| dc.description.abstract | Technical Brief 2: Mechanical seals are used in a wide range of industrial applications, sealing gases in a compressor or sealing liquids in a pump. Reliability, longevity, emission control and safety are now more important than ever. This purpose sounds simple, but designing mechanical seal components and selecting the most appropriate materials is a real challenge, especially when sealing fluids under harsh operating conditions. This paper describes two applications using a unique sealing solution, an engineered seal design and a specific sliding face diamond material. In the first case, the end-user in Venezuela is using Multiphase Pumping Technology to transfer a mixture of crude oil and gas in a single pipeline without separation. The installed seals have to handle a mixture of crude oil, formation water, solids and natural gas. Previously, no mechanical seals were available for such conditions and consequently engineered seals have been developed for this purpose. The pumped fluid does not provide the required stable liquid lubrication film for their mechanical seal faces. Another challenge is the presence of abrasive particles. So the selection of the seal face materials is important. Extremely robust face materials are required to avoid unacceptable deformations and to minimize abrasive wear which may result in a mechanical seal failure. Multiple seal arrangements available today can handle multiphase fluids, using hard/hard face materials in combination with a complex auxiliary/flush system, but have only limited capabilities with regard to poor lubrication and necessary cooling, when handling crude oil with high viscosity and natural gas. In this specific application described in this paper, a sophisticated Single Mechanical Seal has been used successfully over many years. However, due to changing oil well conditions, the lifetime of their mechanical seals was reduced dramatically. To solve this problem, a slurry seal design in combination with the diamond seal face material, well-known for its ultimate hardness, was installed. Seal faces with diamond surfaces offer outstanding abrasive resistance due to their unique hardness similar to natural stone and, at the same time provide considerably improved dry running performance due to their low friction coefficient. In the second case, the end-user in Brazil is using High Pressure Pipeline Pumps for the transportation of the heavy crude oil. In case of high pressures, high speed and abrasive particles, which is typical in crude oil applications, their mechanical seals need special attention. Extremely hard and strong face materials are required to avoid unacceptable deformations and to minimise abrasive wear which may result in high leakage. State of the art hard/hard face material combinations cannot handle crude oil with high viscosity and have limited capabilities with regard to poor lubrication associated with the necessary cooling. In both applications, in a multiphase twin screw pump and in a centrifugal pipeline pump, engineered mechanical seals with diamond seal face material solved the problem and are used successfully since the start-up of the pumps. This new sealing technology offers significant benefits to the end-user. | en |
