The Sannazzaro de' Burgondi refinery is located in northern Italy, approximately 31 miles (50 km) to the south of Milan. It was commissioned in 1963 and belongs to ENI, the crude oil and energy group. Investments in sustainable technical expansions and innovations were made over the years, and the daily processing capacity increased to over 180,000 barrels of crude oil. Approximately 45 different refinery products are produced and supplied primarily to the northwest of Italy and to Switzerland. Due to its efficiency, flexibility and high environmental standards, the refinery is a valuable company in the portfolio of the end user, the ENI Refining & Marketing Division.
The Challenges: High Process Temperatures, High Solids Content of the Medium
Changed process conditions in one sector of the plant some time ago resulted in the notably changed behavior of an installed Nuovo Pignone refinery pump. The mechanical seals originally installed by a competitor quickly reached the limits of their performance.
This was caused by high temperatures in conjunction with the solids-contaminated medium that was inclined to carbonize. The sliding faces of the shrink-fit seal faces and stationary seats of the seals deformed. Together with the carbonized deposits at the atmosphere side of the seal, this caused an instable sealing gap, or hanging up of the seal, with immense leakage as the consequence.
As a result, the seals exhibited an extremely unsatisfactory MTBF (Mean Time Between Failure) value of just four weeks and posed a high risk to the environment and the plant personnel due to the discharged leakages.
The end user took this as an opportunity to contract EagleBurgmann with a safe and permanent sealing solution.
Suction pressure: 44 PSI (3 bar)
Outlet pressure: 119 PSI (8.2 bar)
Temperature: 538 ˚F (281 °C)
Speed of rotation: 1,470 min-1
Medium: Hydrocarbons with hard solids content
The specification sheet contained a number of challenges: Despite the problematic composition of the media and difficult operating conditions, only a single mechanical seal could be installed. The cramped conditions at the set-up site of the pump did not allow for operation of a dual seal with a buffer/barrier fluid system as per API Plan 53 or Plan 52.
The new single seal therefore needed to be equipped with the safety of a double seal. Also, in the event of a failure, there was to be absolutely no leakage to the atmosphere.
Extremely Tough: The EagleBurgmann Sealing Solution
EagleBurgmann was able to provide a convincing solution that satisfied all aspects of the customer’s requirements. A MFLWTI metal bellows seal with diamond coating and an integrated API Plan 66A in the seal cartridge.
The key element of the MFLWTI is the loosely inserted seal face combined with the DiamondFace diamond coating of the sliding faces. Even the choice of material for the seal face highlights its flexibility: the inserted ring offers more options in this respect than shrink-fit seal faces. It also impresses with its positive deformation behavior in operation and, as it is able to move, it will not tilt or cant. The diamond coating makes the seal immune to dry running and solids in the medium.
EagleBurgmann DiamondFace has already proven its worth in numerous applications in the oil and gas industry, refining and power plant technology, for example. Minimal friction, practically no wear and maximum chemical resistance - with the DF coating from EagleBurgmann, previously unachievable operating periods and MTBR or MTBF intervals are now possible, even under the most difficult conditions.
Maximum Safety: Plan 66A Integrated in Seal Housing
Integrating safety into the seal housing guarantees the operation of the seal with a combination of API plans, especially API Plan 66A. It has been available since the publication of the API 682 4th edition and principally includes two throttles on the atmosphere side and one pressure transmitter.
In the event of sudden seal failure, the inner floating bushing is capable of withstanding the entire product pressure. At the same time, the pressure change in the space between the bushings triggers an alarm while the minimized low pressure leakage is conducted away over a safe collection system in specific accordance with Plan 65. On the product side, the seal is supplied with steam quench in accordance with Plan 62, condensed leakages are conducted away also in accordance with Plan 65. These measures achieve maximum operating safety.
Successful Retrofit: The EagleBurgmann Solution in Operation
The Nuovo Pignone pump was equipped with the EagleBurgmann solution and put into operation in October 2015. Since then, the DF-MFLWTI has been running reliably in all operating states with constant sealing performance and without complaint or interruptions. System availability increased significantly. The application of the modified Plan 66A enormously increased the safety of the personnel and of the environment.
Sealing systems with modified Plan 66 are technically "state-of-the-art" and are now being successfully deployed by EagleBurgmann in other applications, such as the EagleBurgmann mechanical seal SHVI in high pressure crude oil pumps. This is also equipped with loosely inserted seal faces and has been running for several thousand operating hours already.
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