ASTM D4051-99(2004)
(Practice)Standard Practice for Preparation of Low-Pressure Gas Blends
Standard Practice for Preparation of Low-Pressure Gas Blends
SIGNIFICANCE AND USE
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.
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.
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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D4051 – 99 (Reapproved 2004)
Standard Practice for
Preparation of Low-Pressure Gas Blends
This standard is issued under the fixed designation D4051; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope proportional to gas volumes, are normalized to give mol
percent composition of the blend.
1.1 This practice covers a laboratory procedure for the
preparation of low-pressure multicomponent gas blends. The
3. Significance and Use
technique is applicable to the blending of components at
3.1 The laboratory preparation of gas blends of known
percent levels and can be extended to lower concentrations by
composition is required to provide primary standards for the
performing dilutions of a previously prepared base blend. The
calibration of chromatographic and other types of analytical
maximum blend pressure obtainable is dependent upon the
instrumentation.
range of the manometer used, but ordinarily is about 101 kPa
(760 mm Hg). Components must not be condensable at the
4. Apparatus
maximum blend pressure.
4.1 Blending Manifold—Construct manifold as shown in
1.2 The possible presence of small leaks in the manifold
Fig. 1. Details of construction are not critical; that is, glass,
blending system will preclude applicability of the method to
pipe, or tubing with welded or compression fittings may be
blends containing part per million concentrations of oxygen or
used. The manifold must be leak free and arranged for
nitrogen.
convenience of operation. More than one feedstock connection
1.3 This practice is restricted to those compounds that do
point may be included if desired. Connections to the pump and
not react with each other, the manifold, or the blend cylinder.
manometershallfollowacceptedvacuumpractice.Valvesshall
1.4 This standard does not purport to address all of the
have large enough apertures to permit adequate pumping in a
safety concerns, if any, associated with its use. It is the
reasonable length of time.
responsibility of the user of this standard to establish appro-
4.1.1 The finished manifold shall have a leak rate no greater
priate safety and health practices and determine the applica-
than 1 mm Hg/h (0.133 kPa/h).
bility of regulatory limitations prior to use.
4.2 Gage, open manometer, vacuum, or pressure, consisting
of a full-length U-tube mounted on a vertically adjustable
2. Summary of Practice
meter scale.
2.1 Through the use of a blending manifold, the blend
components are combined based upon partial pressure. Com-
NOTE 1—A well-type manometer such as the Miriam Model 30EB25
ponents are added in order of ascending vapor pressure; that is, may be used in place of the U-tube manometer.
NOTE 2—A high-vacuum gage of the McLeod Manostat type pressure
components of lowest vapor pressure are added first, with the
transducer ora0to2bar (absolute) may be included in the manifold
exception that components at concentrations of 5 % or less
system to determine how well the system has been evacuated.
would usually be added first. Compressibility factors are
4.2.1 Alternatively, an electronic pressure gage may be used
applied to the component partial pressures to convert them
in place of a mercury manometer.
from ideal to real gas. The real partial pressures, which are
4.3 Pump, high-vacuum, two-stage, capable of pumping
–4
down to a pressure of 1.33 3 10 kPa (0.1 µm).
This practice is under the jurisdiction of ASTM Committee D02 on Petroleum
Products and Lubricants and is the direct responsibility of Subcommittee D02.04 on
5. Reagents and Materials
Hydrocarbon Analysis.
Current edition approved May 1, 2004. Published May 2004. Originally 5.1 Blend Components, high-purity, as required depending
approved in 1981. Last previous edition approved in 1999 as D4051 – 99. DOI:
on the composition of the proposed blend.
10.1520/D4051-99R04.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D4051 – 99 (2004)
FIG. 1 Manifold System
5.2 Mercury, reagent grade, triple distilled. (Warning— close valve 3. Open valve 1 and wait until the manifold is
Mercury may be harmful if inhaled or swallowed.) thoroughly evacuated.
5.3 Nitrogen, high purity, as required, for purging and for
6.1.3 If the manifold includes only one feedstock connec-
balance gas, where applicable.
tion point it will be necessary at this time to remove the first
feedstock cylinder, connect the second, and evacuate the line
6. Procedure
back to the feedstock cylinder valve. Assume this to be the
6.1 Connect the blend cylinder to the manifold at positionA
case; value 4 will, therefore, always be used as the feedstock
(see Fig. 1 for valve and position designations). Open valves1,
control valve.
2, 3, and 6 and evacuate the manifold system thoroughly.
6.1.4 When manifold evacuation is complete, close valve 1
Valves 4 and 5 are closed.
and 4. Open the feedstock cylinder valve and then slowly open
NOTE 3—A McLeod gage may be used at various times during the valve 4, allowing the second blend gas to flow into the
procedure to determine how well the system has been evacuated and to
manifold. Carefully watch the mercury level of the manometer.
indicate if there are leaks present. Otherwise, a steady state condition of
the mercury in the manometer can be taken as an indication that an
NOTE 4—All additions should be made slowly to avoid temperature
acceptable vacuum has been attained.
changes.
6.1.1 When a good vacuum less than 0.01 kPa (0.1 mm Hg)
6.1.5 When the pressure in the manifold is several pascals
is reached, connect one or more blend component cylinders to
(or millimetres of mercury) higher than the previous reading
the manifold at positions B or C, or both. Close valve 2 and
and is still slowly rising, slowly begin to open valve 3 so as to
open valves 4 and 5, thereby evacuating the connecting lines
admit the component to the sample cylinder. Valve 4 will
up to the blend component cylinder valves. When a good
remain partially open. Continue to open valve 3 while control-
vacuum is again reached, close valves 4 and 5 and open the
ling the flow through valve 4 until the next desired pressure
blend component cylinder valves. Ensure that the pressure of
level is reached, always maintaining a higher pressure in the
any blend component delivered to valves 4 and 5 does not
manifold than that in the cylinder. Close valve 4, allow the
exceed 200 kPa (1500 mm Hg). Record the initial pressure
pressure to equilibrate, and record the manometer reading from
readings from both sides of the manometer.
both sides. Close valve 3. When additional components are to
6.1.2 The first component to be added will either have the
be included in the blend, repeat the procedures outlined above
lowest vapor pressure or will be present in the final blend at a
for each component.
concentration of 5 % or less. Assume that the first component
6.1.6 When all components have been added, and valve 3 is
feedstock is connected to manifold valve 4. Close valve 1 and
closed, evacuate the manifold, close valve2 and disconnect the
openvalve2.Whilecarefullywatchingthemercurylevelinthe
blend cylinder from the manifold at position A. To shut down
manometer, slowly open valve 4. Allow the blend gas compo-
the apparatus, close the feedstock cylinder valve and open
nent to flow into the blend manifold until the desired precal-
valve 4 to evacuate the connection. Close valve 4, remove the
culated manometer reading is reached (see 7.1). Close valve 4
and be sure that the pressure remains constant. Tap the feedstock cylinder, close valve 1, and by using valve 2 or 4,
slowly admit air into the system until it is at atmospheric
manometer lightly to be certain the correct reading is obtained.
Record the reading of both sides of the manometer and then pressure.
D4051 – 99 (2004)
6.2 The blend must be mixed before it is used. This can be mixtureshavingheaviercomponentsorco
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