Stopwatch technique

The stopwatch technique for determining emission volume flow rate is based on measuring with a stopwatch the elapsed time for fume to rise between two known levels (e.g., Zj, Z,). For this test procedure to be valid, the test must be carried out in a region where the rising fume clearly exhibits buoyancy-dominated plume behavior. The calculation procedure depends on a good estimate of the location of the virtual origin of the plume and the heat release for the process. 

This technique permits estimation of the volumetric flow rate at any level above a source, provided that the result is matched to the gravitational fume acceleration terms applicable near the source. The result of such an analysis is shown in Fig. 13.30. The emission flow rate from an electric arc tapping process has been estimated at any level above the steel ladle using the stopwatch technique in conjunction with the plume theory. 

Discharged centrate is usually directed to drain but on smaller facilities where instrumentation is limited it may be necessary to resort to measuring the centrate using a bucket and stopwatch technique. 

After the identification of constant and variable tasks, the work content associated with each task is measured. The work content could be measured using any of the traditional work-measurement techniques such as stopwatch time study, predetermined motion time systems, and work sampling. Work content could also be established using the Delphi approach in which a group of individuals familiar with a well-defined task try to reach a consensus about the time required to accomplish the task. The frequency at which each variable task occurs per day is also determined. The total number of hours of work to be performed for each skill level is then determined by adding the time taken... 

Direct work is that segment of the operation that discernibly advances the progress of work. For example, in operating a fax machine, the direct work elements may include insert document into paper feed, locate and dial telephone number, press send button. Such direct work can be measured using conventional techniques such as stopwatch time study, standard data, and fundamental motion data. Fundamental motion data systems such as Work-Factor, MTM-2, and MOST have been widely applied in establishing standards. 

---