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A stochastic model of the wear process of a shaft lip seal that takes into account random changes in the temperature and external load is described. The results of a numerical analysis of the process of seal wear in relation to the conditions of operation in open space at near-Earth orbital stations are presented. The importance of taking into account random changes in temperature and external load for predicting the seal durability is evaluated. [ABSTRACT FROM AUTHOR]

No matter the scale, stirred tank bioreactors are the most commonly used systems in biotechnological production processes. Single-use and reusable systems are supplied by several manufacturers. The type, size, and number of impellers used in these systems have a significant influence on the characteristics and designs of bioreactors. Depending on the desired application, classic shaft-driven systems, bearing-mounted drives, or stirring elements that levitate freely in the vessel may be employed. In systems with drive shafts, process hygiene requirements also affect the type of seal used. For sensitive processes with high hygienic requirements, magnetic-driven stirring systems, which have been the focus of much research in recent years, are recommended. This review provides the reader with an overview of the most common agitation and seal types implemented in stirred bioreactor systems, highlights their advantages and disadvantages, and explains their possible fields of application. Special attention is paid to the development of magnetically driven agitators, which are widely used in reusable systems and are also becoming more and more important in their single-use counterparts. Key Points • Basic design of the most frequently used bioreactor type: the stirred tank bioreactor • Differences in most common seal types in stirred systems and fields of application • Comprehensive overview of commercially available bioreactor seal types • Increased use of magnetically driven agitation systems in single-use bioreactors [ABSTRACT FROM AUTHOR]

The pressure between a shaft and a reinforced rubber cuff (a lip seal) is considered. An algorithm is derived for calculating the contact pressure, taking account of the properties of the material, the thickness of the cuff's active section, its inclination to the shaft, the spring's tensile force, and the geometric parameters of the cuff's free section. [ABSTRACT FROM AUTHOR]

In this study, a test system is developed in order to determine the effect of interference on the lifetime of the sealing element. A set of experiments are carried out with thermoplastic polyurethane radial lip seals with three different inner diameters varied by lip surface tolerance (40, 39.80 and 39.60 mm), and EP gear oil is used as lubricant. In order to determine the lifecycle of the sealing element, mass of the leaking oil is measured. Meanwhile, in order to determine the frictional performance of the sealing element, four load cells are mounted on the cylindrical housing of the system and frictional force values are monitored by a data acquisition terminal and frictional torque values are calculated. As a result, the frictional moment values of the seals increased with the increase in interference. Moreover, the increase in interference leads to a longer service life. [ABSTRACT FROM AUTHOR]

The radial force is a critical factor to determine the sealing performance of radial lip seals. The effects of radial force produced by garter spring and interference on the static contact properties and sealing performance of a radial lip seal are investigated by numerical simulations and experiments. Finite-element analysis and mixed elastohydrodynamic lubrication simulation are used. Radial force, contact width, temperature in the sealing zone, the reverse pumping rate and friction torque are measured. A critical value of interference for a cost-effectively designed radial lip seal is found. Spring force is required to compensate the decrease of the radial force because of the interference and used as a possible way to obtain intelligent control of sealing performance. The quantitative results gotten in this study could provide guide for the seal design and improvement. [ABSTRACT FROM AUTHOR]

The feasibility of using SMA wires to improve the seal effectiveness has been studied experimentally and numerically. In this article, we present only the numerical study of simulating the thermo-mechanical behavior for an SMA enhanced lip seal, leaving the test setup and results in the experimental counterpart. A pseudo 3D SMA model, considering 1D SMA behavior in the major loading direction and elastic response in other directions, was used to capture the thermo-mechanical behavior of SMA wires. The model was then implemented into ABAQUS using the user-defined material subroutine to inherit most features of the commercial finite element package. Two-way shape memory effect was also considered since the SMA material exhibits strong two-way effects. An axisymmetric finite element model was constructed to simulate a seal mounting on a shaft and the sealing pressure was calculated for both the regular seal and the SMA enhanced seal. Finally, the result was qualitatively compared with the experimental observation. [ABSTRACT FROM AUTHOR]

A model for the effect of two-phase liquid on pump seals is developed based on vortex bursts near the surface of lip seals and the generation of sound waves in the liquid. It is experimentally found that these waves can destroy the contact surfaces of lip seals if the frequency of vortex bursts reaches the frequency of natural transverse acoustic oscillations. [ABSTRACT FROM AUTHOR]