Fluiten Italia supplies Mechanical Seals to an important multinational company, leader in the production of additives for high performance synthetic oils. The collaboration was born over 20 years ago, with the aim of improving the performance of the Mechanical Seals installed into the plant, implementing technical support and assistance, too.
The replacement process, which took place in about two years on the centrifugal and volumetric pumps for transferring the various liquids, was done just before the installation of Fluiten Mechanical Seals also on the mixers, where the critical production phases take place. Over the years, the process has required sealing systems more suited to variations in production processes, necessary to follow market demand: this led to an increase in operating limits, in addition to adapting to safety standards and last, but not least, to control emissions to the atmosphere.
Production of additives for synthetic oils
The frictions that are generated by moving mechanical elements produce heat and wear. With adequate lubrication, friction and wear are reduced, improving mechanical performance. Lubricants are various and their properties are chosen according to the final destination of the product; the use of a specific lubricant instead of another intended for different purposes can therefore be extremely harmful (i.e., gear oil instead of engine oil).
The lubricants are all derived from a base (usually around 90%) which can be mineral, vegetable or synthetic, to which other substances are added, called additives (about 10%). If the raw materials that make up the bases were used alone, for example in internal combustion engines, this would cause overheating and in a short time they would catch fire, evaporate or emulsify, bringing the moving surfaces into contact.
Additives avoid these problems by stabilizing the characteristics of the lubricant. The production of mineral or synthetic oil originated by crude oil, from whose distillation it is possible to obtain oils with different viscosity; through other processes the chemical-physical properties are changed in relation to the specific use.
It is surprising to know that not all raw mate- rials are suitable to produce lubricants, in fact only about 1.5% of the world refineries production can be used as a base. The mixing process is crucial: modern mixing plants are automatic and controlled, most of the times including equipped laboratories for quality control, where chemical-physical analysis are carried out and the main characteristics are verified: humidity, impurities, specific weight, viscosity, color, acidity, freezing point, flash point, demulsibility and more.
“Case History” – Seal group for additive mixer
The development of a new sealing solution, to be adapt to the new operating conditions on an existing plant mixer, on which a Fluiten Mechanical Seal was installed since 1991, is the solution to be proposed for similar applications. Following the change in operating conditions and the end customer’s need to increase production levels, a new solution was requested, with the aim of increasing reliability and reducing intervention times due to unscheduled maintenance. The analysis carried out by Fluiten technicians has highlighted the main problem causing premature failure was the crystals deposition inside the sealing surfaces on the product side.
The double seal in back-to-back execution originally fitted is the most common selection in mixers and reactors applications with top entry, where the seal is normally in contact with the process vapours. If the process liquid tends to crystallize, is viscous or contains a high percentage of solids, these are deposited in front of the product-side rotating gasket and prevent it from moving, inhibiting the necessary elasticity that the seal must maintain to tolerate the angular movements of the shaft which, especially in vertical mixers, may be present.
When the rotating ring is not free to move on the shaft sleeve and the shaft undergoes a radial thrust due to the process, the sealing surfaces open and cause the unwanted and continuous leakage of the barrier oil, forcing to stop the equipment.
Disassembling and repairing a seal installed in a vertical mixer with a shaft 180 mm and a tank over 6 meters high can be really difficult, in some cases requiring using a crane or assembling a scaffold around the tank, with average times for disassembly, repairing, reassembly and commissioning of about 2 working days.
IMG. BACK TO BACK solution with process inside the sealing surfaces.
FOCUS TC type seal
The design of the TC type seal allows the process to be outside the sliding surfaces and not inside, like the case for the double back-to-back configuration. The rotating ring is fitted to the shaft sleeve and the stationary ring to the seal gland.
The springs are outside the process and work on the stationary ring, remaining in a clean area.
Fluiten GTA15188 – consisting of TC-BL3X
The Fluiten Seal GTA15188, with overall dimensions 100% interchangeable with the previously installed Fluiten Mechanical Seal, is the seal type TC 200 (shaft diameter 180 mm) on the product side; with this solution a proper elasticity is guaranteed, even if the product tends to crystallize in the upper part of the tank.
The outer seal is a BL3X210 type, balanced and able to tolerate the pressurization given by the barrier liquid, which in this application is close to 10 bar (the closing force on the sealing surfaces is about 650 kgf). GTA15188 is pre-assembled with an oscillating roller bearing to tolerate the radial thrusts coming from the shaft and minimize run-out. This simplifies assembly operations, avoiding possible errors in seal positioning.
Another parameter that has changed over time is the temperature, which was increased; this increase must be taken into strong consideration, since the double seal lubrication is guaranteed by an external pressurized reservoir (Plan 53A), which has a cooling coil integrated in it. The calculation of the heat exchange must consider the temperature that the process transfers to the seal through the shaft and the tank surface (heat soak), but also by the temperature generated by the sealing surfaces, with their diameter of 200 mm and a pressurization level of about 10 bar.
To remove the heat generated and keep the temperature of the barrier oil below a safety threshold, needed for proper seal faces lubrication, a circulating pump was selected and then installed. The selection of sintered silicon carbide for seal rings and elastomers according to the process guarantees excellent resistance to chemical aggression.
The reduction in maintenance costs associated with interventions on the seals in the plant have been reduced by 30% in 5 years.
Goal was reached!
The seal works with the customer satisfaction, for relable and safe operations, having maintenance carried out according to scheduled production stops.
The analysis made by Fluiten on seals that have worked, shows that there is no evidence of wear, allowing standard maintenance operations, to have seals repaired and ready for another succesful work cycle.
Who produces lubricating oils?
The main Oil and Gas companies produce or have their own branded lubricants: Eni, Shell, CNPC, Chevron, Exxon-Mobil, Fuchs, Kluber Lubrication, Total, Lukoil, Repsol, FCL, Rowe.
What other industries are interested in the Engineered CT Solution?
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