piping and components inspection.pdf
TRANSCRIPT
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3.5 Piping and Component
Inspection
API RP 574
.
Major Piping Inspection CodesAPI 570
Piping Inspection Code
Design StandardsNew Construction
MitigationStandards
Quality SafetyOther Inspection
Codes / Documents
ASMEB16.34Valves - Flanged
Threaded andWelding ends
API 651Cathodic Protection ofAboveground Storage
Tanks
NACE RP0169Control of External
Corrosion onUnderground or
Submerged MetallicPiping Systems
ASME BPVC Sec IX,"Welding and Brazing
Qualifications"
API RP 750Management ofProcess Hazards
Of Materials
API 510Pressure VesselInspection Code
ASME BPVC Sec VIII,Division 1 & 2
Pressure Vessels
R:0170Protection of
Austenitic StainlessSteels from PolythionicAcid Stress Corrosion
Cracking During
NACE RP0274High-Voltage ElectricalInspection of Pipeline
Coatin s Prior to
CP-189Standard for Qualification
and Certification ofNondestructive Testing
Personnel
NFPA 704Identification ofthe Fire Hazards
of Materials
API RP 574Inspection of Piping
SystemComponents
ut own o
Refinery Equipment
InstallationASME B31.3Process Piping
Application of OrganicCoatings to the
External Surface ofSteel Pipe for
Underground Piping
SNT-TC-1A API 598Valve Inspection
and Testing
Notes:
1. The source of this data is from API Standard 570 "Piping Inspection Code", Second
Edition October 1998, Section2 "References";
2. API 570 references directly all of the standards shown on this diagram and they are
applicable and mandatory under the appropriate conditions as indicated in API 570.
3. API Standards are revised, reaffirmed, or withdrawn at least every 5 years.
4. API Standards, revision or addenda are effective 6 months after the date of issuance
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API 570 - Piping Inspection Code
Coverage
, , ,rerating procedures for metallic piping systems thathave been in-service.
Intent
API 570 was developed for the petroleum refiningand chemical process industries but may be used,where ractical for an i in s stem.
It is intended for use by organizations that maintain
or have access to an authorized inspection agency, arepair organization, and technically qualified pipingengineers, inspectors, and examiners, all as defined inSection 3.
API 570 Framework Section 9 of API 570 recognizes two distinctions
re ardin buried i e:
Significant External Deterioration,
Inaccessibility.
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API 570 Framework
Subsections of Section 9 are:
T es and Methods of Ins ection.
Direct and indirect monitoring (limited reference).
Frequency and Extent of Inspection.
Repairs to Buried Piping System.
Records.
API RP 574 - Inspection Practices For
Piping System Components
This recommended practice describes to the inspector on
describes ins ection ractices for i in tubin valves other
than control valves), and fittings used in petroleum refineries
and chemical plants.
Common piping components, valve types, pipe joining
methods, inspection planning processes, inspection intervals
and techniques, and types of records are described to aid the
ins ector in fulfillin their role im lementin API 570.
This publication does not cover inspection of specialty items,
including instrumentation and control valves
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API RP 574 - Definitions
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.
NOTE The following are not considered alterations:
compara e or up ca e rep acemen ; e a on o any
reinforced branch connection equal to or less than the size
of existing reinforced branch connections; and theaddition of branch connections not requiring
reinforcement.
API RP 574 - Definitions
condition monitoring locations
CMLs
Designated areas on piping systems where
periodic inspections and thickness
measurements are conducted.
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API RP 574 - Definitions
deadlegs
Components of a piping system that normally have no
significant flow.
Examples of deadleg locations include: blanked
branches, lines with normally closed block valves,
lines which have one end blanked, pressurized
ummy suppor egs, s agnan con ro va ve ypass
piping, spare pump piping, level bridles, relief valve
inlet and outlet header piping, pump trim bypass
lines, high point vents, sample points, drains,
bleeders, and instrument connections.
