Procedures batch process considerations

Chapter 4 addresses procedure writing, including format selection, the types of references and resources needed, and the human factors of procedures. It describes how to begin writing, how to address technical data, and special considerations for maintenance procedures and batch processes. 

Identify special considerations for maintenance procedures and batch processes... 

The basic principles of effective procedure writing previously presented apply equally well to batch processes, but batch processes also have specific procedure considerations. Batch equipment often is used to produce multiple products with the same components. Typical batch operations are ... 

Automation considerations. The layup of a composite, the actual placement of plies in their expected final position in the laminate, cannot be separated from the total manufacturing process in some procedures, e.g., filament winding or pultrusion. In other techniques, e.g., automatic tape laydown or RTM, the layup process is a separate batch process and is completely separate from the compaction and cure phase. AU composite manufacturing processes can be automated to some extent, and the amount of automation depends on how amenable the optimum manufacturing technique is to total or partial automation, the capital costs of the automation machinery, eventual total number of piece parts to be manufactured, the expected cost of each, the time frame available, and a host of other factors. 

If operating procedures need to be developed from scratch, this could account for a considerable portion of the pre-startup work. If current, valid standard operating procedures exist, and the toll is only introducing a new set of batch instructions, the task becomes simpler. However, it is recommended that the new batch instructions are reviewed simultaneously with the existing startup, shutdown, normal and emergency operating procedures for the equipment to help ensure potential process deviations are examined and addressed. 

The solvent method may also be performed either by continuous (in cascades) or by batch operation. Continuous techniques in particular have gained considerable technical importance. A phthalonitrile/copper chloride solution is typically treated at 120 to 140°C in a flow tube furnace and the temperature subsequently increased to 180 to 250°C. The entire process requires approximately 1.5 to 2 hours and affords the pigment in practically quantitative yield. The excellent purity of the product eliminates the need for additional purification with dilute acid or base prior to finishing, a procedure which plays a major role in the baking process. These... 

Notes. (1) Warming the suspended solid in the solvent may be necessary by removing the porridge to a suitable flask and heating under reflux. Care must be taken if such is the case to supervise this operation carefully as there may be considerable tendency towards bumping . It should also be borne in mind that this batch-extraction process uses open-type vessels and usually large volumes of solvents precautions must therefore be taken in relation to the possible fire and toxic hazards involved in the use of a particular solvent. (2) As a first step, this procedure would involve solvent extraction procedures to divide the multicomponent mixture into acidic, basic and neutral fractions (see above). Subsequently chromatography, fractional crystallisation, etc., would be employed as appropriate. 

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