TITLE: RBI and Similar Service Internal Inspection Intervals

DATE:February 8, 2007

TITLE: RBI and Similar Service Internal Inspection Intervals

AGENDA ITEM:653-167

SOURCE: Technical Inquiry

PURPOSE:To provide industry with guidance on risk based inspection methodologies as they relate to internal inspection intervals

CONTACT:Jeff DeArmond

bp North American Products

219-473-3035; FAX 219-473-3304

E-mail:

IMPACT:Currently, there is no clear guidance on conducting RBI assessments on storage tanks, specifically as it relates to establishing internal inspection intervals. This could lead to inconsistencies in the way RBI assessments are performed. Hopefully, this effort will provide the user with information necessary to make informed decisions involving RBI and conduct effective RBI assessments.

STATUS:Fall 2006 - Item was balloted for the first time. Ballot results were: 50 affirmative, 11 negative, and 4 abstentions.

Spring 2007- Item was balloted for second time. Ballot results were: 53 affirmative, 7 negative and 6 abstentions.

Proposed Wording

6.4.2 Inspection Intervals

6.4.2.1 The interval from initial serviceuntil the initial internal inspection shall not exceed 10 years. Alternatively, wheneither a risk-based inspection (RBI) assessment per 6.4.2.4, or a similar service assessment per Appendix His performed, and the tank has one of the following leak prevention, detection, or containment safeguards or combination of safeguards, the initial internal inspection interval shall not exceed the applicable maximum interval as shown below:

NOTES:

1. For purposes of 6.4.2.1, effective cathodic protection of the soil-side of the primary tank bottom means a system installed and maintained in accordance with API RP 651.

2. For purposes of 6.4.2.1, lining of the product-side of the tank bottom means a lining installed, maintained and inspected in accordance with API 652.

3. For purposes of 6.4.2.1, a release prevention barrier means an under-bottom leak detection and containment system designed in accordance with API 650, Appendix I.

6.4.2.2 The interval between subsequent internal inspectionsshall be determined in accordance with either the corrosion rate procedures of 6.4.2.3 or the risk-based inspection procedures as outlined in 6.4.2.4. and shall not exceed the applicable maximum intervals as shown below:

6.4.2.3 An owner-operator who has obtained data on the thickness and condition of the tank bottom during an internal inspection may calculate the interval until the subsequent internal inspection using the measured tank bottom corrosion rate and the minimum remaining thickness in accordance with 4.4.7.

6.4.2.4Asan alternative to the procedures in 6.4.2.3, an owner-operator may establish the internal inspection interval using risk-based inspection (RBI) procedures in accordance with this section.

RBI assessment shall be performed by an individualor team of individualsknowledgeable in the proper application of API 580 principles to aboveground storage tanks and experienced in tank design, construction details, and reasons for tank deterioration, and shall be reviewed and approved by an authorized inspector and a storage tank engineer. Theinitial RBI assessment shall be subsequentlyre-assessed at intervals not to exceed 10 years, at the time of a premature failure, and at the time of proposed changes in service or other significant changes in conditions.

RBI assessment shall consist of a systematic evaluation of both the likelihood of failure and the associated consequence of failure, utilizing the principles of API RP 580. RBI assessment shall be thoroughly documented, clearly defining all factors contributing to both likelihood and consequence of tank leakage or failure. Factors that should be considered in tank RBI assessments include, but are not limited to, the following:

6.4.2.4.1 Likelihood Factors:

a. Original thickness, weld type, and age of bottom plates

b. Analysis methods used to determine the product-side, soil-side and external corrosion rates for both shell and bottom and the accuracy of the methods used,

c. Inspection history, including tank failure data

d.Soil resistivity

e.Type and quality of tank pad / cushion

f.Water drainage from berm area

g.Type / effectiveness of cathodic protection system and maintenance history

h.Operating temperatures

i.Effects on internal corrosion rates due to product service

j.Internal coating / lining / liner type, age and condition

k.Use of steam coils and water draw-off details

l.Quality of tank maintenance, including previous repairs and alterations

m.Design codes and standards and the details utilized in the tank construction, repair and alteration (including tank bottoms)

n.Materials of construction.

