An LNG import terminal is a just-in-time business run at minus 162 degrees Celsius. Cargoes arrive on a schedule, the grid pulls on demand, and everything in between is cryogenic inventory that never stops trying to turn back into gas. When a terminal runs blind, the failures compound quietly. Boil-off creeps up, a vaporizer derates during a cold snap, a stratified tank sits primed for rollover, and the first anyone hears about it is a flare event or a curtailed nomination. By then the money is already gone.

The fix isn’t more reports. It’s a short list of KPIs, live, in front of the people who can act on them. Here are the ten that matter most.

Send-Out Rate vs. Nomination

• Why it Matters: Send-out is the terminal’s product. Miss nominations and you’re facing imbalance penalties and shippers who remember at contract renewal.
• What it Measures: Actual gas send-out to the grid compared against confirmed shipper nominations for the current gas day.
• What Happens if Missed: Imbalance charges accrue, the grid operator intervenes, and your reliability record takes a hit that outlasts the gas day.
• Formula: (Actual Send-Out Volume / Nominated Volume) x 100
• Indicator Type: Current. Deviation shows up within the gas hour, leaving time to adjust the vaporizer lineup before penalties accrue.
• Unit of Measure: %
• Ideal Visualization(s): KPI trend with real-time alerts; bullet chart against the nominated target
• Frequency: Real-time
• Data Required: Send-out flow, confirmed nominations, gas day schedule, vaporizer throughput
• Pro Tip: Track the cumulative intraday balance, not just the instantaneous rate. A flat deficit discovered at hour 18 is unrecoverable.
• Red Flag: Repeated late-day catch-up ramps mean vaporizer availability, not grid demand, is shaping your send-out profile.

Boil-Off Gas (BOG) Rate

• Why it Matters: BOG is product evaporating in place. Managed well, it feeds fuel or send-out. Managed poorly, it becomes flared money.
• What it Measures: Volume of LNG vaporizing across tanks and lines, expressed as a percentage of stored inventory per day.
• What Happens if Missed: Excess BOG overwhelms the compressors, tank pressure climbs, and you end up venting or flaring gas you already paid for.
• Formula: (BOG Mass Flow / Total LNG Inventory Mass) x 100 per day
• Indicator Type: Current. A rising BOG rate reflects heat ingress or pressure management problems happening right now, not last week.
• Unit of Measure: % per day
• Ideal Visualization(s): KPI trend with real-time alerts; SPC trend (control chart) to catch slow drift
• Frequency: Real-time
• Data Required: BOG compressor flow, tank pressures, LNG inventory levels, ambient temperature
• Pro Tip: Baseline BOG per tank and per ambient temperature band. A tank drifting above its own baseline matters more than the site average.
• Red Flag: BOG rising with stable ambient conditions and steady inventory points to insulation degradation or a passing valve.

Tank Inventory and Days of Cover

• Why it Matters: Inventory is the buffer between cargo arrivals and grid demand. Too low risks curtailment; too high blocks the next cargo.
• What it Measures: Current usable LNG volume across all tanks, translated into days of send-out at the forecast demand rate.
• What Happens if Missed: You either curtail send-out waiting on a cargo or hold a laden carrier at anchor while demurrage accumulates.
• Formula: Usable LNG Inventory / Forecast Daily Send-Out
• Indicator Type: Leading. Days of cover projects forward, flagging supply gaps before they become curtailment events.
• Unit of Measure: Days
• Ideal Visualization(s): KPI block with sparkline; bullet chart against minimum and maximum operating bands
• Frequency: Hourly
• Data Required: Tank levels, tank densities, send-out rate, forecast demand, scheduled cargo arrivals
• Pro Tip: Run cover against the demand forecast, not the trailing average. Cold snaps eat inventory faster than history suggests.
• Red Flag: Cover repeatedly dipping below the planning threshold means your cargo scheduling assumptions no longer match demand reality.

