Detector Rankings on Sub-Zones


As of version 2.46, Detect3D allows for the Detector Rankings Tool to be used with sub-zones. Follow the steps below for assessing the rankings results for sub-zone regions:


  1. Open the Detector Rankings Tool ( ), again for the Main Zone. Notice that now Flame Detector 05 has a label of 'No effect' as it has been disabled.

  2. Click the checkbox next to the gray Sub-Zone text.

  3. Choose the Upper Flanges 2m as the Sub-Zone

  4. Click the Update button to update the ranking results



Tutorial 11 - Figure 11 - Updated Rankings Window for sub-zone rankings


Once updated, the results show the change in coverage of the Upper Flanges 2m sub-zone when each detector in the project is disabled. The coverage of the Main Zone is ignored when doing this. Here Flame Detector 06 has been ranked as the 'worst' for the Upper Flanges 2m region.


Have a look at the other results of the Upper Flanges 2m rankings in Figure 12 below. Notice that even though Flame Detector 06 is ranked the worst, both Flame Detector 01 and Flame Detector 04 have a 1ooN Deficit of less than 1% (indicated in blue).


Additionally, Flame Detector 01 also has a low 2ooN deficit - 5.6%, indicated in green. This happens because the averaged Weighted Rank (Final Rankings Bias slider positioned at center) does not look at the coverage values themselves but only the ranks. Thus, it is important to keep watch on the values of both the 1ooN and 2ooN deficits as well as the rankings results when using the Detector Rankings Tool.



Tutorial 11 - Figure 12 - Upper Flanges sub-zone rankings


Repeat Steps 2-4 above to change the Sub-Zone of the Detector Rankings Tool to Lower Valves 2m and press the Update button. Here we see a slightly different order of the rankings, which is to be expected as one sub-zone is at ground level and the other is a few meters above the ground. However, for both sub-zones, Flame Detector 06 is ranked the worst performing. This provides a strong indication that Flame Detector 06 should be removed next, or is there another which might be just as beneficial to remove? In some cases the worst performing detector may not be the best detector to remove, factors such as wiring, maintenance, height above ground, potential false alarm sources should all be considered.



Tutorial 11 - Figure 13 - Lower Valves sub-zone rankings


Compare the results in Figures 12 and 13. Which device(s) could be removed and still achieve the performance target of 90% 1ooN and 70% 2ooN for the sub-zones? The current coverage results with Flame Detector 05 removed has been provided below.



Tutorial 11 - Figure 14 - Coverage results with Flame Detector 05 disabled


For this tutorial, it was decided that Flame Detector 06 should be disabled. Justification is from the low 2ooN deficit when looking at the Upper Flanges 2m as well as the 'worst' ranking for the Lower Valves 2m. An argument can also be made for disabling Flame Detector 03 or Flame Detector 01.



Disabling Additional Detectors

Disabling Flame Detector 06 in the project results in the following coverage results which is compliant to the client's performance standard. It can then be reported to the client that Flame Detector 05 and Flame Detector 06 can be removed from the layout while still achieving the performance requirements with four devices.



Tutorial 11 - Figure 15 - Final coverage results with Flame Detector 05 and Flame Detector 06 disabled



Bonus - Can this layout be further improved with the 4 detectors? Just because the rankings tool helped reduce the detector count doesn't mean further optimization isn't possible. Try changing the orientation of the devices to improve the coverage further or perhaps use the detector contributions chart (discussed in the next section) to help.


Continue to the next section to review the Detector Contributions Chart.