Seal Manufacturers Research Articles

Discussion on Structural Design of O-Ring Seal Used in Aviation 28MPa Hydraulic System

Most of China's newly developed fighters are equipped with 28MPa hydraulic system rather than previous 21MPa hydraulic system since introduction of Russian S27 fighter production line. However, there is no truly applicable design standard guiding the sealing design of 28MPa hydraulic products in aviation applications although 28MPa hydraulic system has been applied in China's fielded fighters for quite a long time. In this article, the sealing standards both abroad and home and the sealing materials used by world-famous seal manufacturers are respectively investigated. In addition, calculation methods and allowable limits are recommended for the tensile and compression rate used in design calculation for sealing structure. All these recommended values can be referenced by sealing design engineers before China's high pressure sealing design standards are implemented.

Polyurethane for Special Sealing Applications and a Comparison to Rubber

Polyurethane materials have been known for decades. More recently thermoplastic polyurethanes (TPUs) have been introduced. These materials represent an alternative to either conventional thermoplastics or rubber, depending on the hardness. TPUs have a substantially higher tear propagation resistance and abrasion resistance than rubber, but for a long time they remained very vulnerable to hydrolysis and had poor compression set. Recent developments by raw material manufacturers have significantly improved the hydrolysis resistance. However, as sealing applications also require very good compression set values, the greatest improvements in this area have been achieved by the major seal manufacturers who synthesise their own polyurethane. TPUs are clearly the sealing material of choice for applications in hydraulics systems and are increasingly taking over from rubber. Recent developments have succeeded in obtaining excellent low-temperature flexibility combined with good compression set at high temperatures. For special sealing applications in the food sector, however, good hydrolysis resistance is no longer sufficient in itself. A new range of materials developed for this sector offers resistance to CIP/SIP media that is even better than that of many conventional elastomers.

High Performance and Speciality Elastomers 2007

One of the major application areas for high performance elastomers is to manufacture seals and so it was no surprise that there was plenty of interest from seal manufacturers at the High Performance and Speciality Elastomers 2007 conference in Frankfurt on 5-6 December.

Modelling and optimization of rotary vane seals

The present study deals with the formulation of the mechanics and elastohydrodynamics, and performance of composite vane seals of rectangular cross-section and goalpost shape, such as those used in rotary vane actuators in aviation, automotive, and industrial applications. After constructing the mathematical and computational model of such seals, results are obtained for an application involving a rotary vane actuator for aircraft wing control surfaces. Examples are presented for both steady-state and transient conditions (steady and unsteady motion). These are followed by an extensive parametric study to establish the effects of various parameters on sealing performance, such as the effects of the seal interferences, sealed pressure, speed, design clearances, operating temperature, and the degree of lubricant starvation. Sealing performance is assessed on the grounds of the mass leakage rate, hydrodynamic friction force and extrusion size during operation. The parametric study resulted in the construction of 144 diagrams with 432 performance curves in total. Based on this, the design and operational sealing parameters were optimized to maximize sealing performance, that is, to minimize leakage, friction, and extrusion. There was an excellent agreement between the theoretically derived optimum values and those recommended semi-empirically by the seal and actuator manufacturers as initial estimates. The parametric study showed that vane seals are objects of complex mechanical behaviour, requiring attention to details in their design and application, not only to maximize performance, but, primarily, to establish sufficient sealing and avoid premature failure that could prove very costly indeed.

Seminar provides an update on mechanical seals

The Chairman John Middleton assembled an impressive range of presenters for the seminar on Mechanical Sealing Technology held at the Institution of Mechanical Engineers HQ in London, UK, on 18 April 2007. The papers were neatly grouped into subject areas of legislation, reliability, liquid seals and gas seals. A very healthy attendance of nearly 90 delegates came from a broad range of interested parties including seal manufacturers, pump suppliers, contractors and plant operators.

Effects of Geometry on Brush Seal Pressure and Flow Fields—Part I: Front Plate Configurations

Pressure and flow fields lay at the basis of such common phenomena affecting brush seal performance as bristle flutter, blow-down, hang-up, hysteresis, pressure stiffening, wear, and leakage. Over the past two decades of brush seal evolution, manufacturers and researchers have applied many geometric configurations to the front and backing plates of a standard brush seal in order to control the flow field and consequent seal performance. The number of studies evaluating the effect of geometric configurations on the brush seal flow field remains limited in spite of the high number of filed patent disclosures. This study presents a numerical analysis of brush seal pressure and flow fields with regard to common conceptual front plate configurations. A CFD model has been employed to calculate pressure and flow fields in the seal domain. The model incorporates a bulk porous medium approach for the bristle pack. The effectiveness of various conceptual geometries has been outlined in terms of flow field formation. Results disclose unique effects of geometry on pressure and flow fields such that a longer front plate drives outward radial flow while playing a protective role against upstream cavity disturbances. Findings also indicate that variations in front plate geometry do not directly affect leakage performance. A long front plate or damper shim considerably changes the flow field while at the same time having limited effect on the pressure field. Moreover, a strong suction towards the clearance enhances inward radial flow in clearance operation.

High-pressure gas testing of elastomer seals and a practical approach to designing for explosive decompression service

Laboratory Explosive Decompression (ED) tests are now widely used to evaluate the performance of elastomer seals in high-pressure gas applications. These include four test protocols in common use, as well as project-specific test regimes and screening tests used by seal manufacturers. However, the complex interaction between the chemistry of elastomer compounds and their environment, and the influences of physical factors such as housing and seal design, suggests that the use of these ED tests to predict the performance of seals in field applications is not straightforward. This article discusses the variability in results obtained from tests and the influence of test parameters. Practical measures that can be taken to reduce the risk or severity of ED damage are discussed, along with recent developments in computer modeling.

Pumps: mechanical seal or magnetic drive?

Reviews recent advances in shaft sealing technology, aimed at reducing maintenance cost by improving reliability. Looks in detail at the evolution of the conical seal housing and the magnetic drive. Reports on a research programme initiated three years ago involving user representatives, mechanical seal manufacturers, pump manufacturers and the British Hydrodynamics Research Group. As a result, five different seal designs were tested. Concludes that magnetic drive pumps are very reliable and that ultimately the use of a mechanical seal or a magnetic drive rests with the user in discussion with the pump manufacturer.

Meeting emission legislation requirements with today's advanced technology mechanical seal systems

Seal manufacturers have responded to market and legislative pressure by developing extremely low emission seals. Increased life of 3+ years has been reliably attained with low emission single seals and dual seals These results have been obtained through the use of improved designs, high quality face materials, attention to manufacturing and assembly details, and enhanced seal chamber environment. These advances in seal technology go hand in hand with improved installation, maintenance and operating procedures, to enable reductions in fugitive emissions, and hence substantial savings for the operator.

Long term oil‐seal embrittlement

AbstractThe effect of antioxidant concentration in mineral oil on polychloroprene rubber vulcanizate, based on different types of carbon black, has been studied. This study shows that, with the increase of antioxidant, the percentage volume swelling of the rubber increases, the hardness of the rubber decreases, and the embrittlement time is prolonged. The properties achieved are important for oil seal manufacturers.