Summary:
This article outlines best practices for how long RG59-Mini coaxial cable can remain in a blast hole ("sleep time") before firing. It also covers environmental factors that may affect cable performance and reliability.
Standard Recommendation
ShotTrack recommends that RG59-Mini cable be left in a blast hole for no more than 24 hours before firing. This ensures optimal signal integrity and reduces the chance of degradation due to environmental or mechanical stress.
Extended Sleep Time
In many cases, the cable can remain in the hole for several days or up to a week, provided certain precautions are taken. However, extended durations do increase risk and should be managed carefully.
Key Risk Factors
The following factors can affect how long the cable can safely remain in the hole:
1. Moisture and Water Ingress
RG59-Mini is not fully waterproof.
Prolonged exposure to moisture can degrade signal quality, particularly if water enters the cut end of the cable.
Recommendation: Seal the cut end of the cable using heat shrink, waterproof tape, or epoxy.
The BNC connector end must remain unsealed so it can connect to the VoD unit, but it should not be left sitting in water. If the site is very wet, cover the connector end with a plastic bag or similar protective cover to keep it dry.
2. Stemming Pressure
Stemming material can apply pressure that may compress or damage the cable over time.
Avoid sharp bends or stress points, especially near the hole collar.
3. Ground Movement
Shifting ground can cause the cable to move, become pinched, or sustain mechanical damage.
Where possible, route the cable to minimise tension or stress from shifting material.
4. High Temperatures
Excessive ground heat may soften the cable insulation or impact its electrical characteristics.
In hot climates or near reactive ground, minimise sleep time and consider shielding the cable where possible.
5. Reactive or Corrosive Ground Conditions
Acidic groundwater, sulphides, or leftover chemical residues can corrode the cable or degrade insulation over time.
In aggressive ground conditions, consider adding a protective sleeve or sacrificial outer sheath.
6. Rodents and Insects
In some regions, exposed cables may be vulnerable to damage from burrowing insects or rodents, particularly near the surface.
Best Practices
If longer sleep times are unavoidable:
Seal the cut end of the cable with heat shrink or epoxy to prevent moisture ingress.
Keep the BNC connector end dry and off the ground. Use a protective cover or bag if necessary in wet conditions.
Avoid tight bends or pinching, especially at the collar of the hole.
Use the VoD unit to check cable continuity before firing.
Log the time of placement to track cable exposure duration.
Conclusion
For best results, limit cable time in blast holes to under 24 hours. If it must stay in longer, use proper sealing, physical protection, and verify continuity before firing. These steps help ensure safe and reliable operation in varied field conditions.
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