Service experience

Table 1 shows materials of construction for general planning when specific service experience is lacking. 

Table materials are for general use, specific service experience is preferred when available... 

The first source of information for the behavior of a material in the proposed service environment is the potential supplier of the item of plant. Except for new (or significantly modified) processes, specialist suppliers or fabricators have relevant information and service experience. The supplier should be provided with all process or environmental details that are of possible relevant to corrosion. The most important are listed below ... 

Barnard, K. N., Christie, G. L. and Gage, D. G. Service Experience with Lead Silver Alloy Anodes in Cathodic Protection of Ships , Corrosion, 15, 11, 581-586 (1959) Peplow, D. B. and Shreir, L. L. Lead/Platinum Electrodes for Marine Applications , Corr. Tech. Apr. (1984)... 

Table 7.29 Service experience with thermocouple protection tubes in reducing gases and other...

In process streams where there are large changes in process temperature over a short time, the fact that the temperature of the protected element will lag behind that of the exposed element can give rise to considerable errors. The most recent development is the use of test and reference elements that are both exposed to the corrodent. The comparator element has a much larger area than the measuring element so that its resistance varies much less than that of the measuring element during their corrosion. Several drawbacks to this type of monitor, deduced from service experience, may be quoted ... 

London, shows, for example, that every year more than 800,000 patients using the UK National Health Service experience adverse drug reactions [13 and references therein]. 

The NACE Landrum Wheel velocity test, originally TM0270-72, is typical of several mechanical-action immersion test methods to evaluate the effects of corrosion. Unfortunately, these laboratory simulation techniques did not consider the fluid mechanics of the environment or metal interface, and service experience very seldom supports the test... 

The limits described by these curves are based on service experience originally collected by G.A. Nelson and on additional information gathered by or made available to API. 

Materials With Limited Service. The desirability of specifying some degree of production impact testing, in addition to the weld procedure qualification tests, when using materials with limited low-temperature service experience below the minimum temperature stated in Table IX-2. 

The component design temperature shall be the fluid temperature unless calculations, tests, or service experience based on measurements support the use of another temperature. 

The principal observation, which the laboratory scientist should not forget, was that most lifetime assessment of polymers is based on experience from service. Many of the respondents to the survey report examining parts taken from service at the end of life, or those that failed during warranty. Service experience is the principal source of information for the definition of insured lifetimes for polymer components in the construction industry. 

This book is concerned with assessing the useful life of plastics and accelerated testing follows service experience and simulated life tests in importance as a basis for life prediction. However, the results of accelerated tests are not always used to predict service life directly. Indeed, the majority of accelerated tests are carried out for quality control purposes, to show conformity with a specification or to make a comparison of materials. 

Electrical insulation is an example of a database being built up based on a combination of Arrhenius type extrapolation and service experience, but highlights the expense and difficulties of full scale Arrhenius testing. 

In practice, most lifetime prediction is based on service experience. Depending on the industry concerned, this can take the form of planned examination of components at the end of their service life or be limited to the explanation of warranty returns. Experience with polymers is now sufficiently long for service experience to be a prime source of information for components with lifetimes of up to 35 years. The construction industry provides a good example of systematic listing of component lifetimes, related to minimum quality levels and modified according to the service conditions. The electrical industry applies statistical methods to life components and predict failures. This, however, strays into the general field of engineering component lifetimes. In this book we are concerned with materials rather than components. 

Problems with service experience include obtaining sufficient information on the actual conditions of service, finding that these conditions are much milder than the design conditions, or that the polymer formulation used has now been superseded. Life prediction cannot consider failures caused by poor workmanship, incorrect use or maintenance, or faulty design, particularly of joints, attachments or in the choice of neighbouring materials. Many failures in practice are due to degradation in processing, faulty assembly, or to abuse. 

The basic question of whether accreditation or certification is appropriate arises when a laboratory is trying to meet the needs of the customers for testing and/or calibration services. Experience shows that the real nature and objectives of ISO 9001 are not always clearly imderstood by the stakeholders. The situation may be different in each case, depending on the customer. 

Field service experience has proved that stop-leak materials cannot be depended upon to correct cylinder head joint leakage due to high combustion pressures at the joint and thermal stresses in the joint metals. 

For volume production of an aerosol fog of small particle size, on a large scale (suited to indoor use), the thermal aerosol fog generators appear to be very efficient. The Science Service experiments were mostly with this type. Two principal varieties have been developed. One discharges the insecticide solution or suspension as a relatively coarse spray into a jet of superheated steam delivered by a flash boiler of the tubular coil t3rpe. The other discharges that insecticide solution or suspension as a relatively coarse spray into a blast of hot gas emerging from a combustion chamber. The temperature is regulated by the controlled admixture of cold air. 

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