ASTM D4051-10(R2021) pdf free download

ASTM D4051-10(R2021) pdf free download.Standard Practice for Preparation of Low-Pressure Gas Blends
1. Scope
1.1 This practice covers a laboratory procedure for the preparation of low-pressure multicomponent gas blends. The technique is applicable to the blending of components at percent levels and can be extended to lower concentrations by performing dilutions of a previously prepared base blend. The maximum blend pressure obtainable is dependent upon the range of the manometer used, but ordinarily is about 101 kPa (760 mm Hg). Components must not be condensable at the maximum blend pressure. 1.2 The possible presence of small leaks in the manifold blending system will preclude applicability of the method to blends containing part per million concentrations of oxygen or nitrogen. 1.3 This practice is restricted to those compounds that do not react with each other, the manifold, or the blend cylinder. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Summary of Practice
2.1 Through the use of a blending manifold, the blend components are combined based upon partial pressure. Com- ponents are added in order ofascending vapor pressure; that is, components of lowest vapor pressure are added first, with the exception that components at concentrations of 5 % or less would usually be added first. Compressibility factors are applied to the component partial pressures to convert them from ideal to real gas. The real partial pressures, which are proportional to gas volumes, are normalized to give mol percent composition of the blend.
6. Procedure
6.1 Connect the blend cylinder to the manifold at position A (see Fig. 1 for valve and position designations). Open valves 1, 2, 3, and 6 and evacuate the manifold system thoroughly. Valves 4 and 5 are closed.N OTE 2—A McLeod Manostat type gauge may be used at various times during the procedure to determine how well the system has been evacuated and to indicate if there are leaks present. Otherwise, a steady state condition of the manometer or electronic pressure gauge reading can be taken as an indication that an acceptable vacuum has been attained. 6.1.1 When a good vacuum less than 0.01 kPa (0.1 mm Hg) is reached, connect one or more blend component cylinders to the manifold at positions B or C, or both. Close valve 2 and open valves 4 and 5, thereby evacuating the connecting lines up to the blend component cylinder valves. When a good vacuum is again reached, close valves 4 and 5 and open the blend component cylinder valves. Ensure that the pressure of any blend component delivered to valves 4 and 5 does not exceed 200 kPa (1500 mm Hg). Record the initial pressure readings from both sides of the manometer. 6.1.2 The first component to be added will either have the lowest vapor pressure or will be present in the final blend at a concentration of 5 % or less. Assume that the first component feedstock is connected to manifold valve 4. Close valve 1 and open valve 2. While carefully watching the manometer or electronic pressure gauge reading, slowly open valve 4. Allow the blend gas component to flow into the blend manifold until the desired precalculated manometer reading is reached (see 7.1). Close valve 4 and be sure that the pressure remains constant. If using a manometer, tap it lightly to be certain the correct reading is obtained. Record the reading of both sides of the manometer and then close valve 3. Open valve 1 and wait until the manifold is thoroughly evacuated. 6.1.3 If the manifold includes only one feedstock connec- tion point it will be necessary at this time to remove the first feedstock cylinder, connect the second, and evacuate the line back to the feedstock cylinder valve. Assume this to be the case; value 4 will, therefore, always be used as the feedstock control valve.