Pressure hold test measurement

An important influence on the measurement of the pressure hold test is the upstream air volume within the filter system. This volume has to be determined first to specify the maximum allowable pressure drop value. The larger the upstream volume, the lower will the... 

The integrity of sterilizing fillers is most often validated and routinely monitored by nondestructive methods. The U.S., European, and U.K. guidelines on sterile filtration refer to four methods of integrity measurement filtration flow rate, bubble point tests, diffusion (forward flow) tests, and pressure hold tests. Each of these has its uses in determining that routinely used filters are per-forming to the same standards as those validated for the particular products and processes. 

When a test gas (for example ambient air) is applied over a water moistened filter, just below the pressure level of the bubble point, test gas diffusion will occur through the water in the wetted membrane filter. This diffusion happens in all water filled pores, not only in the largest. This principle is the basis for two tests, which use different approaches to measure gas diffusion the pressure hold test and the diffusive-flow (forward flow) test. Other names for the same principle tests exist. These tests are performed at a pressure of about 80 % of the theoretical bubble point pressure of the filter. It is important that the largest pores are still filled with liquid. In this phase, diffusion occurs more or less linearly with the pressure drop over the... 

In the pressure hold-test, the filter membrane or candle in its tightly closed case is set under test gas pressure. Next, the test gas supply to the filter holder is shut. On the side where the pressure was applied (measured in the filter case) the pressure decrease, as a result from gas diffusion through the wetted membrane filter element, is measured. Very sensitive and calibrated manometers in the testing device are required... 

The execution of this test with a 0.2 pm hydrophobic filter membrane is as follows. The entire filter case is filled with water and brought under a pressure of about 200 kPa using pressurised air. This pressure is not sufficient to fill the pores and cause a liquid flow through the filter this would require around 1,200 kPa. Transport of water due to evaporation does occur. The amount of water that evaporates per time unit is dependent on the pore size. As a result of this evaporation, the pressure in the filter case would decrease. The amount of air that is added to the filter case to maintain the air pressure is measured. This amount should not exceed a value provided by the manufacturer. The method strongly resembles the pressure hold test and can be regarded as the hydrophobic variant of this test. 

Before and after each test, measurements were made of the tank liquid level (with a movable thermocouple probe) and of the pressure in the pressurizing-gas manifold. These were the only measurements made outside the control center. The general procedure for testingwas as follows the tank was pressurized to the desired level by manual operation of the ullage pressure control valve liquid transfer was initiated approximately 1 to 9 min after the tank was pressurized the tank pressure during the hold and transfer periods was maintained constant. 

There are many ways to measure these properties and some of them are proprietary. However, most laboratory tests are standardized by American Standard Testing Methods (ASTM). Many of them are interactive to various degrees. The rate and state of vulcanization is especially important to consider for components of heavier and thicker tines. The heat used to vulcanize the tine in a mold under pressure requites time to penetrate from both sides of the giant tine to the innermost portions. Securing a balanced state of cure, ie, the maximizing of physical properties in all the components, results in the innermost components having a faster rate of cure. The peripheral compounds should have a cure system which holds its physical properties well when overcured. 

The measurement of the linear velocity as a function of shaft RPM can be done at room temperature and pressure in air. It is best to do this on the catalyst already charged for the test. Since u is proportional to the square of the head generated, the relationship will hold for any fluid at any MW, T, and P if the u is expressed at the operating conditions. The measurement can be done with the flow measuring attachment and flow meter as shown in Figure 3.5.1. 

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). 

Many CST are listed which were measured above the boiling point of one of the components. For temperatures up to 60° above the boiling point, a pierced stopper and thermometer wired into the test tube usually sufficed to hold the pressure while the phases mixed. Much higher CST observations were possible with sealed tubes attached to a thermometer in a bath, or by using a visual autoclave. 

The objective of this test method is to measure the cohesive stress and the time to failure of a crystalline polymer craze layer under rapid, uniform extension. The method is an impact variant of the Full Notch Creep test used by Fleissner [12], Duan and Williams [13], Pandya and Williams [14] and others. The specimen (Fig. 2), a square-section tensile bar, is injection moulded. At the mid-plane of the gauge length a sharp, deep circumferential notch reduces the cross-section to about one fifth of its original area. This notch plane is formed by a moulded-in, hardened steel washer. Specimens were injection moulded at 210°C into a warm (100°C) mould and air cooled to 40 C using a hold pressure of 45-50 bar. 

AATCC Test Method 35 -2000 " is designed to simulate a rain event. A special apparatus is used to hold the 20 x 20 cm fabric sample in a vertical position backed by a weighed piece of blotter paper. The fabric face is sprayed with water under constant hydrostatic pressure for 5 min and the blotter paper reweighed. The increase in weight of the backing paper is a measure of the resistance of the fabric to penetration by the simulated rain. 

The experiments must be done, preferably at steady state, at the same conditions of temperature, pressure and concentrations (even of minor components) as in the intended process, to avoid unpredictable changes in coalescence. They must be carried out in a system of the recommended configuration, preferably at similar power per unit volume and superficial gas velocity as may be used at full scale. The agitator speed should be varied to check whether mass transfer is important and gas hold-up should be measured (e.g. by level probe or y-ray density scan). In cases involving chemical reactions, further tests are required as described in section 15.10. 

For the ground-hold condition, the pressure in the test chamber was maintained at atmospheric, while the insulation was evacuated to within the range of 5 to 10 /i Hg. The pressure within the test tank itself was kept at 0.3 5 psig by means of a back-pressure regulator. The flow rate of the hydrogen gas was measured by an 0.1955-in.-diameter Venturi meter and data recorded for a period of 10 hr before the test was terminated. For the second run, the test chamber w as evacuated to a pressure of about 10 atm and the insulation to 0.5 /it Hg. Continuous boil-off data was recorded for a period of 220 hr, with a wet-drum gas meter used in place of the Venturi to measure this lower flow rate. Finally, a series of tests was conducted at several test chamber pressures from 0.29 to 5 psia, which provided corresponding compressive loads on the insulation. The boil-off rate was allowed to stabilize for at least 8 hr at each external pressure condition before data were recorded. Each test lasted 12 to 24 hr. 

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