Short answer: commission a new or reconfigured top-hammer drill string as a controlled system test, not by sending it straight into production. Confirm the approved bill of materials, inspect every interface, verify flushing before percussion, run a staged first-hole test, then compare joint seating, rotation, flushing, vibration, temperature pattern and tool condition against a known-good baseline. Release the string only when the evidence is repeatable and no stop condition is present.
This guide is for mines, quarries, contractors, distributors and procurement teams installing new R32, T38 or T45 rods, coupling sleeves, a shank adapter or a button bit. It covers the post-installation commissioning decision. It does not replace pre-shipment inspection, thread identification, the rig manual or the tool manufacturer's operating limits.
When a drill string needs commissioning
Use a documented commissioning check when a complete string is new, when a different rod or coupling configuration is introduced, when a shank adapter or bit changes the interface chain, or when a new supplier batch enters service. The objective is to prove that the installed parts work together under the site's actual rig, feed, flushing and ground conditions.
Commissioning is not the same as receiving inspection. A rod can pass dimensional and visual checks before shipment and still reveal a system-level problem after assembly. It is also not a general slow-drilling or loose-joint diagnosis. Those tasks begin after a defined symptom appears. Commissioning establishes the clean baseline that later troubleshooting needs.
Seven commissioning gates
| Gate | Evidence to confirm | Hold trigger |
|---|---|---|
| 1. Approved configuration | Rig and rock-drill model, shank adapter, thread family, rod body and length, coupling design, bit and flushing path match the approved drawing, quotation or manual. | Any item is identified only by appearance, a partial thread name or an old invoice. |
| 2. Condition before assembly | Threads, shoulders, rod bodies, flushing holes and protectors are clean, undamaged and traceable to the intended batch. | Cracks, impact damage, burrs, corrosion loss, blocked passages, uncertain straightness or mixed quarantine status. |
| 3. Controlled assembly | Interfaces start and seat normally using the approved handling, cleaning and thread-product procedure. | Forced engagement, cross-thread feel, abnormal gap, one joint behaving differently or improvised adapters. |
| 4. Flushing verification | The complete path from shank to bit is open and stable under the machine's approved static check. | Restriction, leakage at an interface, contaminated return or a change that follows one component. |
| 5. First-hole behavior | Collaring, rotation, penetration, cuttings return and joint behavior are stable during a staged low-risk trial. | Unexpected vibration, binding, erratic rotation, joint movement, poor return or a new abnormal sound. |
| 6. Post-test inspection | Joint seating, contact marks, thread condition, bit condition and temperature pattern are consistent across comparable positions. | One joint is distinctly hotter, looser, tighter, marked or damaged than the others. |
| 7. Release record | Configuration, batch IDs, test conditions, observations and disposition are signed and retained. | The result depends on memory or cannot be tied to the components tested. |
Step 1: Freeze the bill of materials before assembly
Record the complete interface chain: rock-drill model and shank adapter; thread family; rod architecture; body diameter and length; male–male or male–female end configuration; coupling type; bit connection and diameter; flushing arrangement; and any centralizer or rod-handling constraint. A nominal label such as “T38” does not prove that every geometry, length and machine interface is approved.
Compare the installed items with the controlled source that governs the site: the rig and tool manuals, approved drawing, purchase-order attachment or supplier confirmation. If substitutions were made after ordering, stop and obtain written compatibility evidence before the field test. The top-hammer drill-string anatomy guide helps identify each interface, while the mixed new and worn rod guide covers the separate decision about mixed-age components.
Step 2: Build a clean pre-installation baseline
Lay out the parts in string order and assign each rod and coupling a position or temporary ID. Photograph both ends before assembly. Confirm that thread protectors were present, flushing passages are clear, and contact surfaces are free from transport debris. Use the manufacturer's approved cleaning and thread-product procedure; do not use grease to hide damaged or uncertain threads.
Inspect the rod body and both ends under good light. A pre-shipment certificate is useful evidence, but it does not replace a site check after transport and handling. If straightness, thread form or dimensions are disputed, use the controlled method and acceptance limit in the applicable drawing or inspection plan. The pre-shipment inspection guide covers that supplier-side task in detail.
Step 3: Assemble without forcing the evidence
Install the shank adapter, rods, couplings and bit in the approved sequence. Each interface should start and seat in a repeatable way. A joint that needs unusual force or stops at a visibly different position is evidence, not a problem to overcome with extra machine power. Isolate the equipment, identify the two mating parts and compare them with a known-good matched pair.
Record the initial seating reference for each accessible joint. The reference can be a photograph or a removable inspection mark permitted by site procedure; it is not a substitute for the manufacturer's torque or makeup instructions. Do not grind, chase, heat, weld or otherwise alter a hardened drilling-tool interface at the rig.
Step 4: Verify flushing before percussion
Use the rig manufacturer's approved static or low-energy method to prove the flushing path before impact drilling. Confirm that supply reaches the bit, returns are not restricted and leakage does not appear at the shank, coupling or damaged rod end. If the flow is weak, divide the string into controlled sections and add components one at a time until the restriction follows a part or position.
Do not compensate for a suspected restriction by exceeding the approved air or water setting. The flushing-hole compatibility guide covers full path isolation across supply, shank, rods, joints and bit.
