The Advantages of Gas Seals in Process Pumps

Gas seal technology has been a vital part of rotating equipment for more than three decades, offering significant improvements in reliability, emissions reduction, and cost efficiency. While earlier discussions have sometimes blurred distinctions between compressor dry gas seals and those designed for process pumps, it is important to understand the unique advantages of gas seals when applied in pumping systems.

Environmental and Economic Benefits

The primary driver for gas seal adoption has been evolving environmental regulations aimed at limiting fugitive emissions. Non-contacting, dry gas seals provide a proven zero-emissions solution, maintaining product purity and preventing toxic release. A reasonable estimate of 105,000 pump gas seals in use over the past 31 years, with an average six-year lifespan, equates to 272.2 million pounds of potential emissions avoided.

This reduction aligns with Maximum Achievable Control Technologies (MACT) and Air Quality Management District (AQMD) standards, with the Environmental Protection Agency (EPA) estimating emissions as high as 2,200 pounds per pump annually. Beyond environmental compliance, these seals deliver measurable cost savings. In 1993, they saved about $500 per seal at 6 cents per kilowatt hour (kWh). Today, at 10 to 16 cents/kWh, savings are approximately $1,350 per seal each year.

Evolution of Seal Design

Historically, fluid pumping relied on fiber packing lubricated with wax or graphite, but these materials generated heat and reduced service life. Mechanical shaft seals later replaced packing, requiring effective lubrication to improve performance. Advances in tribology and fluid science led to refined seal face designs that resist distortion, minimize wear, and operate under demanding pressures.

Spiral groove technology, pioneered in the 1990s, became the foundation for non-contacting gas seals. These grooves, etched into a seal face, create hydrodynamic lift during shaft rotation, separating the faces by micrometers and eliminating friction. The result is zero emissions with significantly reduced wear.

Applications Across Industries

Gas seals are now widely used in pumps, mixers, blowers, and fans. They are effective across a range of pressures, speeds, and temperatures, and have been applied in industries requiring strict purity standards such as pharmaceuticals, food processing, and petrochemicals. Recent advancements have introduced high-temperature seals capable of handling up to 800°F (425°C), expanding the scope of applications.

Gas Seal Support Systems

Dual gas seals rely on regulated inert gas, typically nitrogen, supplied at pressures 30 to 50 pounds per square inch (psi) above the process fluid. According to API 682 standards, the designated piping plan is Plan 74, which regulates barrier pressure and ensures reliable performance. To function effectively, gas seals require:

1. Pressure regulation to maintain proper seal cavity conditions.
2. Filtration of the barrier gas to less than one micron, due to tight seal face clearances.
3. Monitoring of pressure and flow, often supported by transmitters for continuous seal health feedback.

End-User Advantages

Several key benefits distinguish gas seals from traditional wet seals:

• Cost of ownership:
  Wet seals require utilities such as cooling water, pumps, and heat exchangers, while gas seals need primarily nitrogen supply.
• Barrier fluid compatibility:
  Wet seals rely on process-compatible fluids, while gas seals use inert nitrogen, avoiding cross-contamination.
• Maintenance:
  Wet seals demand frequent barrier fluid replenishment; gas seals primarily require barrier pressure monitoring.
• Energy use:
  Wet seals consume about 1,300 kWh annually, while gas seals consume just 350 kWh. This equates to a reduction of two tons of carbon dioxide emissions per pump, per year.
• System flexibility:
  Gas seal panels can be located away from the pump, improving accessibility for maintenance and retrofitting.

Conclusion

The widespread adoption of non-contacting, dry gas seal technology has created clear environmental, operational, and economic advantages. By reducing emissions, lowering energy use, and extending mean time between repairs, these seals have become a sustainable solution for process pumps. With proper application and monitoring, gas seals remain a key technology for meeting future regulatory and operational demands.
 
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