Every plant engineer knows the feeling: alarms are quiet, the daily throughput numbers look acceptable on paper, but something in the gathering or processing loop feels off. Liquids are showing up where they shouldn’t, pressure differentials are creeping up, or amine units are suddenly foaming without an obvious chemistry change.
In gas processing, subtle visual or mechanical symptoms are rarely isolated events—they are early warnings of thermodynamic or physical underperformance. This field guide breaks down five common operational red flags, what is happening under the hood, and how targeted engineering intervention fixes them.
1. Unexpected Liquid Drop-Out in Downstream Lines
The Symptom: Hydrocarbon liquids or heavy NGLs are accumulating in dry gas discharge lines, fuel gas headers, or downstream sales points where only vapor should exist.
The Root Cause: Liquid carryover usually stems from compromised separation efficiency or unexpected phase behavior changes. Common culprits include:
Mechanical failure or liquid re-entrainment in upstream inlet separators or coalescers.
Retrograde condensation caused by unmonitored pressure variations along the line.
Operating above the critical velocity of vessel mist eliminators (vane packs or mesh pads).
The Fix:
Start with a targeted phase-behavior evaluation using accurate gas composition analysis (GC) to map your true dew point curve. Credence’s field engineers perform on-site separator troubleshooting and computational simulation to determine if your vessels need internal retrofit modifications, revised liquid dump cycling, or updated operational setpoints to keep heavy fractions in the liquid phase where they belong.
2. Gradual Pressure Differential ($\Delta P$) Spikes Across Vessels
The Symptom: Differential pressure across glycol contactors, amine absorbers, or inlet filter-coalescers is rising steadily over days or weeks.
The Root Cause: Internal vessel fouling, particulate plugging, or fluid degradation:
Microscopic solids, iron sulfide, or pipe scale clogging filter media or packing beds.
Heavy hydrocarbon condensation in amine or glycol fluids causing liquid-phase foaming and column flooding.
Chemical degradation products forming viscous sludges inside tray columns or structured packing.
The Fix:
Monitoring $\Delta P$ is only step one; identifying the exact mechanism prevents repeated vessel entry. Credence works directly with plant operations to perform diagnostic fluid testing, flow distribution modeling, and root-cause analysis. We help design targeted chemical washing routines, optimize filtration specs, or re-engineer column internals to restore design pressure drops without requiring extended shutdowns.
3. Dehydration Failure and Hydrate Formation
The Symptom: Water dew point specs are consistently missed, or gas-hydrate freezes are actively restricting flow in low-temperature chokes or cryogenic units.
The Root Cause: TEG (Triethylene Glycol) or molecular sieve performance degradation:
TEG dehydration loops running at sub-optimal reboiler temperatures, leading to insufficient lean glycol purity.
Hydrocarbon contamination fouling molecular sieve beads, causing premature breakthrough.
Thermal channeling through desiccant beds due to uneven gas distribution.
The Fix:
A full thermal and mass-balance assessment of the dehydration train. Credence’s consulting team reviews reboiler duty, stripping gas rates, and circulation efficiency for TEG systems. For solid-bed dehydrators, we conduct bed distribution audits and breakthrough curves to determine whether bed replacement, regeneration profile adjustments, or dynamic switching cycles are necessary.
4. Amine Unit Foaming and Solvent Loss
The Symptom: Sudden pressure surges, severe liquid carryover in the overhead vapor lines, or elevated $H_2S$ and $CO_2$ slip in the treated gas stream.
The Root Cause: Foaming occurs when surface tension changes dramatically within the absorption column, typically caused by:
Heavy hydrocarbon condensation mixing with the circulating amine.
Suspended particulate matter acting as a foam stabilizer.
Incompatible corrosion inhibitors, valve greases, or wellhead chemicals entering the plant inlet.
The Fix:
Defoamers only buy time—they do not solve the root cause. Credence conducts thorough inlet separation reviews to block liquid hydrocarbon ingress before it hits the tower. Our engineers optimize mechanical filtration (carbon beds and particulate filters) and recalibrate lean/rich heat exchanger temperatures to keep the amine solution at the correct margin above the hydrocarbon dew point.
5. Temperature Profile Anomalies in Heat Exchangers
The Symptom: Gas-to-gas or gas-to-liquid heat exchangers are failing to meet target temperatures despite clean tube surfaces and rated flow rates.
The Root Cause: Reduced heat transfer rates due to:
Internal scale, wax, or asphaltene deposition on the process side.
Fluid maldistribution across tube passes.
Off-design gas compositions causing significant enthalpy deviations from original equipment engineering calculations.
The Fix:
When plant inlet gas shifts—as it frequently does in maturing or multi-well gathering systems—original heat exchanger sizing often falls out of alignment. Credence evaluates current composition trends against existing surface area specs, identifying whether cleaning, baffle modifications, or process loop re-configurations are needed to regain thermal efficiency.
Turning Field Symptoms Into Long-Term Process Efficiency
Ignoring minor plant anomalies usually leads to unplanned downtime, off-spec gas penalties, or premature equipment failure. Resolving them doesn't always require expensive capital expenditure—often, it takes fresh eyes and deep process engineering expertise.
At Credence, our field engineering and consulting teams specialize in diagnostic plant audits, debottlenecking, and real-world operational fixes. Whether you are dealing with persistent liquid carryover, tower flooding, or dew point instability, we partner with your operations team on-site to pinpoint the root cause and restore your facility to maximum profitability.