Every extra day you keep a delayed coker online protects millions of dollars in margin and avoids the scramble of unplanned maintenance. Best-in-class operations routinely achieve extended heater runs, yet the shift to heavier crudes has pushed many units into significantly shorter cycles.
Some refineries have seen a dramatic collapse in the run length due to rapid fouling. The cost isn’t limited to decoking crews and replacement tubes; every lost day starves downstream units of feed and erodes overall refinery profitability.
Whether you’re a COO, VP of Operations, plant manager, or process engineer, the following proven strategies focus on practical moves you can start today and the advanced optimization path that follows. Plants executing these steps can add days—or even weeks—of safe operation between spalls, translating into lower maintenance spend and steadier product yields.
Why Delayed Cokers Lose Run Length
Run length is the time between tube decoking outages. Under ideal conditions, delayed coker heaters can stay on-stream for extended periods before cleaning is required, yet many plants fall short of that target. Every unexpected shutdown erodes throughput and inflates maintenance budgets, often by millions.
The dominant culprit is heater fouling, where deposits drive up pressure drop and tube-wall temperature until safe limits are reached. Fouling begins when rising film temperature thermally destabilizes asphaltenes—they precipitate, stick to rough metal surfaces, then dehydrogenate into hard coke. Contaminants such as iron and sodium accelerate the process, making heater fouling the leading unplanned-shutdown driver.
Extending run length starts with dependable data:
- Calibrated sensors – Ensure flow, ΔP, and wall-temperature sensors are properly calibrated and in place
- Data collection – Maintain a historian of one-minute data
- Cross-functional team – Assemble specialists from operations, process, maintenance, and digital departments
- Baseline metrics – Document your starting point, including average run length, fouling rate, and cleaning cos,t to measure improvements against
Balance Heater Passes Early & Continuously
A single starved pass creates a cascade of problems. Coke builds rapidly, tube-metal temperatures spike, and the entire delayed coker shuts down unexpectedly. Uniform flow and heat flux across every coil are the first safeguards against premature shutdowns.
Start each shift by comparing the pressure drop for every pass. Even a small rise pinpoints a starving coil before major issues develop. When you detect an imbalance, throttle orifice plates or slide valves until flows converge and the skin-temperature spread narrows to an acceptable range. Weekly audits of tube-metal temperatures and outlet flows keep the passes aging together.
Embed automatic alerts in your distributed control system (DCS) so deviations appear before operators notice them manually. Don’t rely on a single bulk flowmeter—fouling often hides inside individual coils. Confirm that steam-to-oil splits remain even across all passes. Excess steam in one pass strips heat from another, creating the very imbalance you’re trying to prevent.
Consistent, balanced firing maintains the high velocities that delay coke laydown, buying precious months of run length while larger optimization projects come online. This foundational step creates the stable operating environment that advanced systems thrive on.
Avoid Counter-Productive “Obvious Fixes”
When throughput starts to slip, the knee-jerk reaction is often to crank up furnace duty or push more feed through the coils. This quick fix does more harm than good. Higher firing rates spike tube wall film temperature—already the single strongest driver of coke lay-down—and extend residence time above critical thresholds, accelerating fouling in every pass.
A smarter path is to treat heat input like a throttle, not a light switch. Incremental duty changes give metal temperatures time to stabilize and let you verify that skin-bulk spreads stay within safe limits. At the same time, keep mass velocity high—adequate shear scrubs nascent deposits before they anchor to the tube wall, as AFPM Q-35 guidelines demonstrate.
Steam helps only within a narrow window. Optimal levels give enough gas velocity to thin the boundary layer, but not so much that backpressure balloons and drums bulge. Industry best practices pair this with uniform heat flux across burners to slow coke growth without surrendering conversion—a disciplined alternative to the obvious fix that shortens your run.
Implement Predictive Monitoring for Fouling
Predictive monitoring transforms raw signals from delayed coker heaters into an early-warning system that spots fouling days or weeks before throughput or tube-metal temperature forces you to spall. High-resolution data already lives in the historian, yet fouling still surprises plants because the right indicators aren’t surfaced in time.
Focus first on these critical variables that move fastest when deposits begin to form:
- Pressure drop across each coil – Monitors flow resistance caused by deposit buildup
- Spread between skin and bulk temperatures – Indicates the insulating effect of coke formation
- Unexpected rise in oxygen at coil outlet – Signals combustion efficiency changes
When trended together, these signals reveal the accelerating boundary-layer reactions that drive heater fouling and coke laydown.
Historian data feeds simple inferential models, creating soft sensors that smooth out noisy instruments. Machine learning techniques then combine those inferentials with feed properties and firing patterns to forecast when any pass will hit its metallurgical limit.
A pilot typically provides sufficient validation: pull the last year of data, train the model, back-test against manual fouling inspections, and validate predictions during routine operation.
Troubleshooting remains essential even with advanced models. If thermocouples read erratically, compare them with infrared imagery. If pressure drop spikes without a matching temperature rise, check for steam-to-oil imbalances or burner maldistribution.
By combining disciplined data hygiene with learning models that update as feed quality shifts, you give front-line operations a clear view of emerging fouling and the confidence to schedule cleaning on your terms rather than the heater’s.
Automate Real-Time Adjustments with AI
Traditional advanced process control (APC) depends on static linear-program models that break down when feed quality shifts. A Closed Loop AI solution, powered by reinforcement learning (RL), learns continuously from historian and live data and writes new set points to the distributed control system (DCS) in real time, keeping furnace duty and drum conditions on target.
Governance comes built-in. Models undergo audits, operators complete courses through training programs, and transparent dashboards explain every control move. The system integrates with existing APC, preserving prior investments while documenting margin uplift and longer intervals between decokes, proof of ROI that finance teams can trust.
Stabilize Upstream & Connected Units
You can only squeeze so much run length out of a coker if its upstream partners are misbehaving. Temperature swings in the crude distillation unit (CDU) or vacuum tower ripple straight into the delayed coker heater, changing feed density, metals, and asphaltene loading. Each upset forces the heater to chase a moving target, accelerating fouling and trimming weeks from the campaign.
A coordination checklist keeps the whole train aligned:
- Lock in CDU cut points so the vacuum furnace never sees shock loads
- Maintain constant vacuum furnace coil-outlet temperature to avoid surges in resid viscosity
- Balance visbreaker recycle so the coker feed’s metals and Conradson carbon stay within design limits
When these variables stay flat, heater firing can run lower, tube-metal temperatures drop, and fouling slows markedly. Advanced optimization solutions now link historian data from all three units, learning their interactions in real time and nudging set points across the network.
Instead of reacting to an upset after coke has already formed, the model trims a fraction of a degree or a few kilopascals upstream, preserving steady feed quality and buying precious days of additional run length.
Extend Your Coker Run Length With These Proven Strategies
Balance every heater pass early and often so no starved coil dictates the unit’s shutdown clock. Avoid the knee-jerk fix of cranking duty or feed—higher film temperatures only accelerate coke deposition. Stand up predictive monitoring that turns temperature, pressure, and ΔP data into a live fouling index you can trust.
Move from monitoring to action by allowing closed-loop optimization to adjust duty, steam, and recycle in real-time. Keep upstream crude and vacuum units steady, giving the coker a consistent, low-contaminant feed.
If you’re seeking sustainable efficiency improvements, advanced optimization solutions offer a data-first approach grounded in real-world operations. Plants deploying these models recover millions in lost production while cutting emissions. As industrial AI continues to mature, the plants that close the loop fastest will set the pace for refinery optimization.
