PITOPS
Closed-loop PID tuning software that identifies process models from normal operating data, so loops on refrigerant compressors and feed control valves can be retuned without step tests that disturb LNG production.
FocusNo step tests required
LNGProcess Control Software for LNG: PID Tuning, APC, and Loop Monitoring
Process control software for LNG plants optimizes PID tuning, advanced process control, and control loop monitoring across refrigeration compression trains, feed gas conditioning, and the Joule-Thomson valve that sets subcooling margin. Every LNG train balances refrigeration load, feed composition, and production rate differently, from a single mixed-refrigerant train to a multi-train cascade-refrigeration facility, so it needs control strategies matched to that configuration rather than plant-wide defaults.
The approach
How It Fits Your LNG Plant
No rip-and-replace
An Optimization Layer
PiControl Solutions builds this software as an optimization layer that sits above an LNG plant's installed DCS or PLC hardware, whether the train runs propane-precool mixed refrigerant, cascade refrigeration, or a nitrogen expander cycle.
Underperforming loops, fixed
Finds & Retunes Loops
It finds underperforming loops on refrigerant compressor suction pressure, JT valve position, and feed flow control, then retunes them against real closed-loop operating data instead of disruptive step tests.
Built to last
Keeps Models Accurate
It keeps advanced control models accurate across max-rate and reduced-rate operation, so the control assets already in the plant deliver the performance they were specified for.
The challenges
Control Challenges Specific to LNG
LNG process loops face conditions that generic tuning rarely handles well, because refrigeration load, feed gas composition, and production rate mode all shift at once. PID controllers account for over 95% of all control loops in industrial plants, so tightening these loops is where LNG variability is won or lost.
Cascade / mixed refrigerant
Refrigeration Cycle Coupling
Propane, ethylene, and methane refrigeration circuits are linked through cascade or mixed-refrigerant heat exchangers, so a load shift on one circuit shows up as a disturbance on the other two within minutes, and loops tuned for one refrigerant balance drift as that balance shifts.
Main feed flow control
Feed Flow Maximization
Main feed flow is the single most important manipulated variable on an LNG train, tied to nearly 20 controlled variables including HRC temperature, sub-cooling delta-T, and delta-pressure limits across chillers and coolers, so pushing it toward the constraint without tripping a limit takes constant coordination that fixed setpoints cannot provide.
Joule-Thomson valve
JT Valve Subcooling Margin
The Joule-Thomson valve between the heavies recovery column and methane economizer sets the subcooling margin, a hard safety limit, so its pressure has to be pushed as high as safely possible to sustain production without eroding that margin.
Max rate / half rate
Full-Rate to Half-Rate Transitions
Loss of feed gas from the pipeline or a compressor trip drops a train from max-rate to half-rate operation for hours or days at a time, and process dynamics differ enough between the two modes that a single fixed control model cannot hold both well, especially with ambient temperature and feed composition also shifting underneath it.
Read more on LNG process control challenges.
The software
Software Matched to LNG Applications
Three PiControl products carry most LNG optimization work, and each targets a different stage of the control problem.
Swipe
COLUMBO
Handles closed-loop MPC model identification, refreshing the models behind feed maximization and JT valve advanced controllers as ambient conditions and feed gas composition drift.
FocusModels stay current
APROMON
Provides continuous control loop monitoring, flagging oscillation, valve stiction, and degrading performance across refrigeration and feed control loops before they erode production rate.
FocusCatches degradation early
Compatible with every major DCS and PLC via OPC-DA and OPC-UA, or over Modbus TCP/IP where LNG APC schemes need to avoid an external OPC server, these products read live data from the control assets already installed, so no new control hardware is needed. They form the LNG slice of PiControl's process control software range.
Services
Consulting and Training for LNG Teams
Process optimization software depends on two things in LNG plants: experienced engineers to apply it, and often-young control room teams who can sustain the gains.
Step 01 · Optimization
PID Tuning Consulting
PiControl's PID tuning consulting deploys PITOPS and SUPERTUNE directly on LNG refrigeration and feed control loops, typically covers 40 to 250 loops per engagement, and documents before-and-after results.
FAQ
LNG Process Control FAQ
To see how the same optimization layer applies in other sectors, explore process control software by industry.
LNG plant process control is the practice of holding liquefaction refrigeration cycles, feed gas conditioning, and the Joule-Thomson valve at safe, on-spec operating points using PID and advanced controllers. Process control software improves it by tuning those controllers against real operating data, which reduces variability and lets the train run closer to its true production and safety constraints.
Advanced process control manipulates the setpoints of the base-level PID loops underneath it, so if those loops are poorly tuned, the APC layer inherits that error and cannot hold its targets. Base-level PID tuning and optimization is the prerequisite step on every LNG train, and it commonly cuts controller deviation from setpoint enough to give the plant smoother, more stable operation across every downstream loop before any APC work begins.
PiControl's APC automatically identifies the active constraints on an LNG train and pushes production against them, led by two manipulated variables: main feed flow and Joule-Thomson valve pressure. It also switches models automatically between max-rate and reduced-rate operation. Across engagements this has increased average production rate by 4 to 5 percent, which converts directly into higher plant profit.
Yes. The software reads and writes through OPC, so it is compatible with every major DCS and PLC via OPC-DA and OPC-UA. Where an LNG APC scheme needs to avoid the cybersecurity review that an external OPC server can trigger, it can instead communicate over Modbus TCP/IP. Either way it runs as an optimization layer on top of the control assets already installed, which means no rip-and-replace and no new control hardware to justify.