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SEMI F23-0697 © SEMI 1997, 2003 1 SEMI F23-0697 (Reapproved 0303) PARTICLE SPECIFICATION FOR GRADE 10/0.2 FLAMMABLE SPECIALTY GASES This specification was technically reapproved by the Global Gases Committee and is the d…

SEMI F22-1102 © SEMI 1997, 2002 15

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SEMI F23-0697 © SEMI 1997, 2003 1

SEMI F23-0697 (Reapproved 0303)

PARTICLE SPECIFICATION FOR GRADE 10/0.2 FLAMMABLE

SPECIALTY GASES

This specification was technically reapproved 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 October 25, 2002. Initially available at www.semi.org December 2002; to be

published March 2003. Originally published June 1997.

1 Purpose

1.1 The purpose of this document is to set a maximum

permissible particle concentration for 10/0.2 grade

flammable specialty gases and to describe a reference

method for its verification.

2 Scope

2.1 This document applies only to flammable gases

delivered through specialty gas systems at pressures up

to 8 × 10

Pa (8 atmospheres). This method is not

suitable for direct sampling from high pressure

cylinders at pressures above 8 × 10

Pa (8

atmospheres). This document applies only to the

following gas:

Hydrogen (H

)

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 and health practices and determine

the applicability of regulatory or other limitations prior

to use.

3 Referenced Standards

3.1 SEMI Standard

SEMI C6.3 — Particle Specification for Grade 20/0.2

Hydrogen (H

) Delivered as Pipeline Gas

3.2 JIS Standard

JIS B 9921 — Japanese Industrial Standard (1989),

“Light Scattering Automatic Particle Counter”

NOTICE: Unless otherwise indicated, all documents

cited shall be the latest published versions.

4 Terminology

4.1 Variables

= Volume of the i

sample interval of the system gas

= Volume of the i

sample interval of the background

1 Japanese Industrial Standards, Available through the Japanese

Standards Association, 1-24, Akasaka 4-Chome, Minato-ku, Tokyo

107-8440, Japan. Telephone: 81.3.3583.8005; Fax: 81.3.3586.2014

Website: http://www.jsa.or.jp

= Concentration of particles observed in the i

sample o

interval of the system gas

= Concentration of particles observed in the i

sample o

interval of the background

= Number of sample intervals of the system gas

= Number of sample intervals of the background

Average observed concentration of counts in the

system gas sample

Average observed concentration of background counts

Calculated concentration of particles in the system gas

Standard deviation of

4.2 gas sample volume (V

, V

) — The volume of the

sample interval, expressed in standard liters at standard

conditions, 0°C (32°F) and 1 × 10

Pa (1 atmosphere)

pressure. Standard cubic feet (SCF) is defined at

21.1°C (70°F) and 1 × 10

Pa (1 atmosphere) pressure.

4.3 average observed concentration of counts

(

X ,

X ) — The average concentration of counts, i.e.:

4.4 calculated concentration of particles (

X ) — The

concentration of particles in the system gas obtained by

correcting the observed concentration in the system gas

for the observed concentration in the background, i.e.:

= X

− X

4.5 standard deviation (S

, S

) — 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.:

SEMI F23-0697 © SEMI 1997, 2003 2

( X

− X

)

∑

−1)

( X

− X

)

∑

− 1)

NOTE 1: The third is obtained from the first two, i.e.:

= S

+ S

5 Requirements

5.1 Maximum Permissible Particle Concentration —

10 particles per 25 standard liters as determined by the

instrument specified in Section 6.

5.2 The specification will be considered met if the

calculated concentration of particles plus 2 times the

standard deviation does not exceed 10 particles per 25

standard liters, i.e.:

+ 2 × S

≤10 particles/25 standard liters

6 Apparatus

6.1 Particle Counter — An instrument suitable for

counting particles in compressed flammable gases at a

pressure of up to 8 × 10

Pa (8 atmospheres) with a

50% counting efficiency should reach 90% at 0.3

micrometer or smaller. The resolving power of the

instrument near 0.2 micrometer should be no worse

than 10%. The counting efficiency is determined by a

calibration at 1 × 10

Pa (1 atmosphere) pressure using

polystyrene latex spheres in an inert gas and a reference

particle counter with a proven counting efficiency of

not less than 95% at 0.2 micrometer.

NOTE 2: Suitable test methods for determining counting

efficiency and resolving power are contained in Japanese

Industrial Standard JIS B 9921 (1989), “Light Scattering

Automatic Particle Counter”. More sensitive particle counters

result in a higher measured particle concentration.

7 Test Method

NOTE 3: The details of the 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. Material

safety data sheets should be referred to for safe handling of

specialty gases.

7.1 Determine the average observed concentration of

counts in the background (

X ) by passing nitrogen,

believed to be free of particles 0.2 micrometer or more

in diameter, through the instrument and recording the

total number of counts. The nitrogen purge assembly

for performing this test, using a filter which removes

particles in this size range, is shown in Figure 1. Count

a minimum of 3 equal intervals, each of at least 25

standard liters (0.95 SCF), or 30 minutes, whichever is

greater. Calculate

X as defined in Section 4.

must not exceed 2 counts per 25 standard liters.

Figure 1

Schematic Diagram of Configuration for Obtaining

Particle Samples from Flammable Specialty Gas

Systems

7.2 The sampling point should be near the point of use,

and sampling lines should be clean and as short as

possible.

7.3 The sampling system configuration is shown in

Figure 1. The specialty gas system should be connected

through a sample valve directly to the particle counter,

a pressure gauge, and a flow control device (FCD).

When sampling is performed using wall tap sample

ports, the aspiration efficiency should be checked using

the method described in Related Information 1. The

sampling system should contain minimum dead volume

and sample tube length. All components in the

sampling system should be leak tight and cleaned in

accordance with good engineering practice. A leak

check of the system should be performed in accordance

with normally accepted practice. The FCD may be part

of the particle counter. The particle counter should be

maintained at the pressure of the gas system. The FCD

can be a metering valve and a flow meter or a critical

orifice. The exhaust line should be leak tight and piped

to an appropriate exhaust system. The exhaust line

diameter should be large enough to produce no more

than 1 × 10

Pa (1.5 psi) pressure drop during purge and

sample flow.

NOTE 4: The alternative sampling configurations described

in SEMI C6.3 can also be used for hydrogen.

7.4 Using the high purity nitrogen system shown in

Figure 1, purge the sampling system and particle

counter for at least 5 minutes at the instrument

manufacturer’s specified flow rate. The exact purge

time should take into account the reactivity of the gas