Stemming Criteria

  • Chapter 4.14 (1) of the Mine Health & Safety Act states in short that the employer must take reasonable steps to ensure that holes are stemmed with material determined for that purpose to prevent risk associated with explosives detonating outside the shot hole, blowouts, fly rocks and harmful gasses.
  • Effective stemming is thus the most important criteria to achieve the best possible blast result
  • To achieve this, the planned stemming area must be dry and filled with dry drill chippings or aggregate to confine the explosives within the hole.
  • With this water extractor, the water within the stemming area can be removed in a very short time to be able to stem a dry hole.
  • The type of material is dependent on the stemming length.
  • Short stemming: - less than Burden, 10% aggregate may be needed.
  • Longer stemming: + more than Burden, drill chippings may be used.

Interested Parties

  • Mine responsible persons
  • Mining contractors.
  • Explosives companies.
  • Blasters
  • Blasting Helpers


  • Comply with MH & S Act.
  • Prevent risks associated with wet stemming and overcharging.
  • Overcharged explosives can be timeously removed.
  • Guaranteed best blast result.
  • Enhance explosives efficiency.
  • Reduce stemming time.
  • Cost-saving - Consider drill chippings in dried out hole versus aggregate {wet hole)

Present Operational Stemming ChallengesDrill Chippings

Waterlogged Holes

Bottom priming is done which forces the water to the top of the charge and fills the stemming area.

Some challenges are;

  1. Stemming with drill chippings and aggregate.
  • Water and explosives sludge in the stemming area prevents the stemming material to go down to the top of the explosives to consolidate and contain the energy.
  • A charging stick is then used to tamp the chippings excessively to create stemming that should consolidate from the explosives charge. It;
    • may damage the accessories.
    • will create a sludge plug within the stem area with little or no consolidation.
  • Fly rock, blow out, out of hole detonation, excessive air blast, harmful gasses and underperforming explosives are eminent.

The Solution - Water Extractor

  1. The benefits of dewatering the stemming length in a charged hole.
  1. Ensuring that the stemming length is clear and dry.
  2. The intended stemming can confidently be applied.
  3. Chippings (dry drill chippings in ROT lengths) can be used effectively.
  4. Time-saving - stemming a dry hole is quicker than feeding chippings into the water and/or sludge mixture.
  5. Eradicate bad practices -tamping only the top of the hole which results in insufficient stemming creating blowouts and fly-rock.
  6. Any depth of water can be removed. It will remove water in internal deck charged holes by lengthening the rope.
  7. Removing excess emulsion from the hole ensures intended results.
  8. Better explosives efficiency,
  9. Using the correct stemming material as intended in a dry hole will guarantee fly-rock and air blast control.

Using the Water Extractor to Remove Water Within the Stemming Area.water extractor

  1. Operation

This operation serves as a check to ensure that the correct stemming can be applied, and holes are not overcharged.

  1. Extracting water and excess explosives from the holes is a one-person operation
  2. The designated person to dewater the holes must follow the pump truck at a safe distance determined via risk assessment. i.e. Sm.
  3. He drops the extractor into the hole and removes water and emulsion sludge to a pre-determined depth as marked on the extractor's rope.
  4. He pours the water outside the hole where it cannot return or flow into any other hole.
  5. If a hole is overcharged, remove the access explosives by pushing the pipe down into the explosive’s column to the required stemming depth with a stick of sufficient length.
  6. The excess explosives must be poured into the nearest primed hole.
  7. He repeats the process until he reaches the intended stemming depth in the explosive’s column.
  8. When the hole is cleared down to the twined depth, it must be left to gas and then stemmed normally.

Water Extractor Pipe

Non Ferrous metal PVC Pipes are used for the manufacturing of the extractors.

Extractors Pipe Dimensions

Extracter Pipe Dimensions

50mm 75mm 75mm 110mm
Inside dia Outside diameter Length Inside dia Outside diameter Length Inside dia Outside diameter Length Inside dia Outside diameter Length
46mm 55mm 2m 67mm 91mm 1,5mm 67mm 86mm 1,5m 104mm 117mm 1m
Capacity litre Rope Capacity litre Rope Capacity litre Rope Capacity litre Rope
3 2m 5 3.5 5 3.5 8 4m

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