API RP 574 - Definitions
minimum alert thickness
c ness grea er an e m n mum a owe c ness
that provides for early warning from which the future
service life of the piping is managed through further
inspection and remaining life assessment.
minimum allowed thickness
structural minimum thickness at a CML. It does not
include thickness for corrosion allowance or mill
tolerances.
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API RP 574 - Definitions
piping circuit
omp ex process un s or p p ng sys ems are v e n o
piping circuits to manage the necessary inspections,
calculations, and recordkeeping.
A piping circuit is a section of piping of which all points
are exposed to an environment of similar corrosivity and
which is of similar desi n conditions and construction
material.
When establishing the boundary of a particular pipingcircuit, the Inspector may also size it to provide a
practical package for recordkeeping and performing field
inspection.
API RP 574 - Definitions
repair
A repair is the work necessary to restore a piping
system to a condition suitable for safe operation at the
design conditions.
If any of the restorative changes result in a change of
design temperature or pressure, the requirements for
rera ng a so s a s ou e sa s e . Any welding, cutting, or grinding operation on a
pressure containing piping component not specifically
considered an alteration is considered a repair.
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API RP 574 - Definitions
rerating
Rerating is A change in either or both the design
temperature or the maximum allowable working
pressure of a piping system.
NOTE: A rerating may consist of an increase,
decrease, or a combination. Derating below original
es gn con ons s a means o prov e ncrease
corrosion allowance.
structural minimum thickness
Minimum pipe wall thickness typically needed to
support non-pressure loadings, e.g. weight of pipe,
process fluids, insulation, other live and dead loads,
etc.
NOTE : The thickness is either determined from a
s an ar c ar or eng neer ng ca cu a ons. oes noinclude thickness for corrosion allowance or mill
tolerances
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API RP 574 - Piping
Piping can be made from any material that can be rolled and
welded cast or drawn throu h dies to form a tubular section.
The two most common carbon steel piping materials used in
the petrochemical industry are ASTM A 53 and A 106.
The industry generally uses seamless piping for most services.
Piping of a nominal size larger than 16 in. (406 mm) is usually
made by rolling plates to size and welding the seams.
Centrifugally cast piping can be cast then machined to any
desired thickness.
Steel and alloy piping are manufactured to standard
dimensions in nominal pipe sizes up to 48 in. (1219 mm).
Table 3 Permissible Tolerances in
Diameter and Thickness for Ferritic Pipe
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API RP 574
Tubing - With the exception of heater, boiler, andexc anger u es, u ng s s m ar o p p ng, u s
manufactured in many outside diameters and wall thicknesses.
Tubing is generally seamless, but may be welded. Its stated
size is the actual outside diameter rather than nominal pipe
size. (ASTM B 88 tubing, which is often used for steam
tracing, is an exception in that its size designation is 1/8 in.
. . Tubing is usually made in small diameters and is mainly used
for heat exchangers, instrument piping, lubricating oil services,
steam tracing, and similar services.
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API RP 574
Valves
The basic types of valves are gate, globe, plug, ball,
diaphragm, butterfly, check, and slide valves. Valves are made
in standard pipe sizes, materials, body thickness, and pressure
ratings that permit them to be used in any pressure-temperature
service in accordance with ASME B16.34 or API 599, API
600, API 602, API 603, API 608, or API 609, as applicable.
a ve o es can e cast, orge , mac ne rom ar stoc , or
fabricated by welding a combination of two or more materials.
The seating surfaces in the body can be integral with the body,
or they can be made as inserts. The insert material can be the
same as or different from the body material.
API 574 - Reasons for Inspection
The primary purpose of inspection is to perform activities
usin a ro riate techni ues necessar to identif active
deterioration mechanisms and to specify repair, replacement,
or future inspections for affected piping.
This requires developing information about the physical
condition of the piping, the causes of its deterioration, and its
rate of deterioration.
,
predict and recommend future repairs and replacements, and
act accordingly, to prevent or retard further deterioration and
most importantly, prevent loss of containment.
