Process Plant Piping Maintenance & Repair
I. Introduction
The structural integrity of piping systems must be maintained after they have
been placed into service so that they will provide safe, reliable, long-term
operation. Therefore, existing piping systems require periodic inspection to
determine their current condition and permit evaluation of their structural integrity
to permit future operation. Should unacceptable deterioration or flaws be
identified, pipe repairs may be required. Existing piping systems might also
require alterations or rerating to accommodate new operational needs (or to
accommodate deterioration that cannot or will not be repaired).
Process plants must adopt and follow established procedures for the inspection,
repair, alteration, and rerating of piping systems after they have been placed into
service. API 570, “Piping Inspection Code – Inspection, Repair, Alteration, and
Rerating of In-Service Piping Systems,” provides the basic procedures to be
followed by process plants. This course is based on API 570.
Scope of API 570
API 570 was developed for the petroleum refining and chemical process
industries. But since most of its requirements have broad applicability, it may be
used for any piping system. It must be used by organizations that maintain or
have access to an authorized inspection agency, a repair organization, and
technically qualified piping engineers, inspectors, and examiners (as defined in
API 570).
While API 570 applies to all petroleum refineries and chemical plants, its scope
defines both specific included fluid services, and excluded and optional piping
systems. Thus, API 570 requirements do not necessarily have to be applied to
every piping system in a refinery or chemical plant.
Included Fluid Service
Unless identified by API 570 as being an excluded or optional system, API 570
applies to piping systems for process fluids, hydrocarbons, and similar flammable
or toxic fluid services. Examples of these are the following:
• Raw, intermediate, and finished petroleum or chemical products.
• Catalyst lines.
• Hydrogen, natural gas, fuel gas, and flare systems.
• Sour water and hazardous waste streams or chemicals above threshold
limits, as defined by jurisdictional regulations.
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Excluded and Optional Piping Systems
API 570 permits the following fluid services and classes to be excluded from its
specific requirements. This is done to focus attention (with associated manpower
and budget expenditures) on applications that would have the most significant
consequences should a pipe failure occur. However, any of these excluded
systems may be included in a plant’s API 570 program at the option of the owner.
• Fluid services that are excluded or optional include the following:
- Hazardous fluid services below threshold limits, as defined by
jurisdictional regulatories.
- Water (including fire protection systems), steam, steam condensate, boiler
feedwater, and Category D fluid services (as defined by ASME B31.3).
• Classes of piping systems that are excluded or optional are as follows:
- Piping systems on movable structures covered by jurisdictional regulation
(e.g., piping systems on trucks, ships, barges, etc.).
- Piping systems that are an integral part or component of rotating or
reciprocating mechanical devices (e.g., pumps, compressors, etc.) where
the primary design considerations and/or stresses are derived from the
functional requirements of the device.
- Internal piping or tubing of fired heaters or boilers.
- Pressure vessels, heaters, furnaces, heat exchangers, and the fluid
handling or processing equipment (including internal piping and
connections for external piping).
- Plumbing, sanitary sewers, process waste sewers, and storm sewers.
- Piping or tubing with an outside diameter not exceeding that of NPS ½
- Nonmetallic piping and polymeric or glass-lined piping.
API 570 permits these services and systems to be excluded from its specific
requirements to focus inspection, engineering, and maintenance resources on
areas that would have the largest potential effect should leakage or failure occur.
However, this should not be interpreted that these “excludable or optional”
systems should be completely ignored. Furthermore, the consequences of a
failure in some of these systems could be dangerous or unacceptable in
particular circumstances. Therefore, owners may wish to include some of these
services or systems in their API 570 program in all respects, and different
requirements and procedures may be used for other services or systems. For
example:
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• The failure of a high pressure steam or boiler feedwater system could have
significant personnel safety consequences. An owner might include such
services in his API 570 program.
• The failure of an NPS ½ vent connection in an “included” fluid service could
have significant personnel safety and economic consequences. An owner
might wish to include such systems in his API 570 program.
Definitions
API 570 contains definitions of technical terms that are used in the standard.
The following are several of these terms used in this course:
• Alteration A physical change in any component that has design
implications affecting the pressure containing capability or
flexibility of a piping system beyond the scope of its design.
• Repair The work necessary to restore a piping system to a condition
suitable for safe operation at the design conditions.
• MAWP The maximum internal pressure permitted in the piping
system for continued operation at the most severe condition
of coincident internal or external pressure and temperature
(minimum or maximum) expected during service.
• Rerate A change in either or both the design temperature or the
maximum allowable working pressure.
• Piping Circuit A section of piping that has all points exposed to an
environment of similar corrosivity and that is of similar design.
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