Barrier & seal systems.
Precision at the interface.
Barrier and buffer fluids for mechanical seals and compressor seal systems, with selection based on compatibility and operating requirements.
Every operating condition
informs the formulation.
Barrier and buffer fluids provide lubrication, cooling and controlled fluid conditions within dual mechanical seals and compressor wet-seal systems.
MECHANICAL & COMPRESSOR SEALS
The correct terminology depends on the seal arrangement. An unpressurized dual mechanical seal uses a buffer fluid operating below seal-chamber pressure. A pressurized dual seal uses a barrier fluid maintained above seal-chamber pressure. Compressor wet seals use a related but distinct system in which pressurized seal oil forms a liquid barrier against process-gas leakage.
Fluid selection must consider pressure differential, leakage direction, operating temperature, viscosity, process compatibility, seal materials and any process medium or lubricant that the fluid may contact. In gas-compressor wet seals, process gas can also dissolve into the seal fluid and change its operating viscosity.
NEXT Lubricants supplies PAO, PAG and PEG barrier and buffer fluids for dual mechanical seals, compressor wet seals and related seal-support applications across chemical processing, food production, gas compression, petrochemicals and industrial rotating equipment.
Start with your
operating environment.
Explore the conditions, lubricant technologies and selection requirements for your application.
Dual Mechanical Seal Systems
Dual mechanical seals are the standard sealing solution for pumps and rotating equipment handling hazardous, toxic or high-value process fluids — providing a secondary containment barrier that prevents process fluid from reaching the atmosphere even if the inner seal fails.
Compressor Seal Systems
Compressor seal systems prevent process gas from escaping along the shaft of a compressor to the atmosphere — a critical function in any application where the gas being compressed is flammable, toxic, explosive or valuable.
Lubricants for your application.
Explore the relevant NEXT formulations. Final selection depends on equipment requirements and actual operating conditions.
Barrier N
Synthetic Barrier Fluid (Series 182)
Barrier XL
Extended Life Synthetic Barrier Fluid (Series 188)
Barrier PAG
PAG Barrier Fluid (Series 187)
Barrier PEG
PEG Barrier Fluid (Series 225)
PROCESS, APPLICATION & FLUID ROLE
API Plan 52 Buffer-Fluid Systems
API Plan 52 Buffer-Fluid Systems
API Plan 52 uses an external reservoir containing unpressurized buffer fluid for an Arrangement 2 dual seal. The buffer system normally operates below seal-chamber pressure. Leakage across the inboard seal therefore moves from the process into the buffer system, where changes in level, pressure or fluid condition can be monitored. The buffer fluid must remain compatible with expected process leakage because the two fluids can mix during normal or abnormal operation.
API Plan 53 Barrier-Fluid Systems
API Plan 53 Barrier-Fluid Systems
API Plan 53 maintains the barrier fluid above seal-chamber pressure for an Arrangement 3 pressurized dual seal. This pressure differential causes clean barrier fluid to migrate across the inboard seal toward the process rather than allowing process fluid to migrate outward. The barrier fluid must therefore be acceptable if small quantities enter the process. Plan 53A uses a pressurized reservoir with a gas–liquid interface. Plan 53B uses a bladder accumulator to separate the pressurizing gas from the barrier fluid. Plan 53C uses a piston accumulator that can track changes in process pressure.
API Plan 54 Barrier-Fluid Systems
API Plan 54 Barrier-Fluid Systems
API Plan 54 supplies clean, pressurized barrier fluid from an external circulation system. It is used where the seal cannot provide sufficient internal circulation or where centralized pressure, cooling, filtration and fluid management are required. The external system must remain energized and maintain the required barrier pressure during operation.
Compressor Wet-Seal Systems
Compressor Wet-Seal Systems
Traditional centrifugal-compressor wet seals circulate pressurized seal oil between rings surrounding the compressor shaft. The oil forms a liquid barrier between the pressurized process gas and the atmosphere. Some gas can become entrained in or dissolve into the inboard seal-oil stream. The contaminated oil may then require separation, degassing and controlled recirculation. Seal-fluid selection must consider gas composition, pressure, temperature, gas solubility, operating viscosity, oxidation stability and the design of the seal-oil recovery system.
