Flare Gas Recovery
Lubricants for flare gas recovery compressors recover gas from flare headers and return it to a fuel gas system, a process unit, or, where treatment and specifications permit, a sales-gas system.
Flare-header composition varies with connected processes. Recovered gas contains light and heavier hydrocarbons, water vapor, CO₂ (carbon dioxide), H₂S (hydrogen sulfide), and frequently hydrogen and nitrogen. Where this gas contacts the lubricant, dissolved gas and hydrocarbon condensate reduce its operating viscosity.
NEXT Lubricants supplies PAO (polyalphaolefin), PAG (polyalkylene glycol), PAG-WS (water-soluble polyalkylene glycol), and PEG (polyethylene glycol) formulations for gas-contact lubrication in flare gas recovery compressors. Selection depends on the complete gas composition, pressure, temperature, compressor design, and water exposure across the operating envelope.
For technical background on rich wellsite gas and lubricant dilution, see [Associated Gas and Flare Gas Capture: Compressor Lubricants for Rich Wellsite Gas].
Flare gas recovery captures gas that would otherwise be burned and returns it to a fuel, process, or suitable sales-gas system. Refinery, gas-processing, and production headers carry different gas compositions and operating profiles, which determine the lubrication requirements.
Oil-injected compressors and lubricated cylinders expose the lubricant directly to recovered gas. Dissolved gas can reduce its operating viscosity. Bearings, gearboxes, and drives isolated from the process gas require lubricants selected for their own equipment requirements.
Gas composition, pressure, and lubricant temperature act together to determine dilution. Heavier hydrocarbons can substantially reduce viscosity, but hydrocarbon content alone does not establish severity. Selection must consider the conditions at the actual lubrication point.
Select for the most demanding credible combinations of composition and conditions within the recovery compressor’s operating envelope. An average gas analysis can hide significant changes. Include normal operation, load changes, and relevant shutdown and restart conditions.
Flare gas recovery can operate continuously or intermittently. Some systems recover sustained routine flows; others cycle with gas availability. Where lubricant remains exposed to gas during shutdown, retained pressure, temperature, and contact time can affect its condition at restart.
Gas analysis and dilution calculations support lubricant selection, while used-oil analysis tracks its condition in service. Dissolved gas can escape during sampling, so laboratory viscosity may be higher than operating viscosity. Interpret the results alongside the actual compressor conditions.
Recommended NEXT Flare Gas Recovery Compressor Lubricants
NEXT GPL PAG
Light–Medium Hydrocarbon / Dilution-Prone Recovery
Base Oil: PAG
ISO Range: 32 – 680
NEXT GPL PAG-WS
Medium–Heavy Hydrocarbon / Higher-Dilution Recovery
Base Oil: PAG-WS
ISO Range: 32 – 460
NEXT GPL PAG-EO
Heavy Hydrocarbon / Lowest Hydrocarbon Dilution
Base Oil: PEG
ISO Range: 32 – 220
NEXT GPL PAO
Light Hydrocarbon / Lower-Dilution Recovery
Base Oil: PAO
ISO Range: 32 – 320
How Flare Gas Recovery Works and the Compressor's Role
Refinery Flare Systems
Recovery from refinery flare headers for return to fuel gas or process systems, with treatment where required.
Gas Plants & Processing Facilities
Flare-header recovery at natural gas processing, NGL (natural gas liquids) recovery, and gas-treating facilities.
Production Facilities & Offshore
Recovery of gas routed to flare systems at oil and gas production facilities, including offshore installations.
LNG & Storage Terminals
Recovery from designated flare systems at liquefaction, regasification, and storage facilities.
Factors affecting lubricant selection
Vapor recovery combines hydrocarbon-rich vapor, low suction pressure, variable flow and the possibility of condensation. The following factors determine the lubricant chemistry and viscosity required.
-
Compressor Design and Lubrication Point
Whether the lubricant contacts process gas in an oil-injected chamber, cylinder, or packing, or serves an isolated bearing, gearbox, or drive — these positions require different products. -
Gas Composition and Variability
The full gas analysis, including heavier hydrocarbons and non-hydrocarbon components, and the credible composition changes within the recovery unit's operating limits. -
Hydrocarbon Dilution and Operating Viscosity
Determines whether the chemistry and viscosity grade maintain the required lubrication performance after gas dissolves into the lubricant. -
Condensation and Liquid Separation
How liquids form and how the separation system controls carryover. Lubricant selection does not negate the compressor's requirements for preventing liquid ingress. -
Pressure and Temperature
Suction, interstage, and discharge conditions, along with lubricant temperatures at lubrication points, determine solubility, in-service viscosity, condensation, and thermal stress. -
Water, CO₂, H₂S, and Other Contaminants
These factors establish corrosion risk, chemical stability, and material compatibility. Hydrocarbon dilution resistance alone does not guarantee suitability for wet or sour streams. -
Operating Profile, Shutdown, and Restart
This includes continuous operation, turndown, cycling, and shutdown procedures. If lubricant remains exposed to gas during standstill, retained pressure, temperature, and contact time determine its condition at restart.
What NEXT needs to recommend a lubricant
A lubricant recommendation is based on the information below. Provide whatever information is available; NEXT will identify whether any additional details are required.
- Compressor Details Manufacturer, model, serial number and compressor type, such as reciprocating, rotary screw or centrifugal.
- Current Lubricant and Performance Current oil, oil volume, operating hours and any problems with viscosity, deposits, consumption, carryover or lubricant life.
- Gas Composition Main hydrocarbon components and any water, CO₂, H₂S, nitrogen, oxygen or other substances present. An existing gas-composition report also serves.
