What counts as “high pressure” for a screw compressor?
“High pressure” depends on the application. Most factory air systems run at 6–8 bar (87–116 psig) at the point of use, and standard stationary screw compressors are commonly offered at 7.5, 8.5, 10 and 13 bar ratings. For stationary plant air, anything from about 13 bar (188.5 psig) upwards is usually treated as high pressure.
Above the range that a single-stage oil-injected airend handles well, manufacturers use two-stage screw designs, screw compressors with a booster, or reciprocating compressors. Portable diesel screw compressors for drilling go much higher. For borewell and DTH drilling, typical packages deliver 600–1,500 cfm at 200–400 psig (13.8–27.6 bar), and special units reach about 35 bar (507.6 psig).
| Pressure band | Typical applications | Usual compressor type |
|---|---|---|
| 7–10 bar (101.5–145 psig) | General plant air, pneumatic tools, packaging, breakers and rock drills | Standard stationary or portable screw |
| 10–13 bar (145–188.5 psig) | Longer distribution networks, some machine tools, blasting, cable blowing | Higher-pressure single-stage screw |
| 13–15 bar (188.5–217.6 psig) | Laser cutting assist gas, some process and test duties, pneumatic conveying boosts | High-pressure single-stage or two-stage screw |
| 14–28 bar (203.1–406.1 psig) | Borewell and DTH drilling, quarry drilling, pipeline work | Portable two-stage diesel screw |
| Around 35 bar (507.6 psig) and above | Deep drilling, PET bottle blowing (usually with a booster), special tests | Special high-pressure screw, booster or reciprocating |
Why higher pressure costs more
Every extra bar of discharge pressure takes more energy. A useful rule of thumb is about 7% more power for each extra bar on a typical screw compressor. Higher pressure also increases internal leakage across the rotor clearances, raises discharge temperature and loads the bearings more heavily.
That means you should only generate the pressure you need. Some practical points:
- A plant that needs 13 bar for one machine and 7 bar for everything else should not run its whole system at 13 bar. Consider a separate high-pressure compressor or a booster for that one user.
- Pressure losses in pipework, filters and dryers between the compressor and the tool must be added to the required pressure. Fixing undersized pipes is usually cheaper than buying a higher-pressure machine.
- A higher pressure setting on a standard compressor reduces its FAD. A machine rated 10 bar does not give its 7 bar FAD at 10 bar.
Pressure and flow must both be right
High pressure without enough air is the wrong machine. So is plenty of air without enough pressure. A DTH hammer, laser cutter or blasting nozzle needs a specific pressure and a specific volume of air at that pressure.
When you compare machines:
- Confirm the pressure needed at the point of use, from the tool or process supplier’s data.
- Add realistic losses through hoses, pipes, dryers and filters.
- Confirm the FAD needed at that pressure, with a margin for wear, future growth and high ambient temperature.
- Compare only FAD figures measured at your working pressure to the same standard, usually ISO 1217.
- Check motor or engine power and specific power, in kW per m³/min, at that pressure.
- Look at duty cycle, cooling, controls, service access and spare parts.
Motor kW or HP alone tells you very little. Two machines with the same motor can give very different FAD at high pressure, depending on the airend and staging.
Single-stage, two-stage or booster?
| Option | How it works | Strengths | Watch for |
|---|---|---|---|
| Single-stage high-pressure screw | One airend compresses from atmosphere to final pressure | Simple package, fewer parts | Higher discharge temperature and lower efficiency near its upper limit |
| Two-stage screw | Two airends in series, often with oil cooling between stages | Better efficiency and lower temperature at high pressure | Higher purchase cost; more complex airend overhaul |
| Screw compressor plus booster | A standard screw feeds a booster that raises part of the air to high pressure | Only the air that needs high pressure is raised to it | Two machines to maintain; booster usually reciprocating |
| Reciprocating compressor | Multi-stage pistons | Reaches very high pressures; suits small flows | More vibration, wear parts and maintenance |
For stationary plants, a two-stage design is worth considering when the machine will run long hours at high pressure. For a small high-pressure user in a large low-pressure plant, a booster is often the more economical layout.
Design features that matter at high pressure
- Cooling capacity. High pressure means more heat. In Indian summers, with ambient temperatures of 45 °C or more, check the package is rated for your highest ambient, not a 20 °C test condition. Keep the oil cooler clean and the room well ventilated.
- Discharge temperature. Keep it in the normal oil-injected range of about 75–95 °C. A machine that creeps upwards is telling you something about coolers, oil or ventilation.
- Pressure-rated components. Separator vessels, hoses, receivers, valves and dryers must all be rated for the full working pressure, plus margin.
- Safety shutdowns. High discharge temperature, high pressure and motor protection must work. On portable diesels, low engine oil pressure and high coolant temperature shutdowns matter just as much.
- Minimum pressure valve and separator. These keep oil separation and lubrication working; worn parts let oil carry over into the air.
