Quick answer: treat an air-leg rock drill as three connected but different systems: a compressed-air path to the drill, a separate water-flushing path through the drill steel and bit, and a model-matched pneumatic/mechanical air-leg arrangement that supports and feeds the drill. Isolate and depressurize the equipment before connection work. Confirm every port, thread, hose rating, oiler direction, water limit and air-leg suffix from the exact manuals and approved site design before pressurizing.
How to use the diagram above: it is a reference architecture—not a P&ID or installation drawing. The node order is a verification framework; the compressor package, treatment equipment, exact ports, controls, ratings and local safety devices must be engineered for the selected drill, air-leg suffix and site.
Read the diagram as three systems—not one hose layout
| System | What it delivers | What must remain separate or controlled |
|---|---|---|
| Compressed air | Required flow and dynamic pressure to the rock-drill air inlet | Do not confuse source pressure with pressure at the operating tool; size every restriction in the full path |
| Air-leg feed and support | Controlled pneumatic feed plus mechanical support and working geometry | The air-leg circuit, mount and controls must match the approved drill + air-leg combination |
| Water flushing | Water through the flushing inlet, drill-steel passage and bit holes to remove cuttings | Never connect water to an air port; use the exact model’s pressure, flow and backflow requirements |
Compressed-air path: what each numbered node does
- Compressor: the starting point is delivered capacity at the required discharge pressure and actual site conditions—not only motor power or theoretical displacement.
- Receiver or header: provides site-specific storage/distribution functions. Capacity, drainage, location and protection belong to the approved compressor and piping design.
- Branch service point: gives the crew an approved isolation point and any required separator/filter, regulator and gauge. The exact equipment and sequence can differ by compressor package and site.
- Line oiler: use an external unit only when the exact drill requires or permits it. Confirm the flow arrow, rated capacity, oil, setting and whether the drill already has an integral lubrication arrangement.
- Rated air hose and coupling: select by required flow, true hose ID, length, minimum coupling bore, pressure rating, locking profile and required restraint/safety device.
- Rock-drill air inlet: confirm the exact port and coupling profile. Verify dynamic pressure near this inlet while the planned tools are operating.
- Approved air-leg circuit: confirm which drill control/port supplies the matched air leg, its hose route and permitted control logic. The diagram deliberately does not invent a universal port position.
- Matched pneumatic air leg: confirm the full suffix, retracted/extended geometry, feed stroke, mounting point, locks, controls and approved drill pairing.
Why hose size and coupling safety are separate checks
A hose can be large enough for flow and still be unsafe at the connection. It can also be securely connected but starve the drill through an undersized nipple, valve or stacked adapter. Record the complete route and the smallest clear bore, then apply the positive locking, restraint and source/branch protection required by the manufacturer, site procedure and local law.
For U.S. construction work, OSHA 1926.302(b) includes requirements on positive hose-to-tool security, manufacturer safe working pressure and source/branch protection for certain larger hoses. This is one jurisdictional reference, not a substitute for the rules that control your site.
Water flushing: a separate path into the drill
The water path begins at a clean supply, passes through the approved shut-off and pressure/backflow arrangement, continues through a rated water hose to the correct drill flushing inlet, and then travels through the drill-steel passage and bit holes to the bore. A restricted flushing path can leave cuttings at the bit and make a healthy drill appear underpowered.
There is no universal water-pressure number for every YT-labelled drill. Confirm the relationship between air and water pressure, permitted flow, connection and shutdown sequence from the final supplier manual. Do not copy the Y19A water-pressure rule to a YT24, YT27, YT28 or YT29A configuration.
Recommended installation and verification sequence
- Identify the exact rock drill, manufacturer/revision and complete air-leg suffix; obtain the approved manuals and drawings.
- Check the planned hole direction, working envelope, air-leg retracted/extended geometry, feed stroke and mechanical mounting arrangement.
- Confirm compressor delivered capacity at site, required pressure and the credible simultaneous load.
- Map the receiver/header, drains, branch isolation, separator/filter, regulator/gauge and every reduction in the air path.
- Confirm whether an external line oiler is required; verify its direction, capacity, oil and setting before installation.
- Select rated air hose, water hose, fittings, coupling profile, minimum bore and required positive locking/restraint devices.
- With all energy isolated and the system depressurized, install the matched drill, air leg and drill string according to the approved procedure.
- Connect the air line only to the confirmed air inlet, the air-leg circuit only to its approved port and the water line only to the flushing inlet.
- Pressurize under the site procedure, check for leakage/abnormal movement and run a controlled low-risk functional test.
- Run the planned production load and record compressor/header pressure, dynamic pressure near the drill, water performance, lubrication delivery and air-leg behavior.
