What is a Sling to Load Angle Factor?Simply put, the sling to load angle factor (SAF) is the multiplier used to determine the additional tension on a sling (or other rigging hardware) when angles are applied. ASME B30.9 and B30.26 recommends that horizontal angles not be below 30 degrees. How is this figured out?Mathematically, the length of the sling is divided by the height from the load to the hook.
Example: The sling is 10′ long and the height is 5′, divide the length by the height, for a sling angle factor of 2, which is the SAF for a 30-degree horizontal angle. How is this done easier in the field?The problem can be done easier with a shortcut called “The Ten Inch Rule”. Once the load is rigged, with a tape measure, find where the sling is 10″ high over the load – you do not have to measure the total height of the sling, only to the point where it is 10″ above the load. Measure from this point, down along the sling to the attachment point, giving you the sling length. Example: If the sling, from the 10″ above the load to the attachment is 16.25 inches long, simply take the decimal point and move it one place to the left, making the SAF 1.625 (or 16.25 divided by 10).
The accuracy of load angle estimation method depends on voltage. Dependence of parameters determining accuracy is analyzed. The resolution of load angle measurement is in this case 0.36° el. Load angle estimation based on the quadrature-axis synchronous reactance and the equivalent reactance of the transformer and transmission line For the load angle estimation voltage-current vector diagram is used (Fig.4.), where δ 1 is the angle between induced voltage E 0.
Fast, Simple and Easy!Important to Remember: If your measurement of the sling from 10″ above the load to the attachment point is greater than 20 inches, that means the SAF is greater than 2 and the angle is less than a 30-degree horizontal angle. Therefore, the load must be re-rigged prior to picking. Call CICB at (800) 327-1386 to Learn More.
Rock The formula refers to Steady-State operating conditions, i.e., no changes. At 90º the system will not survive System Transients such as electrical-faults or even operational changes.For example, if there is a load change, the prime-mover will respond but because of system-inertia the change is delayed, resulting in a deficit of the area under the Load-Angle vs Power diagram because of the shape of the Sine-curve! At 90º it 'flattens' somewhat thereby precluding recovery.A detailed discussion would probably irk too many posters! However, I believe that anyone who has conducted a Transient-Stability-Study understands the reason for the 20-40º range!I suggest you search the Control.Com Archives for similar topics!Regards, Phil Corso ([email protected]).
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