A compressor can appear large enough on paper while the farthest pneumatic rock drill still loses impact or slows when another drill starts. The problem is often not the sum of nominal airflow alone. A restrictive header, unequal branches, small-bore couplings, long hoses, open drains, leakage or poor pressure measurement can prevent delivered air from reaching each tool.
This guide begins after the tool demand has been estimated. Its task is to turn available compressor FAD into a distribution layout that can be tested at every working drill. Size the common path for the combined simultaneous demand, keep branch restrictions visible, and accept the system from dynamic tool-inlet readings—not compressor-panel pressure.
Separate capacity from distribution
| Question | Capacity decision | Distribution decision |
|---|---|---|
| Can the source supply all users? | Compressor delivered air at required pressure and site condition | Not answered by pipe size alone |
| Can each drill receive that air? | Not answered by compressor kW | Header, branch, valve, treatment, coupling and hose losses |
| Why does the last drill slow first? | Source may still be adequate | Long/restrictive path or unbalanced branches |
| Why do all drills slow together? | Combined demand, source derating or common leak may be responsible | Common header/treatment restriction may also be responsible |
Use the mixed-fleet compressor sizing guide to freeze source demand. Use this page to freeze how the air is distributed after the compressor outlet.
Step 1: draw the actual air path
Create one line diagram from compressor to every drill. Include aftercooler or receiver if present, separator, filter, regulator, main isolation valve, header sections, tees/manifold, branch valves, lubricators, quick couplings and flexible hoses. Mark ID, length and rated pressure for every section.
Do not draw only the intended layout. Walk the line and capture reducers, temporary hoses, partially open valves, damaged couplings, drain points and other users connected later. The smallest internal bore in a branch can control that branch even when the hose around it looks large.
Step 2: freeze simultaneous demand and diversity honestly
List the exact drill models and any other pneumatic tools. Record the controlled airflow figure and pressure basis for each. Define which users can genuinely run at the same time during the busiest operating condition.
Do not reduce demand using an assumed diversity factor simply because operators “normally alternate.” If production can require simultaneous drilling, the distribution must be verified under that condition. If staged operation is an intentional constraint, document it as an operating rule rather than hiding it in the calculation.
For YT28-only setups, use the YT28 compressor sizing guide. For mixed models, keep the calculation in one reference condition and use compressor FAD corrected for altitude and environment.
Step 3: protect the common header
The common line carries the combined flow before it splits. An undersized main hose, filter, valve or water separator can starve every downstream branch. Select the header from the combined required flow, allowable pressure loss, length, fitting count and expansion allowance—not from one drill's inlet size.
Keep the common path as direct as practical. Avoid unnecessary reducers and abrupt restrictions. Place isolation and drainage so the system can be made safe and maintained. Confirm that every component is pressure-rated and installed in the correct flow direction.
The air-hose sizing guide explains why ID, length and coupling bore matter. Where the run is long, use the long-hose pressure-drop guide to document the additional risk.
Step 4: design branches for comparable resistance
Each drill branch should be independently isolated and identifiable. Record branch length, hose ID, fitting count, lubricator and coupling set. Where two drills need comparable performance, avoid giving one a short unrestricted branch and the other a long branch with several small-bore adapters.
Equal length is not always required, but unequal resistance must be recognized and verified. If one branch must be much longer, increase the flow area or change the distribution point based on an engineering check. Do not compensate for one restrictive branch by raising system pressure beyond the approved tool condition.
Provide a dedicated lubricator arrangement according to the tool and site procedure. Confirm that oil delivery to one branch does not depend on another branch operating. Shared treatment equipment must be sized for combined flow.
Step 5: install safe hose connections and restraints
Use compatible pressure-rated hose, couplings and positive locking features. Restraints are a secondary safeguard; they do not make a damaged or mismatched coupling acceptable. Position them so they can control the hose if a connection separates, following the site rule and manufacturer instructions.
Inspect the full connection path before charging. Keep people out of the line of fire, pressurize in a controlled way, and isolate and depressurize before changing any part. The pneumatic hose-restraint guide provides the connection-level checklist.
Step 6: build a dynamic pressure test matrix
Static pressure with the drills stopped does not prove delivery. Use approved test points and instruments to record pressure while the drills operate under a representative load.
| Test state | Header reading | Near-drill readings | What it can reveal |
|---|---|---|---|
| No drill operating | Baseline only | Baseline only | Gross leakage or regulator setting; not full acceptance |
| Drill A only | Under load | A and idle branches | Restriction or leak on A branch |
| Drill B only | Under load | B and idle branches | Restriction or leak on B branch |
| All planned drills operating | Peak simultaneous condition | Every active branch | Source capacity, common-path loss and branch balance |
| Farthest drill plus another tool | Worst credible layout condition | Farthest branch and header | Long-run sensitivity and operating constraint |
Record time, active tools, compressor condition, header pressure, each tool-inlet pressure, hose layout and drilling condition. A reading without the operating state cannot be compared later.
Step 7: interpret the pressure pattern
- Header pressure collapses when all drills start: check compressor delivered capacity, source derating, common leakage and common treatment/header restrictions.
- Header remains stable but one drill inlet falls: inspect that branch's hose, adapters, valves, lubricator, couplings and leaks.
- All inlets meet the controlled requirement but one drill remains weak: move to the drill, lubrication, steel/bit and rock condition rather than enlarging every hose.
- Pressure cycles as another user opens: define whether the source control system, receiver or operating sequence is causing the transient.
- Air use appears high with heavy exhaust: use the excessive-air-consumption guide after the distribution readings are recorded.
Acceptance record
The final record should include the as-built diagram, compressor model and FAD basis, altitude/site condition, simultaneous-user list, component IDs and ratings, hose IDs/lengths, coupling minimum bores, isolation and restraint points, calibrated instrument identification, dynamic pressure matrix, leak-test result and approved operating constraints.
Retest after a major hose change, added user, relocated header, compressor substitution or repeated performance complaint. A distribution system is not permanently accepted when its configuration changes.
RFQ inputs
Send the drill models and quantities, simultaneous operating plan, compressor curve, site altitude, header/branch diagram, hose IDs and lengths, coupling and treatment components, dynamic readings and the symptom at each drill. Review the Pneumatic Rock Drills collection, then request an air-system configuration review.
FAQ
Can one large hose be split into several small hoses?
Yes only when the common hose and every downstream component can carry the combined demand with acceptable loss, and each branch can deliver the required pressure under simultaneous load. The tee alone does not prove that.
Should all branch hoses be the same length?
Not necessarily, but their different resistance must be understood. Long or restrictive branches need explicit sizing and dynamic verification.
Why is compressor-panel pressure not enough?
It is upstream of the losses. The drill depends on pressure and flow at its inlet while operating, after the header, valves, treatment, couplings and hose.