- Dryer and filter ratings. Refrigerated dryers and filters must be rated for the pressure; at higher pressure, a refrigerated dryer still gives a PDP of about +3 °C.
Stationary or portable high-pressure air?
Stationary electric high-pressure screw compressors suit factories with a permanent high-pressure user, such as laser cutting or test benches, where grid power and a compressor room are available. Portable diesel high-pressure screws suit drilling, pipeline work, testing and projects where there is no reliable power or the work moves from site to site. For short projects, hiring is often more sensible than buying. On project hire, our own machines are serviced every 300 running hours, with oil change, because high-pressure site work is hot, dusty and continuous.
Safety: stored energy at high pressure
Compressed air at 14–35 bar stores a large amount of energy. A failed hose, fitting or receiver at that pressure can cause serious injury.
- Use hoses, couplings and whip restraints rated for the full pressure.
- Have receivers and pressure vessels inspected and tested according to the applicable rules and the manufacturer’s instructions.
- Never exceed the rated pressure of any component downstream of the compressor.
- Depressurise fully before any maintenance, and lock out the machine.
- For pneumatic testing, follow the client’s or engineer’s procedures; they govern pressure, exclusion zones and hold times.
Common faults on high-pressure screw compressors
| Symptom | Possible causes | What we check |
|---|---|---|
| Cannot reach set pressure | Demand above FAD, inlet valve fault, airend wear, leaks | Demand, inlet valve, pressure settings, leaks, airend condition |
| High discharge temperature | Blocked cooler, low oil, thermostatic valve, hot room | Cooler, oil level and grade, valve, ventilation |
| Oil in the air | Separator element, scavenge line, minimum pressure valve | Separator, scavenge, valve, oil level |
| Frequent safety valve lifting | Control fault, faulty safety valve, pressure switch setting | Controls, valve rating and condition |
| Motor overload | Pressure set too high, voltage problem, mechanical drag | Settings, current, voltage balance, bearings |
How Reddy Compressors helps
Reddy Compressors, at Tarnaka, Secunderabad, has supplied, rented and serviced compressors since 2002 as an independent multi-brand specialist, not an authorised dealer of any brand. We have tie-ups with all major and reputed brands. For high-pressure rotary screw duty, we:
- Sell new and used/refurbished high-pressure screw compressors of ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other brands, chosen for your pressure and FAD.
- Rent high-pressure diesel and electric compressors from our own fleet, in the 50–2,000 cfm and 2–30 bar range, for drilling, testing and project work.
- Service, overhaul and repair high-pressure machines through more than 20 service engineers and technicians across Telangana and Andhra Pradesh.
- Supply spares identified from the nameplate, and equipment and rentals across India.
What to send us
- The application and the pressure needed at the point of use.
- The air flow needed at that pressure, or the tools and their air consumption.
- Running hours, duty cycle and highest site ambient temperature.
- Power available (voltage, kVA) or whether you need diesel.
- For an existing machine: make, model, serial number and nameplate photo.
Frequently asked questions
What pressure is a high-pressure screw compressor?
For stationary plant air, about 13 bar (188.5 psig) and above is usually called high pressure, with single-stage packages commonly rated up to about 15 bar. Portable two-stage diesel screw compressors for drilling typically run at 200–400 psig, about 14–28 bar, and special units reach around 35 bar. The right pressure is whatever your application needs at the point of use.
Can a normal screw compressor be set to a higher pressure?
Only up to its maximum rated pressure. Above that, the motor overloads, the safety valve lifts and the machine runs hot. Even within its rating, a higher set pressure lowers FAD and raises energy use by about 7% per extra bar. If you need higher pressure than the machine is rated for, choose a high-pressure unit or a booster.
Is a booster better than a high-pressure compressor?
It depends on how much air needs high pressure. If only a small part of the plant needs high pressure, a booster fed by your normal plant-air compressor avoids running everything at high pressure. If most of the air is needed at high pressure for long hours, a dedicated high-pressure or two-stage screw compressor is usually the simpler choice.
What compressor pressure do I need for borewell drilling?
Borewell and DTH drilling compressors typically deliver 600–1,500 cfm at 200–400 psig, about 14–28 bar, with special units up to about 35 bar. The correct choice depends on hole diameter, depth, hammer type and water and ground conditions. Use the hammer maker’s data and allow for losses in the drill string and hoses.
Why does my high-pressure compressor run hot in summer?
Higher pressure produces more heat, and hot Indian summers reduce the cooling margin. Common causes are dusty or blocked oil coolers, poor room ventilation, recirculating hot air, low oil level or the wrong oil, and a faulty thermostatic valve. Clean the coolers, duct hot air out of the room and check the oil before the machine starts tripping.
Can I hire a high-pressure screw compressor in Hyderabad?
Yes. Reddy Compressors rents high-pressure diesel and electric compressors from its own fleet, from 50 to 2,000 cfm and 2 to 30 bar, with service teams across Telangana and Andhra Pradesh and supply across India. Call +91 99590 60718 or +91 92468 88812 with the pressure, flow, duration and site location.
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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.