Mechanical Sealing Research Articles

The Analysis of Twin-Screw Compressor New Liquid Film Seal Structure

Shaft seal lubricating oil leakage of the J-201 Butadiene Gas Twin-screw Compressor occurs from time to time. According to the characteristics and related theories of process medium, the mechanical seal structure and pattern of Twin-screw Compressor had improved design . Using the existing auxiliary system and keeping the existing sealing structure, the non-contact mechanical sealing of process mediumprocess mediumdouble reverse crossing-groove oil film has ‘self-cleaning function’ which was applied to the screw compressor. To analysis its application technology and performance, the problem of Butadiene Gas Twin-screw Compressor shaft seal leakage had been solved.

358 月面探査機器の隙間に侵入するルナダストの静電シールド機構

A unique shield system has been developed utilizing electrostatic force to remove dust breaking into bearings and mechanical seals of equipments used for lunar exploration. A single-phase rectangular voltage was applied to insulated parallel plate electrodes printed on a substrate at the clearance of the mechanical sealing part. Because the performance of the former system was not satisfactory at an inclined angle of 30°, we added support electrodes outside of the main electrodes so that the system with the support electrodes generates wide electrostatic field to improve the performance. As the result more than 80% of dust was repelled from the clearance, and it was predicted by the numerical calculation using the distinct element method that the cleaning performance to charged particles would be further improved in the low-gravity and vacuum environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.

J192033 機器の隙間に入り込むルナダストの静電シールド機構([J19203]ロボティクスと宇宙(3))

A unique shield system of lunar dust has been developed utilizing electrostatic force to remove dust breaking into bearings and mechanical seals of equipment used for lunar exploration. A single-phase rectangular voltage is applied to parallel plate electrodes printed on substrates at the gap of the mechanical sealing part. Approximately 60% of dust was repelled from the gap, and it was predicted by the numerical calculation using the distinct element method that the cleaning performance of the system would be further improved in the low-gravity and vacuum environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.

One-day seminar covers mechanical sealing technology

The Institution of Mechanical Engineers held a useful meeting on mechanical seals in London, UK, on 18 May.

Description of surface topography of sealing rings

A sealing ring is an important component of a mechanical sealing unit, since it influences the tightness of the joint. Investigations were conducted for rings made from five different materials, namely: ceramics Al 2 O 3 , carbon impregnated by antimony, sintered silicon carbide, chromium–molybdenum alloy and tungsten carbide. 2D and 3D measurements have been conducted on rings. All measurements have been conducted using ‘Form Talysurf 120’ roughness measuring equipment at ANGA Mechanical Seals Ltd . For all of the rings, the investigations were performed to demonstrate the effectiveness of sealing. In each case, the 2D measurements have been carried out in five equally distributed areas of the ring. The statistical analysis refers to parameters of the primary profile, roughness and waviness. The correlation analysis for 2D parameters as well as for 2D vs. 3D parameters was carried out. For each of the ring the research of the effectiveness of the seal was performed. This paper presents the examples of topography graphs, some results of 3D parameters measurements, Spearman rank correlation coefficients for 2D parameters and Spearman rank correlation coefficients among 2D and 3D parameters. The tables containing the correlation coefficients can be used to find the 2D equivalents of 3D parameters during the measurements of sealing rings.

Appearance of Mechanical Zinc Coatings and Superficial Pore Sealing Treatment

By using SnSO4 water solution to activate global granular Zn powders of 325 screen mesh, Zn-Sn composite coverage is formed under the action of mechanical impact of the tiny glass beads and work pieces. During and after the formation of coating, acid water liquor will react with metal basal body, and hydrogen gas is bound to emit from the pathway and form micro pores. In addition, there are bond areas between the new and the primary coverage, which may lead to the emergence of micro crack on the coating owing to such causes as too big or uneven impact during plating process, little distortion of global granular zinc dust inside the plating coat, less tight coalescent of the zinc dust flecks. These problems can be confirmed by SEM scanning coating surface and cross section pictures of plating coat. In our study, methyl hydrogen silicone fluid, titanium isopropoxide and benzinum are used as the basal components. This compound has such features as better osmosis for micro pores and cracks formed in the process of dual coverage, strong adhesive force, anti-contraction, high transparence and water proof property. The impact of titanium isopropoxide dosage on the solidifying speed of methyl hydrogen silicone fluid, and that of mechanical plating zinc coating on corrosion proof are studied. Through tests, the proper compound ratio is determined as 11:10:79 of methyl hydrogen silicone fluid to titanium isopropoxide to benzinum(90-120 Centigrade degree). Experiments indicate that when the coating thickness is 0.2 micron, the emergence time of white corrosion on the plating coat doubles, accordingly, that of red rust prolongs, this shows that the anticorrosion of the coverage can be significantly improved through superficial pore sealing in zinc plating coat.

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.

Full day for mechanical seal seminar

The Mechanical Sealing Technology Seminar being organized by the Institution of Mechanical Engineers on 18 April will have a keynote presentation and 11 papers.

Linear elastic contact of the Weierstrass profile

A contact problem is considered in which an elastic half–plane is pressed against a rigid fractally rough surface, whose profile is defined by a Weierstrass series. It is shown that no applied mean pressure is sufficiently large to ensure full contact and indeed there are not even any contact areas of finite dimension — the contact area consists of a set of fractal character for all values of the geometric and loading parameters. A solution for the partial contact of a sinusoidal surface is used to develop a relation between the contact pressure distribution at scale n − 1 and that at scale n . Recursive numerical integration of this relation yields the contact area as a function of scale. An analytical solution to the same problem appropriate at large n is constructed following a technique due to Archard. This is found to give a very good approximation to the numerical results even at small n , except for cases where the dimensionless applied load is large. The contact area is found to decrease continuously with n , tending to a power–law behaviour at large n which corresponds to a limiting fractal dimension of (2 − D ), where D is the fractal dimension of the surface profile. However, it is not a ‘simple’ fractal, in the sense that it deviates from the power–law form at low n , at which there is also a dependence on the applied load. Contact segment lengths become smaller at small scales, but an appropriately normalized size distribution tends to a limiting function at large n . † The authors dedicate this paper to the memory of Dr J. F. Archard, 1918–1989.

The Role of Impregnants in Determining the Behaviour of Mechanical Carbon Sealing Rings

The lifetime of mechanical carbon sealing rings fitted into crude petroleum oil pumps can be increased by a factor of 43 by multiple impregnation with coal tar pitch. For single impregnation, epoxy resin yielded the largest improvement. The results were interpreted on the premise that properties such as viscosity, adhesion forces, and coking value determine the effectiveness of the impregnant. The proper selection of the impregnant and procedure of impregnation is dependent on the pumping pressure and oil properties.