![]() De-rate the heatless dryer by 20% for -100º F. Demand switching and purge shut-off features cannot be used.Ĥ. To obtain very low dew points, the dryer needs to run continuously. Use a heatless dryer – but only at the point of use or for that portion of the air system where an ultra-low pressure dew point is truly required.ģ. This can be eliminated through design modifications, but that will drive up capital and operating costs.Ģ. It’s well known that most industry standard heated dryers will involve a dew point spike at tower change over. Hot to Obtain a Continuous Ultra-Low Pressure Dew Pointīut how does one obtain a continuous ultra-low pressure dew point? Here are some useful guidelines.ġ. ![]() ![]() Most off-the-shelf regenerative desiccant dryers, both heated and heatless, will deliver a -40º F/C 100 psig average pressure dew point. ISO 8573.1 dew point class 1 calls for a pressure dew point of -94 ✯ PDP 100 PSIG. ISO 8573.1 is a common standard for defining compressed air quality. We normally see this requirement in instances where the end-user is conveying chemicals that react with trace amounts of moisture, micro-electronics manufacturing, some food processing facilities, and cryogenic (super-chilled) applications. In rare cases, a pressure dew point lower than -40⁰ F/C 100 psig will be specified. This is especially so in process industries, facilities where air lines will be exposed to cold ambient air, and systems where compressed air interacts with sensitive instruments and processes. Many industrial users of compressed air specify a pressure dew point of -40⁰ F/C at line pressure. What is Atmospheric Dew Point?Ĭonversely, the phrase atmospheric dew point refers to what the dew point would be if fully depressurized to atmospheric conditions. This term usually refers to the dew point of the compressed air at full line pressure. What is Pressure Dew Point?įor this reason, the phrase pressure dew point (PDP) is commonly used. If the air is further expanded to 5 psig, the pressure dew point becomes -77º F 5 psig. If the pressure is eventually reduced to 100 psig, the pressure dew point will fall to -50 ✯ 100 psig. For example, consider compressed air leaving a dryer at 200 PSIG with a pressure dew point of -40º F/C 200 psig. Generally speaking, compression increases dew point, and expansion (i.e. Compression and expansion of air affect its dew point. In compressed air applications, pressure is critical when discussing dew point. Simply put, dew point is the temperature where condensation begins. Dew point is always stated as a temperature. In other words, it’s the point where dew begins to form. Dew point is the temperature where air - or any gas - is saturated with water and moisture will begin to condense. GPSA Databook can also provide you with quality information regarding this subject.The most common measurement of compressed air water content is dew point. On the other hand, if you are based in Kazakhstan or Siberian fields, you'll probably need Mol Sieves equipped with heating regeneration system in order to properly drive the moisture out of the desiccant.Īttached is the link to one file that shows various performance characteristics of different adsorbents: Īs you can see, Mol Sieves are capable of removing more moisture at lower relative humidities of feed stream but, on the other hand, they require more energy for desorption process exactly because of higher moisture holding capabilities at lower partial pressures of water. If you are based in hot, tropical region, Activated Alumina is more than enough (dew point -40C). It is hard to find equipment that can detect moisture contents below 0.1ppm.Īmbient conditions determine the level of air dehydration. For most practical applications this is more than sufficient. By using Mol Sieves, dew point can go as low as < -100C.
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