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Guidance in
defining critical process parameters
关键参数的定义指南
The
criticality of a process parameter is an
assessment of the probability that it can be
consistently and
reproducibly
controlled within the proven acceptable range
(PAR) during routine manufacturing.
工艺参
数的关键性是指在生产中对可接受范围的持续重复控制的可能性的评估，
This probability depends on
可能性主要取决于：
t
he robustness of the
process parameter (the width of the PAR)
工艺参数的稳定性（可接受范围的宽度）
?
t
he
ability to technically control the parameter
(technical limitations)
参数控制的技术能力（技术限制）
?
t
he
uncertainty of the measurement of the parameter
(reflected by the standard
参数测量的不确定性（用标准偏差来反映）
?
deviation σ)
The robustness
of a process parameter is reflected by the width
of the proven acceptable range. The wider
the
range
within
which
a
parameter
could
be
varied
during
process
qualification
without
impacting
product quality,
the more robust it is.
可接受的参数范围反映工艺参数的稳
定性。
在参数确认中不影响产品质量的可改变的参数的范围越
宽
，工艺越稳定。
The ability
to
technically
control
a parameter is a
function of a
combination of
process
properties
and
equipment
capabilities.
For
example,
a
highly
exothermic
reaction
might
be
well
controlled
in
a
small
stainless steel vessel, but could prove
impossible to control in a larger glass-lined
vessel.
参数的技术控制能力是工艺特性和设备能力
的综合功能。例如，一个高放热的反应可能在一个小的不锈钢
反应釜内能够很好的被控制
，但是在一个大的塘玻璃反应釜内证明是不可能控制的。
The
uncertainty
of
a
measurement
(
σ
)
is
the
combined
uncertainty
of
the
calibration
of
the
probe,
the
variance of the probe
itself, and the variance of the signal
transmission from the probe to the distributed
control system (DCS). If the
measurement is normally distributed, 3.4 out of a
million data points will be
outside a
range of +/-
4.5 standard deviations.
This is the basis of the ‘six sigma’ theory. The
difference of
1.5
between
4.5
and
6
is
an
empirical
value
chosen
based
on
the
observation
that
the
mean
of
real
processes tends to
drift by this value over time.
Based on
the ‘6
σ
’
-concept
we define a parameter as
‘critical’
when the proven acceptable range is narrower than
± six standard deviations.
测量的不确定性是探头或检测器的校验，监测器本身的变化和从探头到
DCS
的信号传输的变化的
不确定因素的综合。如果测量结果是正态分布的，
3.4PPM
（百万分之一）将在
+/-4
.5
标准偏差的范
围之外。这是六西格玛理论的基础。
4.5
和
6
之间
1.5
的差异是一个经验值基于观察实际工艺趋势
相对时间数值的漂移。基于六西格玛概念当一个参数的可接受的范围比
+/-
六个标准偏差窄时，我
们定义这个参数为关键参数。
< br>
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figure 1:
critical parameter
set
point
figure 2: non-critical
parameter
set
point
5
5°
6
0°
5
5°
6
0°
4
0°
4
5°
5
0°
6
5°
7
0°
4
0°
4
5°
5
0°
6
5°
7
0°
6
σ
6
σ
6
σ
6
σ
proven acceptable range
lower/upper
edge of failure
proven acceptable
range
lower/upper edge of
failure
Whereas
a
proven
acceptable
range
depends
only
on
the
process,
the
variance
of
a
control
system
is
equipment-specific. The variance of a
control system for the same process parameter
might be different in
another
operational
environment,
which
could
result
in
a
different
criticality
assessment
(e.g.
a
critical
process
parameter
in
one
plant
may
be
judged
to
be
non-
critical
in
another
plant
which
has
a
control
system
with a lower variance).
如果一
个可接受的参数范围仅仅依赖于工艺，
控制系统的变异是设备属性。
对同样的工艺参数的控
制系统的变异可能在另一个操作环境下不同，
这个可能导致一个不同的关键性评估
（比如在一个工
厂
的一个关键参数在另一个有较低变异的控制系统的工厂就可能被判定为不关键）
The following table can be used for
guidance to assess the criticality of a process
parameter
以下列表在指南中用于评定一个工艺参数的关键性
assumption
for
σ
minimum
PAR
for
non-critical parameter
Comment
(±
6
σ
)
备注
判
定
不
关
键
的
最
小
可接受范围
For
the
typical
measurement
type of process
parameter
工艺参数的类型
Temperature
温度
+/-4%
0.6%
range)
C:
+/-
(of
measurement
range
of
-20
to
180°
8°
C
对
于
典
型
的
测
量
范
围<
/p>
-20~180°
C
，范围为
+/-8°
C
(
检测范围的
)
Amount (quantity) by weight
重量
The
limits
of
the
balance
0.8%
+/-5%
(of set point)
（设定点的）
have
to
be
taken
into
account. See:
称的限度应该带进数量
Amount (quantity)
by volume
体积数量
pH
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2%
+/-12%
(of set point)
（设定点的）
Important:
a
certain
minimal
flow has to be exceeded
重要提示
：
必须超过确定的
最小流量
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