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API 574 - Reasons for Inspection
(continued)
This should result in
increased operating safety,
reduced maintenance costs, and
more reliable and efficient operations.
API 570 provides the basic requirements for such an
nspec on program.
This recommended practice supplements API 570 by
providing piping inspectors with information that can
improve skill and increase basic knowledge and practices
API 574 - Inspection Plans
An inspection plan is often developed and implemented
.
Other piping systems may also be included in the
inspection program and accordingly have an inspection
plan.
An inspection plan should contain the
,
scope of inspection, and
schedule required to monitor damage mechanisms and
assure the mechanical integrity of the piping components in
the system.
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API 574 - Inspection Plans
The plan will typically
a) define the type(s) of inspection needed, e.g. external,
b) identify the next inspection interval and date for each
inspection type,
c) describe the inspection and NDE techniques,
d) describe the extent and locations of inspection and NDE,
inspection and examinations,
f) describe the requirements of any needed pressure test, e.g.type of test, test pressure, and duration, and
g) describe any required repairs.
API 574 - Inspection Plans
Other common details in an inspection plan include:
escr ng e ypes o amage mec an sms an c pa e or
experienced in the equipment;
defining the location of the damage;
defining any special access requirements.
Inspection plans for piping may be maintained in
,
inspection software databases. Proprietary software,
typically used by inspection groups, often assists in
inspection data analysis and record keeping.
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API 574 - Inspection Plans
For piping systems, inspection plans should address
a) condition monitoring locations (CMLs) for specific
damage mechanisms;
b) piping contact points at pipe support
c) welded pipe supports;
d CUI
e) injection points;
f) process mix points;g) soil-to-air (concrete-to-air) interfaces;
h) deadleg sections of pipe;
API 574 - Inspection Plans
i) positive material identification;
k) critical utility piping as defined by owner-user;
l) vents/drains;
m) threaded pipe joints;
n) internal linings;
o critical valves
p) expansion joints;
Inspection plans may be based upon various criteria but should
include a risk assessment or fixed intervals as defined in API
570.
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API RP 574: Risk Based Inspection
Inspection plans based upon an assessment of the
piping system or circuit is RBI.
RBI may be used to determine inspection intervals and
the type and extent of future inspection/examinations.
API RP 580 details the systematic evaluation of both the
likelihood of failure and consequence of failure for
establishing RBI plans.
API Publication 581 details an RBI methodology that hasall of the key elements defined in API RP 580
Minimum Alert Thickness
The alert thickness signals the inspector that it is timely for a
remainin life assessment. This could include a detailed
engineering evaluation of the structural minimum thickness,
fitness-for-service assessment, or developing future repair
plans. In addition, when a CML reaches the alert thickness, it
raises a flag to consider the extent and severity at other
possible locations for the corrosion mechanism. Alert
minimum thicknesses are usually not intended to mean that
pipe components must be retired when one CML reaches thedefault limit.
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Table 6Minimum Thicknesses for
Carbon and Low Alloy Steel PipeDefault Minimum Structural
Thickness for Tem eratures Minimum Alert Thickness for
NPS< 400oF (205 oC)
in. (mm)
Temperatures < 400oF (205 oC)
in (mm)
to 1 0.07 (1.8) 0.08 (2.0)
1 0.07 (1.8) 0.09 (2.3)
2 0.07 1.8 0.10 2.5
3 0.08 (2.0) 0.11 (2.8)
4 0.09 (2.3) 0.12 (3.1)
6-18 0.11 (2.8) 0.13 (3.3)
20-24 0.12 (3.1) 0.14 (3.6)
API 570 SECTION 5 - Inspection,Examination and Pressure Testing Practices
An inspection plan shall be established for all piping
.
The inspection plan shall be developed by the inspector
and/or engineer.
A corrosion specialist shall be consulted as needed to
clarify potential damage mechanisms and specific locations
where degradation may occur.