Tank Stratification and Rollover Risk

• Why it Matters: Rollover releases massive BOG in minutes and can lift relief valves. It’s the tank event nobody wants to explain afterward.
• What it Measures: Density and temperature differentials between LNG layers in each tank, indicating stratification after mixing heel with new cargo.
• What Happens if Missed: A sudden rollover overwhelms BOG handling, forces emergency venting, and can trigger a full terminal shutdown.
• Formula: Density Differential = Bottom Layer Density – Top Layer Density
• Indicator Type: Leading. Stratification builds over days after a cargo, giving ample warning before rollover conditions develop.
• Unit of Measure: kg/m³
• Ideal Visualization(s): KPI trend with real-time alerts per tank; table of layer densities and temperatures across tanks
• Frequency: Every 15 minutes
• Data Required: In-tank density profiles, temperature profiles by level, tank pressure, fill history
• Pro Tip: Flag any incoming cargo whose density differs from the tank heel beyond your mixing threshold before unloading starts, not after.
• Red Flag: Unusually flat BOG from a recently filled tank can mean vapor trapped under a stratified layer. That’s the quiet before rollover.

Ship Unloading Duration

• Why it Matters: Berth windows are scheduled tight. Slow discharges cascade into delayed cargoes, demurrage claims, and inventory shortfalls downstream.
• What it Measures: Elapsed time from arms connected to arms drained, benchmarked against the discharge plan for each carrier class.
• What Happens if Missed: Demurrage accrues by the hour, the next arrival slips its window, and send-out planning unravels behind it.
• Formula: Actual Discharge Duration – Planned Discharge Duration
• Indicator Type: Lagging. The final number lands after the ship sails, so watch live transfer rate to catch a slow discharge mid-cargo.
• Unit of Measure: Hours
• Ideal Visualization(s): Bar chart by cargo; Pareto chart when ranking carriers by schedule deviation; KPI trend with real-time alerts on live transfer rate
• Frequency: Per cargo, with real-time transfer rate during discharge
• Data Required: Arm connection timestamps, transfer flow rates, ship pump pressures, vapor return flow, planned durations
• Pro Tip: Watch the transfer rate curve in the first two hours. A slow ramp usually predicts the whole discharge running long.
• Red Flag: The same carrier class consistently running long points to a vapor return or receiving constraint on your side, not theirs.

Vaporizer Capacity Utilization

• Why it Matters: Vaporizers set your maximum send-out. Fouled or derated units quietly cap capacity right when winter demand peaks.
• What it Measures: Actual regasification throughput per vaporizer against rated capacity, alongside approach temperature on ORVs and fuel efficiency on SCVs.
• What Happens if Missed: You discover the missing capacity during a cold snap, curtail send-out, and shippers buy expensive replacement gas elsewhere.
• Formula: (Actual Throughput / Rated Capacity) x 100
• Indicator Type: Current. Approach temperature drift flags fouling as it develops, well before throughput visibly suffers.
• Unit of Measure: %
• Ideal Visualization(s): Group rollup bars across vaporizers; KPI trend with real-time alerts on approach temperature; Pareto chart when ranking vaporizers by capacity deviation
• Frequency: Real-time
• Data Required: Throughput per unit, gas outlet temperature, seawater inlet and outlet temperatures, fuel gas consumption
• Pro Tip: Trend ORV approach temperature by season. Marine fouling accelerates in warm months and shows up as a slow, steady climb.
• Red Flag: Outlet temperature hunting near the low-limit trip means you’re one demand spike away from a cold gas excursion.

BOG Compressor Availability and Spare Capacity

• Why it Matters: BOG compressors are the pressure relief you actually want to use. Lose one and flaring becomes your fallback plan.
• What it Measures: Running status, load, and remaining spare capacity across the BOG compressor train, measured against current BOG generation.
• What Happens if Missed: Tank pressure rises unchecked during unloading, forcing flaring or, worse, a discharge stoppage mid-cargo.
• Formula: Spare Capacity = Total Available Compressor Capacity – Current BOG Load
• Indicator Type: Current. Spare capacity is what stands between a routine unloading and a flaring event tonight.
• Unit of Measure: %
• Ideal Visualization(s): KPI blocks per compressor; bullet chart for spare capacity; status history trends for availability
• Frequency: Real-time
• Data Required: Compressor running status, suction pressure, throughput per machine, BOG generation rate
• Pro Tip: Check spare capacity against forecast BOG for the next unloading, not current generation. A discharge can double BOG within an hour.
• Red Flag: Frequent recycle valve operation at low load signals a machine running outside its envelope and heading for a trip.

