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SEMI C6.2-93 © SEMI 1989, 2002 1 SEMI C6.2-93 (Reapproved 1102) PARTICLE SPECIFICATION FOR GRADE 20/0.02 OXYGEN DELIVERED AS PIPELINE GAS This specification was technically approved b y the Globa l Gases Com mittee and i…

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SEMI C6.7-93 © SEMI 1993, 2002 3
7 Report
The report shall contain the value of the measured
sample volumes, values of all the variables defined in
Section 3, the mass of the steel ball, and length of the
chain.
Figure 1
Figure 2
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forth herein for any particular application. The
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International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o
f
the contents in whole or in part is forbidden without express written
consent of SEMI.
SEMI C6.2-93 © SEMI 1989, 2002 1
SEMI C6.2-93 (Reapproved 1102)
PARTICLE SPECIFICATION FOR GRADE 20/0.02 OXYGEN
DELIVERED AS PIPELINE GAS
This specification was technically approved by the Global Gases Committee and is the direct responsibility of
the North American Gases Committee. Current edition approved by the North American Regional Standards
Committee on July 21, 2002. Initially available at www.semi.org October 2002; to be published November
2002. Originally published in 1989; previously published in 1993.
1 Purpose
1.1 The purposes of this document are: (1) to set a
maximum permissible particle concentration for
20/0.02 grade oxygen bulk supply gas, and (2) to
describe a reference method for its verification.
2 Scope
2.1 This document applies only to oxygen gas
delivered through pipelines; it is not applicable to
cylinder gas or oxygen gas in its liquid state.
2.2 This standard does not purport to address safety
issues, if any, associated with its use. It is the
responsibility of the users of this standard to establish
appropriate safety health practices and determine the
applicability or regulatory limitations prior to use.
3 Terminology
3.1 Variables
V
Mi
= Volume of the i
th
sample interval of the pipeline
gas
V
Bi
= Volume of the i
th
sample interval of the
background
X
Mi
= Concentration of particles observed in the i
th
sample interval of the pipeline gas
X
Bi
= Concentration of particles observed in the i
th
sample interval of the background
N
M
= Number of sample intervals of the pipeline gas
N
B
= Number of sample intervals of the background
M
X =
Average observed concentration of counts in
the pipeline gas sample
B
X=
Average observed concentration of
backgroundcounts
C
X =
Calculated concentration of particles in the
pipeline gas
S
M
=
Standard deviation of
M
X
S
B
=
Standard deviation of
B
X
SE
C
=
Standard error of
C
X
3.2 Gas Sample Volume (V
Mi
, V
Bi
) — The volume of
the sample interval, expressed in standard liters at
standard conditions, 0°C (32°F) and 1.00 atmosphere
pressure. Standard Cubic Feet (SCF) is defined at
21.1°C (70°F) and 1.00 atmosphere pressure.
3.3 Average Observed Concentration of Counts
(
M
X ,
B
X ) — The average concentration of counts, i.e.:
X
M
=
X
Mi
∑
N
M
X
B
=
X
Bi
∑
N
B
3.4 Calculated Concentration of Particles (
C
X ) —
The concentration of particles in the pipeline gas
obtained by correcting the observed concentration in
the pipeline gas for the observed concentration in the
background, i.e.:
X
C
=
X
M
-
X
B
3.5 Standard Deviation (S
M
, S
B
, S
C
) — A statistical
measure of the spread of the concentration of the counts
or particles. The first two are obtained from the interval
and average concentrations and the number of intervals,
i.e.:
S
M
=
X
Mi
– X
M
(
)
2
∑
N
M
– 1
()
S
B
=
X
Bi
– X
B
()
2
∑
N
B
– 1
()
The third is obtained from the first two, i.e.:
S
C
= S
M
2
+ S
B
2
(
)
1
2
NOTE 1: These expressions are derived from an assumption
of a Gaussian (Normal) distribution.
3.6 Standard Deviation (S
M
, S
B
) — A statistical
measure of the spread of the concentration of the counts
or particles. The first two are obtained from the interval
and average concentrations and the number of intervals,
i.e.:
S
M
=
X
Mi
– X
M
(
)
2
∑
N
M
– 1
()
S
B
=
X
Bi
– X
B
()
2
∑
N
B
– 1
()
NOTE 2: These expressions are derived from an assumption
of a Gaussian (Normal) distribution.
SEMI C6.2-93 © SEMI 1989, 2002 2
3.7 Standard Error (SEC)
SE
C
=
S
M
2
N
M
+
S
B
2
N
M
1
2
4 Apparatus
4.1 Particle Counter — An instrument suitable for
counting particles in gaseous oxygen with a counting
efficiency of 50 percent at 0.02 micrometers as
determined by the manufacturer of the particle counter.
Condensation nucleus counters (CNCs) typically satisfy
this requirement.
4.2 Pressure Reducer — An accessory required for
counters operated at atmospheric pressure, it should
preferably use expansion of the gas through a critical
orifice.
5 Test Method
NOTE 3: The details of sampling configuration,
measurement procedure, and instrument calibration procedure
and frequency must be agreed upon by the user and supplier,
taking into account good engineering practice.
5.1 Determine the average observed concentration of
counts in the background (
B
X ) by passing air or
nitrogen or oxygen believed to be free of particles of
0.02 micrometers or larger in diameter, through the
instrument and recording the total number of counts.
Count a minimum of 8 sample intervals, each at least
25 standard liters (0.95 SCF) or 30 minutes, whichever
is greater. A suggested assembly for performing this
test, using a filter which removes particles in this size
range, is shown in Figure 1. Calculate
B
X as defined in
Section 3.
B
X must not exceed 2 particles per 25
standard liters.
5.2 The sampling point should be at outlet of system,
and sampling lines should be as short as possible.
5.3 A suggested sampling probe configuration for
turbulent main line flow is shown in Figure 2. The flow
rate in the sampling tube at pipeline pressure should be
set so that the mean sampling flow velocity at the probe
inlet matches as closely as possible the axial flow
velocity in the pipeline. The pitot sampling tube ID
should be no less than 2 mm (0.08 inch). The orifice
and sampling horn should be sized so that the mean
flow velocity at the particle counter probe inlet matches
the axial flow velocity in the horn as closely as
possible.
5.4 Count the particles in each of at least 8 sample
intervals. Each sample interval must be at least 25
standard liters or 30 minutes, whichever is greater.
Record the number of counts and the sample volume
for each interval. Calculate
C
X and SE
C
, as defined in
Section 3.
6 Specification
6.1 Maximum Permissible Particle Concentration —
20. particles per 25 standard liters as determined by the
instrument specified in Section 4.
6.2 The specification will be considered met if the
calculated concentration of particles plus two standard
errors does not exceed 20. particles per 25 standard
liters, i.e.:
C
X + 2*SE
C
≤ 20. Particles/25 standard liters
7 Report
7.1 The report shall contain the values of all the
variables defined in Section 3.
8 Precision
8.1 This test procedure defines the requirements to
satisfy the specification at the 95 percent confidence
level.
Figure 1
Suggested Assembly for Determining Particle
Counter Background
Figure 2
Schematic Diagrams of Configurations of
Different Merit for Obtaining Particle Samples
from Pipelines