What is a 20 bar portable compressor?
It is a high-pressure mobile compressor, usually diesel-driven and mounted on the rig, a truck or a towable chassis, with a working pressure of about 20 bar gauge (290 psig). Most are two-stage or high-ratio oil-injected screw machines with large engines, strong cooling packages and heavy-duty receiver-separators. Many offer two or more pressure-flow settings.
Reddy Compressors supplies all types, all brands and all models of borewell compressors: new sales, used and refurbished machines, rentals, service and spare parts.
| Borewell band | Pressure | Typical flow |
|---|---|---|
| Shallow to medium holes | 14–17 bar (203.1–246.6 psig) | 600–900 cfm |
| Medium to deep holes | 17–21 bar (246.6–304.6 psig) | 800–1,200 cfm |
| Deep or water-bearing holes | 21–28 bar (304.6–406.1 psig) | 1,000–1,500 cfm |
| Special duties | Up to 35 bar (507.6 psig) | Selected for the job |
A 20 bar machine sits in the middle of the borewell range, which is why it is one of the most common rig compressors in Telangana, Andhra Pradesh and across southern India.
Why does pressure matter for DTH drilling?
A down-the-hole hammer converts air pressure into impact energy at the bit. Higher pressure generally gives more blow energy and faster penetration in hard rock, within the hammer’s rated limits. The air then flows up the annulus between drill pipe and hole wall, carrying cuttings to the surface. That requires enough volume to keep the uphole velocity high.
Two things work against the compressor as the hole deepens. Friction in the drill string and annulus rises, and any water in the hole adds back-pressure that the air must overcome. In water-bearing formations the compressor must lift a water column as well as drive the hammer. This is why deep or wet holes often need pressure above 20 bar, or a booster.
Flow falls as pressure rises
On a selectable-pressure machine, the engine’s power is shared between pressure and volume. Maker tables commonly show a model delivering more cfm at 17 bar than at 20 bar. That difference can decide whether a hammer gets enough air.
Consider a hypothetical illustration: a machine gives 700 cfm at 17 bar and 670 cfm at 20 bar, and an assessment puts demand at 690 cfm. At 17 bar there is a small surplus; at 20 bar there is a shortfall. In reality hammer demand also changes with pressure, so both supply and demand must be rechecked. The lesson is that a duty checked at one pressure cannot simply be carried to another. These figures are illustrative, not a drilling case.
How do you match the compressor to the hammer?
- Identify the hammer make, model and size, and the bit diameter.
- Take the hammer maker’s air consumption at the intended operating pressure.
- Check uphole velocity for the hole and pipe diameters, so cuttings clear properly.
- Add allowance for drill-string and hose losses, and for water back-pressure where expected.
- Compare with the compressor’s free air delivery at the chosen setting, after allowing for site ambient and altitude.
- Keep a working margin for airend and hammer wear over the season.
Hammers are designed for a pressure range. Running a hammer well above its rating shortens its life; running well below it slows penetration and wastes rig time.
Planned depth versus demonstrated capability
A request for “a 20 bar compressor for a deep bore” states an intention, not a selection. The real limits come from hole diameter, formation, water inflow, hammer and rig as a set. Record what is known and what is assumed:
- rig, hammer, bit and drill-pipe sizes;
- expected formations, from nearby holes where available;
- expected water levels and inflow;
- planned depth and the point at which you would reassess the air.
Agree in advance what triggers a review: hitting heavy water, slowing penetration, changing bit size or drilling deeper than planned. At that point, the air duty should be reassessed rather than pushed harder.
Common drilling symptoms and air-side causes
| Symptom | Possible air-side cause | Check |
|---|---|---|
| Slow penetration | Low pressure at the hammer, worn hammer, wrong setting | Gauge at compressor and rig, pressure setting |
| Poor cuttings return | Insufficient flow for the hole size | Free air delivery at the setting used, uphole velocity |
| Hammer stops in water | Pressure too low for the water column | Depth of water, need for higher pressure or booster |
| High-temperature trip | Dusty coolers, low oil, summer ambient | Clean coolers, oil level, airflow |
| Oil carry-over to the hole | Separator element or scavenge fault | Separator condition and oil level |
Normal oil-injected screw discharge temperature is about 75–95 °C. Standard safety shutdowns are high discharge temperature, low engine oil pressure and high coolant temperature; never bypass them.
