Safety performance control charts

Statistical process controls (cause-and-effect diagrams, control charts, etc.), as applied in quality management, can serve as performance measures for safety, if they are used prudently and with caution. 

There are other routinely practiced procedures in terms of intralaboratory and interlaboratory quality control, such as the control chart, round-robin interlaboratory testing, and various proficiency tests offered by different agencies, such as the PATs (Proficiency Analytical Testing) by AHA in the US and WASPs (Workplace Analysis Scheme for Proficiency) by the Health and Safety Laboratory in Great Britain. In normal circumstances, a combination of these quality control measures should be used in performing workplace air analysis. 

A control chart is a statistical device used for the study and control of safety performance in the workplace. The basis of control chart analysis is the knowledge of chance variations in the data (Duncan 1974,375). If a series of safety measurements are plotted and the obtained measurements are truly random, the distribution would approximate the normal bell-shaped curve. Plotting the data on a control chart, one would obtain measurements over time that fall into the ranges depicted in Figure 4.1, with more measures occurring at or near the average more frequently and readings at the extreme ends of the possible measurements infrequently. 

The purpose of constructing the control chart is to graphically identify trends in data that indicate areas that must be addressed. When using control charts, safety managers will want to note data that is a trend or data that is out of control. Data that consistently falls between the upper and lower control limits, or data that is in control, may indicate that the control limits need to be recalculated with the more current data, thus tightening the control limits and thereby further improving the expected performance levels. 

Because of the underlying statistical processes used with control charts, the safety manager can identify safety performance problems when they become statistically significant. The safety manager can also use control charts to implement continual improvement programs related to safety activities. 

Valid statistical measures, such as control charts, are convincing. In some situations, such as initiating the cultural change necessary to call attention to serious injury prevention, the frequency of occurrence data on such incidents that would be placed on a control chart will not be available since the subject is low-probability/severe-consequence events that do not occur often. Cost data for such events can be influential. For an additional reference, see Measurement of Safety Performance in On The Practice Of Safety. 

Petersen (2005) included an 18-page appendix on Statistical Process Control in Measurement of Safety Performance. Janicak (2010) has a 30-page chapter on Run Charts and Control Charts in Safety Metrics Tools and Techniques for Measuring Safety Performance. Other authors in years past have suggested the use of control charts to track safety performance. Yet, the subject does not appear in the current safety-related literature. 

This author proposes that safety professionals consider the use of control charts as a means of communicating performance results to... 

The proposed method allows the continuous monitoring of OHS conditions in workplaces associated to workers safety performance. The combination of a checklist of dendritics and a control chart seems to be an adequate and sustainable approach for this purpose. On the one hand, the checklist, developed by mean of a Preliminary Hazard Analysis, includes all the hazardous conditions of the company and in particular all the at-risk behaviours. On the other hand, the control chart allows identifying all the hazardous conditions that are critical for the employees. 

Miner s safety performance recognition, circa 1920s 20 The systems model of health and safety management 24 The size of mobile mine equipment continues to increase 27 Simple model of outcomes dependent on culture and systems 32 Statistical control chart with incident rate variation 33 Universal Copper and Metals Mine accident frequency rate control chart 55... 

This small plant size presented a problem for safety measurement in the company. In 1993 the company was well along with the implementation of a total quality management implementation. Based on the recent training in variation and the use of control charts, the safety managers had begun to use U charts when looking at incident-rate measures. The wide limits of variation encountered with small plant sizes convinced them that incident rates would not be particularly useful as a measure of performance in the company, at least for small sites and for short time periods. 

Inspections of the workplaces at randomly selected intervals to observe the items and whether the performance is correct or not. Plotting the safety performance index on a control chart. The safety performance index is defined as the percentage of the observed items that are judged as correct. 

Discuss the problems connected with the application of the LTI rate and control charts in monitoring the safety performance of a company. 

These conditions, known as dendritics, may become hazards and could result in an accident or occupational disease. Continuous safety sampling methodology performs a random sampling for the occurrence of these dendritics. The collected data are then used to generate a control chart. Based on the pattern of the control chart, a system under control is not disturbed whereas a system out of control is investigated for potential conditions becoming hazardous. Appropriate steps are then taken to eliminate or control these conditions to maintain a desired safe system. 

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