Storage policies

Figure 7.4-4. Various intermediate storage policies (a - UIS, b - NIS, Table 7.4-6 Processing times for a four-product and three-stage plant (t.u.) c-ZW).

A/ote Data for frequency of production changes come from preliminary ideas concerning the. storage policy the time for cleaning comes from experience in similar plants. 

The following process is proposed for the production of Product C. For the scheduling of the production campaign, overlapping is allowed and a zero-wait transfer is applied for storage policy. The process is represented in Figure 14.28. 

Another important aspect of process flow requirements is reflected in inventory policies. These often involve finite and dedicated storage, although frequent cases include shared tanks as well as zero-wait, non-intermediate and unlimited storage policies. Material transfer is often assumed to be instantaneous, but in some cases such as in pipeless plants delay is significant and must be accounted for. 

Process topology Equipment assignment Equipment connectivity Inventory storage policies Material transfer Batch size... 

Enhanced continuous-time unit-specific event-based formulation for short-term scheduling of multipurpose batch processes Resource constraints and mixed storage policies. Ind. Eng. Chem. Res., 43, 2516-2533. 

A non-periodic plant operating mode defined over a given time horizon is considered. Mixed storage policies, shared intermediated states, material recycles and multipurpose batch plant equipment units with continuous sizes, are allowed. 

For the analytical laboratory in the process of implementing GLPs, the standards will require some changes in record retention and storage policies. 

Sale of surplus, 135 Storage policy, 103 Storage requirements, 20-21 Ammunition Depots, Home Commands, 132 Ammunition examination, 69 Ammunition Selection Branch (Corsham), 132... 

Goetschalckx, M., and Ratliff, H. D. (1990), Shared Storage Policies Based on the Duration Stay of Unit Loads, Management Science, Vol. 36, No. 9, pp. 53-62. 

Furthermore, batch plants can operate under different storage policies. Five main storage policies can be identified (Shah, 1998 Voudouris and Grossmann, 1996) some of these are... 

Figure 8.3 Different storage policies for batch plants.

A process schedule making use of the selected resources to achieve the new required level of production (that is, timing of all tasks, storage policies, batch sizes, amounts transferred and allocation of tasks to equipment)... 

The so-called zero-wait transfer policy is used when a batch at any stage is immediately transferred to the next stage because there is no-intermediate storage vessel available or when it cannot be kept in the current vessel. This policy is extremely restrictive. The other extremum is the unlimited intermediate storage policy, where a batch can be stored without any capacity limit in a storage vessel. Finally, there is a transfer option called no-intermediate storage, which allows the batch to be kept inside the vessel. Normally, the zero-wait transfer reqnires the longest CT. In practice, plants normally have a mixtnre of the three transfer policies. 

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