Compressor rental and temporary air engineering

What does compressor rental actually include?

A rental compressor that arrives on a trailer is only part of the job. What the plant or site needs is usable air at the point of use: the right flow, at the right pressure, at the right quality, for as long as the work lasts. That depends on the machine, and also on the hoses, the treatment train, the tie-in, the fuel or electrical supply and the people who run it.

Photographs from Reddy Compressors’ own fleet and workshop.

When we quote a hire, we are quoting a temporary air service. Depending on the duty, the scope can include:

• One or more compressors, diesel portable or electric, oil-injected screw or oil-free, sized to the duty rather than to the nearest available nameplate.
• Air hoses, couplings, whip checks and manifolds sized for the flow and distance.
• Aftercoolers, moisture separators, refrigerated or desiccant dryers and filters where the air quality needs them.
• Transport, placement, connection and commissioning at site.
• Servicing on hire: on our hire jobs we change oil and service every 300 running hours, and we attend breakdowns on the hired machine.
• Operators on shifts where the client wants us to run the machine.
• Diesel generator sets from Reddy Generators, our sister business under the same management, when an electric compressor or site lighting needs power.

What is excluded matters as much as what is included. Fuel supply, site permits, the client’s own isolation and process decisions, and any work inside the client’s air network are normally the client’s responsibility unless agreed in writing. Our scope and exclusions guide sets these boundaries out so there are no surprises on site.

Our rental range at a glance

We run our own rental fleet. That matters because we can inspect, service and prepare the machine ourselves before it leaves Secunderabad, and send our own engineers when something needs attention. For long-term projects we can also supply brand-new machines to site.

Oil-free rental is available for plants where oil carry-over is not acceptable, such as pharmaceutical, food and electronics duty. Brands across our sales, hire and service work include ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic, Doosan and others. We are an independent multi-brand business, not an authorised dealer for any of them. We have tie-ups with all major and reputed brands.

When do plants and sites hire compressed air?

Each rental situation asks a different engineering question. Treating them all as “send a compressor” is how temporary air goes wrong.

A breakdown and a planned shutdown can need the same machine, but the planning is opposite. In a breakdown there is no time for a survey, so the brief and our questions do the work. In a shutdown there is time to survey, tie in, test and prove the rental before the permanent station is switched off.

How do you size a rental compressor correctly?

Most hire problems trace back to the duty being stated as a single number, “we need 600 cfm”, without the context that makes that number usable. Our duty specification guide covers this in depth. The short version is to define the air service at the delivery point, not at the compressor.

1. Flow. Use free air delivery (FAD) in cfm or m³/min, at the real working condition. Measure or estimate the actual demand from the existing compressors’ loading, not the sum of the nameplates. Add a margin for leaks and for tools starting together.
2. Pressure. State the minimum pressure needed at the user, then add the pressure drop through dryers, filters and hoses. Running higher than needed costs fuel or power: as a rule of thumb, each extra bar takes about 7% more power.
3. Air quality. State the class you need, using ISO 8573-1 where it applies: particles, water (pressure dew point) and oil. A refrigerated dryer typically gives a pressure dew point around +3 °C; desiccant dryers typically give −20 °C or −40 °C.
4. Duration and duty cycle. Hours per day, days per week and expected total hire period. Round-the-clock duty changes servicing, fuel and staffing.
5. Site conditions. Ambient temperature (Indian summers reach 40–45 °C, and above 45 °C on open sites), dust, altitude, access for a trailer or crane, ground conditions and distance to the tie-in.
6. Energy. Diesel, or electric with a confirmed supply of the right size, voltage and protection.

Two cautions from the field. First, a low-pressure problem is not always a capacity problem; a failed drain, a blocked filter or a closed valve can mimic a missing compressor. Second, bigger is not automatically safer. An oversized machine runs unloaded for long periods, which is wasteful for diesel engines and can upset the pressure control of the permanent station it is working alongside.

Diesel or electric, oil-injected or oil-free?

The drive and the compression technology are separate decisions. Our diesel or electric guide and temporary oil-free air guide go into detail.

Oil-injected screw compressors suit most construction, drilling and general plant duty, with filtration and drying added for the quality required. Where the process cannot accept any risk of oil, an oil-free rental removes the source. Even then, dryers and filters are still needed for water and particles.

For an electric hire, power is often the hidden constraint. Our electrical supply guide covers feeder capacity, starting current, cable sizing and earthing. For diesel hires, the fuel supply and refuelling guide covers storage, refuelling under load, fuel quality and spill control.

Air treatment, hoses and distribution

A rental compressor delivers hot, saturated air. Discharge temperature on an oil-injected screw is typically about 75–95 °C inside the machine, and the air leaving the package still carries water vapour that condenses as it cools. For tools, that may be acceptable. For blasting, painting, cable blowing, instrument air or process air it is not.

