API 570 8 Repairs, Alterations, and
Rerating of Piping Systems
8.1 - ANSRepairs and Alterations
8.1.1 General - ANSThe principles of ASME B31.3 or the code to which the piping system
was built shall be followed to the extent practical for in-service repairs. ASME B31.3 is
written for design and construction of piping systems. However, most of the technical
requirements on design, welding, examination, and materials also can be applied in the
inspection, re-rating, repair, and alteration of operating piping systems. When ASME B31.3
cannot be followed because of its new construction coverage (such as revised or new
material specifications, inspection requirements, certain heat treatments, and pressure
tests), the piping engineer or inspector shall be guided by API 570 in lieu of strict conformity
to ASME B31.3. As an example of intent, the phrase "principles of ASME B31.3" has been
employed in API 570, rather than "in accordance with ASME B31.3."
The principles and practices of API 577 shall also be followed for all welded repairs and
modifications.
8.1.2 Authorization - ANSAll repair and alteration work shall be done by a repair organization
as defined in Section 3 and shall be authorized by the inspector prior to its commencement.
Authorization for alteration work to a piping system may not be given without prior
consultation with, and approval by, the piping engineer. The inspector will designate any
inspection hold points required during the repair or alteration sequence. The inspector may
give prior general authorization for limited or routine repairs and procedures, provided the
inspector is satisfied with the competency of the repair organization.
8.1.3 Approval - ANSAll proposed methods of design, execution, materials, welding
procedures, examination and testing shall be approved by the inspector or by the piping
engineer, as appropriate, Owner/user approval of on-stream welding is required.
Welding repairs of cracks that occurred in-service should not be attempted without prior
consultation with the piping engineer in order to identify and correct the cause of the
cracking. Examples are cracks suspected of being caused by vibration, thermal cycling,
thermal expansion problems, and environmental cracking.
The inspector shall approve all repair and alteration work at designated hold points and after
the repairs and alterations have been satisfactorily completed in accordance with the
requirements of API 570.
8.1.4 - ANSWelding Repairs (Including On-stream)
8.1.4.1 Temporary Repairs - ANSFor temporary repairs, including on-stream, a full
encirclement welded split sleeve or box-type enclosure designed by the piping engineer may
, be applied over the damaged or corroded area. See various articles in ASME PCC-2 for
more information on repairs to piping systems. Longitudinal cracks shall not be repaired in
this manner unless the piping engineer has determined that cracks would not be expected to
propagate from under the sleeve. In some cases, the piping engineer will need to consult
with a fracture analyst. The design of temporary enclosures and repairs shall be approved by
the piping engineer.
If the repair area is localized (for example, pitting or pinholes) and the SMYS of the pipe is
not more than 40,000 psi (275,800 kPa), and a Fitness-For-Service analysis shows it is
acceptable, a temporary repair may be made by fillet welding a properly designed split
coupling or plate patch over the pitted or locally thinned area (see 8.1.4 for design
considerations and Annex C for an example). The material for the repair shall match the
base metal unless approved by the piping engineer. A fillet-welded patch shall not be
installed on top of an existing fillet-welded patch. When installing a fillet-welded patch
adjacent to an existing fillet-welded patch, the minimum distance between the toe of the fillet
weld shall be less than:
d=4(square root)Rt
where
d is the minimum distance between he toes of fillet welds of adjacent fillet weld attachments,
in inches (millimeters);
R is the inside radius in inches (millimeters);
t is the minimum required thickness of the fillet-welded patch in inches (millimeters).
For minor leaks and thinning below Tmin, properly designed enclosures may be welded over
the leak or thin piping while the piping system is in-service, provided the inspector is satisfied
that adequate thickne
8.1.4.2 Permanent Repairs - ANSRepairs to defects found in piping components may be
made by preparing a welding groove that completely removes the defect and then filling the
groove with weld metal deposited in accordance with 8.2.
Corroded areas may be restored with weld metal deposited in accordance with 8.2. Surface
irregularities and contamination shall be removed before welding. Appropriate NDE methods
shall be applied after completion of the weld.
If it is feasible to take the piping system out of service, the defective area may be removed
by cutting out a cylindrical section and replacing it with a piping component that meets the
applicable code.
Insert patches (flush patches) may be used to repair damaged or corroded areas if the
following requirements are met:
a) full-penetration groove welds are provided;
b) for Class 1 and Class 2 piping systems, the welds shall be 100% radiographed or
ultrasonically tested using NDE procedures that are approved by the inspector;
c) patches may be any shape but shall have rounded corners [1" (25mm) minimum radius].
See ASME PCC-2 Part 2 for more information on various welded repairs to piping systems.
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