Design stages

Over the lifetime of the field, the total undiscounted operating expenditure (opex) is likely to exceed the capital expenditure (capex). It is therefore important to control and reduce opex at the project design stage as well as during the production period. 

Disposal of exhausted soHds can be easily overlooked at the plant design stage, particularly when these have no intrinsic value alternative disposal methods might include landfiU of inert material or incineration, hydrolysis, or pyrolysis of organic materials. Liquid, soHd, and gaseous emissions are aU subject to the usual environmental considerations. 

The way a pilot plant is designed affects its cost, operabiUty, and effectiveness. AH operating ranges may not yet be fully defined at the initial design stage, but a reahstic preliminary range is required before the design is commenced, as is a clear definition of the pilot plant s purpose. 

The toxicity of both feeds and products must be carefully considered during the preliminary design stages (53,54) especially if the feeds or products contain known or suspected carcinogens. Special testing may even be requked prior to operation to determine the toxicity of unknown materials. 

Hazard and Risk Assessment Tools The hazard and risk assessment tools used vary with the stage of the project from the early design stage to plant operations. Many techniques are available, both quahtative and quantitative, some of which are hsted in the following section. Reviews done early in projects often result in easier, more effective changes. 

Very often steel sheet pilings exist in conjunction with steel-reinforced concrete structures in harbors or locks. If cathodic protection is not necessary for the reinforced concrete structure, there is no hindrance to the ingress of the protection current due to the connection with the steel surfaces to be protected. The concrete surface has to be partly considered at the design stage. An example is the base of the ferry harbor at Puttgarden, which consists of reinforced concrete and is electrically connected to the uncoated steel sheet piling. 

Internal cathodic protection of water tanks and boilers is most economical if it is taken care of at the design stage. It can, however, be installed at a later stage as a rehabilitation measure to halt the progress of corrosion. Tanks and boilers in ships were described in Section 17.4. Further applications of internal protection are dealt with in Chapter 21. 

To extract die EPBC liquids, die plant employs a cryogenic temperature process in combination with a refluxed demedianizer process in two trains. The two turboexpander trains are die heart of die process and bodi have operated at efficiencies higher dian originally expected at die design stage. 

Improperly set tolerances and uncontrolled variation are one of the greatest causes of defects, scrap, rework, warranty returns, increased product development cycle time, work flow disruption and the need for inspection (Gerth and Hancock, 1995). If manufacturing processes did not exhibit variation, quality problems would not arise, therefore reducing the effects of variability at the design stage, in a cost-effective way, improves product quality (Bergman, 1992 Kehoe, 1996). 

Variation is an obvious measure for quality of conformance, but it must be associated with the requirements set by the specification to be of value at the design stage. Unfortunately, difficulty exists in finding the exact relationship between product tolerance and variability. Approximate relationships can be found by using process capability indices, quality metrics which are interrelated with manufacturing cost and tolerance (Lin et al., 1997). ... 

Quality-eost models ean help a business understand the influenee of defeet levels on eost during produet development. More importantly, designers should use models to prediet eosts at the various stages. These results make the deeision-making proeess more effeetive, partieularly at the design stage (Hundal, 1997). The estimation of quality eosts in the literature is eommonly quoted at three quite different levels ... 

In the next chapter, we introduce the concepts of component manufacturing capability and the relationships between tolerance, variability and cost. The Component Manufacturing Variability Risks Analysis is then introduced, the first stage of the CA methodology, from which process capability estimates can be determined at the design stage. The development of the knowledge and indices used in the analysis... 

Toleranees alone simply do not eontain enough information for the effieient manufaeture of a design eoneept (Vasseur et al., 1992). At the design stage, both... 

Validation of the Component Manufacturing Variability Risk, is essential to CA in determining estimates for component characteristics at the design stage. Collecting component parts from various industrial sources with known statistical histories was central to this. The components were taken from a number... 

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