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| Safety and Health Topics > Mineral Processing Dust Control > Substantial Time Savings Achieved Through Computer... |
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Substantial Time Savings Achieved Through Computer Dust Analysis Andrew B. Cecala, John J. McClelland and Robert A. Jankowski Bureau of Mines, U.S. Department of the interior, Pittsburgh Research Center, Cochrans Mill Road, Pittsburgh, Pennsylvania 15236-00700 Reprinted from Applied Industrial Hygiene, Vol. 3, No. 7, July 1988 |
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This article describes a computer analysis system used presently by the Bureau of Mines to analyze quickly and accurately large volumes of information obtained from real-time dust monitors during research studies. It substantially reduces the time necessary to perform various data analysis calculations and manipulations including graphics. It also provides raw data files that can be transferred to other software packages for other required manipulations. A major benefit of the computer analysis system is the availability of information at the end of each test day. On-site analysis makes it possible to modify a study during the field evaluation process. The system does not alter the data collection process, other than requiring a small data logger instrument to be connected to each dust monitor. In some cases, the system has reduced manpower requirements during the data gathering phase. The system reduces the analysis time required by previous methods while improving many aspects of the data evaluation process. Although this article deals solely with the use of the data analysis system with instantaneous dust monitoring equipment, it can and is being used with other monitoring equipment. The system has much flexibility and thus can be used in many different applications. Cecala, A.B; McClelland, J.J.; Jankowski, R.A.: Substantial Time Savings Achieved Through Computer Dust Analysis. Appl.Ind.Hyg. 3:203-206; 1988. Introduction The article describes a computer analysis system now being used by the Bureau of Mines so analyze large volumes of data accumulated by real-time dust monitors. The system consists of a solid-state data logger that has the capability to accept a wide range of input signals. Through the use of a software package, the data accumulated on the solid state data logger device are transferred to a personal computer for data storage and is then available for various analytical calculations and manipulations including graphics for each logger, a raw data file can be created and used with other software packages such as Lotus 123 for other necessary data manipulations.A Dust sampling has become a mandated practice in mining operations since passage of the 1969 Federal Mine Health and Safety Act. Gravimetric dust samplers have been the primary means of determining respirable dust concentrations since that time and are still used by the Mine Safety and Health Administration (MSHA) for all compliance sampling. Various studies with this gravimetric sampling system have shown its ability to simulate dust deposition in workers' lungs.(1.2) By attaching a cyclone sampler to the lapel of a worker's clothing and a sampling pump to his or her belt, the personal average respirable dust concentration can be calculated for an 8-hour shift. For many research studies, this technique is not desirable due to the time required to obtain dust data. In addition, it does not provide the flexibility of looking at different time periods or dust producing events because it averages the entire sample period to yield a single value. These drawbacks let to the development of an instantaneous dust monitor called the Real-time Aerosol Dust Monitor (RAM-1), developed by GCA Corporation under a Bureau contract in 1978. The RAM-1 measures respirable dust concentrations by a light "scattering" technique. The dust concentration is determined by the light scatter of particles in an air sample drawn through a sensing chamber by an internal sampling pump. The RAM-1 has been shown to simulate gravimetric measurements closely when calibrated for the specific dust type.(3) Whereas the data accumulation process with gravimetric sampling is a time consuming process, instantaneous monitors obtain continuous dust readings throughout the entire work day, thereby allowing for comparisons of different dust producing events. This is ideal for research purposes as it permits a quick evaluation of one dust control system versus another. The drawback of this system is that, although large quantities of dust data can be obtained in short time periods, analyzing large volumes of information can be a time consuming process.  To correct this, the Bureau pursued an alternative system to analyze the information obtained using instantaneous dust monitors. The basic system chosen uses the 331 data logger along with the Metrosoft software package, which is commercially available from Metrosonics, Inc., Rochester, NY, the system described in this article has been modified to better meet the Bureau's needs (3). This system does not change the sampling technique or physical setup other than requiring a data logger instrument to be interfaced with each instantaneous dust monitor. Although this article deals only with the use of the system with instantaneous dust monitors, it can be and is being used with other types of continuous monitoring equipment. Its benefits include speed, accuracy, and flexibility in analysis, as well as the capability of using the data with other commercially available software packages. The equipment used with this computer analysis system can be found in Table 1. Previous Analysis Methods Initially, two different methods were used to store and analyze data obtained from these instantaneous dust monitors. In the first method, a research worker would use a small permissible tape player to record instantaneous measurements obtained visually from the dust monitor's LED display. This method was used mainly in underground operations where most strip chart recorders do not meet intrinsic safety standards, and those that do are usually too large and heavy for effective underground use. The research worker voice records values on to the tape either at constant time intervals, usually 10 to 20 seconds, or at predetermined locations along the working face (usually ranging from every 3 to 5 supports for a longwall study). One major drawback with this method is that it totally occupies the worker's time and allows minimal visual evaluation of the test. It is also manpower intensified in that it requires one worker for each monitor. After completion of previous field testing, the tapes were transcribed to obtain the recorded values, and then hand calculations were performed to determine the actual dust concentrations. The second method was used mainly for surface operations and for laboratory testing where a strip chart recorder could record dust levels relative to time. Dust concentrations were determined by analyzing the strip chart, using a planimeter to calculate the area under the curve. Using this information, hand calculations were performed to determine the dust concentrations. Because of the time required to perform data analysis with either of these methods, developments of a computer analysis method was pursued.   