Hermetic sealing hermeticity testing

Hermeticity testing was required to test the integrity of the package seal. 

Hermetically sealed electrical devices must be verified by a testing laboratory to meet mechanical abuse and to withstand aging and exposure to expected chemicals. Devices potted with common silicones and similar materials by an end user or even a manufacturer, without testing, and devices merely provided with O-rings seldom meet acceptable criteria. Normally, hermetically sealed devices must be sealed through metal-to-metal or glass-to-metal fusion. Many electrical relays, switches, and sensors are available as hermetically sealed devices for common oil and gas producing facility applications. Hermetically sealed devices are often desirable to protect electrical contacts from exposure to salt air and other contaminants. 

To assess unknown incompatibilities it is customary to make a small mix of drug substance with an excipient [54,55], place it in a vial, place a rubber stopper in the vial, and dip the stopper in molten carnauba wax (to render it hermetically sealed). The wax will harden and form a moisture barrier up to 70°C. A list of common excipients characteristic of this type of test is shown in Table 1. At times it is possible to obtain quantitative relationships of... 

Ampoules that have been sealed by fusion must be tested to ensure that a hermetic seal was obtained. The leaker test is performed by immersing the ampoules in a dye solution, such as 1% methylene blue, and applying at least 25 in. (64 cm) of vacuum for a minimum of 15 minutes. The vacuum on the tank is then released as rapidly as possible to put maximum stress on weak seals. Next, the ampoules are washed. Defective ampoules will contain blue solution. 

The arrangement is then placed in a furnace, heated to 800°C, and the pressure decay test is repeated. The setup can be subjected to thermal cycles with pressure decay tests at room temperature and at 800°C. A good hermetic seal, however, will not show any pressure decay at a low pressure differential. The results of one series of tests using a glass composite material that has a glass transition temperature (Tg) of about 700°C, at 5 psi are shown in Figure 5.10. The combination of pressure and thermal cycle tests showed that the seal is capable of withstanding the pressure... 

When dealing with small, hermetically sealed parts where the enclosure is leaky, krypton 85, a gaseous, radioactive isotope, can first be forced into the device by applying pressure from the outside. Once an exactly measured holding period has elapsed the pressure will be relieved, the component flushed and the activity of the gas charge will be measured. In the same way it is also possible to use helium as the test gas (see Section 5.7.4, bombing test). 

The bombing test is use to check the tightness of components which are already hermetically sealed and which exhibit a gas-filled, internal cavity. The components to be examined (e.g. transistors, 1C housings, dry-reed relays, reed contact sw/itches, quartz oscillators, laser diodes and the like) are placed in a pressure vessel which is filled with helium. Operating with the test gas at relatively high pressure (5 to 10 bar) and leaving the system standing over several hours the test gas (helium) will collect inside the... 

Since chemical reactions are accelerated by temperature increases, the recommendation is to store materials at the highest possible temperature consistent with practical limits—i.e.y 165°F., for the longest possible storage period. Storage data generated for liquid and slurry propellants are of two types (1) laboratory controlled experiments, and (2) field tests in hermetically sealed containers. The laboratory experiments provide for rapid and convenient determinations and are used primarily for comparing one propellant with another or for comparing the relative... 

Litmus test (Vieille test). This test introduced by Vieille [88] consists in warming a sample of nitrocellulose (2.5 g) or smokeless powder in a hermetically sealed test tube (Fig. 2) in presence of a band of blue litmus paper inserted within the tube. The tube is kept in a thermostat warmed to 110°C. The temperature inside the test tube is 108.5°G In U.StS.R. the temperature of the thermostat is 106.5°C. The blue paper should not turn definitely red in less than 7 hr. 

Emulsion stability using a storage stability test Measure droplet size distribution and concentration at the top and bottom of a hermetically sealed container during storage Results usually expressed as plots of mean droplet size and concentration (volume fraction) as a function or storage time... 

Exudation tests are described in Vol 6, E507-R. One now used involves tightly wrapping a 1 "x5/f casting of the expl sample with Whatman No 1 filter paper and sealing it hermetically in a heavy-walled A1 cylinder. The sample is then held at 71° for 6 days. The exudate absorbed by the paper is measured. Military grade TNT... 

The basic light-sensitive substance used in all of these papers is silver chloride with an excess of silver nitrate. Once the image has been printed and toned, it is fixed, washed, dried, and preserved in much the same way as a silver print. Because the silver particles of printed out images are a much finer size than those of developed out prints, they are often more susceptible to deterioration. But with proper processing, they will stand the test of time as well as any process. Indeed, collodio-chloride is actually the most stable silver printing process because the nitrocellulose binder hermetically seals the silver from the harmful atmosphere that fades all silver base photographic prints. 

The -> Lead Block Test has been used for the same purpose the block is sealed hermetically by a plug, and held in position by a steel construction. After detonation of the explosive sample in the block, the gas content has been vented by a special sealed drilling tool. 

Set the hermetically sealed pressure cell 2 j containing a standard substance (lmg of DNT or 2mg of BPO) on the test apparatus, and heat at a rate of 10 0 C/min. Determine the exothermic start temperature and calorific value on the recording chart 4. Perform the test five times, and determine the average of the five runs. 

Quinine was introduced as a "...primary calibration standard for light testing." In this draft, a "... 5% solution of quinine monochloride dihydrate in water..." Approximately 20 mL of this solution, hermetically sealed in two colorless ampoules (Japanese Industrial Standards No. 5) colorless ampoules or equivalent were to be used. One of these ampoules was to be protected from exposure by being wrapped in aluminum foil, the other exposed at a distance of about 30 cm for three hours. It was specified that "the transmittance of the exposed solution in 1cm cells should lie between 55% and 60%, and that the control should show no significant change (about 70%)." Radiometers were permitted as "...secondary standard UV measuring devices."... 

All types of povidone, with exception of povidone K 90, have very good storage stability in the pure form. Table 24 lists the minimum stabilities in the original sealed container at room temperature when these are stored and tested according to the requirements of the pharmacopoeias (see Section 2.2.1.2). Recently some povidone grades are commercialized with hermetically sealed aluminium-PE inliners under nitrogen and vacuum to increase the long term stability. This is mainly of interest for povidone K 90. 

Crystal Scintillation Detector. The well detector is a common type of a crystal scintillation detector and has a hole drilled in the end or side of the cylindrical crystal to accept a test tube. Because it is hygroscopic, the crystal is hermetically sealed in an aluminum can with a transparent quartz window at one end through which the blue-violet (420 nm) scintillations are detected. The photons of gamma emitters, such as Cr, Co, Fe, and (Table 1-14) in the sample easily penetrate the specimen tube and the thin, low-density can and enter the crystal where they are likely to... 

Hermetically sealed packs should not leak under normal conditions, so laboratory testing could include a vacuum/ vibration cycle, in vertical, inverted or horizontal pack modes, if relevant to the product, the market, or the distribution system (e.g. in the pressurised freight hold of an aircraft). 

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