1. Are Black Holes Vacuums

LEAK DETECTION METHODS AND DEFINING THE SIZES OF LEAKS - February 1999,LEAK DETECTION METHODS AND DEFINING THE SIZES OF LEAKSAndrej Pregelj, Marjan Drab, IEVT, Teslova 30, LjubljanaMiran Mozetic, ITPO, Teslova 30, LjubljanaTABLE OF CONTENTS. The 4th International Conference ofSlovenian Society for NondestructiveTesting'Application of Contemporary Nondestructive Testing inEngineering'24 - 25 April 1997, Ljubljana, Slovenia.ABSTRACTThere is a constantly growing need for products and technologies that for their realisation require hermetically closed elements, vessels and tubes. Envelopes with greater or smaller vacuum tightness had to assure a satisfactory isolation between external atmosphere and inside over- or underpressure.

Vacuum forming ceramic fiber. Standard,High Pure, High Aluminum,Al-Zirconium,Zirconium. Classification Temperature. Applications.Applications that require high-temperature toughness, high strength from the load-bearing areas.For high air flow, mechanical damaging large areas of. What size of parts can be vacuum formed? Mayfield has the capabilities to vacuum form parts as small as an ice cube to dimensions as large as 8 feet by 5 feet. Any thermoplastics with the appropriate melt strength can be vacuum formed, and Mayfield Plastics’ dedicated staff has the expertise and technical know-how to help you select.

Are Black Holes Vacuums

Crytical leak spots in closed systems are usually: connections, gaskets, welded and brazed joints, defects in material etc. Regarding to quality demands in different production processes, technical people very often encounter with standards for tightness testing. Wishing to state if an element or system meets with corresponding standards we have to be familiar with the procedures enabling the following appointments:- question if there is leakage or not- settlement of the leak size- detection of leak localityFor solving the mentioned problems different treatments and techniques are known but among them there is no an universal method, Each testing is suitable only for a selected leak rate or for fixed forms and technologies. Our article presents the leak types, their sizes and various leak detection techniques.Keywords: tightness, leakage, trace gas, helium mass spectrometer leak detector, hermetic sealing1. INTRODUCTIONThe words 'leak' and 'leakage' appear in the field of vessels' hermetical closing and do not confront only with vacuum technologists but also engineers working with high pressures. A leak means an unintended crack, hole or porosity in an enveloping wall or joint which must contain or exclude different fluids and gases allowing the escape of closed medium.

The basic functions of leak detection are the localization and size measurement of leaks in sealed products and systems For majority of examples, a leak test procedure is a quality control step to assure a device integrity, and is one-time nondestructive test.Tipical products in which the leak detection has to be used are: vacuum chambers, TV-, and othercathode tubes, hermetically sealed electronic components, pressure vessels, aerosol containers,vacuum thermal isolation (e.g. Dewars), pumps, refrigerating systems, chemical and nuclear plants,beverage cans, products containing metal bellows, electron microscopes, peace makers, etc.In spte of modem technologies it is practically impossible to manufacture a sealed enclosure or system that can be guaranteed to be leakproof without first being tested. The main question is: what is the maximum acceptable leak rate consistent with resonable performance life of the product.We can distinguish different tipes of leak sources.Leaks caused by defects in the containing envelope. For example a too thin wall of a plastic bottle becomes microscopic cracked at enough high pressure difference, or in canning industry if the score mark is too deep in ring pull-tab can top, or porous cast in machine housing metallurgy, etc.Leaks in newly manufactured products are most commonly imperfect joints or seals by which various parts are assembled to form the final article. There are known demountable and fixed joints. Between them the most often used are welds, brazed and soldered joints glass-to-metal and ceramic-to-metal seals, O-rings and other gaskets, etc.Materials permitting gas diffusion and permeation through the wall.Virtual leak, a special type of leak in vacuum technique, which is not really a leak but is the internal source of gas or vapor. These are cavities in a chamber wall with thin connections to theinner vessel space such as improper welds, closed threads and holes etc.2.

LEAK SIZES AND MEASUREMENTS OF LEAK RATESThe shapes of leaks (cracks, fissures, porosity, damages, etc. ) are very different, unknown and non-uniform. Therefore it is impossible to measure their sizes with any geometrical dimension except of course in the case of an ideal or artificial leak as used for calibration. How then to define the leak size? A generally accepted method became the observation of gas or fluid flow through it in certain conditions of temperature and pressure difference. Consequently leak rates can be defined in two ways:. in terms of the application, e.g.: 3 g of refrigerant R-12 in 2 years at 5 bar, or 65 m of oil per year at 60 °C at atmosferic pressure, etc.

in terms of vacuum leak detection method, e.g.: 2 mbar pressure increase in I hour or 3x 10-7 mbarl/s helium (using He-detection method)Each of the mentioned examples gives a legitimate description of leak rate but the generally accepted unit is the last one because of very simple and understandable helium leak detection. Its efficiency is the result of a fierce and highly competitive developments within the last 15-20 years.The basic experiment explaining the leakage of hermetic system (increasing pressure method) is presented in Figure 1. The tested vessel or system with known volume (V o) is by a valve connected to pump. After evacuation the connecting valve should be closed and then the pressure in volume registered for a suitable long time periode. There are more possibilities: system is tight and clean (a), fight and not clean (b), not tight and clean, i.e.: ideal leak (c), not tight and not clean, i.e.: combination of leak and degassing.As we can see in each case (except for a tight vessel) we have pressure increase and regarding to the shape of diagram we can conclude the type of leak. Using the curve inclination data the leak size can be determined by the following formula:Q = ^p. V o/^t (mbarl/s)This simple test helps us to describe the situation at the begining of leak tracing procedure.