Computer Analysis Method The computer analysis system is very simple to implement and requires minimal training to operate. Since the system is designed to be user friendly, total training time is usually 30 to 60 minutes. The only additional requirement is that a solid-state data logger be interfaced with each instantaneous dust monitor during the data gathering stage to receive the analog signal. After the test is completed, the data logger is switched to the standby mode until the data can be transferred to a computer, a process that is controlled by the software package and takes two minutes per data logger. Once the data have been transferred, the monitor displays a graph of the dust concentration data versus time followed by a summary of the results including the actual sampling period, cumulative average dust concentration, standard deviation, peak dust concentration and time, and several other factors (Figure 1). The user then has the option of either storing or deleting the information. To store the information, six different fields of identification are available. Figure 2 compares the necessary steps for each method of data analysis. The basic software system sold by Metrosonics, Inc., called "Metrosoft", was modified to better meet the Bureau's needs. It allows for greater flexibility for data manipulations, analysis, and graphics. Figure 3 shows a graphic printout from one particular instrument for the entire sampling period. One main improvement was the ability to isolate, store, and analyze a particular segment out of the entire sampling period. Thus, if a particular time segment is of interest, the software has the flexibility to analyze only that particular segment (Figure 4, subset of data taken from Figure 3). Another improvement was the availability of a raw data file that can be used with other commercially available software packages. Since software is being developed and improved by industry continually, this makes it possible to utilize improved packages without continually modifying the existing program. For instance, if the 1-hour graph shown in Figure 4 is desired for a report, an improved graph can be created using the Lotus 1-2-3 software program (Figure 5). Another advantage of the Lotus program is the capability of plotting multiple curves on one graph, which is not possible with the Metrosonics program. 
Figure 3. Computer generated graphic printout of entire test period. Field evaluations usually follow a somewhat standard routine. Testing at a mine or mill normally requires using three to six instantaneous dust monitors. After completion of testing, each data logger is switched to the standby mode and usually brought back to the hotel room where the personal computer is set up.  Figure 4. Computer generated graphic printout of any time segment.  Figure 5. Graphic printout of raw data file using commercially available software packages. The data loggers are dumped, and the data is stored on a floppy disk. The disk is checked to make sure that each file has been saved, and a backup copy of the disk is made. The data-loggers can be turned off, leaving the data to be manipulated or analyzed at the user's convenience. In many cases, the data can be analyzed the same evening so as to provide insight into possible ways to improve the system being evaluated, or simply to provide the mine or plant with a copy of the results for the following day of testing. Case Study Analysis Comparison A simple evaluation was performed comparing the time to perform a dust analysis with method 2 of the old system and the computer analysis system (method 3 from Figure 2). This comparison required one day of testing at four different monitor locations, separately analyzing five different time segments for each monitor. The breakdown of the time to perform the various steps with each system can be found in Table II.  If these values are projected for a one-week analysis (5 says of testing), the approximate analysis time would be 14 hours and 45 minutes with method 2, as compared to 4 hours and 10 minutes with method 3. Added to this is the advantage of having immediate graphics availability with method 3.B Method 1 would normally be even more time consuming than method 2 because of the substantial amount of time it takes to transcribe the tapes. In addition, with method 1 a worker must be assigned to each dust monitor during field testing, which is not the case with the other methods. The exact time savings with the computer analysis system versus the two earlier methods would be different in each case but would always be substantial. The total time saved would be five to ten times ore than with the previous methods, taking account data manipulation, analysis, and graphics capabilities. Recommendations Large volumes of data can be accumulated relatively quickly with the different continuous monitoring instruments available today. The Bureau of Mines has shown that a commercially available dust monitoring system could be modified slightly to meet the specific requirements for analysis by connecting a small data logger unit to each continuous monitor. After each day of testing, the information is dumped and stored for use on a personal computer. Quick and effective data manipulations, analysis, and graphic capabilities are available, as is the capability to create data files for use with other commercially available software packages. This system saves substantial time and, thus, money. A major benefit is that it allows results to be evaluated immediately after each day of testing, thus increasing the flexibility, capability, and accuracy of the field evaluation process. References 1. Hatch, T.F., Gross, P. Pulmonary Deposition and Retention of Inhales Aerosols, p. 150 Academic Press, New York (1964) 2. Committee on Threshold Limit Values, Threshold Limit Values of Airborne Contaminants for 1968, American Conference Governmental Industrial Hygienists, Cincinnati, OH (1968) 3. Willuiams, K.L. Timko, R.J. Performance Evaluation of a Real-Time Averosol Monitor, P 20 BuMines IC 8968 (1984) Received 8/24/87, review decision 12/28/87, revision 1/13/88, accepted 1/28/88 A Reference to specific products does not imply endorsement by the Bureau of Mines. B The above comparison is not intended to provide an exact calculation of the time savings with the computer analysis system versus the other previous methods, but is intended solely to provide an approximate comparison. |
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