Chemical Engineering June 2016 - 40

Manufacturing design range example: 100 psig
+10/-5% manufacturing design range
Pressure
psig
85
Pressure
psig
85
Pressure
psig
85
Pressure
psig
85
90
95
100
105
110
115
*Rupture discs manufactured with a 0% manufacturing design range will receive a marked burst pressure at the
requested burst pressure, every time. Manufacturing tests bursts are still performed but are not averaged to determine
the marked burst pressure. Those manufacturing tests bursts must fall within the burst tolerance.
Requested burst
pressure 100 psig
Highest possible
marked burst pressure
Manufacturing test bursts
Lowest possible
marked pressure
Manufacturing design range - marked burst
pressure must fall within this range
Marked burst pressure - determine by average
of manufacturing test bursts, except for 0%
mfg. design range
Figure 2. To determine the marked burst pressure, several manufacturing test bursts are run and
their results averaged. The marked burst pressure on any rupture disk must fall within the parameters
defined by the manufacturing design range. As shown in these examples, the marked burst
pressure may be above or below the requested burst pressure, depending on the manufacturing
design range available and the results of the manufacturing test bursts
Burst tolerance examples applied to various manufacturing design ranges: 100 psig
Burst tolerance for +10/-5% manufacturing design range
Pressure
psig
85
Pressure
psig
85
Pressure
psig
85
90
95
100
105
Burst tolerance for 0% manufacturing design range*
Pressure
psig
85
Requested burst
pressure 100 psig
Manufacturing
test bursts
90
95
100
105
Highest possible marked burst pressure,
and its associated + burst tolerance
Lowest possible marked burst pressure,
and its associated + burst tolerance
110
Marked burst
pressure, and its
associated + burst
tolerance
Figure 3. The burst tolerance is the range in which a rupture disc will burst upon activation, relative
to its marked burst pressure. ASME code defines the standard burst tolerance for rupture discs as
±5% of the marked burst pressure for pressures above 40 psig. For pressures up to and including 40
psig, the standard burst tolerance is ±2 psi
Key terminology
Key rupture disc specification terms are
discussed as follows:
Manufacturing design range. the
40
115
110
115
90
95
100
105
Burst tolerance for -5% manufacturing design range
110
115
90
95
100
105
Burst tolerance for -10% manufacturing design range
110
115
90
95
100
0% manufacturing design range*
105
110
115
90
95
100
-5% manufacturing design range
105
110
115
90
95
100
-10% manufacturing design range
105
110
115
manufacturing design range is an agreement
between rupture disc manufacturer
and user that specifies how close
the marked burst pressure must be to
the requested burst pressure. specifically,
asMe defines manufacturing design
range as follows in the endnote 47
of ref. 1:
" The manufacturing design range is
a range of pressure within which the
marked burst pressure must fall to be
acceptable for a particular requirement,
as agreed upon between the rupture disk
manufacturer and the user or his designated
agent. The manufacturing design
range must be evaluated in conjunction
with the specified burst pressure to ensure
that the marked burst pressure of
the rupture disk will always be within applicable
limits of UG-134. Users are cautioned
that certain types of rupture disks
have manufacturing ranges that can result
in a marked burst pressure greater
than the specified burst pressure. "
rupture disc manufacturers typically
acquire and stock a limited selection of
material types and thicknesses. early
rupture disc designs had limited means
of adjusting the burst pressure - other
than by selecting a different material thickness.
as a result, rupture disc manufacturers
often were not able to achieve the
exact requested burst pressure. for this
reason, the manufacturing design range
must be agreed upon and specified.
the way that manufacturing design
range is expressed depends on the
rupture disc brand, model and in some
cases, designated burst pressure. rupture
discs may be specified with manufacturing
design ranges of -10%, -5%,
or 0% of the requested burst pressure,
or in some cases, with a positive or
negative pressure unit value (table 1). a
manufacturing range of -10% for a rupture
disc with a requested burst pressure
of 100 psig will be marked somewhere
between 90 psig and 100 psig. rupture
discs ordered with a 0% manufacturing
design range will be marked at the requested
burst pressure. all other manufacturing
design ranges will be marked at
the average value of the test breaks that
were done to qualify the lot.
some older designs may not be available
in the tightest ranges. for these designs,
most manufacturers may offer a
tighter manufacturing range for an added
cost, while others may offer a zero manufacturing
range as standard on premium
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Chemical Engineering June 2016

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