How Do the Management System’s Deficiencies Affect On Safety A Case Study of Accomplishment of FMEA in a Paper Mill
The purpose of this study was to see how the existing management system can affect on safety activities like identification of hazards in the Digester by FMEA technique. Majority of managers did not believe that hazard identification can also be affected by some deficiencies of management system. Digester is the main apparatus in the paper mill, in which wood chips after Pre-Steaming Bin enter and by aid of chemicals convert to pulp. The under study Digester was a continues one-stage KAMYER system, producing KRAFT pulp in the capacity of ∼ 200 M. tons per day.
After listing all components of Digester (totally 28 components) and recognizing the failure modes of each component, for determination of failure rates we had to go through existing record keeping system. Three different sources, namely maintenance & process department and spare parts store records, were used. It was found that the records had two major inadequacies. One was their degree of accuracy; eg. In the process department records it was written that the Digester was shot down in such a time of a particular day and nothing about the reasons of this act and the duration of shot down. At the same time the records of two other sources did not show any thing related to this. The second major inadequacy was the long process of ordering spare parts from the store by maintenance department. There was a form for ordering parts, which required after filling by maintenance department few signatures and this was the reason for prolongation of the ordering process. When one of those bosses who should sign the form, was not accessible (this was the case on many occasions) the form would be left in his office for as long as he was not in. Therefore the maintenance department when in need of for instance a new filter for the In — Line Drainer to replace the old failed one, because of time consuming ordering process, they filled on the form the number of filters needed not one but eg. 5 filters in order to have 4 of them in the workshop and save them for the next time when filter fails. In the records of maintenance and process departments it was reflected as the filter of In — Line Drainer changed but in the spare parts store it was recorded 5 filters were delivered. Next time when the filter failed and had to be replaced the maintenance department did not fill the form and used one of those filters saved from previous time. As a result the records of store were again different than the other two sources of records. The maintenance department was also admitted that in many occasions some of those extra ordered filters which had been kept in workshop got lost or damaged during moving them from one location to another. Therefore it was not possible to find out how many filters have failed and replaced during the past 15 years.
As a result of this situation our FMEA work sheet was completed with some approximation and its validity were questioned. The highest failure rate was 69 per year for the In-Line Drainer and the lowest was 0.33 Per year for Blower and valve 128 A. From all 28 components only one (valve 128 A) had a failure rate of 0.33 / y, which was in the range of failure rates for control valves given in the book of An introduction to machinery reliability assessment, by H.P. Bloch and F.K. Geitner, Van Nostrand Reinhold -1990. There was not any more failure rates to be verified in any of our references. It was concluded that for at least the sake of safety the management system should get rid of all those old fashioned bureaucratic procedures.
KeywordsFailure Rate Failure Mode Control Valve Paper Mill Failure Detection
Unable to display preview. Download preview PDF.