Mechanical seals: Reducing fugitive emissions in chemical processing

Fugitive emissions continue to be a persistent challenge for chemical and petrochemical operators, driven by tightening regulations and increasingly stringent operating conditions. The first part of this two-part series examined how fugitive emissions are defined, the regulatory landscape that governs them and the specific challenges facing modern chemical and petrochemical industries.

The second part examines the mechanical seals, seal support systems and digital monitoring technologies that help mitigate the issue of fugitive emissions.

Mechanical seals: A proven solution

Mechanical seals are used in sites throughout both industries, installed in rotating equipment such as pumps, compressors, mixers and agitators to prevent leaks at shaft interfaces.

Options include O-ring pusher seals, metal bellows seals, seals specifically for vessels and agitators, secondary containment seals and non-contacting seals. In applications requiring additional safeguards, dual-seal arrangements with buffer or barrier fluids are often specified instead of single-seal options. Therefore, many John Crane solutions are compliant with the industry best practice standards. They include the API Standard 682 (for pumps) and API Standard 692 (compressors). Both drive high seal reliability and excellent emissions control.

Fugitive emissions detection

Prevention is just one aspect of controlling greenhouse gas (GHG) emissions. John Crane also supports detecting and quantifying releases through the Asset Condition Management offering within the wider John Crane Performance Plus™ modular services framework.

As part of Asset Condition Management, we offer proactive, data-driven asset condition services that include integrated diagnostics, focused support and actionable insights for all rotating equipment. This is where digital analysis meets analogue technology.

Measuring fugitive emissions in practice

John Crane engineers and technicians use quantitative optical gas imaging cameras and imaging software to detect fugitive emissions. This technology can detect and quantify hundreds of fugitive Volatile Organic Compounds (VOCs) and hydrocarbon emissions as small as 12 grams per hour. Meanwhile, understanding what causes leaks can help prevent them from recurring.

John Crane experts undertake root cause analysis (RCA) using Motion Amplification®, a powerful troubleshooting tool. This technology visualises and amplifies subtle vibrations and movements in rotating equipment, undetectable to the eye, without the need for physical sensors. This video-based technique helps diagnose complex vibration issues by converting invisible motion into clear, visual insights.

Similarly, John Crane services support upgrades, retrofits and improvements to existing equipment, such as wet-to-dry gas seal retrofits and seal gas recovery units, through the same John Crane Performance Plus™ service solutions.

Pump seals

John Crane offers a broader range of mechanical pump seal products than any other seal manufacturer. Designed to meet international standards, including API 682, they are ideally matched to the rigours of the industry.

Seals such as the Type 5610, Type 5610V, Type 5610VP and Type 5610VQ are O-ring pusher cartridge seals. Some models offer quench options, suitable for hazardous chemical applications in centrifugal, rotary and positive displacement pumps.

Metal bellows seals

The Type 5615, 5615Q and 5615L seals are ideal for higher-temperature, corrosive and abrasive chemical environments. Similarly, the Type 4615 is an option when working with chemicals, pulp, wastewater and food processing processes.

Edge-welded metal bellows, such as the Type 670, are ideal for corrosive fluids and low-temperature duties, while the Type 515E asymmetric metal bellows seal suits biotechnology and chemical processing.

Both the Type 5600 and Type 4600 series of single-cartridge metal bellows are modular families – deploying the same design site-wide simplifies inventory and maintenance, an issue we identified for owners of larger sites.

Available in low- and high-temperature designs, dedicated emission containment seals such as the ECS, a dry-running seal for emission containment and safety/backup that successfully controls VOC and Volatile Hazardous Air Pollutant (VHAP) emissions. Similarly, the 48SC can operate in dry-running mode, with the containment chamber between the seals vented to a flare or vapour recovery system to prevent emissions from escaping.

Reducing emissions through seal design

Minimising emissions is a core design objective across the Type 2800 Series. The Type 2800EX uses spiral groove technology to maintain seal integrity on small-bore equipment, while the Type 2800XA and Type 2800XP service large-bore pumps. The Type 2800XS is designed for operation outside the normal parameters of Types 2800XA and 2800XP.

