Good Afternoon
I want to ask something related with Velocity of Detonation
I was measuring VoD an explosive in open pit using Mictrotrap Mrel, and the data like in below.
I want ask about why in the graphic initial VoD primer has so high until 1 meter? What phenomenon of this?
Can anyone explain to me?
Thanks very much.
Hi
I see that the length of the trace is about 75 cm. What is the VOD of the remaining explosive column, which is not shown in you plot?
Usually a run-up or run-down VOD can be seen during the detonation of the bulk explosives column in the blasthole, when the detonation starts. This run-down or run-up is due to the influence of the booster (usually having a VOD well above 6000 m/s) in the bulk explosive. This run-down stage for ANFO (VOD about 3500 m/s) is about 4 – 6 diameter in length. You mention open pit, so I assume that the diameter of the blasthole is above 150 mm (6 inches). The length of the trace is 75 cm, which is 5 diameter in length, so what you see is a run-down of the VOD until the explosive column reaches its steady VOD. The problem is that the trace is quite nice and straight – the trace is not decaying, which I would expect. Do you have the full trace? Was the product in the explosive sensitised?. You may want to provide more information.
Regards
Miguel
Miguel Araos Sir, this the full graphic.
Yes, my question is why the trace just 75 cm?
I use Pentolite as primer and Blasting agent is Bulk Emulsion. I charge Heavy ANFO to the hole for 1,65 m. Why trace for Bulk Emulsion not from zero? But from 1 meter?
Thank you
Hi Sa'dur rifki
Forget my assumption in my previous post (runup / rundown VOD).
Probably this is what happened:
· The booster and detonator were placed into the blasthole
· Then the truck loaded the HANFO up to 1.65 metres
Then the person in charge of checking the explosive height, etc. grabbed the nonel line and pull it up, which brought the booster up too – about 90 cm. This is a common field practice to ensure the booster is surrounded by product. Otherwise, if you do not do that, the booster will stay at the bottom of the blasthole, in a micture of mud, cutting, and emulsion – the booster may fail to initiate the explosive column.
Therefore, when the booster detonated, cut 90cm of the MREL green cable (which is what you assume a high VOD in the plot). Then the column of explosive is detected and you get abot 75cm of trace
By the way, the VOD trace is for a gassed HANFO? The VOD is quite high for ungassed product. What density?
Regards
Miguel
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