What counts as a high-pressure portable compressor?
Most construction and plant-maintenance portables work at 7 bar (101.5 psig), with some at 10 bar (145 psig). Machines that deliver 14 bar (203.1 psig) and above are usually called high-pressure portables. They are built for duties where pressure itself does the work: driving a down-the-hole (DTH) hammer against deep rock, overcoming the water column in a borewell, pushing air through long ducts or pipelines, or supplying a downstream booster.
In practice the high-pressure range divides into a few working classes:
| Pressure class | Typical flow band | Typical duties |
|---|---|---|
| 14–17 bar (203.1–246.6 psig) | 600–900 cfm | Shallower borewells, quarry and construction drilling, pipeline drying support |
| 17–21 bar (246.6–304.6 psig) | 800–1,200 cfm | Medium-depth borewells and DTH drilling, foundation drilling, temporary process air |
| 21–28 bar (304.6–406.1 psig) | 1,000–1,500 cfm | Deep borewells, hard-rock DTH, high-pressure drilling packages |
| Up to 35 bar (507.6 psig) | Special units | Very deep wells, special drilling and testing duties |
These bands describe the market in general terms. The capability of any individual machine comes from its maker’s documentation for that model and configuration, and our rental fleet covers 50–2,000 cfm at 2–30 bar.
How a high-pressure portable package works
Most current high-pressure portables use an oil-injected rotary screw airend driven by a diesel engine. Some designs use two compression stages, or a single stage with a high built-in pressure ratio. Oil injected into the airend seals the rotor clearances, lubricates the bearings and carries away the heat of compression. The oil separator vessel then removes oil from the air before it leaves the machine, and the oil cooler and engine radiator reject heat through a shared cool box.
Three features make the high-pressure package different from a standard 7 bar machine:
- Heat load. Compressing to 20 bar puts much more energy into the air than compressing to 7 bar, so the oil cooler, fan and cool-box airflow carry a heavier load. High ambient heat in Telangana and Andhra Pradesh summers, often 40–45 °C and above 45 °C on open sites, eats into that margin.
- Engine power. More pressure at the same flow needs more shaft power. The engine is sized for the rated point, and fuel use rises with pressure and load.
- Pressure-rated components. The separator tank, safety valve, minimum-pressure valve, hoses and couplings must all suit the working pressure, with a suitable margin.
Many machines offer selectable pressure-and-flow settings: higher flow at a lower pressure, or lower flow at a higher pressure, within the engine’s power limit. The variable-pressure page explains how that trade-off works.
Why the pressure requirement must be traced to the equipment
Many high-pressure enquiries start with a number copied from the last machine on site. That setting may have suited a different hammer, a different hole depth or a different hose run. Before you specify a pressure, find out where it comes from.
- Name the equipment that needs the pressure: the DTH hammer, the drill rig, the test procedure or the downstream process.
- Check its documented operating pressure and air consumption at that pressure.
- Add the pressure drop through the hoses, manifold, lubricator, drill string and any treatment equipment between the compressor and that equipment.
- For borewells, allow for the back-pressure of the water column when the hammer works below the static water level. Each 10 m of water adds roughly 1 bar (14.5 psi).
- Choose a compressor whose documented free air delivery at the required discharge pressure covers the demand, with a working margin.
Where the requirement is uncertain, say so in the enquiry. An honest “about 20 bar, to be confirmed” helps us more than a firm figure with no basis behind it.
Keep the pressure terms separate
Several pressure figures appear on a datasheet and a site, and mixing them up causes most selection errors.
| Term | What it means | Why it matters |
|---|---|---|
| Rated working pressure | Discharge pressure at which the maker states the free air delivery | Flow figures only apply at this pressure |
| Maximum pressure | Upper limit of the control range or unloading setting | Not a sustained working point |
| Safety-valve setting | Pressure at which the relief valve lifts | Hoses and fittings must be rated above it |
| Pressure at point of use | Pressure available at the hammer or tool | This is what does the work |
| Gauge versus absolute | psig and bar(g) read above atmosphere | Altitude and calculations may need absolute values |
Free air delivery (FAD) is the flow measured at the compressor inlet conditions, usually quoted in cfm or m³/min. One m³/min is about 35.3 cfm. A machine sold as “1,000 cfm, 350 psig” may deliver its full flow only at its rated pressure, not at every setting.
Applications in India
High-pressure portable air is used across Telangana, Andhra Pradesh and the rest of India for:
- Borewell and water-well drilling with DTH hammers, from agricultural and irrigation wells to government water projects and industrial borewells.
- Quarry, mining and foundation drilling with crawler rigs.
- Oil and gas support work, such as temporary air for drilling and well-site activities, as on the gas-development project described below.
- Pipeline drying, pigging support and pneumatic testing, always under the client’s approved procedure because stored energy in compressed air is a serious hazard.
- Feeding boosters for still higher pressures, and temporary process air during shutdowns.
One of our own projects shows the scale involved. For an international oilfield-services contractor on a natural-gas development at Kakinada, Andhra Pradesh, our team supplied and commissioned a temporary power-and-air package. It included three compressors rated 1,100 cfm at 300 psig (20.7 bar), two rated 1,000 cfm at 275 psig (19 bar) and one rated 750 cfm at 150 psig (10.3 bar), with generators, distribution boards, operators and a technician on site.
Site set-up and safety
A high-pressure line holds a lot of stored energy. A burst hose or a coupling that comes apart can whip violently and injure people. Basic good practice:
- Use hoses and couplings rated for the compressor’s maximum pressure, not just the working pressure, and check their condition and date marks.
- Fit whip restraints (safety cables) across hose joints and secure long runs.
- Depressurise fully before you disconnect anything. Never kink a hose to stop the air.