- Operating Conditions Suction and discharge pressures and temperatures, oil temperature and relevant operating limits for each compression stage.
- Application and Specific Requirements How the compressor is used and any purity, catalyst, material-compatibility, minimum-viscosity or other application-specific requirements.
- Final Recommendation NEXT evaluates the available information and confirms the recommended product, lubricant chemistry and ISO viscosity grade, with compatibility and changeover guidance where required.
Operational Benefits of Correct Lubricant Selection
Selecting the lubricant according to the compressor, gas composition and operating conditions can provide several operational benefits.
-
Stable Operating Viscosity
Maintains sufficient film strength even when process gas dissolves into and dilutes the lubricant. -
Reliable Operation Across Changing Loads
Sustains lubrication through the load changes and cycling of the intended duty. -
Reduced Unplanned Downtime
Prevents lubrication-related wear, overheating, deposits, and unexpected compressor shutdowns. -
Extended Component Life
Protects cylinders, piston rings, packing, bearings, rotors, and other lubricant-served components. -
Clean Running and Deposit Control
Minimizes varnish, carbon, and deposit formation in valves, cylinders, and lubricant-system components. -
Longer and More Predictable Service Intervals
Resists oxidation, viscosity loss, and contamination for controlled maintenance planning.
Our technical team can help identify the right product.
Lubricant Selection, Technical Support and Compatibility Documentation
NEXT combines application knowledge, laboratory data and an extensive internal cross-reference database to support lubricant selection, conversions and compressor troubleshooting.
Depending on the application, we can provide:
- Application-Specific Product Recommendations Lubricant recommendations based on gas or refrigerant composition, compressor design, operating conditions and current performance issues.
- Lubricant Cross-Referencing Identifies suitable NEXT alternatives by comparing base-oil chemistry, viscosity, application, specifications and operating requirements.
- Compatibility and Conversion Documentation Provides chemistry comparisons, mixture-test data, material compatibility, flushing requirements and top-off or changeover guidance.
- Dilution Data and PVT Graphs Shows how gas or refrigerant concentration, pressure and temperature affect lubricant dilution, density and operating viscosity.
- Troubleshooting and Root-Cause Support Supports investigations into foaming, oil carryover, dilution, deposits, corrosion, high lubricant consumption and reduced oil life.
What type of lubricant is used in a flare gas recovery compressor?
Lubricant chemistry is determined by duty, not application name. For gas-contact lubrication, the range extends from mineral and PAO base stocks for leaner, drier headers, through PAG and water-soluble PAG, to PEG as the recovered stream becomes richer. Selection is based on dissolved-gas behavior, operating viscosity, water exposure, and compatibility. Separately lubricated bearings and drives have their own requirements. NEXT provides a conclusive recommendation for a specific header, machine, and lubrication point.
Why does flare gas reduce compressor lubricant viscosity?
Where gas contacts the lubricant, soluble components dissolve into it and reduce its viscosity—heavier hydrocarbons far more readily than lighter ones. Hydrocarbon condensate also adds a liquid contamination path. The severity depends on composition, chemistry, pressure, and temperature: rich, wet headers dilute fast; lean, dry ones barely at all.
Should selection use the average or the peak flare composition?
Neither alone. Selection uses the most demanding credible combination of composition and conditions within the compressor’s intended envelope. The average day understates the duty, and the richest composition by itself is not the whole answer either: pressure and lubricant temperature influence dilution as much as richness does. Emergency releases routed directly to the flare are outside the recovery compressor’s duty and do not factor into its sizing.
What is the difference between flare gas recovery and vapor recovery?
The collection source. Vapor recovery units collect vapors from storage tanks, loading operations, and production equipment; flare gas recovery units recover gas from the flare collection system. The lubricant mechanics—low suction pressure, condensable gas, variable composition—are shared, which is why the duties share a chemistry range. Compositions are site-specific, so selections are too.
Does a liquid-ring compressor need one of these gas compressor lubricants?
Not for the ring itself, as the service liquid is a separate selection. The lubricated bearing and drive end require an oil or grease according to the manufacturer’s design. Where these points are isolated from the process gas, flare-gas dilution is not a selection criterion. The products on this page are for gas-contact lubrication; they do not include liquid-ring service liquids.
Does low suction pressure prevent lubricant dilution?
No. Suction pressure is one of several inputs. Gas composition, lubricant chemistry, and the pressure and temperature at the actual gas–lubricant contact points determine dissolved-gas behavior, and hydrocarbon condensate contaminates the lubricant regardless of suction pressure. Low suction pressure changes where dilution occurs, not whether it does.
What happens to the lubricant during shutdown?
It depends on the isolation arrangement. Lubricant in contact with header gas under retained pressure continues to absorb gas during standstill and starts the next run pre-diluted. An isolated, depressurized sump does not. Shutdown and restart scenarios are evaluated alongside normal operation. Warming at restart drives dissolved gas out over time, not instantly.
Can one lubricant serve the flare recovery unit and other compressors on site?
This is sometimes possible and worth investigating, as inventory consolidation offers real value. The condition is that the product satisfies each machine’s viscosity, chemistry, and compatibility requirements. A lubricant selected for the most severe stream is not automatically suitable for every lubrication point on site. NEXT reviews all machines together and advises where one product genuinely covers the needs and where separate products are required.
Explore Other Gas Compression Applications
Natural Gas Processing & NGL
Natural Gas Gathering
Lubricants for compressors handling raw, wet and variable-composition gas from wells and field gathering systems.
Vapor Recovery Units
Lubricants for compressors recovering low-pressure hydrocarbon vapors from storage tanks, loading operations and production facilities.