Warning lines

The upper control line and the upper warning line are given by... 

Upper control line Dqqq R Upper warning line >0.025 ... 

Upper action line - Upper warning line... 

For a Gaussian distribution, 95.5% of all observations are within 2oVV/t from the mean and 99.7% are within a 3o-/V/, where n is the number of tablets (=25) that are averaged each hour. The 2oVVn limits are warning lines and the 3cr/Vn limits are action lines. We expect —4.5% of measurements to be outside the warning lines and —0.3% to be outside the action lines. It is unlikely that we would observe two consecutive measurements at the warning line (probability = 0.045 X 0.045 = 0.002 0). 

FIGURE 19.4 Quality Control Chart with Warning Lines and Control Lines. 

Control charts often have a center line and two control lines with two pairs of limits a warning line at m 2s and an action line at m 3s. Statistics predict that 95.45% and 99.7% of the data will fall within the areas enclosed by the 2s and 3s limits. The center line is either the mean or the true value. In the ideal case, where unbiased methods are being used, the center line would be the true value. This would apply, for example, to precision control charts for standard solutions. 

When the process is under statistical control, the day-to-day results are normally distributed about the center line. A result outside the warning line indicates that something is wrong. Such a result need not be rejected, but documented procedures should be in place for suitable action. Instruments and sampling procedures should be checked for errors. Two successive values of the Quality Control sample falling outside the action line indicate that the process is no longer under statistical control. In this case, the results should be rejected and the process investigated for its unusual behavior. Further analyses should be suspended until the problem is resolved. 

FIGURE 12.22 Control charts and outliers. (A) pEC50 values (ordinates) run as a quality control for a drug screen over the days on which the screen is run (abscissae). Dotted lines are the 95% c.l. (upper and lower warning lines) and the solid lines the 99.7% c.l. (upper and lower action lines) Data points that drift beyond die action lines indicate significant concern over the quality of the data obtained from die screen on those days. (B) The effect of significant outliers on the criteria for rejection. For the data set shown, the inclusion of points A and B lead to a c.l. for 95% confidence that includes point B. Removal of point A causes the 95% limits to fall below point B, causing them to be suspect as well. Thus, die presence of the data to be possibly rejected affects die criteria for rejection of other data. 

Having drawn on the control chart the lines for the reference value, and warning and action limits (or other warning lines), as based on the results of repeatability experiments, the results subsequently obtained for control preparations are entered on the chart daily. These are plotted as differences (positive or negative) between the observed and the reference values or, for the ratio method of recording results, as the ratio between them. Individual points obtained on successive days or in succeeding batches of analyses are joined by lines on the chart. 

A warning line is used 15 feet or more from the edge (or the nearest edge of a hole) ... 

No work or work-related activity is to take place in the area between the warning line and the hole or edge and... 

The employer effectively implements a work rule prohibiting the employees from going past the warning line. ... 

The use and operation of guardrail systems, personal fall arrest systems, safety net systems, warning line systems, safety monitoring systems, controlled access zones, and other protection to be used ... 

Employers can select fall protection measures and equipment compatible with the type of work being performed. Fall protection can generally be provided through the use of guardrail, safety net, personal fall arrest, positioning device, and warning line systems. 

Safety monitoring system — Used when working on low-slope roofs only. It must be used with a warning line system. 

Warning lines — must be must be erected around all sides of the roof work area and shall consist of ropes, wires, or chains, and supporting stanchion. 

The fall protection rule lists other systems and equipment you can use in certain situations. Some of them are safety monitoring systems, warning lines, and positioning devices. 

Failure to provide a warning line system around the entire perimeter of the roof,... 

Explain the requirements for providing a warning line system ... 

The warning line must be erected around all sides of the roof work area. 

When mechanical equipment is not being used, the warning line must be erected not less than 6 feet from the roof edge. 

When mechanical equipment is being used, the warning line must be erected not less than 6 feet from the roof edge which is parallel to the direction of mechanical equipment operation, and not less than 10 feet from the roof edge which is perpendicular to the direction of mechanical equipment operation. 

Points of access, materials handling areas, storage areas, and hoisting areas must be connected to the work area by an access path formed by two warning lines. 

When the path to a point of access is not in use, a rope, wire, chain, or other barricade, equivalent in strength and height to the warning line, must be placed across the path at the point where the path intersects the warning line erected around the work area, or the path must be offset so that a person cannot walk directly into the work area. 

Warning line system.Fall Protection — Citations... 

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