- Keep the safety valve, gauges and shutdown functions working. Never block or adjust a relief valve.
- Park the machine level, with clear airflow to the cool box and its exhaust pointing away from people and the drill cuttings.
- Keep the engine air intake away from dust plumes from drilling, and service the pre-cleaner and air filter more often in dusty work.
Standard safety shutdowns on these machines usually cover high discharge temperature, low engine oil pressure and high engine coolant temperature. Treat a shutdown as information, not a nuisance: find the cause before you restart.
Common problems on high-pressure duty
| Symptom | Likely causes | What to check |
|---|---|---|
| Pressure will not reach setting | Demand above FAD, worn hammer, leaking joints, intake restriction, control fault | Actual demand, hose leaks, air filter, regulator and inlet valve |
| High discharge temperature shutdown | Blocked cooler, low oil level, wrong oil, hot ambient, thermostatic valve fault | Cooler fins, oil level and grade, cool-box airflow, recirculation of hot air |
| Oil carry-over into the line | Separator element worn, oil level too high, scavenge line blocked, frequent light loading | Separator differential pressure, scavenge orifice, oil level |
| Engine loses power under load | Fuel filter, dirty air filter, injector or turbocharger problems | Fuel system, air intake, engine service history |
| Safety valve lifting | Control setting wrong, minimum-pressure valve fault, blocked discharge | Settings against the manual, valves, downstream restrictions |
Our diesel portable troubleshooting page covers these faults in more depth.
Buy, rent or buy used?
Rig owners who drill every day usually own their machines. Contractors with a fixed-term project, or anyone covering a peak or a breakdown, often rent. A good used or refurbished machine can make sense where its history is known and its condition can be checked: airend sound and temperature, separator condition, engine hours and compression, and the state of the chassis and pressure vessel. Whatever you choose, plan service and spare parts from the start, because high-pressure machines work hard and pay back well-kept maintenance.
How Reddy Compressors helps
Reddy Compressors has worked with industry since 2002 from our office at Tarnaka, Secunderabad. We sell new and used/refurbished high-pressure portable compressors, rent them from our own fleet, and service them and supply their spares. We work across ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic, Doosan and other brands as an independent multi-brand specialist, not an authorised dealer of any of them. We have tie-ups with all major and reputed brands.
- Selection support: we work out the pressure and flow from your hammer, rig or process, rather than just the nameplate.
- Rental of diesel and electric machines from our own fleet, with hoses and treatment equipment where the job needs them, operators where required, and servicing on hire every 300 running hours.
- Brand-new machines supplied to site for long-term projects.
- Service, breakdown repair and overhaul by our team of more than 20 service engineers and technicians, covering the whole of Telangana and Andhra Pradesh.
- Spare parts identified from the machine’s make, model, serial number and nameplate, with fit confirmed before we quote.
- Supply of machines, rentals and spares across India, with project-based site support where feasible.
What to send us
- The application: drilling (hole diameter, expected depth, hammer model), testing, process or other duty.
- Required pressure at the point of use and where that figure comes from.
- Air consumption of the connected equipment, if known.
- Site location, hose length and expected ambient conditions.
- Duration and hours per day, and whether you want to buy, rent or buy used.
- For service or spares: make, model, serial number and a nameplate photo.
Frequently asked questions
What pressure is considered high pressure for a portable compressor?
Standard portable compressors usually work at 7 bar (101.5 psig), with some at 10 bar (145 psig). Machines delivering about 14 bar (203.1 psig) and above are generally called high-pressure portables. Borewell and DTH drilling machines commonly work between 14 and 28 bar (200–400 psig), and special units can reach about 35 bar (507.6 psig). The right pressure depends on the hammer or process, line losses and, for borewells, the water column.
How much cfm do I need for a borewell compressor?
Borewell compressors typically range from 600 to 1,500 cfm. The flow must keep the hammer working and lift the cuttings out of the hole, so it depends on hole diameter, drill-pipe size, hammer consumption and depth. Shallower wells may need 600–900 cfm at 14–17 bar, while deep hard-rock wells may need 1,000–1,500 cfm at 21–28 bar. Send us your rig and hammer details and we can help you work it out.
Can I run a high-pressure compressor at a lower pressure?
Yes, within limits. Many machines have selectable pressure settings, and some deliver more flow at lower pressure because the engine has power to spare. Others simply deliver their rated flow and waste energy by throttling. Running a high-pressure machine at low pressure for long periods can also lead to moisture build-up in the oil if it runs cool. Check the manual for the permitted operating range of your model.
Why does my high-pressure compressor keep shutting down on high temperature?
The most common causes are a cooler blocked with dust, low or wrong oil, hot air recirculating back into the cool box, or a faulty thermostatic valve. High-pressure machines carry a heavier heat load than 7 bar units, so a summer ambient of 45 °C leaves less margin. Clean the cooler, check the oil level and grade, and move the machine so it draws cool air. If it still trips, have the sensor and valve checked.
Is it better to rent or buy a high-pressure portable compressor?
If you drill or work at high pressure most days of the year, owning usually makes sense. For a fixed-term project, a peak in work or breakdown cover, renting avoids tying up capital and puts maintenance in the supplier’s scope. A checked used machine sits between the two. We sell new and used machines and rent from our own fleet, so we can compare the options for your workload.
What hoses should I use with a 25 bar compressor?
Use hoses and couplings rated for at least the compressor’s maximum pressure and safety-valve setting, not just the working pressure, with a suitable safety factor from the hose maker. Fit whip restraints across every joint, keep runs as short and straight as practical, and inspect for cuts, bulges and worn fittings before each shift. Undersized hoses also cost you pressure at the hammer, so size them for the flow as well.
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 7 November 2026. How our engineering content is reviewed.