Volume-pneumatic test

With a volume-pneumatic test, mechanics can detect defects in the parts due to incorrect replacement parts, incorrect machining, corrosion, or weak springs. Each of these problems can be discovered by such characteristics as early simmer, only a partial lift or leakage after the test. Defects such as inadvertently installing a spring too strong for the set pressure can be detected by short blow-down or chatter. Competent SRV test craftsmen can pinpoint defects with this type of test equipment. 

With a volume-pneumatic test, mechanics can detect defects in the parts due to incorrect replacement parts, inconect machining, corrosion, or weak springs. Each of the.se... 

Santa Clara, CA). The column had a diameter of 3.2 mm, and the exit frit was crimped into place so that a column end fitting was not required. The geometry of the electrochemical cell is shown in Figure 4. The chromatographic system included a pneumatically operated loop Injector (Model 3XL, Scientific Systems, Inc., State College, PA). The injection loop had a 10 pL volume, and mixtures of catecholamines were used as test compounds. The electrode could be positioned with 100 pm resolution in three dimensions with a micromanipulator (Narlshige Co., Ltd., Tokyo, Japan). The vertical resolution was enhanced with a piezoelectric positioner with 0.5-pm resolution (Burleigh Instruments, Inc., Fishers, NY). 

The experimental facility and instrumentation are shown in Fig. 1. The flow facility consists of a vertical 2.5 cm diameter, 15 cm long Pyrex glass test cell mounted beneath a low-pressure reservoir of volume 0.27 m. The test cell is sealed by an aluminum foil diaphragm, which is ruptured by pneumatically driven knife blades. The test cell is surrounded by a liquid-filled jacket with flat windows. This serves two purposes to eliminate the cylindrical lens effect of the test liquid (by choosing a jacket liquid with a refractive index similar to that of the test liquid) and to provide temperature control (by circulating the jacket liquid through a heat exchanger). 

In process plant, it had become normal practice to subject new, large pressure vessels to hydraulic proof pressure tests. The distinction between hydraulic and pneumatic pressure tests is an important one. Water is essentially incompressible - its volume barely changes when it is pressurized. Gas (or steam) is, however, highly compressible. Hence, in a hydraulic pressure test, the pressure vessel is filled with water, and if any failure should occur, as soon as the enclosed volume begins to increase because of the developing failure, the pressure immediately collapses. This means there is no explosion - just a bang as the metal fails, followed by a flood of water. By contrast, if a pressure vessel fails when pressurized with gas or steam, as in the boiler explosions described above, the energy of the compressed gas/steam drives the failure to create a violent explosion, and pieces of the failed pressure vessel become missiles. 

---