From wet to dry: How mechanical seal retrofits drive operational savings and emissions reduction

Natural gas pipeline operators face mounting pressure to curb methane emissions while improving equipment efficiency and reliability. Compressors, essential to keeping gas flowing across vast transmission networks, are among the largest contributors to process gas leakage when fitted with traditional wet seal systems. Each cubic foot of gas lost to venting represents a financial cost and a missed opportunity to advance toward environmental and regulatory goals.

By replacing ageing wet seals with dry gas seal technology, operators can achieve measurable performance gains across multiple fronts: reduced methane emissions, lower energy consumption, simplified maintenance and extended mean time between repair (MTBR).

The retrofit opportunity: wet vs dry mechanical seal technology

For decades, oil-lubricated wet seals have been a mainstay in centrifugal compressor design. While they provide effective sealing, they also carry operational and environmental drawbacks.

Limitations of wet seals include:

• Continuous venting of process gas, up to 100 standard cubic feet per minute (scfm), to prevent oil ingress into the compressor
• High operating and maintenance costs due to complex seal oil systems
• Oil degradation caused by process gas contamination

By contrast, dry gas seals operate without oil lubrication. A thin, stabilised gas film between the rotating and stationary faces provides sealing and lubrication, allowing the compressor to run cleanly and efficiently.

Key advantages of retrofitting to dry gas seals:

• Lower gas losses: The face gap in dry gas seals is about 0.003 mm, compared with labyrinth clearances of up to 0.76 mm in wet seals, allowing the majority of gas to re-enter the compressor instead of venting to the atmosphere.
• Reduced power consumption: Elimination of seal oil systems removes energy-intensive pumps, heaters and coolers, lowers auxiliary power requirements. The reduced seal lubricant viscosity reduces the compressor driver power consumption.
• Extended maintenance intervals: Without oil degradation or fouling, dry gas seals can extend mean time between repair (MTBR) from three to seven years.
• Enhanced safety and reliability: Simplified systems result in fewer potential failure points and help eliminate the risk of oil leaks contaminating process gas.

Case study spotlight: seal retrofitting for efficiency and emissions reduction

A natural gas pipeline station in Louisiana, U.S, operating along the corridor between the Gulf Coast and the Midwest, faced mounting operational costs and emissions from wet seal leakage. Methane venting reached roughly 100 scfm per compressor, representing both product loss and direct Scope 1 emissions. Seeking measurable reductions in emissions, the operator needed a solution that would also improve compressor reliability and energy efficiency, while meeting a tight turnaround and budget window.

Implementing a retrofit for lasting efficiency

John Crane replaced the existing wet seals with Type 28XP non-contacting dry gas seals, a proven solution for natural gas applications. The retrofit included:

• Decommissioning the existing seal oil console
• Installing a new gas conditioning unit
• Adding a dry gas seal control and monitoring console to support continuous, reliable operation

Quantifying the impact

• Estimated annual savings of $332,000 in operational costs and energy efficiency gains
• Methane emissions reduction from eliminating continuous venting associated with wet seals
• Extended MTBR from three to seven years, lowering maintenance frequency and associated costs
• On-time delivery of retrofit and commissioning, and completed in nearly half the originally projected timeframe

This case underscores how well-planned retrofits can simultaneously enhance performance, reduce emissions and lower the total cost of ownership for compressor operators.

Three operational efficiency gains delivered by dry gas mechanical seals

Seal retrofits offer a direct path to improved efficiency across multiple areas of compressor operation.

1. Reduced process gas loss

In a wet seal system, large labyrinth clearances allow process gas to escape continuously to a flare or vent. In a dry gas seal system, the gap is microscopic, allowing most of the gas to return to the process rather than being lost to the atmosphere. This recaptured gas translates into improved yield and reduces environmental impact.

2. Lower energy consumption

Removing oil systems eliminates energy-intensive components, including:

• Seal oil pumps
• Electric or steam-driven heaters
• Cooling systems and degassing tanks

The lower viscosity of the gas lubricating dry gas seals compared to liquid lubricants in wet seals results in reduced power consumption or the seals themselves and a savings in compressor driver power consumption.

These reductions in auxiliary and compressor driver power demands contribute to measurable savings in both Scope 1 and Scope 2 emissions.

3. Simplified maintenance

Oil systems require constant monitoring to manage viscosity, contamination and leaks. By eliminating oil, operators reduce:

• Downtime due to fouled filters and degraded oil
• Labour and material costs related to oil replacement
• Risk of unplanned shutdowns from oil contamination

Together, these efficiencies extend system uptime, allowing maintenance teams to focus on higher-value tasks.

Emissions reduction: supporting decarbonisation goals

Transitioning from wet to dry gas seals directly supports industry decarbonisation targets. Methane is a potent greenhouse gas, and even small reductions in leakage deliver significant climate benefits.

Emission-reducing impacts of dry gas seal retrofits include:

• Elimination of continuous methane venting from wet seals
• Reduced energy demand from seal oil systems, cutting indirect emissions
• Prevention of oil-related fugitive emissions and flaring events

In the Louisiana retrofit, eliminating wet seals substantially decreased Scope 1 emissions associated with direct gas leakage and Scope 2 emissions linked to compressor and oil system energy consumption.

For operators working toward methane intensity targets or regulatory compliance, these retrofits represent one of the most immediate and effective steps available to achieve their goals.

Broader implications for industry

As natural gas infrastructure continues to modernise, retrofit strategies play a crucial role in balancing operational performance with sustainability. Upgrading existing compressors extends asset life while aligning with net zero roadmaps to avoid the cost and disruption of full equipment replacement.

John Crane Performance Plus™ modular service framework offers a structured approach to these transitions through its Upgrades and Retrofits service pillar. This framework ensures:

• Compatibility with legacy equipment
• Tailored seal selection for pressure, gas composition and duty cycle
• Integration planning that minimises downtime
• Expert commissioning and long-term support

Beyond technical execution, this service model reflects a holistic commitment to operational excellence, delivering measurable results in performance, cost and environmental impact.

Driving the future of cleaner compression through expert services

Retrofitting from wet to dry gas seals is one of the most effective ways for natural gas operators to reduce methane emissions, lower energy consumption, and extend compressor life - all while improving reliability and reducing the total cost of ownership. Supported by John Crane Performance Plus™ modular service framework, these upgrades can help ensure long-term value and measurable progress toward a more sustainable energy future.

For more information on how John Crane recommended replacing the wet sealing technology used by the compressor with dry seal technology by installing Type 28XP non-contacting dry gas seals, which was able to meet expectations in terms of methane emission reduction and significantly lower OPEX costs compared to the existing wet seals, read our case study.

Find out how John Crane Performance Plus™ can support your business.