Why gas-handling compressors need dedicated PAG oil

Gas-handling compressors operate under demanding conditions such as high pressure, changing temperatures and direct contact with the gas stream place significant demands on the lubricant. These compressors are essential in LNG, LPG, offshore and process-gas operations and support applications such as boil-off gas management, gas reliquefaction, vapour recovery and the compression of natural gas and other process gases.

In these applications, compressor oil does more than reduce friction, it removes heat, seals clearances, protects bearings and other moving components, and helps prevent gas from escaping from the compression chamber. If the oil cannot perform these functions consistently, the result can be increased wear, higher oil consumption, shorter maintenance intervals and unplanned downtime.

For this reason, selecting a gas-compressor oil cannot be based on viscosity grade alone. The base-oil chemistry must also be compatible with the composition of the gas being compressed. This compatibility is particularly important when handling hydrocarbon gases. Under pressure, gases such as propane can dissolve into conventional lubricants, reducing the oil’s operating viscosity and weakening the lubricating film. Bearings, rotors and other components may then be left without sufficient protection.

Gas interaction can also create problems beyond viscosity loss. The lubricant or its additives may react with components of the gas stream, contributing to sludge and deposit formation while accelerating lubricant degradation.

The most common consequences include:

• Viscosity dilution and loss of lubricating-film strength
• Premature wear of bearings and compressor components
• Sludge, varnish and deposit formation
• Filter and separator clogging
• Foaming and excessive oil carryover
• Increased oil consumption
• Corrosion in wet CO₂ and other reactive-gas applications
• Shorter oil-drain and maintenance intervals

These effects increase maintenance requirements and reduce confidence in compressor availability. Lubricant selection should therefore be treated as part of the compressor’s reliability strategy, rather than as a routine purchasing decision.

Why choose PAG oil for gas-handling compressors 

Polyalkylene glycol, commonly referred to as PAG, is particularly suitable for demanding gas-compressor applications because it offers strong resistance to hydrocarbon dilution and gas absorption.

Klüber Summit PGS compressor oils are based on polyalkylene glycols and selected additives. Compared with conventional petroleum-based lubricants, these oils are highly resistant to dilution by natural gas and hydrocarbon process gases.

Their high viscosity index also supports effective lubrication across a wide temperature range along with the following benefits:

• Maintains protection in the presence of gas - PAG oils resist dilution and absorption by hydrocarbon gases, helping the lubricant maintain an effective operating viscosity. This protects the lubricating film around bearings, rotors and other moving components, even under pressure and changing temperatures.
• Keeps the compressor cleaner for longer - the chemical stability of PAG technology helps reduce sludge, deposits and residue formation. Cleaner oil circuits mean less filter clogging, lower oil carryover and better protection for valves, piston rings and seals.
• Supports reliability and lower maintenance - stable viscosity, good wear protection and resistance to wet CO₂ corrosion can extend component life and oil-drain intervals. This means fewer oil changes, reduced lubricant consumption and more predictable compressor maintenance.

Making PAG oils an industry best practise for demanding gas-compressor applications.

Matching the PAG oil to the gas-handling system  

Klüber Summit PGS series

Klüber Summit PGS oils are intended for gas compressors handling natural gas and hydrocarbon process gases. The range can be used in piston, rotary-screw and rotary-vane compressors, with the appropriate viscosity selected according to the application and operating conditions.

The PGS range offers strong resistance to hydrocarbon dilution and helps maintain the required operating viscosity. This supports effective lubrication, protects compressor components against wear and can contribute to longer oil-drain intervals and component life.

The range also provides protection against corrosive attack associated with wet CO₂, making it relevant for demanding gas streams where corrosion and viscosity dilution are key concerns.

Klüber Summit PGI series

Klüber Summit PGI 68 is designed for rotary-screw and piston compressors. A typical application is an LNG boil-off gas reliquefaction system using propane within the refrigeration process. The product is also identified for compressors handling propane refrigerant and propylene.

The Wärtsilä system example below illustrates how compressors form part of a wider LNG boil-off gas and fuel-gas handling process.

Within this type of system, boil-off gas from the LNG cargo tank passes through compression and cooling stages as part of the wider gas-handling process. The compressor lubricant must perform reliably while exposed to the gas and changing operating conditions.

Klüber Summit PGI 68 is a fully synthetic, water-insoluble PAG lubricant. Its principal value is its ability to maintain the proper operating viscosity while reducing gas dilution and oil carryover. This supports extended oil-drain intervals, protects compressor components against wear and helps limit lubricant losses into the gas stream or downstream system.

Klüber Summit NGL series

Klüber Summit NGL 444 is designed for high-pressure reciprocating compressors pumping natural gas, carbon dioxide and process gases such as hydrogen, helium and nitrogen.

The product can be used for oil-lubricated compressor components including cylinders, high-pressure packing, bearings and engine components. Its low pour point also makes it suitable for applications involving very low ambient temperatures.

Klüber Summit NGL 444 offers strong resistance to hydrocarbon dilution and absorption, together with chemical resistance to process gases.

Its high viscosity index supports lubrication across a wide temperature range, while protection against wet CO₂ corrosion helps safeguard metal surfaces. Low residue formation can also support longer valve and piston-ring life, reducing maintenance requirements in demanding offshore and process-gas operations.

Proven performance in offshore compressor operation

The value of a dedicated PAG lubricant becomes particularly clear when compressor performance is monitored over time.

As a real example for offshore compressor application, Klüber Summit PGS oil delivered an oil-drain interval improvement of up to 30%. The application also recorded lower deposit formation, contributing to cleaner operation and reduced wear on bearings and seals. The result demonstrates how selecting a lubricant that resists gas dilution can support:

• Longer intervals between oil changes
• Reduced lubricant consumption
• Fewer maintenance interventions
• Cleaner compressor internals
• Improved protection of bearings and seals
• More stable compressor performance

Actual performance depends on the compressor design, gas composition, operating pressure, temperature and maintenance practices.

Through its exclusive partnership with Klüber Lubrication, Wilhelmsen Ships Service combines application-specific compressor oils with maritime technical expertise and global product availability.

The objective is to help operators select an oil based on the compressor, gas composition and actual operating conditions. This reduces the risks associated with using a general-purpose lubricant in an application where oil and gas chemistry are closely connected.

Talk to our Speciality Marine Lubricants experts to identify the right Klüber Summit PAG solution for your compressor and gas application.