Small-Scale Test Procedures

The scale-up of filtration centrifuges is usually done on an area basis, based on small-scale tests. Buchner funnel-type tests are not of much value here because the driving force for filtration is not only due to the static head but also due to the centrifugal forces on the Hquid in the cake. A test procedure has been described with a specially designed filter beaker to measure the intrinsic permeabiHty of the cake (7). The best test is, of course, with a small-scale model, using the actual suspension. Many manufacturers offer small laboratory models for such tests. The scale-up is most reHable if the basket diameter does not increase by a factor of more than 2.5 from the small scale. 

In running the DIN 53436 method hydrocarbon and hydrogen cyanide has only been determined qualitatively. The cyanide concentration has been determined four times during the 30 minute steady state combustion process. From these experiments the average concentration of emission has been estimated. The other results presented in Table V from DIN 53436 experiments have been measured in similar ways as for the other small scale test methods. It may be observed that the amount of material burnt in each experiment is smaller than in previous test procedures. The results presented are average values of two deteminations of each material. 

Various small scale test units and procedures are available to determine slurry characteristics and suitability for a particular application. Buchner funnel, and vacuum leaf test units can be purchased or rented fi om vendors to perform in-house tests, or one can have tests conducted at the vendor s facility. Pilot testing on the actual equipment would be the optimum with a rental unit in the plant. In either case, slurry integrity must be maintained to ensure accurate filtration data. 

Truly satisfactory methods for scale up are not available. Purchas (1977) indicates that scale up has two meanings. While the obvious meaning refers to the prediction of the size of process equipment from small-scale tests, choice of suitable equipment is an equally important part of scale up. Purchas (1977) states none of the test or scale up procedures presented merits being called a standard procedure . The virtual total absence either of existing standards or of serious attempts to involve or develop standards in an area of such major importance can only be regarded as remarkable in the current era. ... 

Often misused rules-of-thumb in the evaluation of thermal hazards are the 100 Degree Rule and similar rules which state that, if the operating temperature of a process is 1(X)°C or some other temperature difference lower than the nearest detectable exotherm observed in a small-scale test, then the process operation will not experience this thermal event and it is not necessary to obtain more detailed information from other, more sensitive tests. Several factors govern the temperature dependent rates of heat generation as detected in small-scale tests. These include the physical aspects of the test procedure such as sample size, the Phi factor, sensitivity and agitation, and the thermokinetic aspects of the reaction being studied, in particular the activation energy. ... 

As a first test the equipment was installed for wireless measurements of strain and aeoustie emissions during load at a large test facility (Fig. 15.3) of the Technical University of Brunswick in Northern Germany, and at a smaller stracture of the University of Stut art. Since not all data of the large test are yet analyzed the test procedure of the small scale test as well as the implemented techniques will be described in die following. 

Full-scale fire tests can give more useful information than small-scale tests with tiny specimens. They can simulate the behaviour of plastics articles such as foam-filled furniture and television sets in fires. Examples include the Steiner tunnel test, the ISO 9705 room comer test and the CAL 133 test. Many fire test procedures are specific to a given industry, such as construction or the railways. In the latter case, the standard of flammability required may depend on whether a train is to be operated through long tunnels. 

Quality control tests or improvement of existing processes. Raw materials from various sources can be used in the manufacture of fine chemicals and pharmaceuticals. The raw materials can contain different impurities at various concentrations. Therefore, before the raw material is purchased and used in a full-scale batch its quality should be tested in a small-scale reactor. Existing full-scale procedures are subject to continuous modifications for troubleshooting and for improving process performance. Laboratory reactors used for tests of these two kinds are usually down-scaled reactors or reactors being a part of the full scale-reactor. 

We have synthesized two small scale batches (PA-DBX 1 and 2) of 2-3 g each and one intermediate scale batch (PA-DBX 3) of 8-10 g of DBX-1 from our NaNT. The procedure used to synthesize DBX-1 was based on literature methods.[5,6] For each batch, sensitivity tests, thermal stability by differential scanning calorimetry (DSC), and performance tests were performed and compared to the standard DBX-1 that was obtained from PSEMC (Pacific Scientific Energetic Materials Company, inventors of DBX-1). 

Larger Scale Testing. The standard card gap test (2) is test No. 1 of a series of larger scale tests designed to determine the sensitivity of liquid propellants to hydrodynamic shock. In this test, relative sensitivities of various propellants are determined in terms of the number of 0.01-inch thick cellulose acetate cards required to attenuate a standard shock sufficiently just to prevent initiation in the test sample. When performed according to the exacting conditions of apparatus and procedure, the results are very reproducible from one laboratory to another. However, small variations in the apparatus or procedure can cause major variations in the resulting data, and therefore the test can be considered only relative. A major drawback of the standard test is that it cannot accommodate materials that are volatile under the test condition. At TCC-RMD some special equipment has been developed that allows tests to be made on confined samples at elevated temperature and pressure. 

Supporting Data — Data, other than those from formal stability studies, that support the analytical procedures, the proposed retest period or shelf life, and the label storage statements. Such data include (1) stability data on early synthetic route batches of drug substance, small-scale batches of materials, investigational formulations not proposed for marketing, related formulations, and product presented in containers and closures other than those proposed for marketing (2) information regarding test results on containers and (3) other scientific rationales. 

In some cases, direct scale-up may be impracticable, for example because of blockage of the small-scale relief line. The requirement for complete emptying of the small-scale reactor by two-phase relief may also not be met in practice. If this occurs for a tempered system, the problem could be overcome by using a small-scale relief system from the bottom of the test reactor to simulate one at the top of the large-scale reactor. This procedure would not be safe for untempered reactions. 

Finally, we developed testing procedures that included Brabender studies and the use of high temperature Mooney machines, and our program began to move. We were able to correlate with production sheet extrusion conditions which enabled us to make our numerous product development changes rapidly on a small scale. 

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