Primer & Detonator Rules

BlastCAD provides both manual primer placement and a rule-based automatic primer system for batch applying initiation hardware across entire blast designs.

Table of contents

1. Manual Primer Placement
   1. Adding a Primer Manually
2. Rule-Based Primer Placement
   1. Rule Structure
   2. Example: Standard Underground Ring Rule
   3. Example: Long Hole Double Primer Rule
3. Managing Primer Rules
   1. Creating a Rule Collection
   2. Applying Rules to the Design
4. Detonator Assignment
   1. Detonator Types
   2. Assigning a Detonator to a Hole
5. Visual Verification

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Manual Primer Placement

A primer is a small, highly sensitive explosive cartridge used to reliably detonate the main explosive column. Each hole can carry one or more primers at specified depths.

Adding a Primer Manually

In the Charge Inspector for a selected hole:

1. Click Add Primer.
2. Set the reference point: ChargeCollar (distance measured from the top of the explosive column) or ChargeToe (distance measured from the bottom of the explosive column).
3. Set the distance in metres from that reference.

The primer is rendered as a glowing red sphere within the explosive column in Charge Mode. If the primer is positioned within a stemming or air deck segment, a warning is displayed.

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Rule-Based Primer Placement

For large blast designs with many holes, manually placing primers one by one is impractical. BlastCAD’s Primer Rule system allows you to define conditional logic that places primers automatically.

Rule Structure

Each primer rule has the following fields:

Field	Description
Enable	Toggle the rule on/off without deleting it
Measure from	ChargeToe or ChargeCollar — the reference end for the distance
Distance value	Fixed distance from the reference (m)
Fraction distance	Fraction of the charge length from the reference (0.0 – 1.0)
Fraction length	Minimum charge length fraction at which this rule activates
Add if length > X	Only place primer if the explosive column length exceeds X metres
Add if length < X	Only place primer if the explosive column length is less than X metres

Distance vs. Fraction: Use distance_value for absolute placement (e.g., “always 1.0 m from the toe”). Use fraction_distance for proportional placement (e.g., “at 20% of the charge length from the collar”). If both are set, the minimum of the two is used.

Example: Standard Underground Ring Rule

This common configuration places one primer 0.5 m from the toe for holes with a charge length greater than 3 m:

Enable:           Yes
Measure from:     ChargeToe
Distance value:   0.5 m
Add if length >:  3.0 m

Example: Long Hole Double Primer Rule

For long holes (> 8 m charge length), place two primers — one near the toe and one near midpoint:

Rule 1:

Measure from:     ChargeToe
Distance value:   0.5 m
Add if length >:  8.0 m

Rule 2:

Measure from:     ChargeToe
Fraction distance: 0.5   (places primer at 50% of charge length from toe)
Add if length >:  8.0 m

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Managing Primer Rules

Primer rules are stored in the Engineering Database under the Primer Rules tab. Rules are project-global — they apply to any hole in the current blast design.

Creating a Rule Collection

1. Open Database → Primer Rules tab.
2. Click New Rule to add a rule.
3. Configure the rule fields.
4. Rules are evaluated in order — rule 1 is processed first, then rule 2, etc.

Applying Rules to the Design

1. With your charge columns defined, go to the Charge Inspector or the Ring Workflow panel.
2. Click Apply Primer Rules.
3. Choose the scope: Selected hole, Current ring, or All holes.
4. BlastCAD evaluates each rule against each hole’s charge parameters and places primers accordingly.

After application, all primer positions are visible in the Charge Mode view and in the Properties Panel primer list.

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Detonator Assignment

A detonator (firing device) is assigned separately from the primer. Detonators are managed in the Detonators section of the Engineering Database.

Detonator Types

Type	Description
Bulk (Non-Electric)	Standard shock tube detonator. Scatter defined by percentage.
Packaged	Pre-assembled primer-detonator unit. Common in small-diameter holes.
Electronic	Programmable electronic detonator with near-zero timing scatter.
Surface Delay	Surface-firing delay element used in the initiation harness (not in the hole).

Assigning a Detonator to a Hole

In the Properties Panel with a hole selected:

1. Click the Detonator dropdown.
2. Select from the database entries.
3. Set the Leads Length (shock tube / wire length from collar to surface, in metres).

The assigned detonator’s nominal delay and scatter percentage are used in the Timing Analysis module. See Vibration & Safety for how scatter affects PPV confidence intervals.

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Visual Verification

After applying rules and assigning detonators:

1. Activate Show Detonators in the Canvas Toolbar display settings.
2. Primer spheres appear in red within the hole column in the 3D view.
3. Detonator markers appear at the collar position.
4. Activate Show Delay Labels to confirm timing assignments.

Run the Statistics report for a complete timing analysis, including inter-hole timing windows and maximum instantaneous charge (MIC) for vibration compliance.