Page 468 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

434 Applied Process Design for Chemical and Petrochemical Plants

Table 7-2
Typical Prebulged Solid Metal Disk
Manufacturing Ranges and Tolerances

Manufacturing Range/Burst Tolerance @ 72°F
Specified Manufacturing Range
Burst Pressure % % Rated (Stamped)
Rating, psig Under Over Burst Tolerance %
2-5 -40 +40 ±25%
6-8 -40 +40 ±20%
9-12 -30 +30 ±15%
13-14 -10 +20 ±10%
15-19 -10 +20 ± 5%
20-50 -4 +14 ± 5%
51-100 -4 + 10 ± 5%
101-500 -4 + 7 ± 5%
Inlet flanges ----......
1-----,1-----, 501-up -3 + 6 ± 5%
Note:
Inlet pipe---....
1. Special reduced manufacturing ranges can be obtained for
the STD prebulged metal disk. ){, Y,, and X ranges are available
Branch connection �
upon request. Please consult your representative or the facto-
ry for additional information.
2. Burst tolerances are the maximum expected variation from
the disk's rated (stamped) burst pressure.
Run pipe 3. Standard-type rupture disks comply with ASME code require-
ments.
1. -I The manufacturing range is defined as the allowable pressure
Manufacturing Range

� Not less than 1 O pipe diameters range within which a rupture disk is rated. IL is based upon the
from any device that causes turbulence customer specified burst pressure. The manufacturing ranges for
Typical installation avoiding excessive turbulence at pressure relief Continental's standard rupture disk are outlined in Table 7-2.
valve inlet.
Bursi Tolerance
Figure 7-20 cont. After the disk has been manufactured and tested, it is stamped
with the rated burst pressure. The rated (stamped) burst pres-
sure is established by bursting a minimum of two disks and aver-
aging the pressures at which the disks burst. This average is the
rated (stamped) burst pressure of the disk. Standard rupture
Rupture disks are often placed below a safety valve to disks above 15 psig@ 72°F are provided with a burst tolerance of
prevent corrosive, tarring or other material from entering ±5% of the rated (stamped) burst pressure. This is in accordance
the valve nozzle. Only disks which do not disintegrate with the ASME code. Burst tolerances for disks below 15 psig @
72°F are outlined in Table 7-2. Burst tolerance applies only Lo the
when they burst (Figures 7-10, 7-11, 7-12, 7-18) can be used rated (stamped) burst pressure of the disk. Burst certificates are
below a safety valve, as foreign pieces which enter the valve provided with each disk lot.
might render it useless. This is acceptable to certain code By permission, Continental Disc Corporation, Catalog STD-1184.
applications [ 1]. These disks are also used to provide sec-
ondary relief when in parallel with safety valves set at lower
pressures. They can also be installed on the discharge of a
safety valve to prevent loss of hazardous vapors, but cau- that in order lo accomplish the required pressure relief
tion should be used in any serious situation. the proper selection and application of type of device is
essential.
Selection Features: Safety, Safety-Relief Valves, and
Rupture Disks Safety Valve: normally used for steam service, but suit-
able for gases or vapors. When used in steam generation
Referring to the description and definitions in the and process steam service the valves conform to the
introduction for this chapter, it is important to recognize ASlv1E Power Boiler Code as well as the ASJ\1E Pressure Vessel