1. General and Capabilities
Q1. What is SPM for Cokers?
Structural Performance Management (SPM) is the system Akselos provides. It continuously calculates the real structural limits of critical infrastructure from operating data, so you can safely increase throughput, reduce downtime, and extend asset life. It does this with physics-based AI and high-fidelity structural twins that show how the steel actually responds under real conditions.
Akselos SPM for Cokers is SPM applied to the coke drums of a delayed coking unit. A structural model of each drum turns the recorded temperature, pressure and liquid level of every cycle into stress at every assessed location. Three assessments, fatigue, bulging and crack, turn that stress into the time each location has before it reaches a limit set by the fitness-for-service standard API 579-1/ASME FFS-1, 2021 edition. The results are read on the Coker Dashboard, a report inside the Akselos Portal.
Q2. How is the Analytical Horizon estimated?
The Analytical Horizon is the shortest of three results, Fatigue Life, Bulging Life and Crack Life, reported in years for the pressurized and the non-pressurized components separately. Each result is projected forward from current operation. Fatigue Life follows the damage rate of the last processed cycle. Bulging Life follows the bulge growth that a machine learning model predicts from the historical laser scans, with similar operating conditions assumed. Crack Life follows the growth of each tracked flaw under the operating stress. For fatigue alone, Fatigue Life Prediction on Fatigue Status adds projections built from stretches of past operation, such as the last 10, 30 or 90 cycles.
Q3. Who reads the results?
Two roles, each from its own set of pages. Operators read the recorded sensor data and the excursions outside the design operating window on Process Monitoring. Structural integrity engineers read fatigue, bulging and crack, and their trends, on Fatigue Status, Crack Status, Bulging Inspection, Crack Inspection, Cycle Inspection and Historical Trends, as an input to turnaround planning and to the scope of each inspection campaign.
2. Technical Inputs and Outputs
Q4. What inputs do the per-cycle assessments need?
Every cycle, all three assessments take the operating data the plant instruments record: temperature, pressure and liquid level. Two further inputs arrive at each turnaround. Laser scans of the inner wall feed the bulging assessment and the ovality check and, through bulging, the crack assessment. Inspected cracks, the depth, length and position of each flaw an inspection records, feed the crack assessment. Operating data reaches the dashboard through a live connection to the site’s data system or through a manual run by Akselos engineers, and both routes produce the same pages.
Q5. What is the main result on the Coker Dashboard?
The Analytical Horizon, on the Overall Coker Analytical Horizon panel of Home: the shortest of Fatigue Life, Bulging Life and Crack Life, in years, for the pressurized and the non-pressurized components separately. A MIN marker sits on the bar of the assessment that sets the figure, and each life has its own page: Fatigue Status, Bulging Inspection and Crack Status. An assessment with no loaded result reads No data rather than zero.
Q6. Can the sensor data be downloaded?
Yes. The download control beside the series list on a chart saves the data behind it as a CSV file: a Timestamp column, then one column for each sensor on that chart, for the period selected. It is offered on the process charts of Process Monitoring, and on Sensor Data of Cycle on Cycle Inspection, where the file covers one cycle. Every timestamp is in Coordinated Universal Time.
Q7. Does the Coker Dashboard show a model of the drum?
Yes, in four views. Model on Home shows the structural model divided into the zones the results are reported against. Sensor’s Location on Process Monitoring places every instrument on the drum. High Fatigue Damage Locations on Fatigue Status marks the ten highest-damage locations of each component group. Result Viewer on Cycle Inspection draws the temperature, displacement and stress of the selected cycle onto the drum geometry. The last three can be zoomed, panned and rotated.
Q8. How does the dashboard report readings outside the design operating window?
Each reading is checked against the design limits listed in Equipment Data on Home. The Temperature and Pressure cards on Home check the last recorded reading against the design operating window, printed as Inside DOW. On Process Monitoring, Max. Temperature and Max. Pressure read Inside DOW or Exceeds DOW for the selected period, with two counters, 30d exc and 90d exc, giving the recorded timesteps above the limit in the last 30 and 90 days. DOW Exceedance Log lists each excursion with its time, sensor, recorded value and exceedance, over a fixed 90 days.