A corrosion specialist shall be consulted when developingthe inspection plan for piping systems that operate at
elevated temperatures (above 750oF (400oC)) and piping
systems that operate below the ductile-to-brittle transition
temperature.
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API 570 - Minimum Contents of an
Inspection Plan The inspection plan shall contain the inspection tasks
mechanisms and assure the pressure integrity of the
piping systems. The plan should:
define the type(s) of inspection needed, e.g.
internal, external, on-stream (non-intrusive);
inspection type;
describe the inspection methods and NDE
techniques;
API 570 - Minimum Contents of an
Inspection Plan
describe the extent and locations of inspection and
describe the surface cleaning requirements needed
for inspection and examinations for each type of
inspection;
describe the requirements of any needed pressure
, . . , ,and duration; and,
describe any required repairs if known or
previously planned before the upcoming
inspection.
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API 570 Table 5-1 Some Typical
Piping Damage Types and MechanismsDamage Type Damage Mechanism
General and local metal loss SulfidationOxidation
cro o og ca y n uence corros onOrganic acid corrosionErosion / erosion-corrosionGalvanic corrosionCorrosion under insulation
Surface connected cracking FatigueCaustic stress corrosion crackingSulfide stress corrosion crackingChloride stress corrosion crackingPolythionic acid stress corrosion crackingOther forms of environmental cracking
Subsurface cracking Hydrogen induced crackingMicrofissuring/microvoid formation High temperature hydrogen attack
Creep
Metallurgical changes GraphitizationTemper embrittlement
Blistering Hydrogen blisteringDimensional changes Creep and stress rupture
Thermal
Material properties changes Brittle fracture
API 570 Table 5-1 Some TypicalPiping Damage Types and Mechanisms
Damage Type Damage Mechanism
Oxidation
Microbiologically influenced corrosion
Organic acid corrosion
Erosion / erosion-corrosion
Galvanic corrosion
Corrosion under insulation
Surface connected cracking Fatigue
Caustic stress corrosion crackingSulfide stress corrosion cracking
Chloride stress corrosion cracking
Polythionic acid stress corrosion cracking
Other forms of environmental cracking
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API 570 Table 5-1 Some Typical
Piping Damage Types and Mechanisms
Damage Type Damage Mechanism
u sur ace crac ng y rogen n uce crac ng
Microfissuring/microvoid
formation
High temperature hydrogen attack
Creep
Metallurgical changes Graphitization
Temper embrittlement
Blistering Hydrogen blistering
Dimensional changes Creep and stress rupture
Thermal
Material properties changes Brittle fracture
API 570 Areas of Deterioration for
Piping Systems
Each owner/user shall provide specific attention to
susceptible to the following specific types and areas
of deterioration:
a. Injection points and mix points.
b. Deadlegs.
c. Corrosion under insulation CUI .
d. Soil-to-air (S/A) interfaces.
e. Service specific and localized corrosion.
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API 570 Areas of Deterioration for
Piping Systemsf. Erosion and corrosion/erosion.
g. nv ronmenta crac ng.
h.Corrosion beneath linings and deposits.
i. Fatigue cracking.
j. Creep cracking.
k.Brittle fracture.
l. Freeze damage.
m.Contact point corrosion
API 570 - General Types of Inspection
and Surveillance
Different types of inspection and surveillance are
piping system (see note). These include the
following:
a. Internal visual inspection.
b. On-stream inspection.
b.Thickness measurement inspection.
c.External visual inspection.
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API 570 - General Types of Inspection
and Surveillanced.Corrosion under insulation (CUI) inspection.
e. rat ng p p ng nspect on.
f Supplemental inspection.
Note: See Section 6 for interval/frequency and extent
of inspection. Imperfections identified during
nspect ons an exam nat ons s ou e
characterized, sized, and evaluated per Section 7.
API 570 - Vibrating Piping and Line
Movement Surveillance
Operating personnel should report vibrating or swaying
assessment.
