600–750 cfm compressors for nitrogen feed air and drilling

What sits in the 600–750 cfm band

At this size you find large diesel portable screw compressors on single- or twin-axle chassis, skid-mounted units for long hires, and stationary electric screw compressors in the 110–132 kW class that serve whole plants. Pressures range from about 7 bar (101.5 psig) for plant air to 14–24 bar (203.1–348.1 psig) for drilling machines. As always, free air delivery (FAD) means something only at its stated pressure.

These are typical industry figures. We confirm the machine and rating for each enquiry.

Nitrogen feed air: two different flows

A nitrogen generator, whether membrane or pressure swing adsorption (PSA), separates nitrogen from compressed air. The air it consumes is several times the nitrogen it produces. The ratio is the air factor, published by the generator maker for each model, purity and set of conditions:

Feed-air flow = nitrogen flow × air factor (both on the same reference basis).

The air factor rises steeply with purity. A generator producing 99.5% nitrogen needs much more air per unit of nitrogen than the same unit at 95%. It also depends on inlet pressure and temperature. Take the factor from the selected generator’s data at your purity and conditions; never borrow a convenient figure from another model or brochure.

• Check what the published factor includes and excludes, such as dryer losses or filter drains.
• Add any air consumed upstream that the factor does not cover, without double counting.
• Keep units consistent: cfm, scfm and Nm³/h use different reference conditions.

A worked feed-air example

Suppose a membrane generator is listed at about 100 scfm of nitrogen at 99.5% purity with an air factor of 3.0, at about 8 bar(g) inlet pressure and 20 °C. These are illustrative figures of the kind makers publish.

Two units land in the 600–750 cfm band; three take you to the next band. Before choosing a compressor:

1. Reconcile reference conditions between the generator’s scfm and the compressor’s FAD.
2. Correct for your inlet temperature: Indian summer ambient of 40–45 °C changes both the compressor’s output and the generator’s performance.
3. Add upstream losses outside the air factor, such as a heatless desiccant dryer’s purge, which consumes a significant share of the dried air.
4. Confirm which generators must run at the same time and for how long.
5. Check the generator’s minimum inlet pressure, plus the pressure drop through filters and dryers.

Air quality at the generator inlet

Membranes and PSA sieves are damaged by oil, water and particles. Generator makers specify an inlet air quality, usually stated as ISO 8573-1 classes for particles, water and oil. A temporary compressor package must meet that specification at the connection point, not just at the compressor outlet.

• Cooling: an aftercooler to bring discharge air close to ambient.
• Water removal: a moisture separator and drains, then a refrigerated dryer (pressure dew point typically around +3 °C) or a desiccant dryer (typically −20 °C or −40 °C) as the generator requires.
• Oil removal: coalescing filters and, where specified, an activated carbon stage. An oil-free compressor reduces the oil risk but still needs drying and filtration.
• Temperature: many membrane generators have an inlet temperature limit; hot afternoon air may need extra cooling.

Define the equipment boundary on a simple sketch: where our supply connects, who owns each component after that point and who is responsible for the nitrogen quality delivered to the user.

Borewell and other high-pressure duties

For borewell and DTH drilling, 600–750 cfm sits at the lower end of the range of 600–1,500 cfm at 200–400 psig (13.8–27.6 bar). Typical pairings are 600–900 cfm at 200–250 psig (13.8–17.2 bar) for shallower holes and smaller bits. Deeper holes, larger bits and water-bearing ground move contractors towards 800–1,200 cfm and higher pressures. Size from the hammer maker’s data, the bit diameter and the annular velocity needed to lift cuttings.

See our borewell and DTH compressor library and DTH compressor sizing for the method.

Reliability, energy and Indian conditions

Large compressors work hard in Indian summers. Keep coolers clean, give the machine clear airflow and watch discharge temperature, which on an oil-injected screw should normally sit around 75–95 °C. Respect the safety shutdowns for high discharge temperature, low engine oil pressure and high coolant temperature on diesel units.

Energy matters at this size. Each extra bar of pressure needs about 7% more power for the same flow, so set pressure to the generator’s or tool’s need plus treatment and hose losses. For electric stationary units, compare specific power in kW per m³/min at your working pressure. For temporary supplies, plan fuel logistics; our temporary air fuel logistics calculator helps.

