EagleBurgmann´s innovative CobaSeal – the next level of separation seal

Reliability has a name – the CobaSeal. This separation seal from EagleBurgmann has proven its reliability and robustness already for over 10 years worldwide in many first fit and retrofit applications.  

Market statistics show that one out of every five dry gas seal failures are the result of contamination with bearing oil. Such failures lead to unplanned compressor shutdown with lost productivity and high maintenance costs.  This issue is common within the O&G industry and to eliminate this problem, EagleBurgmann, a leading specialist in mechanical sealing technology, brought the CobaSeal to the market. A product that represents a significant advancement in separation seal technology. Developed with a focus on reliability and efficiency the CobaSeal offers a range of benefits over the limitations found in the use of traditional separation seal solutions. These, while adequate, had shortcomings, such as failing to prevent transfer of bearing oil across the separation seals leading to contamination of the main Dry Gas Seal. Hence the market need for a more robust solution that could deliver consistent reliability on all operating conditions, and thus the CobaSeal was born. 

The CobaSeal is a co-axial separation seal that is designed and operates to the same principles of a Dry Gas Seal and replaces the existing commonly used segmented carbon ring separation seals and separation labyrinths. It consists of a rotating ring made of stainless steel and a stationary face from silicon carbide. To achieve the additional robustness, both sliding faces are coated with special EagleBurgmann high performance DLC (in situ diamond-like carbon).  

The seal operates by injecting clean Nitrogen or air into the sealing gap between the faces through axial bores into the center of the stationary seal face. It then divides into two flows directed towards both the inner as well as outer edge of the sealing rings, thereby ensuring separation between the rotary and stationary seal faces during dynamic and standstill condition, by the creation of a stiff gas film. The seal has an aerostatic liftoff design, which separates the rotating and stationary seal faces as soon as the CobaSeal is pressurized and leads to a wear-free operation with extremely low leakage. This co-axial design addresses many of the problems commonly associated with traditional carbon ring seals. The gas film protects the sliding faces in all operating modes that occur during operation of a compressor connected to a major gas delivery network, such as “slow roll”, “turning gear” and “coast down”. Furthermore, vibrations at the compressor shaft that are a cause of failure to the previous segmented carbon ring separation seal, are now compensated reliably by the introduction of the CobaSeal. 

With its unique coaxial design, the CobaSeal will also have a much longer service life because it helps ensuring that the sealing rings are non-contacting and therefore non-wearing in all operating conditions. 

A CobaSeal provides the lowest process gas leakage to bearing housing in case of main Dry Gas Seal failure. The CobaSeal can improve the safety of double seals and act together with the second seal of the double seal as tandem seal. The same for single seals – with a CobaSeal it can be transformed to a tandem backup seal. This solution is in operation in numerous applications helping to reduce axial length, very advantageous especially in overhang designs or enables upgrades from oil lubricated mechanical seals to tandem Dry Gas Seals without the need to drill additional holes into compressor housing.  

With EagleBurgmann unique 3D gas groove technology is a key feature ensuring this separation seal has extremely low leakage. By utilizing such technology, along with manufacturing technology that permits to have very narrow gap between the two seal faces, consumption of separation seal gas can be reduced by up to 90-95% compared to conventional separation seals such as labyrinths or segmented carbon ring seals. Additional benefits for this innovative seal design, due to the very small coaxial sealing gap, oil tightness is ensured even if the plant suffers a short time loss of the nitrogen barrier.  

Retrofitting is not only worthwhile for reasons of reliability, but also to permanently reduce the need for nitrogen as a separation gas and thus reduce ongoing operating costs. Compared to other separation seal designs, this reduction in nitrogen consumption, leads to an overall higher economic efficiency = reliability increasing compressor availability and extended maintenance intervals. Previously, maintenance work on the nitrogen gas supply system for the separation seal inevitably meant End-Users shutting down the compressor, due to the seal’s high nitrogen consumption of traditional seals. With the CobaSeal, this has changed. The vastly reduced nitrogen consumption ensures seal and compressor can continue operation while the system is serviced. 

Security of compressor operation for fatal Dry Gas Seal failures can be increased by avoiding process gas migration into the bearing oil system and can help overcome lately detected security gaps by vent studies, which are performed more and more often in accordance to API692 for brownfield applications. 

The CobaSeal separation seal is available for shaft diameters up to 355 mm (13.9 in) and has been successfully tested to normal operating conditions as well as to high pressure secondary vent damage events. It can be operated in applications within temperature range of -20°C (-4°F) to +200°C (392°F) with vent design pressure of 10bar (145PSI) as standard with sliding velocity up to 150m/s (492ft/s) and with no dew point limitation of separation gas (silicon carbide seal face instead of carbon). Of course, project specific designs are possible. 

The special material combination for the stationary seat and seal face also allows operation with ultra-dry nitrogen. The sealing rings are non-contacting in every operating condition and thus non-wearing, so that maintenance intervals of the system can be extended accordingly. Special settings are not necessary for operating conditions at extremely low speeds (slow-roll or turning) or when the compressor slows down (coast-down).  

It is suitable for compressors in any plant in the oil and gas industry, such as refineries, liquefied natural gas (LNG), petrochemical plants and natural gas pipeline stations, the product has been qualified and certified from most major compressor manufacturers. 

The first CobaSeal from EagleBurgmann was commissioned in the field in 2011, to retrofit of a traditional segmented carbon ring seal, which was failing to protect the bearing oil from entering the Dry Gas Seal, resulting in seal changes every 18-24 months. That first installed seal has operated successfully for over 10 years operation without any issues, reduced Nitrogen consumption, and reduced maintenance costs. 

About EagleBurgmann (Thailand) Co.,Ltd.

EagleBurgmann (Thailand) Co.,Ltd. was founded on  8th August 1997 with the vision of recognizing the significant demand in the mechanical seals market in Thailand. Our products are designed to meet the diverse needs of various industrial applications, including Oil & Gas, Petrochemical, Chemical, Food & beverage as well as general industries. We are committed to providing high-quality and reliable mechanical seals that enhance the efficiency and safety of industrial operations to the customers in Thailand market.   

EagleBurgmann is the leading provider of industrial sealing technology worldwide. Our products and comprehensive services are used wherever the key requirements are reliability and safety. 

Our portfolio includes mechanical seals and seal supply systems, magnetic couplings, carbon floating ring seals, expansion joints and gaskets, packings, special products and extensive services. Being part of the German Freudenberg and Japanese EKK group gives us all the resources we need for a reliable partnership built on solid foundations. Worldwide. 

Sealing technology from EagleBurgmann demonstrates every day exactly what reliability, safety and maximum cost-effectiveness really mean. EagleBurgmann with more than 30 years of presence in the Thailand Industrial sector is here to offer world class sealing technology solutions backed up by on-demand local service for its esteemed customers. 

Author

Sylvia Hörndl-Seestaller

Sylvia Hörndl-Seestaller is the Product Manager of Compressor Seals for EagleBurgmann, Germany with more than 17 years of experience in the Dry Gas Seal industry. 

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