Faulty materials

With the widespread acceptance of the independently assessed ISO 9000 scheme, many companies will accept the analysis of the raw material supplier. Once the quality and consistency of the raw material are proven, only vital tests may be carried out. Because of the moisture sensitivity, opening and sampling of the drums may lead to faulty material if the drums are not properly resealed. The three vital control instruments are ... 

In many cases, the consequences of corrosion are not even attributed to corrosion. When a building collapses because of the corrosion of reinforcing steel bar in concrete, it is attributed to faulty materials instead of corrosion. 

If something goes wrong, then the necessary steps must be taken to ensure that the non-conforming or faulty material does not get into the finished product. 

Uneven dyeing n. A fabric dyeing that shows variations in shade resulting from incorrect processing or dyeing methods or from use of faulty materials. 

There are many different causes of failure. One scheme for classifying strucmral failures is the following design errors, faulty materials, physical damage, overloading, poor workmanship, and poor maintenance and inspection practices. 

Construction. In the constmction phase there are two ways problems can arise. The more common of these is poor workmanship. Uneven foundation settlement and faulty constmction, eg, use of the wrong materials or insufficient quantity of rebars, are but two examples. Only qualified builders, close inspection during constmction, and enforcement of a tightly written specification are necessary factors. 

Artifacts introduced through sample preparation are common materials these may be bits of facial tissue, wax, epithelial cells, hair, or dried stain, all inadvertently introduced by the microscopist. Detergent residues on so-called precleaned microscope slides and broken glass are common artifacts, as are knife marks and chatter marks from sectioning with a faulty blade, or scratch marks from grinding and polishing. 

To simulate the effect of small flames that may result from faulty conditions within electronic equipment, the lEC 695-2-2 Needle Elame Test may be used. In this case a small test flame is applied to the sample for a specified period and observations made concerning ability to ignite, extent of burning along the sample, flame spread onto adjacent material and time of burning. 

Check for underventilation caused by obstructed vents, faulty dampers or other HVAC system malfunctions, or from problems within the occupied space. Furniture, papers, or other materials can interfere with air movement around thermostats or block airflow from wall or floor-mounted registers. If office cubicles are used, a small space (i.e., two to four inches) between the bottom of the partitions and the floor may improve air circulation. 

Division 2 Locations where hazardous material exists only in the case of a fault situation (leaky valve, burst pipe, faulty equipment)... 

If faulty specification or unsuitable materials are found to be the cause of defects requiring repairs, replacement work should be considered in anticipation of problems arising on a wider scale. A less disruptive repair program may thereby be adopted compatible with routine maintenance operations. 

It should be noted that lead dioxide will discharge if electronically connected to a more base material, when in an unenergised state. The reverse current leakage of a rectifier will allow this to happen to a small extent if the rectifier is faulty, with the consequent formation of lead chloride and corrosion of the anode. 

Despite the failing of the dental silicate cement under acid conditions it is more resistant to acid attack than all other dental cements with the notable exception of the glass polyalkenoate cement (Norman, Swartz Phillips, 1959 Walls, McCabe Murray, 1985 Beech Bandyopadhyay, 1983 Kuhn, Setchell Teo, 1984 Wilson et al., 1986a). These studies have been confirmed by in vivo observations (Norman et al., 1969). A clinical study carried out by Robinson (1971) over many years showed that when carefully prepared and placed, the dental silicate cement was capable of giving good performance. Many of the failures of this material must be attributed to faulty preparation. 

The care with which a synthesis is analyzed and planned will have a great impact on the likelihood of its success. The investment of material and effort that is made when the synthesis is begun may be lost if the plan is faulty. Even with the best of planning, however, unexpected problems are often encountered. This circumstance again tests the ingenuity of the chemist to devise a modified plan that can overcome the unanticipated obstacle. 

Returning to our discussion of benefits, we note that they fell into two principal areas the time-value of information and the improvement in laboratory productivity. As we saw, assessing the benefits from the time-value of information requires examination of the total process through which that information will be used. For example, using data such as the anticipated improvement in laboratory turn around time, the rate at which material Is produced and its value, and the current the financial losses attributable to scrap or rework, one can estimate the savings in dollars to be accrued (each hour of faulty production avoided through faster lab turnaround time yields as a gain to the firm, the revenue that otherwise would have been lost). 

Changes in demand, breakthroughs by competing companies, fluctuations in the price or availability of raw materials and faulty original estimates can all cause a product to fail. Such market performance dramatizes the uncertainty of marketing new products. Indeed, experience has shown that about half of new commercial ventures fail. 

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. 

Drying, usually by physical methods, is one of the most common unit operations in both laboratory or industrial scale process chemistry, and since heating is usually employed to remove volatiles, thermally unstable materials may decompose if overheated. As a light-hearted example, when a faulty oven thermostat led to overheating of mercuric thiocyanate, a monstrous Pharaoh s serpent resulted. Drying moist cadmium propionate in an electric oven led to explosive ignition of the diethyl ketone vapour produced as an unforeseen by-product. Drying 3,5-dinitro-2-toluamide had more serious consequences. 

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