ASTM D4051-10 (R2021) pdf free download.Standard Practice for Preparation of Low-Pressure Gas Blends.
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 he 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, hut 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.
3. Significance and Use
3.1 The laboratory preparation of gas blends of known composition is required to provide primary standards for the calibration of chromatographic and other types of analytical instrumentation.
4. Apparatus
4.1 Blending Manifold—Construct manifold as shown in Fig. I. Details of construction are not critical: that is, glass, pipe, or tubing with welded or compression fittings may he used. The manifold must he leak free and arranged for convenience of operation. More than one feedsiock connection point may he included if desired. Connections to the pump and manometer shall follow accepted vacuum practice. Valves shall have large enough apertures to permit adequate pumping in a reasonable length of time.
4. 1.1 The finished manifold shall have a leak rate no greater than 1 mm Hg/h.
4 2 Gauge, a well-type manometer such as the Meriam Model 30EB25 (see Note 1).
Note 1—A high-vacuum gauge of the McLeod Manostat type pressure transducer or a 0 bar to 2 bar (absolute) gauge may be included in the manifold system to determine how well the system has been evacuated.
4.2.1 Alternatively, an electronic pressure gauge may be used in place of a manometer.
4.3 Pump, high-vacuum, two-stage, capable of pumping down to a pressure of 1.33 x 10 kPa.
5. Reagents and Materials
5.1 Blend components, high-purity, as required depending on the composition of the proposed blend.
5.2 Nitrogen, high purity, as required, for purging and for balance gas. where applicable.
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.ASTM D4051 pdf download.