RBI of Ammonia Storage Tanks Establish tank inspection protocol based on risk assessment DNV provides risk-based inspection (RBI) and engineering critical assessment (ECA) of ammonia storage tanks Risk-Based Inspection (RBI) Methodology
DNV Applies RBI to Produce Timely Results
A RBI analysis helps determine the required effort by two key parameters: the likelihood of failure of an item and the consequence of its failure of its item. Risk is a combination of the likelihood of failure and the consequence of failure. The purpose of a RBI analysis is to focus inspection activities on those pieces of equipment where failure risks associated with an active damage mechanism are highest. • RBI uses risk as the basis for prioritizing and managing the efforts of an inspection program. • An effective risk-based program results in a reduced level of risk for a given level of inspection activity. • RBI methodology permits the allocation of inspection and maintenance to ◊ provide a high level of coverage on the higher risk equipment and ◊ an appropriate effort on lower risk equipment
DNV employs RBI philosophy to determine the level of RISK for the tank and associated piping components • Follows the intent of API RP 580/581 methodology • Utilizes DNV tools: ORBIT™ RBI software • The DNV assessment route is more rigorous and takes into account more parameters than other tools • Extensive database: ammonia modeled as inventory • Detailed stress and fracture-mechanics modeling • Detailed consequence modeling is based on the DNV PHAST™ software for evaluating business interruption, damage area, and potential loss of life Being risk-based, the method considers • Probability of failure (PoF) as well as • Consequences of failure (CoF) The need for RBI is increased by aging equipment, changing and more demanding operating conditions, code revisions, and economic factors.
DNV Columbus 5777 Frantz Road Dublin, OH 43017 USA 614.761.1214 dnvcolumbus@dnv.com www.dnvcolumbus.com
DNV Houston 1400 Ravello Katy, TX 77449 USA 281.396.1889 John.T.Schmidt@dnv.com
DNV Calgary 2340 Pegasus Way, NE, Suite 123 Calgary, AB T2E8M5 Canada 403.250.9041 dnvcalgary@dnv.com
RBI of Ammonia Storage Tanks Establish tank inspection protocol based on risk assessment Collect tank data and information Reference Methodology Report for • Collecting data
Assess tank history data
• Assigning the effectiveness of past inspections • Setting the input data for calculations
Validate and consolidate data; determine all input settings
• Using analytic results • Planning future inspection • Analyzing cost versus benefit
Perform analyses and generate inspection plan
Assess cost versus benefit
Advantage of RBI for Above Storage Tanks (AST)
Under normal circumstances the AST operator is faced with two methods • API 653 procedure or • A jurisdiction regulated time-based inspection frequency The 1999 addendum to API 653 introduces a third option • RBI provides a basis for better and more pertinent inspection plans ◊ Systematic categorization (risk-based) ◊ Detailed assessment of tank ◊ Focus inspection effort to reduce risk ◊ Improved record keeping ◊ Enables long-term planning Risk ($/yr) = LoF (events/yr) x CoF ($/event)
Base Failure Frequency (events/yr) X Damage Factor Safety Issues + Environmental Damage & Clean-up + Environmental Cost ($) Business Consequences + Repairs ($)
DNV Columbus 5777 Frantz Road Dublin, OH 43017 USA 614.761.1214 dnvcolumbus@dnv.com www.dnvcolumbus.com
DNV Houston 1400 Ravello Katy, TX 77449 USA 281.396.1889 John.T.Schmidt@dnv.com
DNV Calgary 2340 Pegasus Way, NE, Suite 123 Calgary, AB T2E8M5 Canada 403.250.9041 dnvcalgary@dnv.com