Low-pressure applications

These recommendations are for low-pressure applications with water and other fluids that do not significantly affect the properties of the particular thermoplastic. The upper temperature limits are reduced at higher pressures, depending on the comhination of fluid and expected service life. Lower temperature limits are affected more hy installation, environment, and safeguarding than hy strength. 

Flexible tubing for high pressure service, equipped with stainless steel overbraid plus tube adapter end connections, is commonly available with a carbon black-loaded PTFE core tube to dissipate static. Numerous other designs of conductive and antistatic tubing are available for low pressure applications. The utility of conductive tubing in preventing fires during transfer of aromatic hydrocarbon liquids is described in [165]. 

Pipe used for low-pressure applications such as transporting air, steam, gas, water, oil, etc. Employed in machinery, buildings, sprinkler and irrigation systems, and water wells but not in utility distribution systems can transport fluids at elevated temperatures and pressures not subjected to external heat applications. Fabricated in standard diameters and wall thicknesses to ASTM specifications, its diameters range from Vs to 42 in. o.d. 

Standard pipe Pipe used for low-pressure applications such as trans-... 

When using alloy pipe with greater tensile strength than carbon steel, the schedule numbers still apply, but may vary, because it is unnecessary to install thicker walled alloy pipe than is necessary for the strength and corrosion considerations. Schedules 10 and 20 are rather common for stainless steel pipe in low pressure applications. 

Figure 2-8. Light weight stainless steel butt-weld fittings/tubing for low pressure applications. By permission, Tri-Clover, Inc.

These meters are suitable for low-pressure applications (<75mbar) and low flow rates. Meters rated at up to... 

As described above, the precursors traditionally employed for preparation of III-V films have been group 13 metal alkyls (Me3Ga, Me3Al, Me3In) in combination with the group 15 hydride gases (Table 2). These are available on a commercial scale and have appropriate vapor pressures for both atmospheric pressure and low-pressure applications. 

Hoses produced by this method are generally used for comparatively low pressure applications, and are often produced in lengths of up to 500 metres, with a bore size of up to 40 mm. 

The successful application of HPLC was made possible largely by (a) the development of pump systems that can provide constant flow rates at high pressure and (b) the identification of suitable pressure-resistant chromatographic media. Traditional soft gel media utilized in low-pressure applications are totally unsuited to high-pressure systems due to their compressibility. 

To gain universal acceptance in the oil industry, it will be necessary to develop an acceptable combination of pumps and hydrocyclones to cover the many potential low-pressure applications. All research time spent in this area will have a significant impact on the hydrocyclone s market potential. 

The flat dies, or slot dies as they are sometimes called, are used to produce webs in a variety of processes. They all have an interior manifold for distributing the plastic and lips for adjusting the final profile of the web (extrudate). Some dies have movable restrictor bars for changing the manifold for proper melt distribution (Figure 17.10). All flat dies have flexible lips that can be adjusted by bolts to remove humps or bumps in the web s profile. Die lips can have their adjustment bolts push only, where internal plastic melt pressures are adequate to keep the lips positioned against the bolts, or can be push/pull for low pressure applications. Direct acting or differential thread designs (for minute adjustments) are available. Profile variations of at least 3% or less can be achieved with flat dies. 

Gas separation membranes have diameters as small as 135 pm onter diameter by 95 pm iimer diameter. For low-pressure applications such as air, they may run with tube-side feed. Gas membranes operating at high pressure (above 1.5 MPa) are almost always run with shell-side feed. The outer diameter for gas membranes may be as high as 500 pm. 

There is a fall-off of k at low pressures. Application of the rrk treatment led to an s value of 21-23. The rrkm theory was applied to the results, and agreement was obtained provided that a collision efficiency of 0.04-0.09 was assumed. This seems too low, and it is possible that this anomaly would disappear if the back reaction were taken into account . 

Second, we need an equation-of-state for electrolyte solutions. Equations-of-state are needed for modeling high-pressure applications with electrolyte solutions. Significant advances are being made in this area. Given that the electrolyte NRTL model has been widely applied for low-pressure applications, we are hopeful that, some day, there will be an equation-of-state for electrolytes that is compatible with the electrolyte NRTL activity coefficient model. 

Teflon, Buna-N, Neoprene, Kalrez and Viton need to be assessed further for use with oxygen. Teflon seems to work well in low pressure applications. 

Metals such as aluminum, which perform well in low pressure applications are not recommended for high pressure application as the possibility exists for ignition in some circumstances. Aluminum, however, should not be used at all in a system that uses caustics such as potassium hydroxide. 

Casting-solution and environmental variables permit far greater control over the ultimate structure and performance of phase inversion membranes than does the modification of a primary gel into a secondary gel by postformation treatments. Because the properties of the primary gel determine to a large extent those of its secondary counterpart, the former should be considered as more fundamental and important in discussing the effects of fabrication parameters such as casting-solution composition, upon performance. Once a primary gel has been formed, it may be utilized as such (particularly for low-pressure applications) or it may be subjected to various physical and/or chemical treatments for conversion into a more pressure-resistant secondary gel. 

Hybrid processes utilize a physical solvent and an amine to combine the benefits of both chemical and physical solvent processes [1,2]. Typically, hybrid processes are employed at high acid gas partial pressures [1,2], However, it is possible to implement a hybrid process for low-pressure applications when the hybrid process is competitive with aqueous amine processes. A well-known hybrid process is Sulfinol , which combines the organic solvent sulfolane with MDEA or DIPA and varying amounts of water to achieve selective removal of H S from CO [1 ]. Potential disadvantages of hybrid processes relative to aqueous amine processes include increased overall solvent costs and the loss of valuable product gas (i.e., hydrocarbons) dne to the likelihood for increased absorption in the physical solvent [1,2]. 

Carlson BA, Geomaras I, Yoon Y, Scanga JA, Sofos JN, Smith GC, Belk KE (2008) Studies to evaluate chemicals and conditions with low-pressure applications for reducing microbial counts on cattle hides. J Food Prot 71(7) 1343-1348 Cocolin L, Stella S, Nappi R, Bozzetta E, Cantoni C, Comi G (2005) Analysis of PCR-based methods for characterization of Listeria monocytogenes strains isolated from different sources. Int J Food Microbiol 103 167-178... 

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