Machinery directives

The essential objective of a conformity assessment procedure is to enable the authorities to ensure that products placed on the market conform to the requirements expressed in the directives and, these products must meet the high level of safety that the directives seek for a given product or product sector. There are seven modules in 93/465/EEC, and the generic directives (LVD, EMC, etc.) or product-specific directives (machinery, etc.) will set the range of choices that may be considered, as follows ... 

The pressure equipment directive was adopted by the European Parliament and the European Council in May 1997. It harmonises the national laws of the 15 Member States of the European Union relating to equipment subject to the pressure risk. That directive is one of the series of technical harmonisation directives such as for machinery, medical devices, simple pressure vessels, gas appliances and so on, which were foreseen by the Communities programme for the elimination of technical barriers to trade. It therefore aims to ensure the free placing on the market and putting into service of the equipment concerned within the European Union and the European Economic Area. At the same time it permits a flexible regulatory environment, allowing European industry to develop new techniques increasing thereby its international competitiveness. 

The scope of the directive covers the design, manufacture and conformity assessment of pressure equipment and assemblies with a maximum allowable pressure greater than 0,5 bar. A pressure equipment in the sense of the directive is any vessel, piping, safety accessory or pressure accessory. An assembly means several pieces of pressure equipment assembled by a manufacturer to constitute an integrated and functional whole. It is important to be aware that the directive relates exclusively to the pressure risk and that therefore other directives, such as for machinery, low voltage may be applicable to the equipment concerned. 

Certain types of equipment are specifically excluded from the scope of the directive. It is self-evident that equipment which is already regulated at Union level with respect to the pressure risk by other directives had to be excluded. That is the case with simple pressure vessels, transportable pressure equipment, aerosols and motor vehicles. Other equipment, such as carbonated drink containers or radiators and piping for hot water systems are excluded from the scope because of the limited risk involved. Also excluded are products which are subject to a minor pressure risk which are covered by the directives on machinery, lifts, low voltage, medical devices, gas appliances and on explosive atmospheres. A further and last group of exclusions refers to equipment which presents a significant pressure risk, but for which neither the free circulation aspect nor the safety aspect necessitated their inclusion. 

Before considering other concepts and group-theoretical machinery, it should once again be stressed that these same tools can be used in symmetry analysis of the translational, vibrational and rotational motions of a molecule. The twelve motions of NH3 (three translations, three rotations, six vibrations) can be described in terms of combinations of displacements of each of the four atoms in each of three (x,y,z) directions. Hence, unit vectors placed on each atom directed in the x, y, and z directions form a basis for action by the operations S of the point group. In the case of NH3, the characters of the resultant 12x12 representation matrices form a reducible representation... 

Molecular modeling has evolved as a synthesis of techniques from a number of disciplines—organic chemistry, medicinal chemistry, physical chemistry, chemical physics, computer science, mathematics, and statistics. With the development of quantum mechanics (1,2) ia the early 1900s, the laws of physics necessary to relate molecular electronic stmcture to observable properties were defined. In a confluence of related developments, engineering and the national defense both played roles ia the development of computing machinery itself ia the United States (3). This evolution had a direct impact on computing ia chemistry, as the newly developed devices could be appHed to problems ia chemistry, permitting solutions to problems previously considered intractable. 

These benefits directly translate into lower costs and improved operating efficiency for rotating machinery. Lubrication is unnecessary. The bearing is operable in hostile environments and, in many cases, can operate in the process fluid at high pressures and temperatures. Experience shows that total consumption of frictional power is drastically reduced. 

Most turbomachinery is mounted on structural steel platforms sometimes referred to as base plates or skids. These platforms are then installed on a mass of concrete at the jobsite (either by direct grouting or mounting on sole plates) to become the machinery foundation. Platforms should always be considered as part of the foundation rather than as part of the machinery. 

Three-base codons on die mRNA corresponding to specific amino acids direct the sequence of building a protein. These codons are recognized by tRNAs (transfer RNAs) carrying die appropriate amino acids. Ribosomes are the machinery for protein syn diesis. 

The heaviest products obtained directly from oil arc lubricants, waxes, asphalt, and coke. These products have both domestic and industrial uses. Lubricants, for example, are applied in the operation and maintenance of industrial equipment and machinery. Asphalt, because it is not reactive to chemicals in the environment, is a superb material of construction in the building of roads and in roofing. It is also used in the waterproofing of concrete, the manufacture of black paints, and as a material lor tire threads, battery housing, electrical insulation, and other applications. The heaviest of all the petroleum products, coke, is used extensively as a major component of industrial electrodes and as a commercial fuel. 

The machinery employed in the early refineries was rather small in scale and operated iiiefficieutly. Generally, equipment consisted of a series of shell tubes or stills. These were placed in the horizontal position and were connected one to another from the top through the use of vapor pipes. These pipes directed the vapors from the stills into condensers which cooled the gases and so caused the products to separate out. These products were then collected in sequence, often at one point in the plant, as liquids of varying densities and properties. 

Time-domain plots must be used for all linear and reciprocating motion machinery. They are useful in the overall analysis of machine-trains to study changes in operating conditions. However, time-domain data are difficult to use. Because all the vibration data in this type of plot are added together to represent the total displacement at any given time, it is difficult to directly see the contribution of any particular vibration source. 

In typical rotating machinery, the vibration profile generated by a normal machine contains lower amplitudes in the vertical plane. In most cases, this lower profile can be directly attributed to the difference in stiffness of the vertical plane when compared to the horizontal plane. 

Data obtained from a vibration analyzer are not all that are required to evaluate machine-train or system condition. Variables such as load have a direct effect on the vibration profile of machinery and must be considered. Therefore, additional data should be acquired to augment the vibration profiles. 

Reciprocating compressors have unique operating dynamics that directly affect their vibration profiles. Unlike most centrifugal machinery, reciprocating machines combine rotating and linear motions that generate complex vibration signatures. 

Each process parameter directly affects both the machinery dynamics and the vibration profiles. For example, the line tension, strip width, and hardness of the incoming strip radically affect the vibration profile generated by a continuous process line in a steel mill. With few exceptions, process variations such as these must be considered in the vibration analysis. 

Variable speed orders analysis In a variable-speed machine, the unique frequencies generated by components such as bearings and gear sets do not remain constant. As the speed changes, the unique frequency components vary in direct proportion to the speed change. For this type of machinery, the analyzer s orders analysis option is used to automatically adjust each of the filters used to set the bandwidth and narrowbands for each data set to the true machine speed. 

Class 111 or serious machinery include major plant equipment that do not have a dramatic impact on production but that contribute to maintenance costs. An example of the serious classification would be a redundant system. Since the inline spare could maintain production, loss of one component would not affect production. However, the failure would have a direct impact on maintenance cost. 

Indications of misalignment in rotating machinery are shaft wobbling, excessive vibration (in both radial and axial directions), excessive bearing temperature (even if adequate lubrication is present), noise, bearing wear pattern, and coupling wear. 

Failure analysis statistics have consistently shown that many machinery components failures can be directly attributed the equipment being operated outside of design parameters or unintended conditions. Most failure analysis and trouble-shooting activities are usually post-mortem and commence after installation and start-up of the equipment. The maintenance phase is now in motion, and failure analysis and trouble-shooting is now an integral part of that phase. 

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