High Pressure, High Temperature Shaft Seal For A Multiphase Subsea Pump

LectureThe paper describes a totally re-engineered mechanical seal for multiphase subsea pumps with a focus on extended metal and seal face material selection as well as more stable seal behavior, achieved with a new face concept, which provides enhanced reliability and robustness. It reports the design process, starting from the project description with definition of targets followed by a theoretical evaluation of the seal performance and a description of the final design features. Increasing demand for high pressure and high temperature (HP/HT) pumps in Subsea multiphase applications requires the development of mechanical seals designed for pressure levels up to 15 kpsi and product temperatures up to 350°F with the capability to handle reverse pressure conditions. With the high pressure requirements the application of spring-energized polymer gaskets as static and dynamic secondary seals using a specific design for enhanced reverse pressurization capability were selected. To achieve enhanced robustness of the seal faces in transient dry running condition which may occur during upset conditions (such as reverse pressure) the design was optimized to include microcrystalline diamond coated seal faces. A detailed analysis of face deformation and seal performance under load with a combined structure and fluid analysis software together with an extensive test campaign and specific cooling jacket features lead to a robust mechanical seal design with optimized pressure distribution and mechanical contact zones

Comparison of contacting wet and dry gas seals for main pipeline pumps in NGL services

TutorialsRecent incident reports and studies of pipeline equipment indicate that pump seal performance is likely at the root of a significant increase in releases to the environment. Although these releases are small compared to a breach in a pipeline, they are of great concern to pipeline companies. While crude oil and refined fluid pipelines have been around for a long time, the pumping of natural gas liquids (NGLs) such as ethane, propane, butane and various mixtures of these liquids is relatively new and presents demanding challenges for the mechanical seal manufacturer and pump OEM’s. API (American Petroleum Institute) 682, the governing mechanical seal standard for mechanical seals in hydrocarbon services, is a great foundation for the sealing of process plant equipment. However, for pipeline services API 682 is of limited use due to more demanding operating conditions as well as the different operating character of pipeline pumps. Generally, two seal face lubrication technologies can be applied to seal NGL Pipeline Pumps with dual unpressurized seals: A contacting wet lubricated mechanical seal (2CW-CS / Arrangement 2 Contacting Wet – Containment Seal) A non-contacting Dry Gas Seal (2NC-CS / Arrangement 2 Non Contacting – Containment Seal) Both sealing solutions include a high-pressure non-contacting containment seal to protect the environment. Within this paper we discuss the general design aspects for two different sealing technologies, in particular the leakage and friction behavior in NGL services. The impact of critical operating parameters like vapor pressure and temperature margin, flush flow rates, ed. In addition, the safety, leakage containment and monitoring related aspects are described, summarized and compared with the mechanical seal recommendations

First Steps of Retinal Photoisomerization in Proteorhodopsin

The early steps (<1 ns) in the photocycle of the detergent solubilized proton pump proteorhodopsin are analyzed by ultrafast spectroscopic techniques. A comparison to the first primary events in reconstituted proteorhodopsin as well as to the well known archaeal proton pump bacteriorhodopsin is given. A dynamic Stokes shift observed in fs-time-resolved fluorescence experiments allows a direct observation of early motions on the excited state potential energy surface. The initial dynamics is dominated by sequentially emerging stretching (<150 fs) and torsional (∼300 fs) modes of the retinal. The different protonation states of the primary proton acceptor Asp-97 drastically affect the reaction rate and the overall quantum efficiencies of the isomerization reactions, mainly evidenced for time scales above 1 ps. However, no major influence on the fast time scales (∼150 fs) could be seen, indicating that the movement out of the Franck-Condon region is fairly robust to electrostatic changes in the retinal binding pocket. Based on fs-time-resolved absorption and fluorescence spectra, ground and exited state contributions can be disentangled and allow to construct a reaction model that consistently explains pH-dependent effects in solubilized and reconstituted proteorhodopsin