Design Capacity Vs Actual Capacity

I remember a discussion I had with the Operations Manager of a chemical plant. Venting his frustrations he told me that the Company who designed the plant had done a lousy job. The plant produced much less than was promised by the design, he did not understand why and his management was not so happy with his performance. A closer look at the design basics and a detailed study of the batch production process opened his eyes. The assumptions made in the design were different than actual practice, notably the much more stringent product quality necessitated more rigorous purification. The washing step took much more time and as a result, the batch time went up and production decreased.

On another occasion a chemical plant replaced an essential catalyst in the reactor with an improved version. The reactor, which had been the limiting factor for the production rate, could now produce much more and was no longer the bottleneck. As a result the production rate of the plant increased considerably and the the Production Manager got a promotion.

These are clear examples that design capacity is not an iron clad figure carved in stone. The term design capacity is often misunderstood. Add to this the confusion the term 'capacity' causes. The word is used in conjunction with design, actual, nameplate, theoretical, installed, proven, economical etc. Sometimes production rate is used and can be expressed per hour, day, month or year. For simplicity and clarity we define capacity as the ability of a facility (factory/plant) to produce an quantity of product(s) in a certain time frame at a defined quality. It could be the number of ships built at a shipyard per year, the m2 of ceramic floor tiles produced per hour or the tons of gasoline in a month in an oil refinery.

It is quite a normal experience that the intended (design) capacity differs from the actual one. Unfortunately more often than not the actual is lower than the design. There is a great time lag between the conception of a facility and the actual construction and start up. A time span of 2-3 years can be quite common. The design was made years before the facility actually starts producing and during this time conditions might have changed. Cooling water temperature is actually higher, quality of feedstock material worse than assumed, product quality more stringent or government regulations require amended operating conditions. Possibly even simple errors in the assumptions or in the calculations could be a reason, although this would never be admitted. These are just a few examples, but certainly anyone in a manufacturing or engineering position recognises these and can add to this list from his or her own experience.

In the initial years it might not even be apparent that the facility is not able to produce the intended (design) amount of product. It takes time to build up a market, sales are slowly increasing, production is lower than the design capacity calls for and the facility is therefore underutilised. However at a certain stage it may become evident that the facility cannot produce what everybody expected and what was promised by the design. Then the blame game might start. Management blames the Operations staff that they cannot operate the facility properly, Operations replies that Management never allocated enough money to install the right quality equipment, both Management and Operations blame the design contractor for a lousy job and the story might go on for years. In the meantime the production certainly will not increase if adequate measures are not taken.

Instead, it would be much more productive if proper analysis is made of the actual production process versus the design. Properly controlled and well defined test runs should be carried out under representative conditions to assess the capacity of the facility and of each individual piece of equipment. This information can then be used to determine where the bottlenecks in the facility are and might even offer possible solutions to remove the bottlenecks.

As an alternative, Management could consider appointing an experienced, professional consultant to aid them in the efforts mentioned above. This approach has a number of advantages. As plant management is less involved they will have more time to concentrate on their core activity of running the facility. Moreover the consultant’s experience is not confined to this particular facility but covers a much wider range. Last but not least and frequently overlooked outside experience offers a fresh look.

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