Step 5: Run a staged first-hole test
Select a representative but controlled test location under the site's drilling plan. Use trained personnel, the rig's guards and handling equipment, and the approved operating envelope. Keep people clear of rotating and pressurized components. If inspection requires approaching the string, isolate stored, hydraulic, pneumatic and rotational energy first.
- Collar at controlled settings. Confirm stable contact, rotation and cuttings return before increasing the operating demand.
- Pause at the first safe inspection point. Isolate the machine and check joint references, visible leakage, contact marks and any position-specific heating.
- Continue one stage at a time. Do not change feed, percussion, rotation and flushing together. A one-variable record preserves diagnostic value.
- Add length only after the short configuration is stable. When an extension is added, record whether any change appears immediately after that joint or at the same string position.
- Repeat under comparable conditions. One clean interval is encouraging; release requires behavior that can be reproduced without a new stop condition.
Use the manufacturer's limits for settings, joint makeup and allowable temperatures. This guide intentionally provides no universal torque, temperature or penetration threshold because those values depend on the exact rig, tool system and measurement method.
Interpret the result by what the symptom follows
| Observed pattern | Most useful next comparison | Decision |
|---|---|---|
| The symptom follows one rod or coupling after position changes | Compare its identity, threads, straightness, flushing and contact marks with a matched known-good component. | Quarantine that component and retest the string without it. |
| The symptom stays at one string position | Inspect the adjacent interfaces, guide/centralizer, feed alignment and handling sequence at that position. | Hold the string until the position-related cause is controlled. |
| All joints change after one operating adjustment | Return to the last documented stable setting and review feed, rotation, percussion and flushing against the manual. | Correct the setup and repeat the staged test. |
| The problem appears only after adding length | Check the new joint, added rod, flushing loss, handling alignment and whether the approved depth/setup boundary was crossed. | Do not approve the longer configuration from the shorter test. |
| The complete string remains stable and repeatable | Compare the record with the agreed baseline and complete the post-test inspection. | Release with monitoring or full release, as site procedure permits. |
Use one of four release decisions
- RELEASE: all gates pass, the result is repeatable and the complete tested configuration is recorded.
- RELEASE WITH MONITORING: no safety or compatibility hold exists, but a defined observation requires a shorter reinspection interval and named owner.
- CORRECT AND RETEST: a controllable setup, cleanliness, flushing or assembly issue was found. The correction and full relevant retest must be documented.
- HOLD / QUARANTINE: identity is uncertain, damage is present, behavior is not repeatable, or the cause has not been isolated. Do not return the affected string to production.
commissioning record
Site / rig / rock drill: ________
Date / crew / supervisor: ________
Hole requirement and test location: ________
Shank adapter: model, machine interface, rod-side thread, ID/batch ________
Rods: thread, architecture, body, length, quantity, position IDs, batch ________
Couplings: type, thread, position IDs, batch ________
Bit: connection, diameter, design, ID/batch ________
Flushing arrangement and result: ________
Approved operating source and settings recorded: ________
Stage observations: collaring / rotation / return / vibration / sound / joint references / temperature pattern ________
Components changed during test and reason: ________
Final inspection: threads / seating / contact marks / bit / shank / damage ________
Disposition: RELEASE / RELEASE WITH MONITORING / CORRECT AND RETEST / HOLD-QUARANTINE
Approver / next inspection point: ________
What to send with an RFQ or commissioning support request
Send the rig and rock-drill model, complete current string, required hole diameter and depth, rock and water conditions, flushing method, desired rod length and architecture, existing batch evidence, photographs of every interface, and the commissioning record above. For current commercial options, review PerfoMax drill rods, the R32 rod selection route, T38 extension rods, T45 extension rods and the R32 coupling sleeve. Use the RFQ form when the approved configuration still needs confirmation.
Frequently asked questions
Can a string be released after one successful hole?
Only if the site's approved commissioning plan defines that evidence as sufficient. A safer general rule is to require repeatable behavior plus a post-test inspection. One clean hole does not erase uncertain identity, damage or a nonconforming interface.
Should new rods be commissioned with worn couplings?
Not automatically. Inspect and approve every mating interface under the mixed-age decision process. A nominally matching thread family does not prove that a worn coupling will distribute load correctly on a new rod.
What if a joint becomes hotter than the others?
Stop at a safe point, isolate the rig and compare that joint with equivalent positions. Do not apply a universal touch test or temperature limit. Use the exact manufacturer's method and limits, then determine whether the pattern follows the components, position or operating change.
What if joints begin loosening during commissioning?
Hold the string and move to the joint-loosening diagnostic procedure. Do not hide the symptom by increasing makeup force outside the approved instruction.
Safety and evidence boundaries
Commissioning does not authorize work outside the rig and tool manuals or the site's risk assessment. Apply isolation, guarding, competent-person and inspection requirements appropriate to the jurisdiction. General boundaries are available from HSE PUWER guidance and OSHA control-of-hazardous-energy requirements. Exact compatibility, settings, wear limits and acceptance values remain controlled by the selected manufacturer and site procedure.
Last reviewed: September 24, 2026.