The Significance of Seal Retrofits on Emissions & Energy Efficiency

04 March 2024

8 Minute Read

As industries race to achieve net zero emissions by 2050, the pursuit of sustainability has never been more critical. A global focus on green initiatives drives new solutions for CO2 reduction and encourages the adoption of today’s decarbonization technologies.

A shift toward process efficiency began in the 1980s with dry gas sealing technology replacing traditional wet oil seals, mainly in centrifugal compressors. Manufacturing with dry gas seals is now standard practice for compressor OEMs. However, thousands of older units still utilize oil seals. Retrofitting these historical compressors with dry gas seals supports sustainability and offers a proven approach to eliminating the shortfalls inherent in older sealing technologies.

Understanding Oil Seals and Their Limitations

When evaluating the efficacy of wet oil seals, it helps to understand their role in gas management and how the technology works. Oil seals are designed to prevent process gas leakage in equipment — centrifugal compressors, for example — by creating and maintaining a high-pressure liquid barrier between stationary and rotating parts. The barrier — a thin film of pressurized oil — restricts the escape of process gases into the atmosphere while simultaneously separating and lubricating the seal’s face surfaces. However, in terms of efficiency and reliability, oil seal technology presents critical challenges.

  • Potential barrier oil contamination. Harmful process gases (such as those containing hydrogen sulfide) can become entrapped in the seal oil and contaminate the associated lube systems. This contamination poses safety and environmental concerns, as well as substantial treatment and disposal costs.
  • Potential process gas contamination. With an oil seal, there is a possibility that the barrier oil will infiltrate the process gas, affecting its quality and/or composition. This could mean that process gas must undergo additional steps, such as scrubbing, before sale or use. This also requires the management of scrubbed substances once removed from the gas stream.
  • Inefficient energy consumption. The power required to support an oil seal is considerable. A wet oil seal requires an energy-consuming pumping system, and a compressor’s rotating parts must also work to overcome the oil barrier’s shear force.
  • Frequent recurring maintenance. As mentioned, an oil sealing system includes pumps and other components with rotating parts, like motors. Periodic shutdowns are required to maintain these parts and to prevent a failure that could cause unplanned downtime.
  • Lack of support. Oil seals are a legacy technology; it is increasingly difficult to source technicians and operators qualified to service these dated systems. Exacerbating this challenge is the scarcity of replacement parts.
  • Environmental impact concerns. Oil sealing systems have minimal leakage but are not leak-free. Although small, these oil leaks, when added up across numerous operational hours, can result in a significant quantity of hazardous waste that needs to be managed safely.

While wet oil seals have long served the industry, their limitations shouldn’t be overlooked. The drawbacks of this technology have given rise to alternatives that deliver better process and efficiency — including the dry gas seal.

Considering a Wet-to-Dry Gas Seal retrofit? Start with this nine-step guide.

Dry Gas Seal Functionality and Retrofitting

Dry gas seals are an advanced sealing technology that comes standard in most modern high-speed machinery such as turbo-compressors. Rather than using oil as a sealing medium, a dry gas seal creates a gas barrier using the process gas or, in other cases, an external support gas such as nitrogen. The seal gas is kept at a higher pressure than the process gas, effectively closing off the system to prevent leaks.

A notable aspect of dry gas seal technology is the lack of contact between sealing faces. Whereas wet seals depend on oil as a lubricant, dry gas seal faces are contactless and do not touch during operation.

How does this happen? Engineered microgrooves on the face of a dry gas seal’s rings create an aerodynamic effect that forces a gap that’s several microns wide between the seal’s stationary and rotating faces. This contactless operation means the seal experiences minimal friction, resulting in advantages such as reduced maintenance and extended lifespan when compared to an oil seal.

Emissions reduction policies increasingly support technologies like dry gas seals that promote energy efficiency. As the world works to meet net zero goals, retrofitting compressor seals offers a straightforward path toward meeting energy-use standards.

Environmental and Sustainability Benefits of Seal Retrofits

The advantages of contactless seals are significant enough that a wet-to-dry gas seal retrofit can support tangible operational and environmental benefits for many compressor operators. The increase in process reliability is unquestionable; dry gas seals are mainly comprised of static components, which makes for simple, less frequent maintenance.

Wet oil seals are designed for an approximately five-year lifespan, whereas dry gas seals can operate continuously for seven to 10 years. This duration is possible due to the minimal ring-face contact and a lack of friction, which nearly eliminates wear except for consumable components like O-rings.

A dry gas seal retrofit can increase operational uptime, but the advantages extend even further. With the right approach, a Wet-to-Dry Gas Retrofit can deliver measurable environmental and sustainability benefits.

Emissions Reduction & Environmental Sustainability

The IEA estimates that the energy sector accounts for more than 75% of total global greenhouse gas (GHG) emissions. Traditional oil seals are prone to leaking, and in many oil and gas applications fugitive methane leaks through oil seals contribute substantially to CO2 emissions. A dry gas seal can reduce these fugitive emissions by up to 95%.

Oil leakage can also come from the sealing system itself, which contributes to ecological contamination and requires cleanup. With oil seals, substantial volumes of lubricating oil are needed to replenish leaked quantities. This continually drives up operational costs.

Switching to dry gas seals improves emissions reduction through superior sealing. The retrofit removes many environmental challenges associated with oil seals, including the need to capture or treat leaked oil.

Energy Efficiency

Retrofitting improves energy efficiency as dry gas seals consume up to 80% less power than oil seals, primarily because of the contactless seal faces, which don’t experience significant friction or require oil pumping systems.

Dry gas seals also offer better operational stability thanks to their long lifespan. Industrial equipment often has energy-intensive startup and shutdown processes; contactless seals support a longer mean time between repair (MTBR) than oil seals. The power saved by having fewer maintenance-driven shutdowns and startups reduces carbon footprints.

A Real-World Retrofit Case Study

Retrofitting from oil seals to dry gas sealing technology is proven to deliver tangible sustainability gains. The impact for one operator was an impressive 97% reduction in CO2 emissions.

Read the full case study.

Ensuring Retrofitting Success

Spotting the benefits of dry gas seals may be easy, but carrying out a retrofit project is much more complex. From compatibility concerns to operational disruptions, a successful retrofit takes meticulous planning and expertise. Here are three points to consider:

  • Technical details must be current and accurate. The design of a dry gas seal depends heavily on the application, and confirming in-field dimensions and process details is critical. For example, a slight variation in gas composition may not affect operations, but it can significantly influence seal design.
  • Turnkey services could be the optimal choice. Every facility has a different level of technician skill and engineering capabilities. Engaging an internal team to execute the retrofit is appropriate for some operators, while others might decide the best path forward is hiring a turnkey service provider to handle the design, project management and installation.
  • Older compressors require seal design expertise. Modern equipment adheres mainly to standard designs; however, legacy compressors were developed with unique dimensions that can impact the feasibility of a dry gas seal retrofit. At John Crane, we established dry gas seal technology; our considerable retrofitting experience has enabled us to compile a database of modern and legacy compressor information that we can leverage for retrofitting older units.

View our nine-step guide to a successful Wet-to-Dry Gas Seal Retrofit.

John Crane’s Retrofitting and Efficiency Solutions

Transitioning from wet oil seals to dry gas sealing is a significant step toward meeting global environmental goals. Despite a retrofit's complexity, equipping a centrifugal compressor with dry gas seals supports meaningful operational and sustainability benefits — including improved reliability and emissions reductions.

Ready to enhance efficiency and curb emissions through our proven Wet-to-Dry Gas Retrofit service? Contact the retrofitting experts at John Crane.

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