Vessel, mixer and agitator seals

These seals are essential for maintaining process integrity in mixing and agitation applications, especially in batch chemical processing.

Type 32 and CK series: engineered for reliability and safety

The Type 32 family of single, dry-running elastomer O-ring mixer and agitator seals requires neither external cooling nor lubrication equipment or a supply system, due to the self-lubricating seal faces.

Variants of the Type 32 are suitable for explosive atmospheres and are compatible with top-entry mixers. The dry-running, outside-mounted Type 32i integrates analogue build quality and reliability with digital innovation. Meanwhile, Intelli-Face®, our unique seal face technology, reduces the audible noise commonly associated with many single-contacting dry-running seal applications.

John Crane created the Type CK series of dual-pressurised cartridge seals for top-entry mixing and agitating equipment. The wet, pressurised barrier liquid version of the seal – the Type CK 725W – suits more demanding applications, converting it to a contacting dry-running seal creates the Type CK 725D. Both are ATEX-compliant and suitable for operation in potentially explosive atmospheres.

Seal support systems

Similarly, our support systems offer API compatibility and a ‘backstop’ option for safeguarding against emissions. They include reservoirs, control panels and heat exchangers that maintain seal integrity, enable safe operation and allow for early detection of seal failure to minimise environmental impact while reducing maintenance costs.

Some, such as API Plans 53, 54 and 74 completely prevent process fluid emissions to the atmosphere. For example, John Crane's PR 52/PR 53A reservoirs are compatible with API Plan 52 and API Plan 53 (A, B, C) and support unpressurised and pressurised dual seals.

Meanwhile, seal support systems aligned with API Plans 52, 72, 75 and 76 direct mechanical seal leakage to a safe handling system such as a flare or recovery system. Our PG 72 gas panels support API Plan 72, which typically uses nitrogen at low-pressure between the inner and outer seal to sweep primary seal leakage away from the containment seal towards a recovery system. This prevents fugitive emissions from escaping to the atmosphere.

Reducing emissions: Key takeaways

Just as no two chemical processing companies will be identical in terms of what they do and how they do it, there is no one-size-fits-all, industry-wide solution to preventing the escape of fugitive emissions. Nonetheless, a set of shared principles underpins effective emissions control across the industry.

• Seal selection

  Select a mechanical seal and seal support system based on the process fluid being managed, the extremes of pressure and temperature involved in the application and the type of equipment and infrastructure in situ.

• Retrofit where possible

  Revisiting older equipment with modern sealing solutions can improve performance and compliance. In addition, upgrades and retrofits can unlock new value from existing infrastructure investments, which is beneficial for both smaller and larger sites.

• Predict, don't react

  Proactive plant owners extract maximum value from planned downtime and avoid unscheduled production interruptions. Digital monitoring tools such as John Crane Sense® support predictive maintenance and enable real-time performance tracking.

• Be prepared

  Upskilling staff on seal maintenance and best practices for Leak Detection and Repair programmes increases capacity to spot issues before they become problems and helps to prevent unplanned downtime. The Training module within John Crane Performance Plus™ service framework can help.

Moving from emissions management to prevention

While companies involved in chemical processing share many challenges, no two will be identical in terms of site profile, materials managed, regulatory pressures, staffing and budget.

Mechanical seals are essential for reducing fugitive emissions in chemical processing. While the technology will be specific to the use case, mechanical seals are mission-critical components that prevent leakage between a rotating shaft and stationary parts in equipment such as pumps, compressors and agitators.

John Crane's advanced sealing technologies are supported by 100 years of engineering innovation. Looking to the future, we have a solid track record of supporting both large and small chemical plants in achieving compliance and meeting sustainability targets as the focus shifts to new energy sources. For example, our operating CCUS facilities constitute about 50% of the world's CCUS sites.

Meanwhile, our solutions for detection, mitigation and prevention support efforts to reduce emissions. Custom packages of emissions detection, root cause analysis, seals and seal support systems also support improved reliability – a business essential today and in the future. To learn more, contact us today.