API 653 Sec-04 (Suitability for Service) Flashcards
When the results of a tank inspection show that a change has occurred from the original physical condition of that tank, ………… shall be made to determine its suitability for continued use.
an evaluation
Roof plates corroded to an average thickness of ………………………..or roof plates with any holes through the roof plate shall be repaired or replaced.
< 0.09” (2.286mm) in any 100 in2 area
When a frangible roof-to-shell joint is required, evaluate for items impacting compliance with requirements
under API 650
Areas that are pitted shall be evaluated to determine the likelihood of through-pitting occurring prior ……………. If so, the affected areas shall be ………………..
to the next scheduled internal inspection
repaired or replaced
Guidance for the evaluation of existing floating roofs/ external floating roof shall be based on the criteria of ,,,,
API 650, Annex C
Guidance for the evaluation of internal floating roofs shall be based on the criteria of,,,,,,
API 650, Annex H
For internal pressure. The requirements of evaluation and subsequent alterations to the tank roof and roof-to-shell junction shall be considered as per
current applicable standard (e.g. API 650, Annex F)
External pressure as applicable to the
- roof support structure (if any),
- roof-to-shell junction
shall be evaluated for the effects of design partial vacuum. as per The criteria outlined in
API 650, Annex V
All requirements of Operation at Elevated Temperature (>200 F) shall be considered as per
API 650, Annex M
If the operating temperature is changed to a lower temperature than the original design, the requirements of the
current applicable standard for the lower temperature shall be met.
Vents shall be inspected for proper operation and screens shall be verified to ………..
be clear of obstruction.
The evaluation for the suitability of the existing tank shell shall be conducted by a ……….
storage tank engineer and shall include ananalysis
Shell corrosion occurs in many forms and varying degrees of severity and may result in a ………….
generally uniform loss of metal over a large surface area or in localized areas
If the requirements of corroded or damaged areas cannot be satisfied,
- areas shall be repaired,
- allowable liquid level of the tank reduced
- the tank retired
to establish the liquid level limit
The actual thickness, as determined by inspection,minus the corrosionallowance shall be used
Formula to Calculate the critical length, L
L = 3.7 √ Dt2, but not more than 40 in.
For averaged over a length of L, use at least….
five equally spaced measurements over length L.
the value t1 (T avg.) shall be …..
≥ tmin
the value t2 shall be………
≥ 60 % of tmin
corrosion allowance required for service until the time of the next inspection shall be …..
added to tmin and 60 % of tmin.
Widely scattered pits may be ignored provided that……
- remaining shell thickness being not < 1/2 the minimum
acceptable tank shell thickness exclusive of the
corrosion allowance; - sum of their dimensions along any vertical line does
not exceed 2 in. in an 8-in
minimum acceptable thickness for an entire shell course, tmin is calculated as……
tmin = 2.6 (H – 1) DG / SE
minimum acceptable thickness for an locally thinned area, tmin is calculated as……
tmin = 2.6 HDG / SE
for reconstructed tanks, S (stree value) shall be in accordance ……………..
with the current applicable standard;
For unknown plate, the value of Y (specified minimum yield strength) will be ………
30,000 lbf/in.2
T is the smaller of the specified minimum tensile strength of the plate or 80,000 lbf/in.2 than use
55,000 lbf/in.2
when evaluating the retirement thickness in a corroded plate use the value of E (Joint efficiency) for unknown plate as……
E = 1.0
Hydro-static Formula for control thickness of shell course
Ht = St x Etmin / 2.6 D +1
Hydro-static Formula for control thickness of locally thinned area
Ht = St x Etmin / 2.6 D
Shell distortions can be caused by many conditions such as …………..
- foundation settlement,
- over- or underpressuring,
- high wind,
- poor shell fabrication, or repair techniques, and so forth
Flaws such as …………….. shall be thoroughly examined and evaluated to determine their nature and extent
and need for repair
cracks or lamination
Existing welds on the tank shell that are not to be modified or affected by repairs and are closer than required by API 650 (Seventh Edition or later) are acceptable for continued service if the welds are examined by …………..
MPI method and have no rejectable defects or indications
Grinding to eliminate weld defects is permissible if the resulting profile satisfies ……..
base thickness and weld size requirements
Weld repairs may not be used to accept ……………… than permitted by API 650 (Seventh Edition or later)
weld spacings closer
Tanks of welded construction that operate at elevated temperatures (exceeding 200 °F, but less than 500 °F) shall be evaluated for suitability of service. The requirements of this section are based in part on the requirements of
API 650, Annex M
Existing elevated temperature service tanks that were not originally designed and constructed to the
requirements of API 650, Annex M, but have a successful service history of operation shall be evaluated for continued
service as per noted in 4.3.10.1.1
API 650, Annex M- 1a or M-1b
If the tank diameter exceeds 100 ft and the tank was not constructed with a butt welded annular ring, an analysis of the …………. is required
critical zone
tanks that were not originally designed and constructed to the requirements of API 650, ………………… shall be
evaluated for a change to service to elevated temperatures
Annex M
API supports the use of a ……………….to maintain the integrity of tank bottoms
release prevention system (RPS)
With respect to tank bottoms, RPS includes;
- internal inspection of the tank bottom;
- leak detection systems and leak testing of the tank; – - - installing cathodic protection for the underside of the
tank bottom; - lining the bottom of the tank interior;
- providing a release prevention barrier (RPB) under the
tank bottom
Bottom Plate Thickness Measurements are taken by …………
Magnetic flux leakage (MFL) along with
ultrasonic (UT)
Guidance in qualifying personnel and procedures for
obtaining thickness data.
Annex G
Formula for Minimum Thickness for Tank Bottom Plate
MRT = (Minimum of RTbc or RTip) – Or (StPr + UPr)
The thickness of the projection of the bottom plate beyond the shell as measured at the toe of the outside
bottom-to-shell fillet weld shall not be less than
< 0.1 in (2.54mm)
The projection of the bottom plate beyond the outside toe of the shell-to-bottom weld shall be
at least 3/8 in. ( 9.525mm)
Due to strength requirements, the minimum thickness of annular plate ring is usually
> 0.10 in. ( 2.54 mm)
The principal causes of Tank foundation deterioration are
settlement, erosion, cracking
The principal causes of Tank foundation deterioration of concrete initiated by:
calcining,
attack by underground water,
attack by frost, and
attack by alkalies and acids
Calcining (loss of water of hydration) can occur when concrete has been exposed to
sufficiently high temperature for a period of time
When a tank is to be used in elevated temperature [> 93 °C (200 °F)] service, the provisions of …………… shall be considered in the evaluation of the suitability for service of the tank foundation
API 650, Section B.6
Distortion of anchor bolts and excessive cracking of the concrete structures in which they are embedded may be indication of
- serious foundation settlement or
- tank over pressure uplift condition
Cathodic protection systems are intended to mitigate corrosion of steel surfaces in contact with ,,,,,,,,,,
soil
Roof support systems, perimeter seal systems, appurtenances such as a roof rolling ladder, anti-rotation devices, water drain systems, and venting systems shall be evaluated for ,,,,,,,
needed repairs or replacements
