Matters needing attention during the preparation of standard gas
Release time: 2021-06-23 11:09:38
Source: Yuejia Gas
What are the matters needing attention during the preparation of standard gas? In the process of preparation, we need to pay attention to the explosive limit of the combustible gas, the saturated vapor pressure of the gas and other properties, the reaction between the components in the standard gas, the reaction between the components in the standard gas and the material of the cylinder (container), and so on.
1. Explosion limit of combustible gas
From a safety point of view, before preparing the standard gas, the feasibility of mixing the standard gas must be studied. In particular, the explosion limit of each component gas must be considered. When preparing a standard gas composed of combustible gas and hydrogen (or oxygen), attention should be paid to whether the content of the component gas exceeds the explosion limit. Otherwise, an explosion accident may occur during the preparation process.
The explosion limit is an important technical data for flammable gases. Before preparing a standard gas containing a combustible gas component, it is necessary to understand the explosive limit of the component to ensure safety
2. Saturated vapor pressure and other properties of the gas
To understand the saturated vapor pressure and other properties of each component, whether the test will produce condensation, the role of the components in the standard gas with the steel cylinder and the remote wall material, the reaction between the components, etc.
3. Reaction between components in standard gas
Before preparing the standard gas, it should be considered whether there is a chemical reaction between the components in the standard gas (ie, chemical stability issues). In fact, it is necessary to figure out which gas components cannot be chemically matched, otherwise, the prepared standard gas value will be different. Accurate, an explosion may even occur.
4. The reaction between the components in the standard gas and the material of the cylinder (container)
Before preparing the standard gas, it is also necessary to consider whether the component gas has a chemical reaction (such as oxidation, corrosion, adsorption, etc.) with the material used in the cylinder and valve, so as to ensure the stability of the standard gas. According to the compatibility of the component gas and the material of the packaging container, steel cylinders and bottle valves of different materials are selected to store the standard gas.
In addition, before filling each component into the gas cylinder, each pipeline of the gas distribution system should be evacuated, or the component gas to be filled should be repeatedly pressurized-depressurized to replace the cleaning valve and pipeline until Until the requirements are met. In order to avoid the loss of the first stable amount of component gas, when filling the second component into the gas cylinder, the pressure of the component gas should be much higher than the pressure in the gas cylinder. In order to prevent back diffusion of component gases, after filling each component, the cylinder valve should be closed during the entire period of thermal equilibrium, and then weighing.