o.Effectiveness of inspection methods and quality of data

p.Functional failures, i.e. floating roof seals, roof drain systems, etc.

q.Settlement data

6.4.2.4.2 Consequence Factors

a.Tank bottom with a Release Prevention Barrier (RPB)details (single, double, RPB, internal reinforced linings, etc.)

b.Product type and volume

c.Mode of failure, (i.e. slow leak to the environment, tank bottom rupture or tank shell brittle fracture)

d.Identification of environmental receptors such as wetlands, surface waters, groundwaters, drinking water aquifers, and bedrock,

e.Distance to environmental receptors

f.Effectiveness of leak detection systems and time to detection

g.Mobility of the product in the environment, including, for releases to soil, product viscosity and soil permeability

h.Sensitivity characteristics of the environmental receptors to the product

i.Cost to remediate potential contamination

j.Cost to clean tank and repair

k. Cost associated with Lloss of use.

l.Impact on public safety and health

m.Dike containment capabilities (volume and leak tightness)

More qualitative approaches may be applicable that do not involve all of the factors listed above. In these cases, conservative assumptions must be used and conservative results should be expected. A case study may be necessary to validate the approach.

The results of the RBI assessment are to be used to establish a tank inspection strategy that defines the most appropriate inspection methods, appropriate frequency for internal, external and on-stream inspections, and prevention and mitigation steps to reduce the likelihood and consequence of tank leakage or failure.

6.4.2.5 For purposes of 6.4.2.1, effective cathodic protection of the soil side of the primary tank bottom means a system installed and maintained in accordance with API RP 651.

6.4.2.6 For purposes of 6.4.2.1, lining of the product side of the tank bottom means a lining installed, maintained, and inspected in accordance with API 652.

6.4.2.7 For purposes of 6.4.2.1, a release prevention barrier means an under-bottom leak detection and containment system designed in accordance with API 650, Appendix I.

6.4.2.8 Similar service assessments per Appendix H shall be performed and approved by an Authorized Inspector,Storage Tank Engineer and other person(s) having knowledge and experience in performing similar service assessments.

6.4.2.9.Tank oOwners-operators should review the internal inspection intervals of existing tanks, as they could be modified by the requirements of this section. The following outlines the applicability of the intervals determined in 6.4.2 to existing tanks.

a.Tanks that have been internally inspected and whose internal inspection intervals were determined solely by corrosion-rate data per 6.4.2.3 need not be included in this review, as their internal inspection intervalsremain unaffected.

b. Tanks that have never been internally inspectedshould be reviewed for compliance with 6.4.2.1.

c. Tanks that have been internally inspected and whose internal schedules were determined by RBI assessment should be reviewed for compliance with 6.4.2.2. IfaRBI assessment that complies with 6.4.2.4 determinedan interval that has already exceeded the applicable maximuminterval under 6.4.2.2, or will exceed it withina period of five years, then the tank owner-operator may use the RBIassessmentto schedule and complete the inspection, independent of the applicable maximum interval,so long as the inspectionis completedwithinthe five-year period. After the five-year period,the interval shall not exceed the applicable maximum interval under 6.4.2.2.

6.4.2.10 If an RBI assessment or similar service assessment has been performed, the applicable maximum interval under6.4.2.1 or 6.4.2.2 does not apply to a tank storing highly viscous substances which solidify at temperatures below 110 F. Some examples of these substances are: asphalt, roofing flux, resid, vacuum bottoms and reduced crude.

EDITING NOTES;

1. Delete section 6.4.3.

2. Move Table 6-1 to Section 4.4.7.

3. Delete phrase “…or 6.4.3” in 6.4.1.2

4. Delete phrase “…or 6.4.3” in 4.4.1

5. Replace ‘risk-based inspection methodology’ with “RBI assessment per 6.4.2.4” in 4.4.7.3.

6. Add Note to Editors: include effective date of publication when known in 6.4.2.9.c, 2nd sentence after “five years”.