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SEMI C6.7 Document Information:
Title
PARTICLE SPECIFICATION FOR GRADE 10/0.2 NITROGEN IN HIGH PRESSURE GAS CYLINDERS
Semiconductor Equipment and Materials International
Publication Date:
Jan 1, 1993
Scope:
This specification applies to nitrogen contained in high
pressure gas cylinders; it is not applicable to pipeline gases.
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.
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.
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.
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.
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.
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.
Purpose
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.
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