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7/28/2019 Sealing Technology Volume 2004 Issue 11 2004 [Doi 10.1016%2Fs1350-4789%2804%2900401-5] -- Calculation of
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NEWS
3Sealing Technology November 2004
Poorly installed gasket causesammonia leak
A toxic cloud of ammonia whichleaked from McCain Foods
Wendouree factory in Australia was likely to be a one-off incident,according to investigators. The
Victorian WorkCover Authority and Environmental Protection
Agency discovered that a gasket inan ammonia pipe to the rear of the plant was poorly installed,according to a report in theBallarat Courier in Victoria.
People were asked to stay indoorsand roads were blocked as Country Fire Authority crews worked for
more than two hours to contain theleak at the plant. The investigatorsconcluded that the incident wascaused by the failure of a gasket
within an ammonia pipeline, ratherthan improper operating practices.
A WorkCover spokesman said thefindings were different to early inves-tigations; it was initially thought thata safety lockout valve had failed. Thecompany is seeking external assis-tance to put in place measures to pre-vent further incidents. It is thoughtthat the problem occurred during theinstallation of the freezer.
Calculation of brush seal leakagePerkinElmer Fluid Sciences hasreleased an engineering tool that allows its customers to estimatebrush seal performance in many
types of turbomachinery.The performance predictor is
designed to simplify the applica-tion of brush seal technology, by allowing customers to evaluate sealperformance. The user can inputspecific pressure and temperatureconditions, and the software pre-dicts the leakage performance of the turbomachinery system. Theaim is to permit rapid evaluationof the potential benefits of thebrush seals provided by the compa-
ny, and to provide a considerably reduced lead time from evaluationto installation.
The brush seal performancepredictor is a very handy and easy-to-use program for estimating leak-age of brush seals, says Ted Gresh,a senior consulting engineer at
Elliot Turbomachinery Company.Using this program along witha program like Laby Flex by Flexware, makes it easy to deter-
mine the savings involved in con-verting to brush seals.
Contact:
Perkin Elmer Fluid Sciences, 5209 RisingSun Lane, Ellicott City,MD 21043,USA.Tel: +1 410 461 5659, Fax: +1 410 4615109, Email:[email protected],Web: fluidsciences.perkinelmer.com
Editors comment: I have tried this, and it is certainly very conve- nient to use. It is, for example, pos-
sible to quickly scan the effect of changing the operating conditions.If data are available for alternative seal types, it is then very convenient to compare the results. I presume that the calculations are based on either proven science or established empirical data.
Website provides information onbiocompatiblityIn the fields of medical devices,pharmaceutical processing and biological engineering there hasbeen an increasing demand forsealing with biocompatibility.
However, O-rings and the stan-dards for biocompatible rubberproducts are unfamiliar to many designers. Now a new website fromKentucky-based Molding Solutionsprovides a central location for thisinformation. When rubber is requi-
red to be biocompatible, the bestmaterials are classified as USP ClassVI. This term is reserved for mate-rials that have passed a series of testsshowing that the materials do notgenerate reactions in mammals, andis the highest of the six levelsrequired by the USP procedure.
To provide users with a singleresource for information associated
with USP Class VI O-Rings, Mold-ing Solutions has created a websitededicated to this product. The web-site contains information about theUS and international standardsapplicable to these O-rings, O-ring dimensional data, product informa-tion and available sizes.
Contact:
Molding Solutions,781 Enterprise Drive,Lexington, KY 40510,USA.Tel: +1 859231 0031, Fax: +1 859 254 8884,Web:www.class-vi-o-rings.com
Editors comment: To save readers a little time, the standards information provided on this website is as follows:
SAE AS568 Aerospace Size Standard for O-Rings is the bible of standard O-ring sizes. It lists hun-
dreds of O-ring sizes with their dimensional tolerances. USP 23 Biological
Reactivity Tests, In Vivo contains testing procedures for rubber and plastics that will be used in direct or indirect contact with humans or animals. The strictest set of test- ing requirements is identified as Class VI.
ISO 10993 An International standard for Biological Evaluation of Medical Devices. Contains test methods for materials to be used in medical devices. This standard identifies test requirements based on specific applications and usage of the end product.
Terminal seals made in new moldsDP Seals has recently completed the design and production of pro-tective rubber bumpers and gasketsfor the OT40 and PT60 ranges of handheld terminals made by Oyster Terminals UK Ltd.
The project is one of the first thatis possible because of two new mold-ing presses, which enable the compa-ny to produce components of up tothree times the size and thickness of those available previously. Designedto be very robust, the OT40 is capa-ble of withstanding rough industrialhandling, including a 1 m drop ontoconcrete. The nitrile rubber bumperprovides the shock protection if theunit is accidentally dropped, as well
as protecting the Xenoy case.
These terminals may be fitted with special rubber sealing gaskets,also manufactured by DP Seals, which provide water and dust sealing to IP65. Developed to a precise brief from Oysters engineers, the bumperincorporates PVC additives thatenhance appearance and help meetthe performance requirements forhandheld equipment being used infactories, theaters, workshops and warehouses.
Contact:
DP Seals Ltd, Unit 6 Dawkins Road,Hamworthy, Poole, Dorset BH15 4JY, UK.Tel: +44 1202 674671,Fax: +44 1202665581,Email: [email protected],
Web: www.dpseals.com
PPS material delivers economical yetreliable performanceEquipment manufactured by DeSmet for a number of aggressiveenvironments is being fitted withbushing rings of Techtron HPV PPS material from Quadrant Engineering Plastic Products.
The equipment includes machin-ery for oil extraction, protein mealproduction and refining to vegetableoil, protein meal, and protein isolateproduction. The reinforced, inter-nally lubricated polyphenylene sul-fide (PPS) grade, Techtron HPV PPS, demonstrates a suitable combi-
nation of properties including wearresistance, load-bearing capabilitiesand dimensional stability whenexposed to chemicals and high-tem-perature environments.
The material is claimed to over-come the disadvantages of virginPPS, caused by a high coefficient of friction, and of glass-fiber reinforcedPPS, which can cause premature wear of the counter face in moving-part applications. The combinationof wear resistance, friction and fluidcompatibility provides an improve-ment over conventional plastics suchas PA and POM, but a more eco-nomical solution than higher-gradeplastics such as PEEK.
Contact:
Quadrant Engineering Plastic Products, IPNoord R.Tavernierlaan 2, B-8700 Tielt,Belgium.Tel: +32 51 423571,Fax:+3251 423570, Email:[email protected]
mailto:[email protected]:[email protected]:[email protected]://fluidsciences.perkinelmer.com/mailto:[email protected]://fluidsciences.perkinelmer.com/mailto:[email protected]