Evidence of significant line movements that could have
resulted from liquid hammer, liquid slugging in vapor lines,
or abnormal thermal expansion should be reported.
At locations where vibrating piping systems are restrained,
per o c or s ou e cons ere to c ec or t eonset of fatigue cracking.
Branch connections should receive special attention
particularly unbraced small bore piping connected to
vibrating pipe.
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API 570 - Condition Monitoring
Locations Condition monitoring locations (CMLs) are specific areas
alon the i in circuit where ins ections are to be made.
The nature of the CML varies according to its location in the
piping system.
The selection of CMLs shall consider the potential for
localized corrosion and service-specific corrosion as described
in API 574 and API 571. Examples of different types of
locations for thickness measurement,
locations for stress cracking examinations,
locations for CUI, and
locations for high temperature hydrogen attack examinations.
API 570 SECTION 6 Frequency and
Extent of Inspection
The frequency and extent of inspection on piping
affect the piping and consequence of a piping failure.
The various forms of degradation that can affect
refinery piping circuits are described in 5.3, while a
simplified classification of piping based on the
. .
As described in 5.1, inspection strategy based on
likelihood and consequence of failure, is referred to
as risk-based inspection.
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API 570 SECTION 6 Frequency and
Extent of Inspection The simplified piping classification scheme in Section 6.2 is
based on the consequence of a failure. The classification is
used to establish frequency and extent of inspection.
The owner/user may devise a more extensive classification
scheme that more accurately assesses consequence for certain
piping circuits.
The consequence assessment would consider the potential for
explosion, fire, toxicity, environmental impact, and other
potential effects associated with a failure.
The three classes are recommended
Piping Classes
Class 1
erv ces w e g es po en a o resu ng n an mme a e
emergency if a leak were to occur are in Class 1. Such an
emergency may be safety or environmental in nature.
Examples of Class 1 piping include, but are not necessarily
limited to, those containing the following:
Flammable services that may auto-refrigerate and lead to brittle fracture.
,
vapors that may collect and form an explosive mixture, such as C2, C3, and
C4 streams.
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Piping Classes
Class 1 (contd)
H dro en sulfide reater than 3 ercent wei ht in a aseous stream.
Anhydrous hydrogen chloride.
Hydrofluoric acid.
Piping over or adjacent to water and piping over public throughways.
(Refer to Department of Transportation and U.S. Coast Guard regulations
for inspection of overwater piping.)
Piping Classes
Class 2
Services not included in other classes are in Class 2. This
classification includes the majority of unit process piping and
selected off-site piping. Typical examples of these services
include those containing the following:
On-site hydrocarbons that will slowly vaporize during release.
Hydrogen, fuel gas, and natural gas.
On-site strong acids and caustics.
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Piping Classes
Class 3
erv ces a are amma e u o no s gn can y vapor ze
when they leak and are not located in high-activity areas are in
Class 3. Services that are potentially harmful to human tissue
but are located in remote areas may be included in this class.
Examples of Class 3 service are as follows:
On-site hydrocarbons that will not significantly vaporize
ur ng re ease.
Distillate and product lines to and from storage and loading.
Off-site acids and caustics.
Inspection Intervals
The interval between piping inspections shall be established
and maintained usin the followin criteria:
Corrosion rate and remaining life calculations.
Piping service classification.
Applicable jurisdictional requirements.
Judgment of the inspector, the piping engineer, the piping
engineer supervisor, or a corrosion specialist, based on
operating conditions, previous inspection history, currentinspection results, and conditions that may warrant
supplemental inspections covered in 5.4.5.
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Table 6-1Recommended Maximum
Inspection Intervals
Type of Circuit Thickness
Measurement
Visual External
Class 1 5 years 5 years
Class 2 10 years 5 years
Class 3 10 years 10 years
Injection points a 3 years By Class
Soil-to-air interfaces b - By Class
Rerating of Piping Systems
API 570 Piping inspection code: Inspection, repair,-,
covers the inspection, repair, alteration and re-ratingprocedures for in-service metallic piping systems.
