Fluxo Soluções
 / January 2012

Process Optimization and Measurement Management

When the term “measurement management” is mentioned, many understand that we are referring solely and exclusively to the concepts and requirements of measurements that involve the payment of royalties or calculation of volumes moved between parties (transfer of custody). We can understand this focus in view of the technical measurement regulation applied by the National Petroleum Agency (ANP) and the National Institute of Metrology, Standardization and Industrial Quality (INMETRO) and valid for the oil and natural gas production industry.

However, the concept of measurement management is much broader than that and must be applied to many other equally important activities.

Probably one of the noblest areas where this concept should be considered is in high-value processes – for example, in large refineries or petrochemical complexes. In these projects, the maximization of profits is directly linked to the optimization of processes and all units of a large chemical complex have their groups of continuous improvement, which seek to adjust equipment, instruments, valves and controllers to their optimal operating points.

Obviously this work is in the right direction and the use of products with good technologies and low uncertainties reduces the variability of the meshes and with that we have a better optimization. But that's not enough! When we look closely at an audit report performed on one of these critical loops, we are often faced with several unpleasant surprises. It is not uncommon to find instruments totally decalibrated, but properly certified, labeled and sealed. The problem is not in the lack of the calibration routine, but in the execution procedure: either it does not understand the necessary actions or it is being carried out by disabled personnel.

Calibration is basic, but we can mention more significant errors: how many have analyzed an uncertainty calculation of a simple pressure transmitter? It is not uncommon to see these calculations using the first line of the manufacturer's catalog – the “reference accurancy”. Calculate the uncertainty of this mesh using the ISO-GUM: 1995 “Guide to the expression of uncertainty in measurement” and you will find that a basic uncertainty of ±0.04% could actually be ±0.30%. How is it possible to close a petrochemical mass balance if we do not know the correct uncertainty of each critical loop? If we are not sure what is happening in the mesh, how can we optimize it?

We are talking about errors that often occur due to lack of knowledge of correct practices and at this point the implementation of a measurement management system based on the NBR 10012 standard: measurement management system - requirements for measurement processes and measurement equipment - of course can provide significant subsidies for a really effective process optimization.

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