Running a 20 bar rig compressor in Indian conditions
Borewell work in Telangana and Andhra Pradesh means long days, summer temperatures of 40–45 °C, and above 45 °C on open sites, and heavy dust from cuttings. Clean radiators and oil coolers daily, check air filter restriction, keep fuel clean and drain water separators. Fuel use depends on load and pressure setting; each extra bar takes about 7% more power, so use 20 bar where the hole needs it, not by habit. Service on schedule, as a worn airend or a sticking inlet valve shows up first as lost flow at pressure.
Hoses and rig connections at 20 bar
At 290 psig the hose between compressor and rig holds a large amount of stored energy. Use hose assemblies whose rating, including the end fittings, is above the compressor’s safety valve setting. Fit rated couplings with whip checks or restraints on every joint, and inspect the hose daily for cuts, abrasion, bulges and exposed reinforcement. Keep the run short, avoid sharp bends and keep the hose away from the rotary head and vehicle movement. A pressure gauge at the rig end shows how much pressure is lost before the drill string.
When is a booster the better answer?
If a hole regularly needs more pressure than the compressor can give, for example in deep, water-bearing ground, a booster can raise the 20 bar air to a higher pressure. The booster’s outlet duty sets the requirement. Its maker states the inlet pressure, flow and temperature it needs, and the 20 bar compressor must deliver that after the connecting hose and any aftercooler. In other cases a compressor rated for 24–28 bar (348.1–406.1 psig), or a special unit up to 35 bar (507.6 psig), is simpler. We can compare both options for the rig and the holes planned.
- Choose a booster where only some holes need extra pressure and the existing compressor is sound.
- Choose a higher-pressure compressor where most work is deep or wet and one machine is easier to run.
- In either case, confirm the hammer is rated for the higher pressure.
New, used or hire?
| Option | Suits | Check |
|---|---|---|
| New | Rig owners with steady work | Pressure-flow settings for future holes, support and spares |
| Used or refurbished | Owners upgrading or adding a rig | Airend condition, hours, engine health, receiver records |
| Hire | Projects, trials, breakdown cover | Duty, hours, operator need, service interval |
How Reddy Compressors helps
Reddy Compressors, at Tarnaka, Secunderabad, has served industry since 2002 as an independent multi-brand specialist. We offer new and used borewell compressors, rentals from our own fleet, service and spare parts for ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic, Doosan and other makes. We are not an authorised dealer of any brand. We have tie-ups with all major and reputed brands.
We check the hammer and hole against the compressor’s flow at pressure, advise when a higher setting or booster is needed, and identify spares from the machine’s make, model, serial number and nameplate. Our team of over 20 service engineers and technicians covers all of Telangana and Andhra Pradesh, and we supply compressors and spares across India. On hire, machines are serviced every 300 running hours, including oil change.
What to send us
- Rig, hammer, bit and drill-pipe details.
- Planned hole diameter and depth, and expected water conditions.
- Current compressor make, model and serial number, if any.
- Site location and working pattern.
- Whether you need new, used, hire, service or spares.
Frequently asked questions
What is 20 bar in psi?
20 bar is 290.1 psi, using 1 bar ≈ 14.5 psi. Borewell compressors are usually quoted in psig, so a 20 bar machine is a roughly 290 psig unit. Check whether hammer and compressor figures are gauge or absolute, and compare flow at the same pressure, because the difference can affect a close selection.
Is a 20 bar compressor enough for borewell drilling?
For many medium to deep holes in hard rock, yes. Typical borewell machines at 17–21 bar (246.6–304.6 psig) deliver about 800–1,200 cfm. Deep or heavily water-bearing holes may need 21–28 bar (304.6–406.1 psig) or a booster. The answer depends on hammer, bit size, depth and water, not on the pressure label alone.
Why is my borewell compressor drilling slowly?
Common air-side causes are low pressure at the hammer, a worn hammer, insufficient flow at the pressure setting used, water back-pressure, or a compressor losing output through a worn airend, blocked filter or inlet valve fault. Check gauges at the compressor and rig, the setting and filter condition, then have the machine tested if output is low.
