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SEMI C6.6-90 © SEMI 1990, 2002 3 NOTICE: SEMI makes no warranties or representations as to the suitability o f the standards set forth herein for any particular application. The determination of the suitability of the st…

SEMI C6.6-90 © SEMI 1990, 2002 2

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 2: 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 (

X ) by passing air, nitrogen

or argon, believed to be free of particles of 0.1

micrometers or more in diameter, through the

instrument and recording the total number of counts. A

suggested assembly for perfoming this test, using a

filter which removes particles in this size range, is

shown in Figure 1. A method recommended by the

instrument manufacturer, such as internal recirculation

through a filter, may be substituted for the system

shown. Count a minimum of 8 sample intervals, each at

least 25 standard liters (0.95 SCF) or 30 minutes,

whichever is greater. Calculate

X as defined in

Section 3.

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

X and S

, as defined in

Section 3.

6 Specification

6.1 Maximum Permissible Particle Concentration —

10 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

deviations does not exceed 10 particles per 25 standard

liters, i.e.:

∗

≤

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% confidence level.

Figure 1

Suggested Assembly for Determining Particle

Counter Background

Figure 2

Schematic Diagram of Configuration for Obtaining

Particle Samples from Pipelines

SEMI C6.6-90 © SEMI 1990, 2002 3

NOTICE: SEMI makes no warranties or

representations as to the suitability of the standards set

forth herein for any particular application. The

determination of the suitability of the standard is solely

the responsibility of the user. Users are cautioned to

refer to manufacturer’s instructions, product labels,

product data sheets, and other relevant literature

respecting any materials mentioned herein. These

standards are subject to change without notice.

The user’s attention is called to the possibility that

compliance with this standard may require use of

copyrighted material or of an invention covered by

patent rights. By publication of this standard, SEMI

takes no position respecting the validity of any patent

rights or copyrights asserted in connection with any

item mentioned in this standard. Users of this standard

are expressly advised that determination of any such

patent rights or copyrights, and the risk of infringement

of such rights, are entirely their own responsibility.

International), 3081 Zanker Road, San Jose, CA 95134. Reproduction o

the contents in whole or in part is forbidden without express written

consent of SEMI.

SEMI C6.7-93 © SEMI 1993, 2002 1

SEMI C6.7-93 (Reapproved 1102)

PARTICLE SPECIFICATION FOR GRADE 10/0.2 NITROGEN IN HIGH

PRESSURE GAS CYLINDERS

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 1993.

1 Purpose

1.1 The purposes of this document are (1) to set a

maximum permissible particle concentration for 10/0.2

grade cylinder nitrogen, and (2) to describe a reference

method for its verification.

2 Scope

2.1 This specification applies to nitrogen contained in

high pressure gas cylinders; it is not applicable to

pipeline gases.

2.2 A nitrogen cylinder consists of three components:

(1) a cylinder bottle, (2) compressed nitrogen contained

within, and (3) a cylinder valve. Each component can

be a particle source. This specification applied to the

total number of particles detected in the gas as obtained

from the cylinder under a prescribed condition. No

consideration is given to the origin of the particles.

2.3 It is known that pressure reduction, if not

controlled, can produce a large number of artifact

particles through nucleation and condensation. To avoid

this complication, this specification adopts particle

counters that can be operated at a pressure up to 200 bar

(3000 psi), eliminating the need for pressure reduction

and its associated problems.

2.4 It is known that particle content in cylinder gases

varies with time because particles can be lost to

cylinder walls by diffusion or sedimentation, and

detached from cylinder walls by flow pulses or

mechanical shocks. It is important to measure particle

concentration under the worst conditions which

represent typical handling of gas cylinders. This

specification describes a standard shock test that fulfills

the above requirements and provides a procedure to

count particles immediately after the shock.

2.5 If this test method is to be used for more than one

cylinder, then each cylinder must be tested. It is known

that particle contamination in cylinder gases is a strong

function of the handling history of the individual

cylinders. Cylinders in the same batch of filling are

usually returned from various customers after various

periods of service. Uniform quality can not be assumed

for the same batch of cylinders unless each of them has

gone through a dedicated process that erases the

memory of previous history prior to filling. Therefore,

batch sampling at 10% or 20% cannot be accepted

because of the significant differences among cylinders.

2.6 The requirement of 100% sampling restricts the

total amount of gas in each cylinder that can be used for

sampling purposes. This restriction, in turn, calls for

certain relaxation of the statistical requirement for

particle sampling at low concentration levels.

2.7 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

= Observed particle concentration in the i

sample

interval of the background

= Observed particle concentration in the i

sample

interval before shocks

= Observed particle concentration in the i

sample after

shocks

= Number of sample intervals of the background

= Number of sample intervals before shocks

= Number of sample intervals after shocks

Averaged observed particle concentration of the

background

Averaged observed particle concentration before

shocks

Averaged observed particle concentration after

shocks

= Calculated particle concentration before shocks

= Calculated particle concentration after shocks

Standard deviation of

= Standard deviation of X