Holding times

If the holding time is inconveniently short, then the storage conditions have to be changed or the sample may have to be stabilized in some way. 

Draft General Guidelines on Sampling , Document reference ALINORM 04/27/23, Appendix III, Codex Alimentarius Commission, 2004. [http //www.codexalimentarius.net] (accessed 10 October, 2006). 

Sampling Procedures for Inspection by Attributes - Part 0 Introduction to the ISO 2859 Attribute Sampling System , ISO 2859-0 1995, International Organization for Standardization (ISO), Geneva, Switzerland, 1995. 

The time required to empty the drum of liquid at design flow rate is the holding time. This time is normally based on the distance between the maximum liquid level and the bottom tangent line. The small additional time available in the bottom head serves as a slight safety factor. 

The maximum liquid level is frequently set to use the full range of commercially available level gages or controls. This practice can add holding time to the drum. 

Enter the nomograph on the flow scale at the left with the flow rate. No need to convert units — just use the scale having your units. 

Move horizontally to the flow index line. (If your units are hot gph, omit this step. You are starting at the flow index line.) 

Draw a line from the flow index line to the drum diameter. Mark the intersection with the index line. 

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Bonding temp. Holding time Heating speed Cooling speed Load Vacum... 

Preservation Methods and Maximum Holding Times for Selected Water and Wastewater Parameters... 

The sulfuric acid hydrolysis may be performed as a batch or continuous operation. Acrylonitrile is converted to acrylamide sulfate by treatment with a small excess of 85% sulfuric acid at 80—100°C. A hold-time of about 1 h provides complete conversion of the acrylonitrile. The reaction mixture may be hydrolyzed and the aqueous acryhc acid recovered by extraction and purified as described under the propylene oxidation process prior to esterification. Alternatively, after reaction with excess alcohol, a mixture of acryhc ester and alcohol is distilled and excess alcohol is recovered by aqueous extractive distillation. The ester in both cases is purified by distillation. 

Reaction times can be as short as 10 minutes in a continuous flow reactor (1). In a typical batch cycle, the slurry is heated to the reaction temperature and held for up to 24 hours, although hold times can be less than an hour for many processes. After reaction is complete, the material is cooled, either by batch cooling or by pumping the product slurry through a double-pipe heat exchanger. Once the temperature is reduced below approximately 100°C, the slurry can be released through a pressure letdown system to ambient pressure. The product is then recovered by filtration (qv). A series of wash steps may be required to remove any salts that are formed as by-products. The clean filter cake is then dried in a tray or tunnel dryer or reslurried with water and spray dried. 

Separator. Fat is normally separated from the milk before the HTST however, ia one system the airtight separator is placed after the FDV, foUowiag pasteurization. A restricting device and several control combiaations are placed ia the line after the FDV to ensure that constant flow is maintained, that vacuum does not develop ia the line, that the timing pump stops if the separator stops, and that the legal holding time is met. 

Although examples in the Kureha patent Hterature indicate latitude in selecting hold times for the low and high temperature polymerization periods, the highest molecular weight polymers seem to be obtained for long polymerization times. The addition of water to PPS polymerizations has been reported to effect polymer stabilization (49), to improve molecular weight (50,51), to cause or enhance the formation of a second Hquid phase in the reaction mixture (52), and to help reprecipitate PPS from NMP solution (51). It has also been reported that water can be added under pressure in the form of steam (53). 

Load Temperature, °C Holding time. Air removal Heat-up time. Safety Exposure time. 

Infusion Method. Infusion is a classic method for top-fermented beers and is used for ad British types. The whole mash is heated graduady from mashing-in to mashing-off with holding times for the degradation of protein and starch. No part of the mash is boiled and the malt, therefore, must be well-modified to assure the breakdown of ad soluble substances. Because no boiling takes place there is no physical breakdown of the malt, and consequentiy infusion is not as effective as decoction despite the better protection of the enzymes. 

Assay of beryUium metal and beryUium compounds is usuaUy accompHshed by titration. The sample is dissolved in sulfuric acid. Solution pH is adjusted to 8.5 using sodium hydroxide. The beryUium hydroxide precipitate is redissolved by addition of excess sodium fluoride. Liberated hydroxide is titrated with sulfuric acid. The beryUium content of the sample is calculated from the titration volume. Standards containing known beryUium concentrations must be analyzed along with the samples, as complexation of beryUium by fluoride is not quantitative. Titration rate and hold times ate critical therefore use of an automatic titrator is recommended. Other fluotide-complexing elements such as aluminum, sUicon, zirconium, hafnium, uranium, thorium, and rate earth elements must be absent, or must be corrected for if present in smaU amounts. Copper-beryUium and nickel—beryUium aUoys can be analyzed by titration if the beryUium is first separated from copper, nickel, and cobalt by ammonium hydroxide precipitation (15,16). 

In another method, hydrogen peroxide can be added to the Hquid egg white after it has been heated at 52°C for a holding time of 1 minute (18) to inactivate the natural catalase and to allow the hydrogen peroxide to react against bacteria. Hoi ding time after addition of the hydrogen peroxide is 2.5 min... 

Mixing in Agitated Vessels Agitated vessels may frequently be used for either batch or continuous service and for the latter may be sized to provide any holding time desired. They are useful for liquids of any viscosity up to 750 Pa s (750,000 cP), although in contacting two liquids for reaction or extraction purposes viscosities in excess of 0.1 Pa s (100 cP) are only rarely encountered. 

Ensure that safety is not compromised by using manual sampling/analysis as part of the control scheme, e.g., increasing hold times... 

Nc = 0.0 gmol, Nq = 0.0 gmol, respectively. A mixture of A and B is charged into a 1-liter reactor. Determine the holding time required to achieve 90% fractional conversion of A (X = 0.9). The rate constant is k = 1.0 X 10 [(liter) /(gmoP min)] and the reaction is first order in A, second order in B and third order overall. 

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