Series items parallelism

Spiral and plate exchangers can cerate in series or parallel, but, because of their confi ration and main-tenenace requirements, it is preferable to position them as single items. Space is provided at both ar-... 

What is very important in process development is the personnel overlap when changing the scale of the process. The head of the team that is to continue the development of a process should be involved in the research on smaller scale. Also, an important member or head of the team in the smaller scale research should participate in the further step(s) of process development. Often, a parallel operation of teams is required instead of operation in series. A pilot plant, mostly composed of existing equipment items in a company, is often required as the final step in process development. A verification of procedures and models is usually not necessarily the main objective of pilot studies. The most common reason for manufacture at pilot scale is the production of kilograms of the product for market purposes and toxicity tests. A close interaction between chemists and chemical engineers is necessary at all stages of process development. 

Explanation The three items in this series are not conceptually parallel. Both industry and synthesis are broad terms, whereas the creation of amino acid derivatives is a much narrower, specihc task. 

Intermediate heat exchangers. Horizontal tube-and-shell IHXs with three modules connected in series, made of U-shaped tubes are used in the BN-350. The IHX of each loop consists of two sections connected in parallel both for primary and secondary coolant flows. The IHX is located in a suction loop upstream of the primary coolant pump, while in the secondary circuit it is in a pressure loop downstream of the circulating pump. The IHX tube bundles can be removed if necessary and replaced with new ones. The most stressed units in the IHX are the fixing joints for the tube module covers and for the fi-ame which stiffens the flat walls of the IHX body. Measurements of temperatures and stresses in various items of the IHX were carried out during reactor plant operation. On this basis requirements were formulated to limit the rate of the IHX heating-up in steps of 10% specified power with delays of 5-10 h in each step. By 1995 the IHXs have operated more than 160000 h at various power levels without any disturbances and failures. 

One level below the flow network, the analyst must define the Reliability Block Diagrams. Reliability Block Diagrams (RBD) are similar to logic flow networks and describe the interdependency between equipment items. Two configurations are to be defined blocks in series or blocks in parallel. Equipment items in series are required to be operational at all times to keep the system available. Equipment items in parallel, also known... 

The safety assessment therefore needs to consider the implication of unwanted operation (for instance via the functional hazard assessment as a specific functional failure mode applied to specific flight phases). The usual design practice (to ensure high system integrity) is to design parallel multiplex systems. However, when it is important to avoid unwanted operation, items may be put in series to avoid unwanted operation (Lloyd and TVe, p. 47) as demonstrated for the angle-of-attack (A of A) sensors in Fig. 6.4. 

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