How much cfm does a DTH hammer need at 20 bar?
It depends on the hammer size and design. Smaller hammers need much less than large ones, and consumption rises with pressure. Take the figure from the hammer maker’s chart at your operating pressure, then check uphole velocity for the hole size. Send us the hammer and bit details and we will check the match.
Do you sell used 20 bar borewell compressors?
Yes. We supply used and refurbished borewell compressors as well as new machines, rentals, service and spares, across all brands and models. For a used machine, we look at airend condition, running hours, engine health and the receiver’s inspection records, test-run the machine under load, and tell you what we find before you decide.
Can you supply spares for my borewell compressor?
Yes. We supply spare parts for borewell compressors of all brands. Send the make, model, serial number, a nameplate photo and, where possible, a photo of the old part. We confirm fit before quoting, which avoids wrong parts reaching a rig in the field.
Related pages
Calculators and worked examples
These tools give indicative figures for screening, comparison and for preparing an enquiry. They run in your browser and send nothing. No prices or tariffs are assumed: enter your own to see costs. Efficiencies and other figures shown are example values: replace them with your own. Results are not a performance guarantee or a design certificate; final selection is confirmed by a service engineer against the machine data sheet and the site.
DTH hammer duty against two compressors
Check whether each of two compressors can supply a DTH hammer’s documented air consumption at the pressure the hammer needs, after hose, string and water-column losses, and with what margin.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Hammer working pressure at the hammer (bar g): 21
- Hammer air consumption at that pressure (cfm): 950
- Pressure loss from compressor to hammer (bar): 1
- Water column above the hammer to be lifted (m): 0
- Compressor A: maximum working pressure (bar g): 17
- Compressor A: data-sheet flow at the required pressure (cfm): 1150
- Compressor B: maximum working pressure (bar g): 24
- Compressor B: data-sheet flow at the required pressure (cfm): 1000
- Site derating of delivered flow: heat, altitude, condition (%): 0
Result
- Hammer working pressure: 21 bar g = 305 psig
- Water column allowance: 0 bar
- Required compressor discharge pressure: 22 bar g = 319 psig
- Hammer consumption: 950 cfm = 26.9 m³/min
- Compressor A: Fails: cannot reach 22 bar g (maximum 17 bar g); its flow does not count
- Compressor B: flow available at 22 bar g: 1,000 cfm = 28.3 m³/min
- Compressor B: margin: +5.3 % (covers the duty)
- Result: Only compressor B covers the duty
Method. Required discharge pressure = hammer working pressure + pressure loss from compressor to hammer (hose, swivel, drill string, check valves) + water column to be lifted (0.0981 bar per metre of water). A compressor whose maximum working pressure is below the required pressure fails, whatever its flow. Available flow = data-sheet flow at the required pressure × (1 − site derating). Margin (%) = (available flow − hammer consumption) ÷ hammer consumption × 100. Use the same flow basis (FAD or scfm) for hammer and compressor. 1 bar = 14.504 psi; 1 m³/min = 35.31 cfm. Hole cleaning (annular velocity) is a separate check.
What to take from it. Compare flows at the same pressure. More cfm at a lower pressure does not run a hammer that needs higher pressure.
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.
Annular area and return velocity
In drilling, the air must lift the cuttings up the annulus. Check the return velocity from the hole and rod size.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Hole diameter (mm): 115
- Rod outside diameter (mm): 89
- Free air supplied (m³/min): 12
- Bottom-hole back pressure (bar g): 1
- Target return velocity (m/s): 15
Result
- Annular area: 41.7 cm²
- Return velocity: 24.16 m/s = 4,757 ft/min
- Free air needed for the target velocity: 7.45 m³/min = 263 cfm at 15 m/s
- Assessment: Within the commonly quoted range
Method. Annular area = π/4 × (D_hole² − D_rod²). Actual flow at the back pressure = free air × (P_atm / (P_back + P_atm)). Velocity = actual flow ÷ area. A return velocity often quoted for efficient cuttings lift is around 15–25 m/s; confirm for your material.
What to take from it. Low return velocity leaves cuttings in the hole; very high velocity wears the rods and hammer. Both are warnings, not verdicts.