API 653 Tank Inspection Intervals

API 653 Tank Inspection Intervals

Presented by: Mark A. Baker, P.E. Baker Consulting Group, Inc.

Inspection Frequency Considerations

a) the nature of the product stored;

b) the results of visual maintenance checks;

c) corrosion allowances and corrosion rates;

d) corrosion prevention systems;

e) conditions at previous inspections;

f) the methods and materials of construction and

repair;

Inspection Frequency Considerations

g) the location of tanks;

h) the potential risk of air or water pollution;

i) leak detection systems;

j) change in operating mode

k) jurisdictional requirements;

l) changes in service

Internal inspection is required to:

• Ensure that the bottom is not severely corroded and /

or leaking.

• Gather the data necessary for the minimum bottom

and shell thickness assessments.

• Identify and evaluate bottom settlement.

• The interval from initial service

until the initial internal inspection

shall not exceed 10 years.

API 653 Initial Inspection Interval

With one or more of the leak prevention, detection,

corrosion mitigation or containment safeguards:


The initial internal inspection

date shall be based on

incremental credits for the

additional safeguards which

are cumulative.


Tank Safeguard Add to Initial Interval

Fiberglass-reinforced lining of the product-side of the tank bottom installed per API 652.

5 yrs

Installation of an internal thin-film coating as installed per API 652.

2 yrs

Cathodic protection of the soil-side of the tank bottom installed, maintained and inspected per API 651.

5 yrs

Release prevention barrier installed per API 650, Annex I. 10 yrs

Bottom corrosion allowance greater than 0.150 in. (Actual corrosion allowance - 150 mils) / 15 mpy

EXAMPLE

• With Tank Safeguard of:• Thin-film coating• Release Prevention Barrier


EXAMPLEInitial IntervalThin-film coatingRelease Prevention Barrier

Inspection Interval = 22 Years


+10 years+ 2 years+10 years

The initial interval shall not exceed:

• 20 years for tanks without a RPB

• 30 years for tank with a RPB


If an RBI (Risk Based Inspection) assessment has been performed, the maximum initial internal interval does not apply to tanks storing the following:


EXCEPT…..

1. Viscous products which solidify at temperatures of 110°F or below.


2 Any substance that is:not identified or regulated either as a hazardous chemical, and

that the owner/operator has determined will not adversely impact surface or groundwater beyond the facility or affect human health or the environment.


API 653 Subsequent InspectionInterval

(re-inspection)

Determined using the corrosion rate procedures

Or, using the RBI procedures

API 653 Subsequent Inspection Interval

6.4.2.3

6.4.2.4

During any examination to determine corrosion rates the owner/operator should ensure they understand the effectiveness of the inspection techniques employed for detecting and measuring potential damage mechanisms.


Hole

MRT = (Min of RTbc or RTip) – Or (StPr + UPr)


Determine reporting thicknessSteps for corrosion rate calculations

Coated Bottom

Uncoated Bottom

• Scan the bottom

• Perform UT prove up to determine minimum thickness.

Steps for corrosion rate calculations

MRT = (Min of RTbc or RTip) – Or (StPr + UPr)

Finally - Calculate Subsequent Inspection

Subsequent Inspection Interval with no RPB

• Maximum Interval = 25 years


Subsequent Inspection Interval

and a RPB

• Maximum Interval of 30 years


RBI PROCEDURES

6.4.2.4


An owner/operator can establish the subsequent internal inspection interval using risk based inspection (RBI) procedures in accordance with API RP 580 and the additional requirements of API 653


• tank design, construction, and • modes of deterioration, and • the proper application of API RP 580 principles


The RBI assessment shall be performed by a team including inspection and engineering expertise knowledgeable in :

The RBI assessment shall be reviewed and approved by a team at intervals not to exceed 10 years.


Some people BEARly consider the following….

• The tank design and material of construction• Details about the foundation and surrounding area

• Operational history• Inspection history• Product characteristics• Etc.

Factors to Consider in a RBI Assessment

• Product type and volume• Mode of failure

• slow leak, • bottom rupture,• Shell brittle fracture

• Public health and safety• Environmental impact• Cost

Consequences to Consider

• RBI Assessments may include other types of inspections such as acoustic emissions

RBI Inspection

Perception is it provides a methodology to extend the inspection interval

•May shorten the inspection interval

•May result in additional focused inspections

•Allows a company to focus its resources

RBI Assessments

Direct Measurements in API 653: Based on the sum of the product side and soil side bottom corrosion rates

• Traditional approach for determining inspection intervals in API 653

• Tends to be a conservative approach because it is based on the sum of corrosion rates

Comparison

RBI Assessment with 10-Year Update Assessments based on API 580/581 as implemented in API 653: Based on direct measurements or conservative-provided estimates of the bottom corrosion rates

• Tends to be considered realistic estimates because it is based on the maximum corrosion rate of the bottom

Then…

If all else fails….

Comparison

Questions ?

API 653 Tank Inspection Intervals

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