases rather than pure gases (see Appendix A). Determine the mass flow or volume flow of the mass or volume fraction, which can be calculated or measured separately using an appropriate method given in ISO 6145-1. The advantage of this preparation method is that a large amount of mixed gas can be prepared continuously, and as long as an appropriate number of orifices are used, the preparation of multi-component mixed gas is as easy as the preparation of binary mixed gas. Flow rates can range from a few milliliters per minute to 10 L per minute. This method is especially suitable for preparing mixed gas under atmospheric pressure, but it can also be prepared under pressure higher than atmospheric pressure. Practical hints for using this method can be found in Appendix B.