3. Fatigue Assessment
Q9. What is Fatigue Life?
The estimated service life left before the accumulated fatigue damage at a location reaches 100 percent, the failure threshold of the fatigue assessment in API 579-1/ASME FFS-1, 2021 edition. It is expressed in operational cycles or in years. Accumulated damage only rises: each processed cycle adds its own damage, a gentler cycle adds less, and nothing removes what has accumulated. Fatigue Life projects the damage rate of the last cycle forward, so one severe cycle shortens it sharply and one mild cycle lengthens it. Fatigue Status reports it as Min. Est. Fatigue Life for each component group.
Q10. How are the fatigue results grouped?
In two component groups, reported and ranked separately because they carry different loads and use their life at different rates. The pressurized group covers the pressure-retaining components, such as the shell, cone and head, and includes the junction where the skirt meets the shell. The non-pressurized group covers the components not under internal pressure, principally the skirt. Every widget on Fatigue Status reports once for each group.
Q11. Which standard governs cycle counting?
API 579-1/ASME FFS-1, 2021 edition. The fatigue assessment resolves the stress history of each cycle into discrete stress ranges with the cycle counting method of that standard, then reads each range against the material stress-life curves of ASME BPVC Section VIII Division 2, 2019 edition. The clause behind each step is set out in the methodology article.
4. Bulging and Crack Assessments
Q12. What does Bulging Life indicate?
The time from now until the plastic strain at a location reaches 100 percent of its local limiting strain. That share is the plastic strain limit fraction, written PSLF, and the limit comes from the protection against local failure check of API 579-1/ASME FFS-1, 2021 edition: the point at which the material at that location has used its ductility. Reaching 100 percent is not a crack and not a failure, and PSLF is not capped there, so a location can read above it. Bulging Life is projected by re-running the assessment on the bulges a machine learning model predicts from the historical laser scans, and Bulging Inspection reports it as Est. Bulging Life.
Q13. Which rule governs crack growth?
The Paris law, as API 579-1/ASME FFS-1, 2021 edition gives it for subcritical crack growth. Each cycle, the range of the stress intensity at the flaw sets how far it grows, with the stress at the flaw including the secondary stress the bulge leaves behind. The new size is checked on a Failure Assessment Diagram, which judges the flaw against fracture and against plastic collapse at once. Crack Life is the time until the flaw reaches its critical size, where it falls outside the diagram or penetrates the wall. The clause is set out in the methodology article.
Q14. How is a crack assessed where none has been found?
Through a placed flaw. Where an inspection records no crack, the assessment places a conservative screening flaw, 0.100 m long and 0.001 m deep, at each of the locations with the highest PSLF from the bulging assessment, so those locations still return a Crack Life. The depth is the reference depth API 579-1/ASME FFS-1, 2021 edition gives for such a flaw. Crack Status names the two dimensions Bounding Crack Length and Assumed Crack Depth. A placed flaw is a modeling assumption, not a field measurement, and nothing else in Crack Details marks it: a row reading 0.100 m by 0.001 m is a placed flaw.
Q15. When is a placed flaw reset?
At the next inspection that finds no crack at that location. Between inspections the placed flaw grows cycle by cycle under the operating stress, as a measured flaw does, and Crack Status reports its current Crack Life. An inspection that finds no crack there resets it to 0.100 m by 0.001 m. Crack Inspection lists only campaigns that recorded at least one flaw, so a campaign that found nothing does not appear there.
5. Related Articles
Three articles carry the detail behind these answers.
What Your Coke Drum Is Telling You: the user manual for the Coker Dashboard, covering every page and widget named on this page and how to read it.
Coker Assessment Methodology: how each assessment is calculated, with the clause of each standard every step draws on.
Fatigue Use Cases on the Coker Dashboard: two fatigue use cases, followed page by page.
For any other question, contact Akselos support at [email protected].