Service performance

The most effective specification is that which accomplishes the desired result with the fewest requirements. Properties and performance should be emphasized rather than how the objectives ate to be achieved. Excessive demonstration of emdition on the part of the writer or failure to recognize the usually considerable processing expertise held by the vendor results in a lengthy and overly detailed document that generally is counterproductive. Redundancy may lead to technical inconsistency. A requirement that cannot be assessed by a prescribed test method or quantitative inspection technique never should be included in the specifications. Wherever possible, tests should be easy to perform and highly correctable with service performance. Tests that indicate service life are especially useful. Standard test references, eg, ASTM methods, ate the most desirable, and those that ate needed should be selected carefully and the numbers of such references should be minimized. To eliminate unnecessary review activity by the would-be complier, the description of a standard test should not be paraphrased or condensed unless the original test is referenced. 

The composition data should always be appHed to in-service performance (64,65) in order to properly evaluate the behavior of the asphaltic binder under tme working conditions. 

Amongst the factors that will influence service performance are the effect of additives and impurities, temperature, detailed geometric size and shape, orientation and morphology, surface condition, energy and speed of any impacting blow, the shape of the impacting instrument, the environment, and strains in the article due to external loads. For this reason it is desirable, but not always feasible, to test prototype articles under conditions as close to service conditions as possible. 

VINCENT, p. I., Impact Tests and Service Performance of Plastics, Plastics Institute, London (1971)... 

The aluminum alloys most commonly bonded are 2024 bare, 2024 clad and 7075 bare. Clad 7075 was also used extensively in early bonded structure but was largely abandoned after service performance demonstrated that it was susceptible to rapid dissolution or corrosion of the clad layer. Naturally aged tempers such as T3, in particular 2024-T3 because of its widespread use, are restricted to bonding with adhesives that cure at 250°F or below in order to avoid adversely affecting the temper. Various other alloys and tempers are bonded to a lesser extent, though the dominance of 7075 and 2024 is decreasing as higher-performance alloys and tempers are adopted. 

In-service performance. Service performance of bonded composite hardware has been good, at least from the standpoint of adhesive bonding. Like all aerospace hardware there have been occasional in-service problems with materials, design and manufacture of composite parts, but few have been related to adhesive bonding. 

Is product servicing performed and reported in accordance with documented procedures ... 

Objectives for product or service performance - addressing customer needs and competition... 

Certain tools are perishable i.e. they are consumed during the process. Others are reusable after maintenance and this is where adequate controls need to be in place. The tool control system needs to cover tool selection, set-up, tool change, and tool maintenance You will need procedures for withdrawing maintainable tools from service, performing the maintenance, and then putting the tools back into service. You need to build in safeguards that prevent worn tools being used and to replenish tools when their useful life has expired. 

The main difference between the two types are that the reaction products of the silico fluoride types are less soluble in water and are also harder, which may give better in-service performance but at a slightly higher material cost. However, with recent developments in floor-laying techniques, the concrete substrates for industrial floors are laid with much more dense low-porosity surfaces, so that neither silicate nor silico fluoride treatments are as effective as they used to be, when the concrete used had a slightly more open finish and hence was more receptive to these treatments. With modern concrete floors, it is imperative to wash any material not absorbed into the surface within a short period. Otherwise, unpleasant white alkaline deposits, which are difficult to remove, may occur. 

Various authorities and military bodies issue specifications relating to the service performance of engine oils. In some instances the ratings are almost identical with those of the API, but most of them are not precisely parallel because they cover performance factors encountered in particular engines and particular categories of service. 

If the potential suppliers cannot provide documented service performance for similar plant on similar duties, materials suppliers should be consulted. 

Process/equipment/tools Produce service performance] Plant personnel capability ... 

For details of the test methods used to measure physical properties reference is made to Handbook of Plastics Test Methods or the more recent Handbook of Polymer Testing [2, 3]. Standard tests have their limitations most were intended for quality control rather than prediction of service performance and produce arbitrary rather than fundamental measures of the properties. They do have the advantages of making data compatible with others and often have known reproducibility. In many standard methods the user is encouraged to opt for standard or preferred conditions which may not have relevance to the service conditions of the product. It is then sensible to base the testing on standard methods but to use more relevant conditions of, for example, time, temperature or stress. 

An indirect indication of service life is obtained simply by comparison of the performance of materials under given test conditions, the one which shows the smaller change being deemed to perform better. If one material is a standard with known service performance an estimate can be made of the other material s expected performance. Particularly with accelerated tests, this can be a dangerous assumption because the differences seen under the test conditions may not be similar to the differences realised in practice. To make a direct estimate of service life it is necessary to apply some form of extrapolation technique to measured data. 

The parameters used to monitor degradation are not the ones critical to service performance. 

Performance Tests. The underlying goal of corrosion testing is generally the prediction of service performance, whether directly for a device or system, or indirectly in the design or formulation of a... 

Absolute correlations between service performance and electrochemical measurements do not appear frequently in the literature. Based on 300 test systems. Bacon and coworkers (, correlated electrochemical resistance with exposure time. Recently, Mills ( also observed a correlation between salt fog corrosion and electrochemical resistance. We have found open circuit potential measurements to be extremely useful for the routine evaluation of high-nitrile polymer-based photocured coatings. 

Records Usage, maintenance, services, performance verification testing, and location of the records. 

In 1964, Shell Canada conducted full scale paving trials in Oakville, Ontario and St. Boniface, Manitoba in which the in-service performance of SAS systems were compared with conventional asphaltic concrete using both well graded aggregates and poorly graded sands. The results of these trials are summarized below ... 

This classification can be loosely linked to the purposes of testing. For quality control, fundamental properties are not needed, apparent properties will usually be acceptable, although functional properties would certainly be desirable. For predicting service performance, the most suitable properties would be functional ones. For design data, fundamental properties are really needed, although considerable help can often be got from functional properties. For investigating failures, the most useful test will depend on the individual circumstances but it is unlikely that fundamental methods would be necessary. 

In the same way that tests based on arbitrary conditions are deficient for design data purposes, so they may tend to lack in their direct relevance to service conditions and, hence, their value for predicting service performance. The two situations are not identical, in particular a test may simulate service use to enable predictions to be made but not yield data which can be used in design calculations. Not only for product proving but also for quality control, there is increasingly demand for tests which are better in this respect. A prime difficulty is that as effort is made to make the method reflect service so it tends to become more complicated and more expensive. There are many instances in specifications where a more relevant test exists but is not used because it is more time consuming or complex. 

The choice of abradant should be made primarily to give the best correlation with service, and the usual abrasive wheels and papers really only relate to situations where cutting abrasion predominates. Materials such as textiles and smooth metal plates may be more appropriate for other applications. In practice, the abradant is often chosen largely for reasons of convenience and surfaces such as plain steel have the disadvantage of abrading slowly and, if the conditions are accelerated, give rise to excessive heat build-up. Consequently, abrasive wheels and papers are used in situations where they are inappropriate for assessment of service performance. 

Performance In general, a service performs more poorly than an in-process method call due to network latency and bandwidth constraints. To make things worse, a service may call other services to fulfill its responsibilities—a chain of services. Performance has to be a design consideration throughout the development cycle. 

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