Very similar test can be realized by pressurizing the the system (and detecting the pressure decay) but gives only data on leak size and is not used so often.The leak rate Q does not only depend on the geometric dimensions (diameter, lenght) of the leak but also on the physical properties of the gas (or the liquid), such as viscosity, relative molecular mass and on the pressure difference. For example: in the same environment conditions helium flows through orifices 2.7 times faster than air. Because of different results if the same leak is measured by various mediums it must be always noted with which gas a testing was performed.The maximum acceptable leak rate for a given product depends on the nature of product.

Since the cost of leak detection (and manufacturing too hermetic envelopes) increases in inverse proportion to a leak rate, it follows that testing for unnecessary small leaks causes unnecessary rise of production costs. Some examples of tolerated leaks in different elements and systems are shown in Table 1. We can see very wide range of sizes: from great with some tenths mbarl/s in rough vacuum devices, to milion- and more- times smaller in hermetically closed electronic elements. It is possible to state there are no ideal products without leakage. We only can demand they have leaks smaller than the specified leak.Table 1.

Leak rate specification for various elements and systemsElement or SystemMax. Permissible Leakage Remark chemical process equipment10 -1 to 1 mbar l/sgreat process flows beverage can bottom 10 -5 to 10 -6 mbar l/sretention of CO 2 dynamic pumped vacuum s.10 -5 to 10 -7 mbar l/spermanent pumping IC-package 10 -7to 10 -8 mbar l/spacemakercca 10 -9 mbar l/slong time implanted in bodyclosed vacuum elements 10 -8 to 10 -10 mbar l/se.g. TV- and Xray- tubes3.

LEAK DETECTION METHODESA few leak detection techniques are known. Their performances regarding to detecting sesitivity are presented in Fig 2. Because of their advantages we shall concentrate attention on the helium mass spectrometer tecniques but at first a short description of others is presented,The spark coil technique uses a high voltage or Tesla cod and sparkling point to create the electromagnetic radiation which causes the generation of glow discharge in neighbouring evacuated ampoules. Normally it is possible only in non metal envelopes, that means first of all in glass and plastic elements or tubing. Drawing the leak antenna along the tested element we can see plasma inside and coming to the leak, a sharp arc passage between plasma and antenna appears. The defect spot is very clearly marked and a skilled person can from the colour of plasma also estimate the inner pressure. This simple metod however has a number drawbacks; since besides the restricted application it is also to be avoided because of radiodisturbances.Pressure change method uses pressure gauges which are ordinary used to monitor the system performance.

Suspected leak sites can be squirted with a solvent (i.e. Acetone or similar) while watching the gauge for a pressure rise that occurs when the solvent enters the leak. This method has limited sensitivity (depending also on the type of pressure measurement cell) and some shortcomings (possibility of solvent freezing causes temporary stuffing of leak, solvents may attack vacuum grease and elastomer gaskets).Figure 1.

Compatible MaterialsThe FormBox works best with sheet thermo-plastics (plastics that go soft when warmed up). Every FormBox will ship with enough materials to get started. Benjamin Redford:Ben is an inventor and designer who's shipped multiple Kickstarter campaigns before. While at Mint Digital, he worked on Foldable Me, Olly and Polly the web connected robots and launched Projecteo, the Mini Instagram Projector.He then set up a customised candy company, Candy Mechanics and drew the largest crowdsourced drawing in the world - Internetopia.The idea for Mayku came to him when he was manufacturing a product in China and realised that many of the machines in the factories there could be miniaturised. Ben studied design at Goldsmiths and has an unhealthy obsession for noodle soup.Join the CrewOne last plug.Love making stuff?

We want to hear from you. We’re looking for talented individuals with big ambitions to join the team. If that’s you -.The Story so Far. Risks and challengesAs the old saying goes: Hardware is hard.Luckily, we have a great team who have delivered three Kickstarter projects before. We’re bound to come up against challenges in making the FormBox, but we promise we’ll do everything within our power to make it happen on time and at the high level of quality we set ourselves. Sleepless nights, working weekends, all of the fun that comes with running your own hardware business.ManufacturingWe’ve partnered with some truly excellent production partners to help us along the way with manufacturing the FormBox.

With years of experience in bringing products to market, we’re confident they will help us deliver a top notch product on schedule.TeamWe’re a small team at the moment and in order to make Mayku as great as we want to make it, we need to grow. Hiring is hard and takes a lot of time, but we’ll be patient and considered in our approach, and make sure we build an extremely robust team.