African Explosives Limited - Report

Student Name: Tazibana Moyo

Module Coach: Underground Manager

UV 117 HB – Charging Machine Specifications

The UV 117 HB has 4 main tanks

Emulsion tank capacity– 2t

Water tank – for hose flushing purposes

Hose lube (lubrication) – for the purposes of avoiding high pressure build ups and blockages during the charging process

Gassing tank – contains Sodium Nitrate (NaNo2) solution (Sensitizer)

Calibration factor – 0.127

Operational pressure range (pressure gadges) -2000 – 3000 kpa

Pump system is hydraulically driven

Main pump – Orbit or product pump which is driven by a hydraulic motor

The gassing and hose lube tanks are driven by means of Cat pumps

Mixing of emulsion and gassing agent occurs in the Plunger {Homogenizer}

Product only becomes an explosive after passing through the plunger, i.e. at the out let

hose.

Charging lense – 1’’

Average (emulsion) face charging time – 20minutes

Quality Checks

Cup weight range (g) – 575 – 655 (green zone)

Charge density range – 1.05 – 1.2

Emulsion face sampling

Ist reading – Average = 800g

2nd reading – Average = 660

3rd reading - green zone {575 -655}

The cup volume used at Ngezi is 550ml. The scale is first zeroed after attaching

the cup to it, before any readings can be taken.

Note: if sample readings are outside the green zone, gassing may be too much or too

little; in such scenarios charging is forbidden.

Gassing – Hot spots (gas bubbles) reduce the emulsion density. This aids in the

transmission of the shock wave.

Emulsion R100G Specifications

94% - Ammonium nitrate (PPAN)

6% - Gassing solution + Fuel Oil

VOD – 4 500m/s in 45mm diameter holes

Gassing rate – 30 – 45 minutes

Shelf life – 10 -12 weeks

Coupling – 100%

Critical diameter – 22mm

Critical density – 1.29 g/cm3

Repumpability – can be pumped from one stage to another (up to 6 stages)

Water resistant

Post Blast analysis – checks made for the following:

1. Toe burden---if high blast holes struggle to kick2. hole alignment – use of direction rods is critical

3. socket depth – should not exceed 0.2m

4. Socket cleanliness – if clean it may indicate that:

Explosives where not pressed up to the end of the holes.

Holes were not properly flushed

Holes may have collapsed

-On the other hand if there are big rough sockets, it may mean that the burden was too

much, thus the blast holes were struggling to get a free face.

In order to achieve the required blast advances and quality, within the budgeted costs it is

critical that the basics of drilling and blasting be adhered to. This includes the following:

1. Adhering to the design marking standards. Currently there is a problem especially

in the North 1 section where 6 * 2.5 m panels are being drilled, where-as a standard pattern has not yet been developed.

2. Enforcement of high standard drilling practices; i.e, maintaining hole parallelism

through the use of hole directors and drilling to the required depths

3. Cleaning/ flushing all holes, before any charging is done

4. Charging and timing as are according to the design patterns. It is also important to

allow the charged emulsion product to properly gas, this is currently a big

challenge especially for rounds that are last to be charged, since blasting time

would be in certain instances only10 minutes away when charging ends.

N:B The Geology department must play a bigger role in the determination of the

powder factors that must be used in the blasting of certain areas, like in the North

section. This they may do by giving information of the rock hardness in every section, so that specific drilling and blasting standards are designed for specific areas based on rock

formation