Production time requirements, plant

Maintenance and operating costs represent the major expenditure late in field life. These costs will be closely related to the number of staff required to run a facility and the amount of hardware they operate to keep production going. The specifications for product quality and plant up-time can also have a significant impact on running costs. 

Productivity is addressed under Continuous improvement and in order to improve productivity you will need to collect data generally in the form of resource/part produced. Resource can be hours, costs, weight, or volume of material consumed. Graphs showing the productivity trend over time for plants, products, and processes would satisfy this requirement. 

Based on the survey, the actual costs normally associated with the maintenance operation were reduced by more than 50 per cent. The comparison of maintenance costs included the actual labor and overhead of the maintenance department. It also included the actual materials cost of repair parts, tools and other equipment required to maintain plant equipment. The analysis did not include lost production time, variances in direct labor or other costs that should be directly attributed to inefficient maintenance practices. 

Against high levels of computer control Is the pre-batch preparation time required for sequencing, software writing and parameter setting, the full details of the latter of course often not available. This activity Is acceptable as a precursor to full scale production but Is felt restrictive and could Inhibit flexibility In a pilot plant. 

The makespan for multiproduct plants depends on the campaign arrangement. If the campaigns are carried out in series (product A,A,A. .. product B,B,B), the makespan is the sum of times required for all campaigns if time for cleaning between campaigns is negligible. 

Solution. Let N be the number of products and M be the number of units in the plant. Let Cj k (called completion time) be the clock time at which the jth product in the sequence leaves unit k after completion of its processing, and let tjk be the time required to process the jth product in the sequence on unit k (See Table El6.2). The first product goes into unit 1 at time zero, so Cl 0 = 0. The index j in rjk and denotes the position of a product in the sequence. Hence Cn,m is the time at which the last product leaves the last unit and is the makespan to be minimized. Next, we derive the set of constraints (Ku and Karimi, 1988 1990) that interrelate the Cjk. First, the yth product in the sequence cannot leave unit k until it is processed, and in order to be processed on unit k, it must have left unit k — 1. Therefore the clock time at which it leaves unit k (i.e., Cjk) must be equal to or after the time at which it leaves unit k — 1 plus the processing time in k. Thus the first set of constraints in the formulation is... 

The potential uses of a model like this are enormous. As with all dynamic models, the main advantage over plant trials is the much shorter time required to obtain results and the lack of risk to the plant in terms of production and safety. 

Counter-current processes involving, for example, the use of spinning disc or pulse column techniques do not require the same degree of premixing and achieve separation in a shorter period of time. However, as a continuous process it becomes essential to correctly size the plant required in order to maintain an adequate stock. Unlike the batch process, counter-current techniques are not always easily able to accommodate a sudden escalation in product order requirements. 

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