Moisture chambers

Partially blocked nebulizer Partially blocked burner Burner mis-aligned Dirty spray chamber Moisture trap in air supply full... 

Desiccant Method A desiccant covered by the film to be tested and placed in a humid chamber. Moisture from the chamber permeates the film and is picked up by the desiccant. After a measured period of time the test dish is reweighed and the water vapor transmission rate (WVTR) of the material is calculated. 

Mechanical Squeezing of Cakes. Mechanical squeesing of the cake in the so-called variable chamber filters has been used relatively recendy to lower moisture content of the final cake. This is appHcable only to cakes that are compressible. Many filters are available in which some form of mechanical expression of the cake is used either to foUow a conventional filtration process or to replace it. 

Great care is needed in the design of autoclaves and sterilization cycles because of the requirement for the presence of moisture. The autoclave must be loaded to allow complete steam penetration to occur in all parts of the load before timing of the sterilization cycle commences. The time required for complete penetration, the so-called heat-up time, varies with different autoclave constmction and different types of loads and packaging materials. The time may not exceed specific limits in order to guarantee reproducibility and, for porous loads, saturated steam. The volume of each container has a considerable effect on the heatup time whenever fluids are sterilized. Thermocouples led into the chamber through a special connector are often employed to determine heatup times and peak temperatures. The pressure is refleved at the end of each sterilization cycle. Either vented containers must be used or... 

General recommendations for instmmentation include monitoring gas concentration, temperature, time, and the moisture content of the chamber. Hospital sterilizers are not usually equipped with instmmentation providing direct display of gas concentration and moisture content. These rely instead on a specific sequence of steps performed automatically and the recording of pressure which when 100% ethylene oxide is used is a perfect measure for the concentration of this gas. 

Active Dry Yeast (ADY). The production of active dry yeast is very similar to the production of compressed yeast. However, a different strain of yeast is used and the nitrogen content is reduced to 7% of soHds compared with 8—9% for compressed yeast. The press cake made with the active dry yeast strain is extmded through a perforated plate in the form of thin strands with a diameter of 2—3 mm and a length of 3—10 mm. The strands are dried on endless belts of steel mesh in drying chambers (a continuous process) or in roto-louvre dryers (a batch process), with the temperature kept below 40°C. Drying time in drying chambers is 3—4 h and in roto-louvre dryers is 6 h or more. The final moisture level attained is 7.5—8%. 

Vacuum is applied to the chamber and vapor is removed through a large pipe which is connected to the chamber in a manner such that, if the vacuum is broken suddenly, the inrushing air will not greatly disturb the bed of material being dried. This line leads to a condenser where moisture or solvent that has been vaporized is condensed. The noncondensable exhaust gas goes to the vacuum source, which may be a wet or diy vacuum pump or a steam-jet ejector. 

Vapors (from drying) are removed at the feed end of the dtyer to the atmosphere through a natural-draft stack and settling chamber or wet scrubber. When employed in simple drying operations with 3.5 X 10 to 10 X 10 Pa steam, draft is controlled by a damper to admit only sufficient outside air to sweep moisture from the cylinder, discharging the air at 340 to 365 K and 80 to 90 percent saturation. In this way, shell gas velocities and dusting are minimized. When used for solvent recovery or other processes requiring a sealed system, sweep gas is recirculated throu a scrubber-gas cooler and blower. 

The introduction of water, or air to a lesser extent, from the backside of flexible membranes reduces chamber volume and squeezes the cake yielding a further lowering of the moisture content. The filter press may be arranged as a mixed pack of flush and membrane plates, full flush or full membrane pack depending on the application. 

The air, in passing through the chamber at velocities in the range 1.5 to 3.5 m s" comes into intimate contact with the water, and depending on the conditions required, mass transfer of moisture into the airstream occurs. This transfer produces either addition or removal of moisture hot or chilled water is used in this process. 

Speichel-fluss, to. flow of sahva salivation, -fliissigkeit, /. sahva. -kasten, to. sahva chamber (as in a blowpipe) moisture cham ber. -mittel, n. sialagog. -saft, to. sahva. -stoflf, TO. ptyalin. 

Condensation occurs in all compressors, and the effects are most prominent where cooling takes place - in intercoolers and air-receivers, which therefore have to be drained at frequent intervals. Normally the amount of moisture present in a compression chamber is not sufficient to affect lubrication, but relatively large quantities can have a serious effect on the lubrication of a compressor. Very wet conditions are likely to occur when the atmosphere is excessively humid, compression pressures are high, or the compressor is being overcooled. 

If the temperature of dry saturated steam is increased, then, in the absence of entrained moisture, the relative humidity or degree of saturation is reduced and the steam becomes superheated (Fig. 20.5). During sterilization this can arise in a number ofways, for example by overheating the steamjacket (see section 4.2.2), by using too dry a steam supply, by excessive pressure reduction during passage of steam from the boiler to the sterilizer chamber, and by evolution of heat of hydration when steaming... 

---