Particular Test Procedures

The fractions obtained in these schemes are defined operationally or proceduraHy. The amount and type of asphaltenes in an asphalt are, for instance, defined by the solvent used for precipitating them. Fractional separation of asphalt does not provide well-defined chemical components. The materials separated should only be defined in terms of the particular test procedure. 

In the off-line mode of use of the drug file the data-base, stored In a time-shared computer. Is Interrogated through a remote device such as a cathode ray terminal The questions that may be asked Include all the affects of a drug, all the drugs that affect a test, or more specifically does a particular drug affect a particular test procedure by a particular mechanism ... 

A number of subjects common to all areas of physical testing have been addressed in chapter 2. These include discussion of the reasons for testing, the trends in test development, the use of statistics and quality control of laboratories. Whilst these matters are not unique to rubber testing, it is most important that they are fully appreciated in the context of our particular test procedures and class of materials. 

The use of steam at 100°C or above would provide an accelerating effect, although this would probably be considered too severe for most applications. Such a test would, however, be relevant for a product such as hose intended for use with steam and the particular test procedure would be found in the product specification. In designing any tests for exposure to steam it is necessary to control the amount of air (if any) present since oxygen at the temperatures used would have a strong deteriorating action. 

The fractions obtained in these schemes are defined operationally or procedurally. The amount and type of asphaltenes in an asphalt are, for instance, defined by the solvent used for precipitating them. Fractional separation of asphalt does not provide well-defined chemical components. The materials separated should only be defined in terms of the particular test procedure (Fig. 15.5). However, these fractions are generated by thermal degradation or by oxidative degradation and are not considered to be naturally occurring constituents of asphalt. The test method for determining the toluene-insoluble constituents of tar and pitch (ASTM D-4072, ASTM D-4312) can be used to determine the amount of carbenes and carboids in asphalt. 

The specimen is prepared in accordance with the particular test procedure being employed and is then conditioned as necessary. 

It is essential for design, specification, and quality control to have data covering the physical properties of materials. It is also essential that meaningful data is obtained by-using test methods relevant to the materials. The different characteristics and behavior of materials dictate that particular test procedures be developed, and often standardized, for each material type. Polymers, especially, have unique properties that require their own measurement techniques. 

Polystyrene foams applied in building constructions are dealt with in BS 6203 1982. No particular test procedure is prescribed, reference is made only to flammability tests in the building industry, mainly according to BS standards, the properties of polystyrene foams are surveyed, and proposals are made as to the most effective ways of their incorporations into building structures with respect to fire regulations. 

The encapsulated material can be used like the pure material in many applications. The two disadvantages — slight loss in resolution and increase in heat capacity per unit area because of the need to use thicker films — are not serious enough to prevent using the encapsulating material where a particular test procedure necessitates long-term stability. 

The characteristic behaviour of a functional group towards a particular test procedure may be modified or nullified by the influence of the remainder of the molecule, and attention has been drawn to the more serious deviations of this kind in the text. However, it is not possible nor perhaps desirable to list the minor variations that are often found in test results, and it is advisable to gain experience of an unfamiliar test by appl3ring it to known compounds of the appropriate type. Careful observation of such control tests provide a valuable basis for the interpretation of results obtained subsequently in the course of analyses. 

All impact tests are very sensitive to the precise details of the particular test procedure. 

The use of the surface ultrasonic waves seems to be convenient for these purposes. However, this method has not found wide practical application. Peculiarities of excitation, propagation and registration of surface waves created before these time great difficulties for their application in automatic systems of duality testing. It is connected with the fact that the surface waves are weakened by soil on the surface itself In addition, the methods of testing by the surface waves do not yield to automation due to the difficulties of creation of the acoustic contact. In particular, a flow of contact liquid out of the zone of an acoustic line, presence of immersion liquid, availability of chink interval leads to the adsorption and reflection of waves on tlie front meniscus of a contact layer. The liquid for the acoustic contact must be located only in the places of contact, otherwise the influence on the amplitude will be uncontrolled. This phenomenon distorts the results of testing procedure. 