Our own project experience at this size includes a temporary power-and-air package for a natural-gas development at Kakinada, Andhra Pradesh, which included a 750 cfm compressor at 150 psig alongside larger high-pressure machines, generators, distribution, operators and commissioning.

Choosing between portable and stationary at this size

For a permanent installation, compare lifecycle cost: energy usually outweighs purchase price over the life of a machine this size. For a temporary supply, compare hire, fuel, treatment and service, and agree what happens if the duty runs longer than planned.

Whatever the option, plan condensate handling. A machine of this size produces a lot of water in humid weather, and drains must be checked through every shift.

When a generator’s demand is close to a compressor’s rating, consider two smaller machines instead of one large one. Two units give part-load efficiency, allow one to be serviced while the other runs, and keep nitrogen flowing if one trips. A receiver between the compressor package and the generator also steadies pressure when demand changes.

How Reddy Compressors helps

We sell new and used or refurbished 600–750 cfm compressors, rent diesel and electric machines from our own fleet (rentals cover 50–2,000 cfm and 2–30 bar, oil-injected and oil-free), and service, overhaul and supply spare parts. We also supply aftercoolers, separators and dryers for temporary feed-air packages. We are an independent multi-brand specialist working on ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic, Sullair, Doosan and other makes, not an authorised dealer. We have tie-ups with all major and reputed brands.

Our office is at Tarnaka, Secunderabad. Over 20 service engineers and technicians cover all of Telangana and Andhra Pradesh, and we supply compressors, rentals and spares across India with project-based site support where feasible. For nitrogen duties, we work from your generator’s data to define the feed-air flow, pressure, air quality and equipment boundary before we quote.

What to send us

• Nitrogen generator make, model and type (membrane or PSA), with its data sheet.
• Required nitrogen purity, flow and delivery pressure, and how many units run together.
• Inlet air specification: pressure, temperature and ISO 8573-1 classes.
• Whether the existing dryers and filters stay in service, and where we connect.
• For drilling or other duties: tool or hammer data, depth and bit size.
• Site location, power availability, duty hours and dates.

Frequently asked questions

What size compressor do I need for a nitrogen generator?

Multiply the nitrogen flow by the generator’s air factor at your purity and conditions, using the same reference basis. Then add any upstream losses outside the factor, such as dryer purge, and correct for local inlet temperature. A generator producing 200 scfm of nitrogen with an air factor of 3 needs about 600 scfm of feed air before those additions.

Why does higher nitrogen purity need a bigger compressor?

Removing the last few percent of oxygen takes far more air. The air factor rises steeply as purity increases, so the same generator at 99.5% purity uses much more feed air per unit of nitrogen than at 95%. Agree the purity the process actually needs, then size the compressor from the generator’s data at that purity.

Can a diesel rental compressor feed a nitrogen generator?

Yes, with proper treatment. The package needs an aftercooler, moisture separator, dryer and oil-removal filtration to meet the generator’s inlet specification, and the inlet temperature limit must be respected. An oil-free rental compressor reduces oil risk but still needs drying. Define the connection point and who is responsible for each component downstream.

Is 750 cfm enough for a borewell rig?

For many shallower holes and smaller bits, yes, typically at 200–250 psig (13.8–17.2 bar). Deeper holes, larger bits and wet ground often need 800–1,200 cfm or more at higher pressure. Check the hammer maker’s air requirement and the annular velocity needed to lift cuttings for your bit and drill-pipe sizes before choosing.

What is the difference between scfm and cfm in a compressor quote?

cfm on a compressor usually means free air delivery at the inlet conditions of a test standard. SCFM refers to standard reference conditions of temperature, pressure and humidity, which vary between makers. The same air can have different numbers in each. Reconcile the reference conditions before comparing a generator’s scfm demand with a compressor’s FAD.

Do you supply a complete temporary nitrogen package?

Our scope is the compressed-air supply: the compressor, aftercooler, separators, dryers and filtration to the generator inlet, with service and operators where needed. Nitrogen generators and boosters are specialist equipment; where they form part of the job, we define the boundary clearly so it is clear who supplies and guarantees each element of the system.

Related pages

• Nitrogen generator feed air integration
• Oil and gas support: compressed air and nitrogen
• 500–600 cfm compressors
• 750–900 cfm compressors
• Large portable compressors
• Temporary air engineering centre