1.1 This standard establishes guidelines to prevent most
forms of environmental cracking of weldments in carbon
steel refinery equipment, including pressure vessels, heat
exchangers, storage tanks, piping, valve bodies, and pump
and compressor cases. Weldments are defined to include
the weld deposit, base metal HAZ, and adjacent base metal
zones subject to residual stresses from welding.
1.2 This standard covers only carbon steels classified as
P-No. 1, Group 1 or 2. These classifications can be found
in the ASME Boiler and Pressure Vessel Code, Section IX9
for pressure vessels, ASME/ANSI B31.3 for process piping,
or API Standards 620 and 650 for tanks. It excludes steels
with greater than 480 MPa (70,000 psi) minimum specified
tensile strength. Other materials may be vulnerable to
cracking, but these materials are outside the scope of this
standard.
1.3 The types of equipment covered by this standard
include pressure vessels, heat exchangers, storage tanks,
piping, valve bodies, and pump and compressor cases. All
pressure-containing weldments or internal attachment
weldments to the pressure boundary are included. In
addition, weldments in some non-pressure-containing
equipment, such as storage tanks, are included. External
attachment weldments are sometimes included as
discussed in Paragraph 3.5.1.
1.4 Both new fabrication and repair welds are within the
scope of this standard. The practices included herein are
intended to prevent in-service cracking and are not intended
to address cracking that can occur during fabrication, such
as delayed hydrogen cracking. In most cases, however,
these practices are also helpful in minimizing these
fabrication problems. Useful information for preventing
delayed hydrogen cracking is provided by F.R. Coe, et. al.10
1.5 Welding processes covered by this standard include
shielded metal arc welding (SMAW); gas metal arc welding
(GMAW); flux-cored arc welding (FCAW); gas tungsten arc
welding (GTAW); and submerged arc welding (SAW).
Almost all types of weld configurations are included. For
specific exceptions, such as hot taps, hardness limits and
postweld heat treatment (PWHT) requirements should be
reviewed on a case-by-case basis.
1.6 Corrosive refinery process environments covered by
this standard can be divided into two general categories:
services that could cause cracking as a result of hydrogen
charging, and services that could cause ASCC. However,
identification of the specific environments to which the
guidelines set forth in this standard are to be applied to
prevent various forms of in-service environmental cracking
is the responsibility of the user. Figure 1 is a simplified
schematic showing the interrelationships of the various
cracking mechanisms discussed in this standard.
| File Size : | 1
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| ISBN(s) : | 1575901145 |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 31 |
| Published : | 11/07/2008 |