Several countries have developed their own standard test methods for cellular plastics, and the International Organization for Standards (ISO) Technical Committee on Plastics TC-61 has been developing international standards. Information concerning the test methods for any particular country or the ISO procedures can be obtained in the United States from the American National Standards Institute. The most complete set of test procedures for cellular plastics, and the most used of any in the world, is that developed by the ASTM these procedures are pubUshed in new editions each year (128). There have been several reviews of ASTM methods and others pertinent to cellular plastics (32,59,129—131). 

The significance of a particular test is not always apparent by reading the procedure, and sometimes can only be gained through working familiarity with the test (96). The following tests are commonly used to characterize asphalts. 

Laboratory tests used in the development of inhibitors can be of various types and are often associated with a particular laboratory. Thus, in one case simple test specimens, either alone or as bimetallic couples, are immersed in inhibited solutions in a relatively simple apparatus, as illustrated in Fig. 19.34. Sometimes the test may involve heat transfer, and a simple test arrangement is shown in Fig. 19.35. Tests of these types have been described in the literatureHowever, national standards also exist for this type of test approach. BSl and ASTM documents describe laboratory test procedures and in some cases provide recommended pass or fail criteria (BS 5117 Part 2 Section 2.2 1985 BS 6580 1985 ASTM 01384 1987). Laboratory testing may involve a recirculating rig test in which the intention is to assess the performance of an inhibited coolant in the simulated flow conditions of an engine cooling system. Although test procedures have been developed (BS 5177 Part 2 Section 2.3 1985 ASTM 02570 1985), problems of reproducibility and repeatability exist, and it is difficult to quote numerical pass or fail criteria. 

Portland cement is susceptible to corrosion by CO2 and H2S. The chemical attack by CO2 is called carbonation. A microsample technique has been developed to study the CO2 corrosion in cements, because the corrosion is difficult to monitor with common test procedures [264]. This technique is also advantageous as an accelerated testing method. A polymer-modified cement has been tested in field studies [694]. The addition of silica also improves chemical resistance [146], in particular brine corrosion. 

Unfortunately, the basic physical mechanisms that control the attrition process are still poorly understood. As a consequence, particular test methods are used to evaluate the degradation tendency of the materials or to predict the rate of attrition for a given process. There are a lot of procedures using widely different devices and operations. Some of them observe the degradation of only one individual particle, whereas others treat a considerable amount of material. The particles are subjected to stress systems which range from well-defined ones like impact or compression, to those which are similar to the more or less randomized stresses occurring in natural processes. Section 4 attempts to summarize the huge variety of attrition tests in a systematic way. 

The major category of nonconforming work is allocated for any failure of a system to comply with the requirements of the Standard which could lead to invalidity of test results. Examples include absence/non-implementation of a document control system, absence/non-implementation of a procedure for internal audit or management review, staff not technically competent to perform particular tests and failure to control the quality of test data. 

Figure 20.6 illustrates the test procedure. The key model inputs are defined at the left of the illustration and the outputs to the right. Only the essential input variables are shown here others are in fact used by the model but they are either constant for all plant operating conditions or the model equations are not particularly sensitive to them. 

Where the purpose is simply to make a comparison or to check against a specification the value of the results is less critically dependent on the relation of the test conditions to service. This does not mean that the test conditions are unimportant for comparison or quality checks but that their relevance to service need only be established in general terms and not proved rigorously. The essential requirement for comparison is that the test conditions are not such that they give a distorted view of relative performance. For quality control it is particularly important that the test procedures and conditions are standardised and reproducible. 

For practical purposes, saturated flow of a single fluid such as gasoline, kerosene, or another particular petroleum product can be predicted by the use of these equations. Standard units of linear measurement (feet, meters, etc.) and discharge are accommodated for by the corrections for viscosity and density. Field-testing procedures can be conducted using standard water well testing procedures. 

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