API 510 - Section - 7 Flashcards
Corrosion rate is determined by the ,,,,
difference between two thickness readings divided by the time interval between the readings.
Short-term (ST)corrosion rates are typically determined by the,,,,,, thickness readings
two most recent
Long-term(LT) rates use the ,,,,reading and ,,,,, taken earlier in the life of the equipment
most recent
one
For a new vessel or for a vessel for which service conditions are being changed, one of the following methods shall be used to determine the vessel’s probable corrosion rate
- Vessels operating in the same or similar service
- Estimated by a corrosion specialist.
- Published data on vessels in same or similar service
- On-stream inspection approximately 3 to 6 months of service
A ,,,,, analysis may be used in the corrosion rate and remaining life calculations for the pressure vessel
statistical
This ,,, approach may be applied for assessment of substituting an internal inspection or for determining the internal inspection interval
statistical
Statistical analysis may not be applicable to vessels with ,,,,
random but significant localized corrosion
The MAWP for the continued use of a pressure vessel shall be based on computations that are determined
using the ,,,, or the ,,,,, to which the vessel was built
- Latest applicable edition of the ASME Code
- Construction code
The thickness measurement procedure shall be
approved by the ,,,,,
inspector
Evaluation of Locally Thinned Areas:
For a corroded area of considerable size the wall thicknesses may be averaged over a length not exceeding vessels with inside diameters less than or equal to 60 in (150 cm),,,,,,,,which ever is less
one-half the vessel diameter or 20 in. (50 cm),
Evaluation of Locally Thinned Areas:
For a corroded area of considerable size the wall thicknesses may be averaged over a length not exceeding vessels with inside diameters greater than 60 in. (150 cm), ,.,,,,,,,,which ever is less
one-third the vessel diameter or 40 in. (100 cm)
The following criteria must be met in order to use thickness averaging:
1-the equipment does not operate in the ,,,,
2-the component is not in ,,,, service
3-a minimum of ,,,,thickness readings should be included in the data set
4-
5-lowest individual reading cannot be,,,,,
creep range
cyclic
15
less than 50 % of “t” required
If circumferential stresses govern (typical for most vessels), the thickness readings are taken along a
,,,,, length
longitudinal
If longitudinal stresses govern (because of wind loads, saddle support in horizontal vessels, or other factors), the thickness readings are taken along a ,,,, length (an arc).
circumferential
when thickness averaging near structural discontinuities (e.g. a nozzle, conical section transition, and flange connection), the limits for thickness averaging shall be considered ,,,, for the reinforcement window area
separately
When performing remaining life calculations in 7.2, the ,,,, average of any length in the corroded area is
substituted for tactual
lowest
During the current inspection, ,,,,,, pits may be ignored
widely scattered
Evaluation of Pitting:
- widely scattered pits may be ignored, if remaining thickness below the pit is ,,,,,
- total area of the pitting that is deeper than the corrosion allowance does not exceed,,,,,
- the sum of the pit dimensions that is deeper than the corrosion allowance along any straight 8-in. (20-cm) line does not exceed ,,,,
- > 1/2 “t”required
- 7 in.2 (45 cm2) within any8-in. (20-cm) diameter circle
- 2 in. (5 cm).
Evaluation of Pitting:
An alternative to the procedures for components with thinning below the required thickness may be evaluated by employing the design by analysis methods of either ,,,,,,,,,, or ,,,,
ASME Code, Section VIII, Division 2 Appendix 4
API 579-1/ASME FFS-1, Annex B-1
Joint Efficiency Adjustments:
When the vessel surface away from a weld is corroded and the joint efficiency is less than 1.0, an independent
calculation using the appropriate weld joint factor ,,,, can be made
(typically 1.0)
Joint Efficiency Adjustments:
For this joint efficiency calculation, the surface at a
weld includes ,,,, on either side of the weld (measured from the toe) or ,,, on either side of the weld, whichever is greater
1 in. (2.5 cm)
twice the required thickness
Corroded Areas in Vessel Heads:
In the central portion of the head, use the ,,,, head formula in the construction code
hemispherical
Corroded Areas in Vessel Heads:
The central portion of the head is defined as the center of the head with a diameter equal to ,,,, of the shell diameter
80 %
Corroded Areas in Vessel Heads:
For torispherical heads, the radius to use in the hemispherical head formula is the ,,,,, (equal to the outside diameter of the shell for standard torispherical heads, though other radii have been permitted)
crown radius
Corroded Areas in Vessel Heads:
For ellipsoidal heads, the radius to use in the hemispherical head formula shall be the equivalent,,,,,,, where D is the shell diameter (equal to the inside diameter) and K1 is given in Table 7.1
spherical radius K1 × D
Corroded Areas in Vessel Heads:
For many ellipsoidal heads, D/2h = ,,,,,
2.0
FFS Evaluations:
To evaluate metal loss in excess of the corrosion allowance,,,,,,,as applicable
API 579-1/ASME FFS-1, Parts 4, 5, or 6
FFS Evaluations:
To evaluate blisters, HIC/SOHIC damage, and laminations,,,,,
API 579-1/ASME FFS-1, Part 7 and Part 13,
FFS Evaluations:
To evaluate weld misalignment and shell distortions,,,,,
API 579-1/ASME FFS-1, Part 8
FFS Evaluations:
To evaluate crack-like flaws,
API 579-1/ASME FFS-1, Part 9
FFS Evaluations:
To evaluate potential creep damage on components operating in the creep regime
API 579-1/ASME FFS-1, Part 10
FFS Evaluations:
To evaluate the effects of fire damage
API 579-1/ASME FFS-1, Part 11
FFS Evaluations:
To evaluate dent and gouge damage on components
API 579-1/ASME FFS-1, Part 12
Current ASME code design stress value factor is,,,
3.5
Earlier ( Pre-1999) ASME code design stress value factor is,,,
4.0 or 5.0
When the extent of radiography originally performed is not known, use joint efficiency of
,,,,,for Type No. (1)
,,,,, for Type No. (2) butt welds
,,,,,, for seamless shells, heads, and nozzles
- 0.7
- 0.65
- 0.85
Reports & Records:
Permanent records will be maintained ,,,,,,, of each equipment item;
throughout the service life
Reports & Records:
Pressure vessel and pressure-relieving device records shall contain four types of information pertinent to
mechanical integrity
1- Construction and design information
2- Inspection history.
3- Repair, alteration, and rerating information
4- FFS assessment documentation requirements