Dry Gas Seal Systems
Dry Gas Seal Systems
Dry gas seals use a thin film of conditioned seal gas rather than a liquid barrier at the primary sealing interface. Liquid barrier fluids should not be selected for the dry gas seal faces. Separate lubricants or fluids may still be used in the compressor bearings, separation seals or other auxiliary systems, depending on the equipment design.
Food, Pharmaceutical and Catalyst-Sensitive Processes
Food, Pharmaceutical and Catalyst-Sensitive Processes
Certain processes require a particularly clean, low-reactivity or appropriately registered barrier fluid because some fluid may migrate into the process. Selection must distinguish between NSF H1 fluids permitted for incidental food contact and H2 products intended only for areas where there is no possibility of food contact. Catalyst compatibility and process-purity requirements must be evaluated separately.
The details
that matter.
Understand the advantages, operating priorities and practical steps for your application.
At a glance
At a glance
- Buffer systems operate below seal-chamber pressure, including API Plan 52.
- Barrier systems operate above seal-chamber pressure, including API Plans 53A, 53B, 53C and 54.
- Leakage direction matters. The pressure arrangement determines whether process fluid can enter the support system or barrier fluid can migrate toward the process.
- Wet and dry gas seals differ. Wet seals use pressurised seal oil; dry gas seals use conditioned seal gas with no liquid at the primary gas-sealing interface.
Check fluid chemistry, viscosity and cleanliness against the process medium, seal materials, temperature and pressure.
Advantages
Advantages
A compatible fluid supports the pressure arrangement and lubrication requirements of the seal system.
- Controlled lubrication and cooling at the inboard and outboard seal faces.
- Process containment through the intended pressure differential and leakage direction.
- Longer seal and fluid life with protection against wear, oxidation and corrosion.
- Cleaner circulation through appropriate chemistry, cleanliness and material compatibility.
- More predictable maintenance using fluid-level, pressure, temperature, consumption and analysis trends.
Clarity for your
next decision.
01What is the difference between a barrier fluid and a buffer fluid?+
A buffer fluid operates below seal-chamber pressure in an unpressurized dual-seal arrangement such as API Plan 52. Process leakage therefore moves into the buffer system.
A barrier fluid operates above seal-chamber pressure in a pressurized dual-seal arrangement such as API Plan 53, so clean barrier fluid moves toward the process and prevents process fluid from migrating outward under normal operation.
02Is API Plan 52 the same as API Plan 53?+
No. Plan 52 is an unpressurized buffer-fluid system for dual unpressurized seals, while Plan 53A/B/C are pressurized barrier-fluid systems for dual pressurized seals.
03What is the difference between Plan 53A, 53B and 53C?+
All three provide a pressurized barrier fluid, but the pressurization method differs. Plan 53A uses an inert-gas-pressurized reservoir with direct gas/liquid interface, Plan 53B uses a bladder accumulator and Plan 53C uses a piston accumulator.
04Why must a barrier fluid be compatible with the process?+
Because a pressurized barrier system is designed so that clean barrier fluid migrates across the inboard seal toward the process rather than allowing process fluid to migrate outward. The barrier fluid therefore needs to be acceptable if small quantities enter the process.
05Do compressor wet seals use API Plan 52 or Plan 53?+
Not necessarily. API Plan 52 and 53 terminology applies to dual mechanical-seal support arrangements. Traditional centrifugal-compressor wet seals are a separate liquid-film seal technology in which pressurized oil forms a barrier against process gas.
06Can process gas dilute compressor seal oil?+
Yes. In a wet-seal compressor system, some process gas can dissolve into the seal fluid. The amount depends on gas composition, pressure, temperature and fluid chemistry and may change the operating viscosity of the fluid.
Know your current lubricant?
Find your NEXT reference.
Compare published references by manufacturer, product and viscosity. Our technical team can confirm application suitability.