Send-Out Gas Quality (Wobbe Index)

• Why it Matters: Off-spec gas gets rejected at the grid entry point. One quality excursion can shut in the entire terminal.
• What it Measures: Wobbe Index and heating value of send-out gas against grid entry specifications at each export point.
• What Happens if Missed: The grid operator closes the entry valve, send-out stops, and every downstream nomination fails at once.
• Formula: Wobbe Index = Higher Heating Value / sqrt(Specific Gravity)
• Indicator Type: Current. Quality shifts with cargo blend and nitrogen injection, so live measurement is the only real defense.
• Unit of Measure: MJ/Sm³
• Ideal Visualization(s): SPC trend (control chart) with real-time alerts; bullet chart against specification limits
• Frequency: Real-time
• Data Required: Gas chromatograph composition, heating value, specific gravity, nitrogen injection rate
• Pro Tip: Watch the quality trajectory during tank switchovers. Rich heel blending into a lean cargo is where most excursions start.
• Red Flag: Steadily rising nitrogen injection to hold spec means the cargo mix is drifting rich and your ballasting headroom is shrinking.

Flare and Vent Volume

• Why it Matters: Every flared cubic meter is purchased product destroyed, plus emissions your regulator and your neighbors both count.
• What it Measures: Total gas volume flared or vented, coded by cause: pressure relief, maintenance, compressor trips, or unloading peaks.
• What Happens if Missed: Chronic flaring erodes margin, breaches emissions permits, and hands the regulator a reason to look closer.
• Formula: Sum of Flare and Vent Meter Volumes per Period
• Indicator Type: Lagging. The gas is gone, but cause-coded totals point straight at the upstream failures worth fixing.
• Unit of Measure: Sm³
• Ideal Visualization(s): Pareto chart when ranking flare events by cause; KPI trend with real-time alerts on flare flow
• Frequency: Real-time, totalized hourly
• Data Required: Flare meter flow, vent valve positions, event cause codes, compressor trip records
• Pro Tip: Assign a cause code to every flare event within the shift. Uncoded events become unfixable statistics within a week.
• Red Flag: A rising baseline flare with no logged events usually means a passing relief valve, not an operational cause.

Energy Intensity per Unit of Send-Out

• Why it Matters: Regasification margins are thin. Fuel gas and power are your largest controllable costs after the LNG itself.
• What it Measures: Total fuel gas and electrical energy consumed per unit of gas sent out, across the whole terminal.
• What Happens if Missed: Creeping intensity quietly compounds into a material margin hit long before the monthly report catches it.
• Formula: (Fuel Gas Energy + Electrical Energy) / Send-Out Volume
• Indicator Type: Current. Intensity moves with the vaporizer lineup and pump scheduling decisions operators make every shift.
• Unit of Measure: kWh/Sm³
• Ideal Visualization(s): KPI trend with real-time alerts; histogram by operating mode; Pareto chart when ranking consumers by energy per unit
• Frequency: Hourly
• Data Required: Fuel gas flow, electrical power consumption, send-out volume, running equipment lineup
• Pro Tip: Normalize by send-out band before comparing shifts. Intensity at 30% turndown will always look ugly; compare like with like.
• Red Flag: Intensity rising at constant send-out and lineup means an individual consumer, often a pump, is quietly degrading.

Why Real-Time Visibility Matters

An import terminal doesn’t fail loudly. It fails through a stratified tank nobody profiled, a vaporizer that derated over a fouling season, and a BOG train that had no spare capacity the night a Q-Max came alongside. Each of these announces itself days or weeks in advance, but only in live data. Monthly reports tell you what the flare already burned.

The ten KPIs above share one trait: they’re all actionable while the situation is still cheap to fix. Days of cover moves before curtailment does. Density differentials move before rollover does. Approach temperature moves before the cold snap arrives. Put them in front of the shift, with alerts, and the terminal stops running on surprises.

How Transpara Can Help

If real-time operational visibility is a challenge you’re facing, you’re not alone. At Transpara, we help teams like yours gain clarity from complex systems without the need to centralize or overhaul your data stack.
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