Ten checks before the first production start
| Check | Accept only when | If not confirmed |
|---|---|---|
| 1. Identity | Drill model/revision and complete air-leg suffix are recorded | Stop and identify the equipment |
| 2. Mechanical mount | Mount, clamp/pin, locks and geometry match the approved drawing | Do not improvise a bracket or substitute by appearance |
| 3. Air capacity | Delivered capacity covers the real simultaneous demand at site | Recalculate before drilling |
| 4. Air path | Isolation, treatment, regulation and drainage match the site design | Keep the branch isolated |
| 5. Lubrication | Correct architecture, oiler direction, oil and delivery are confirmed | Do not run the drill dry or guess a feed setting |
| 6. Hoses | ID, length, condition, route and pressure/service ratings are acceptable | Remove damaged or unsuitable hose from service |
| 7. Couplings | Profiles match, clear bore is sufficient and positive restraint is installed as required | Do not stack or force adapters |
| 8. Water path | Correct inlet, clean flow, pressure limits, hose and bit holes are confirmed | Do not pressurize an unknown port |
| 9. Drill string | Shank, steel, taper, bit and retainer are compatible and secure | Stop and verify every interface |
| 10. Loaded test | Dynamic tool pressure, flushing, lubrication and air-leg feed are stable under the planned load | Find the failing section before production |
Five connection mistakes this diagram is designed to prevent
- Cross-connecting air and water: similar fittings or improvised adapters are not proof that a port is correct.
- Installing an oiler backwards—or adding one blindly: wrong direction can prevent delivery, while a second unapproved oiler can create a different fault.
- Putting a small restriction after a large hose: one nipple, valve, regulator or coupling can control the flow of the complete branch.
- Pressurizing an unsecured or damaged hose: missing positive locking/restraint, unsuitable clamps or an unsafe hose can create separation and whipping hazards.
- Fitting an air leg by family name alone: “FT160” does not confirm suffix, length, stroke, mount, hose/control arrangement or approved drill pairing.
Stop operation and isolate the system when
- a hose, coupling, clamp, restraint or pressure-bearing component is damaged, loose, leaking or outside its rating;
- the air leg extends unexpectedly, binds, slips, leaks continuously or cannot hold controlled feed;
- dynamic pressure collapses, the branch pulsates abnormally or the compressor/header condition is unstable;
- lubrication delivery cannot be confirmed, the drill heats abnormally or operating sound changes materially;
- water enters an unconfirmed port, flushing is lost/restricted or the site cannot maintain the model-specific water limits;
- the drill steel/bit/retainer is incompatible, loose, damaged or ejecting debris abnormally.
Use the detailed guide for the failing section
- Air-hose sizing: ID, length, couplings and dynamic pressure
- Long-run pressure drop and pressure-location testing
- Line-oiler architecture, oil and daily lubrication checks
- Air-leg leaks, slipping, weak feed and isolation steps
- Narrow-tunnel geometry, hose routing and water flushing
- FT160/FT170 suffix, geometry and drill compatibility
- H22 × 108 shank, drill steel and tapered-bit compatibility
What to send for a matched drilling-system quotation
- rock-drill manufacturer, complete model/revision and clear nameplate/whole-machine photos;
- air-leg complete suffix, retracted/extended length, feed stroke, mounting and control/port photos;
- hole direction, diameter/depth, rock condition, tunnel or quarry working envelope and planned quantity;
- compressor model, FAD curve, site elevation/temperature, discharge pressure and simultaneous air users;
- receiver/header and branch layout; air-hose ID/length; every valve, filter, regulator, oiler and coupling profile;
- water source, available pressure/flow, hose and confirmed drill flushing interface;
- drill shank, drill-steel length/section, taper/thread and bit requirement;
- loaded source/header/tool-inlet pressure readings and any observed leakage, weak feed or flushing problem.
Start with the Air-Leg Rock Drills Collection and the FT160/FT170 air-leg matching page. Then send the complete system inputs for a configuration review and quotation. The final written quotation, approved drawings and supplier manuals control the supplied equipment and installation.
Frequently asked questions
Is the diagram a universal installation drawing?
No. It is a verification architecture that prevents air, water, lubrication, air-leg control and mechanical support from being confused. Exact hardware and order remain model- and site-specific.
Must every drill use a separate line oiler?
No universal answer is safe. Identify whether the exact drill uses an integral oiler, an external line oiler or another approved arrangement, then follow the relevant manual.
Can I use compressor outlet pressure as the drill pressure?
No. Record dynamic pressure near the drill inlet while the planned system is operating. Source pressure alone cannot reveal downstream restriction or loss.
Can air and water hoses share the same connector family?
Do not create a cross-connection risk. Use the identification, connection and segregation required by the equipment and site design, and verify the exact ports before pressurizing.
Does “FT160” confirm the correct air leg?
No. FT160 is a family name. The complete suffix, geometry, mount, controls, connections and approved rock-drill pairing must be confirmed before quotation or installation.