The code establishes the requirements and guidelinesthat allow the owners and users of piping systems tomaintain the safety and mechanical integrity of
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Rerating Definition
- definitions that apply to this code. They include thefollowing definitions that pertain to rerating:
Rerating [3.39]: A change in either or both thedesign temperature or the maximum allowableworkin ressure of a i in s stem.
A rerating may consist of an increase, a decrease,
or a combination of both. Derating below originaldesign conditions is a means to provide increasedcorrosion allowance.
MAWP Determination - 1
Maximum Allowable Working Pressure: (MAWP).
the piping system for continued operation at the mostsevere condition of coincident internal or external
pressure and temperature (minimum or maximum)expected during service.
It is the same as the design pressure, as defined in
. ,to the same rules relating to allowances for variationsof pressure or temperature or both
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MAWP Determination - 2
MAWP for the continued use of piping systems shall.
Computations may be made for known materials if allthe following essential details are known to complywith the principles of the applicable code:
a. Upper and/or lower temperature limits for specificmaterials.
. ua y o ma er a s an wor mans p.
c. Inspection requirements.
d. Reinforcement of openings.
e. Any cyclical service requirements.
MAWP Determination - 3
For unknown materials, computations may be madeassumin the lowest rade material and oint efficienc inthe applicable code.
When the MAWP is recalculated, the wall thickness usedin these computations shall be the actual thickness asdetermined by inspection (see 5.6 for definition) minustwice the estimated corrosion loss before the date of thenext inspection (see 6.3).
Allowance shall be made for the other loadings inaccordance with the applicable code.
The applicable code allowances for pressure andtemperature variations from the MAWP are permittedprovided all of the associated code criteria are satisfied.
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Retirement Thickness Determination 1
The minimum required pipe wall retirement
minimum required thickness, or retirementthickness, and shall be based on
pressure,
mechanical, and
using the appropriate design formulae and code
allowable stress.
Consideration of both general and localizedcorrosion shall be included
Retirement Thickness Determination 2
For services with high potential consequences if,
consider increasing the required minimum thicknessabove the calculated minimum thickness to providefor unanticipated or unknown loadings, undiscoveredmetal loss, or resistance to normal abuse.
In this case, the retirement thickness shall be used in
. .remaining life calculations
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Rerating Requirements
API 570 - Sub-Section 8.3 Rerating piping systems by changing thetemperature rating or the MAWP may be doneonly after all of the following requirements have
been met:
a. Calculations are performed by the piping engineer or theinspector.
b. All reratings shall be established in accordance with therequirements of the code to which the piping system wasu or y compu a on us ng e appropr a e me o s n
the latest edition of the applicable code.
c. Current inspection records verify that the piping system issatisfactory for the proposed service conditions and thatthe appropriate corrosion allowance is provided.
Rerating Requirements
API 570 - Sub-Section 8.3d. Rerated piping systems shall be leak tested in
accordance with the code to which the piping system
was built or the latest edition of the applicable code for
the new service conditions, unless documented records
indicate a previous leak test was performed at greater
than or equal to the test pressure for the new condition.
An increase in the rating temperature that does not affect
allowable tensile stress does not require a leak test.
e. The piping system is checked to affirm that the requiredpressure relieving devices are present, are set at the
appropriate pressure, and have the appropriate capacity
at set pressure.
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Rerating Requirements
API 570 - Sub-Section 8.3f. The piping system rerating is acceptable to the inspectoror piping engineer.
g. All piping components in the system (such as valves,flanges, bolts, gaskets, packing, and expansion joints)are adequate for the new combination of pressure andtemperature.
h. Piping flexibility is adequate for design temperaturechanges.
. ppropr ate eng neer ng recor s are up ate .
j. A decrease in minimum operating temperature is
justified by impact test results, if required by theapplicable code.