ASTM D4051-99

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
An American National Standard
Designation: D 4051 – 99
Standard Practice for
Preparation of Low-Pressure Gas Blends
This standard is issued under the fixed designation D 4051; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3. Significance and Use
1.1 This practice describes a laboratory procedure for the 3.1 The laboratory preparation of gas blends of known
preparation of low-pressure multicomponent gas blends. The composition is required to provide primary standards for the
technique is applicable to the blending of components at calibration of chromatographic and other types of analytical
percent levels and can be extended to lower concentrations by instrumentation.
performing dilutions of a previously prepared base blend. The
4. Apparatus
maximum blend pressure obtainable is dependent upon the
range of the manometer used, but ordinarily is about 101 kPa 4.1 Blending Manifold—Construct manifold as shown in
Fig. 1. Details of construction are not critical; that is, glass,
(760 mm Hg). Components must not be condensable at the
maximum blend pressure. pipe, or tubing with welded or compression fittings may be
used. The manifold must be leak free and arranged for
1.2 The possible presence of small leaks in the manifold
blending system will preclude applicability of the method to convenience of operation. More than one feedstock connection
point may be included if desired. Connections to the pump and
blends containing part per million concentrations of oxygen or
nitrogen. manometer shall follow accepted vacuum practice. Valves shall
have large enough apertures to permit adequate pumping in a
1.3 This practice is restricted to those compounds that do
not react with each other, the manifold, or the blend cylinder. reasonable length of time.
4.1.1 The finished manifold shall have a leak rate no greater
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the than 1 mm Hg/h (0.133 kPa/h).
4.2 Gage, open manometer, vacuum, or pressure, consisting
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica- of a full-length U-tube mounted on a vertically adjustable
meter scale.
bility of regulatory limitations prior to use.For specific hazard
statement, see Note 3.
NOTE 1—A well-type manometer such as the Miriam Model 30EB25
may be used in place of the U-tube manometer.
2. Summary of Practice
NOTE 2—A high-vacuum gage of the McLeod Manostat type pressure
2.1 Through the use of a blending manifold, the blend transducer ora0to2bar (absolute) may be included in the manifold
system to determine how well the system has been evacuated.
components are combined based upon partial pressure. Com-
ponents are added in order of ascending vapor pressure; that is,
4.2.1 Alternatively, an electronic pressure gage may be used
components of lowest vapor pressure are added first, with the
in place of a mercury manometer.
exception that components at concentrations of 5 % or less
4.3 Pump, high-vacuum, two-stage, capable of pumping
–4
would usually be added first. Compressibility factors are
down to a pressure of 1.33 3 10 kPa (0.1 μm).
applied to the component partial pressures to convert them
5. Reagents and Materials
from ideal to real gas. The real partial pressures, which are
proportional to gas volumes, are normalized to give mol
5.1 Blend Components high-purity, as required depending
percent composition of the blend.
on the composition of the proposed blend.
5.2 Mercury reagent grade, triple distilled.
NOTE 3—Warning: Mercury may be harmful if inhaled or swallowed.
This practice is under the jurisdiction of ASTM Committee D-2 on Petroleum
Products and Lubricantsand is the direct responsibility of Subcommittee D02.04 on
5.3 Nitrogen, high purity, as required, for purging and for
Hydrocarbon Analyses.
balance gas, where applicable.
Current edition approved Apr. 10, 1999. Published June 1999. Originally
e1
published as D 4051 – 81. Last previous edition D 4051 – 89 (1993) .
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 4051
FIG. 1 Manifold System
6. Procedure back to the feedstock cylinder valve. Assume this to be the
case; value 4 will, therefore, always be used as the feedstock
6.1 Connect the blend cylinder to the manifold at position A
control valve.
(see Fig. 1 for valve and position designations). Open valves 1,
6.1.4 When manifold evacuation is complete, close valve 1
2, 3, and 6 and evacuate the manifold system thoroughly.
and 4. Open the feedstock cylinder valve and then slowly open
Valves 4 and 5 are closed.
valve 4, allowing the second blend gas to flow into the
NOTE 4—A McLeod gage may be used at various times during the
manifold. Carefully watch the mercury level of the manometer.
procedure to determine how well the system has been evacuated and to
indicate if there are leaks present. Otherwise, a steady state condition of
NOTE 5—All additions should be made slowly to avoid temperature
the mercury in the manometer can be taken as an indication that an
changes.
acceptable vacuum has been attained.
6.1.5 When the pressure in the manifold is several pascals
6.1.1 When a good vacuum less than 0.01 kPa (0.1 mm Hg)
(or millimetres of mercury) higher than the previous reading
is reached, connect one or more blend component cylinders to
and is still slowly rising, slowly begin to open valve 3 so as to
the manifold at positions B or C, or both. Close valve 2 and
admit the component to the sample cylinder. Valve 4 will
open valves 4 and 5, thereby evacuating the connecting lines
remain partially open. Continue to open valve 3 while control-
up to the blend component cylinder valves. When a good
ling the flow through valve 4 until the next desired pressure
vacuum is again reached, close valves 4 and 5 and open the
level is reached, always maintaining a higher pressure in the
blend component cylinder valves. Ensure that the presure of
manifold than that in the cylinder. Close valve 4, allow the
any blend component delivered to valves 4 and 5 does not
pressure to equilibrate, and record the manometer reading from
exceed 200 kPa (1500 mm Hg). Record the initial pressure
both sides. Close valve 3. When additional components are to
readings from both sides of the manometer.
be included in the blend, repeat the procedures outlined above
6.1.2 The first component to be added will either have the
for each component.
lowest vapor pressure or will be present in the final blend at a
6.1.6 When all components have been added, and valve 3 is
concentration of 5 % or less. Assume that the first component
closed, evacuate the manifold, close valve 2 and disconnect the
feedstock is connected to manifold valve 4. Close valve 1 and
blend cylinder from the manifold at position A. To shut down
open valve 2. While carefully watching the mercury level in the
the apparatus, close the feedstock cylinder valve and open
manometer, slowly open valve 4. Allow the blend gas compo-
valve 4 to evacuate the connection. Close valve 4, remove the
nent to flow into the blend manifold until the desired precal-
feedstock cylinder, close valve 1 and by using valve 2 or 4
culated manometer reading is reached (see 7.1). Close valve 4
slowly admit air into the system until it is at atmospheric
and be sure that the pressure remains constant. Tap the
pressure.
manometer lightly to be certain the correct reading is obtained.
Record the reading of both sides of the manometer and then 6.2 The blend must be mixed before it is used. This can be
close valve 3. Open valve 1 and wait until the manifold is accomplished in several ways, one of which is to cause
thoroughly evacuated. convection currents to occur within the cylinder. This may
6.1.3 If the manifold includes o
...