Paper deterioration, mechanisms

Oxidation and acid hydrolysis are the two principal deterioration mechanisms for paper, and recently chemiluminescence (CL) has been used to follow the oxidation of cellulosic materials at temperatures of 40 °C and below (I). CL is thought to be produced by the termination... 

Paper objects may suffer from damage by vermin, insect and microbial attack, theft, fire and flood. However, from a chemist s point of view there are two important mechanisms by which paper deteriorates, both of which may change its hue and make it weaker these mechanisms are acid-catalysed hydrolysis and oxidation. Papers vary a lot in their stability and the worst can become so brittle that they become unusable. Papers made from rags using traditional methods are usually extremely stable, but old papers made from poorly processed wood pulp are often very weak. 

This paper focuses on how to model the deterioration of static pressurized process equipment to enable efficient inspection and maintenance planning. Such equipment tends to gradually deteriorate over time from erosion, corrosion, fatigue and other mechanisms, and at some point of time inspection, repair or replacement is expedient with respect to safety, production and costs. The deterioration of the equipment is influenced by many factors such as type of equipment, system design, operation and process service, material and environment. For hydrocarbon systems, the most critical deterioration mechanisms are corrosion due to CO2 and H2S, microbially influenced corrosion, sand erosion and external corrosion (DNV 2002). In general, CO2 is the most common factor causing corrosion in oil and gas system of low alloy steel (Singh et al. 2007). 

In this paper we will focus on equipment suffering from gradually deteriorating mechanisms. The objective is to discuss the required steps and address the uncertainties and necessary assumptions when modeling deterioration for the purpose of inspection and maintenance optimisation in a risk based context. The discussion will be exempHfied by hydrocarbon containing static process equipment made from carbon steel suffering from CO2 corrosion. 

The approach is theoretically based on preposterior Bayesian decision theory and can be used when deterioration mechanisms such as fatigue, corrosion, wear and erosion are present and can be observed by inspection and monitoring before failure of the component occur. The decision tree described in this paper is illustrated in Figure 7. 

Hertz s last piece of experimental work was done when his health was deteriorating and he was devoting most of his research time to intensive theoretical work on the logical foundations of mechanics. In 1892 in his laboratoi-y in Bonn, he discovered that cathode rays could pass through thin metallic foils. He published a short paper on the subject, but did not pursue the matter further. Instead he handed his apparatus and his ideas over to Philipp Lenard (1862—1947), his assistant in Bonn. Lenard pushed Hertz s suggested research so far that Lenard received the Nobel Prize in Physics in 1905 for his work on cathode rays. ... 

Measurement of pH is a potentiometric technique frequently used for measuring the degree of the deterioration of materials that are subjected to natural aging. The determination of pH levels is commonly carried out on ethnographic objects manufactured with parchment or leather, and it is especially relevant in altered paper due to the formation of acidic compounds from the decomposition of the woodpulps and other raw materials, which can induce the hydrolysis of the cellulose and then decrease the resistance and mechanical properties of the document [29]. 

The technical paper described the interlock testing program to consist of more than merely verifying that the interlock works. There is also inspection of the interlock equipment for deterioration. The function test on instrumentation is required following mechanical work on one or more of the safety system elements. In short, all devices or systems that have been disturbed enough to affect their normal function will be function tested prior to being restored to service. [26]... 

The deterioration of paper is manifested in several ways, for example, extensive discolouration and loss of mechanical strength can occur. The early detection of changes and their measurement needs special apparatus. 

The prime factor in choosing an abradant is its relevance to service, but it also has to be available in a convenient form and, for anything but ad hoc tests, it is essential that it be reproducible. In consequence of these considerations, abrasive wheels and papers or cloths predominate where cutting by sharp asperities is to be simulated. The abrasive wheel is probably the most convenient, because of its low cost, its mechanical stability, and the ease with which it can be refaced to maintain a consistent surface. Abrasive papers and cloths are cheap and easy to use but are not so readily refaced and will deteriorate in cutting power more quickly. Although basically low in cost, both wheels and papers are a considerable c.xpense when bought as standard reference materials. Materials such as textiles or smooth metal plates are more relevant for some applications, but they abrade relatively slowly, and if conditions are accelerated they give rise to excessive heat buildup. 

The problem of reliable structural materials for use at low temperatures has recently become topical. Progress in space research, storage and transportation of liquefied gases, superconducting electrical machinery, and superconducting instrument production requires new structural materials serviceable at long exposures to extreme conditions of operation without deterioration of their physical and mechanical properties. Only some aspects of the development of cryogenic materials science in the USSR are mentioned in this paper, and these have been carried out at the Physico-Technical Institute of Low Temperatures of the Ukrainian Academy of Sciences in Kharkov. 

Deterioration of the mechanical properties of paper (folding ability, etc.). 

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