The treatment train is chosen from the quality required: aftercooler and moisture separator to remove bulk water, then a refrigerated or desiccant dryer, then particle and coalescing filters, and activated carbon where oil vapour matters. In high ambient heat, dryers and aftercoolers lose capacity, so they need to be sized for summer conditions, not catalogue reference conditions. See temporary air treatment trains.

Distribution is where good compressors are often let down. Long, undersized hoses can lose more pressure than the dryer and filters combined. Multiple machines need a manifold with non-return valves so one unit cannot back-feed another. Read hose manifolds and distribution before planning a long run or a multi-machine station.

Large stations, high pressure and redundancy

When the demand is large or the duty is critical, a single machine is rarely the right answer. Several medium machines on a manifold give flexibility: units can be added as demand rises, taken out for servicing, and one failure does not stop the supply.

• High-volume temporary air stations cover multi-machine layouts, common manifolds, load sharing and controls.
• High-pressure temporary air packages cover drilling, pipeline and testing duty from about 10 bar to 30 bar (about 150–435 psig), with the extra care that stored energy demands.
• Redundancy and failure management covers N+1 thinking, what happens when a rental unit trips, and how to keep critical users supplied.

One of our earlier project packages shows what a combined station can look like. For an international oilfield-services contractor on a major natural-gas development at Kakinada in Andhra Pradesh, from 2008 to June 2009, our team supplied and commissioned a temporary power-and-air package: three compressors rated 1,100 cfm at 300 psig, two rated 1,000 cfm at 275 psig and one rated 750 cfm at 150 psig, with generators from 1.5 kVA single-phase to 200 kVA three-phase, junction boxes and distribution boards, operators and a technician on site, and erection, commissioning and transport in our scope.

Planning the hire: survey, mobilisation, tie-in and return

A well-planned hire follows a sequence. Skipping a step usually costs time on site.

1. Brief and enquiry. The duty, the reason for the hire and the dates. See typical rental enquiries and how to brief us.
2. Site survey. Placement, access, ground, tie-in point, power or fuel, ventilation and hazards. See temporary air site survey.
3. Placement. Keep exhaust away from building air intakes, allow hot air to escape, respect noise limits near housing and schools. See placement and community considerations.
4. Transport and mobilisation. Vehicle, route, unloading and positioning. See transport and mobilisation.
5. Tie-in and changeover. Connect to the client’s network with isolation, non-return protection and a tested changeover sequence. See tie-in and changeover.
6. Operation. Shift cover, logs, checks, servicing at 300 running hours and fault response. See operation and shift management and metering and usage management.
7. Demobilisation. Controlled return to permanent supply, disconnection, inspection and transport back. See demobilisation and return.

Our operators are used to long duty. On one hire at a steel plant in Andhra Pradesh, a 450 cfm diesel portable ran round the clock for a coating contractor, with our skilled operators on 12-hour shifts, complete maintenance in our scope and oil changed every 300 hours. On a power-plant project, two 450 cfm machines at 150 psig and one 400 cfm machine at 100 psig were hired with operators able to run and troubleshoot them, and serviced every 300 hours.

Hire, buy, or own the base and rent the peak?

Rental is not always the cheapest way to get air, and buying is not always the most economical way to own it. The decision depends on how long and how often you need the air.

Our hire or buy guide works through the comparison: utilisation, capital, maintenance, energy and residual value. The own the base, rent the peak guide explains how many plants size a permanent station for the base load and hire for predictable peaks.

Where we supply rental air

Our office and workshop are at Tarnaka, Secunderabad. Our service teams cover the whole of Telangana and Andhra Pradesh, and we supply rental compressors across India, with project-based site support where it is feasible. Our hire work has included a 400 cfm compressor with a 25 kVA DG set for an infrastructure contractor at Raichur in Karnataka, three 450 cfm compressors for a lift irrigation project in Kurnool district, and a 400 cfm electric compressor with a 160 kVA DG set at a thermal power project in Karnataka.

We have supplied compressors on breakdown to leading pharmaceutical manufacturers in Hyderabad and Telangana, and supplied leading companies across sectors with new and used machines, long-term rental and breakdown cover.

Local conditions shape the hire. Summer ambient of 40–45 °C, and above 45 °C on open sites, cuts dryer and aftercooler capacity and pushes machines towards high-temperature shutdown if they are badly placed. Dust in quarries, construction sites and drilling yards loads air filters quickly. Pharmaceutical plants in Genome Valley and the industrial estates around Hyderabad need clean, dry air and documented changeovers.

All rental engineering guides

Each guide covers one part of temporary air in depth.

• Situations: compressor breakdown, planned shutdowns, instrument air outages, peak demand, seasonal hire, commissioning and acceptance, construction work zones, blasting, sandblasting compressor hire.
• Specifying: duty specification, diesel or electric, oil-free air, high-pressure air, high-volume air, air treatment trains.
• Site interfaces: site survey, placement and community, electrical supply, fuel supply and refuelling, hoses, manifolds and distribution, tie-in and changeover.
• Running the hire: transport and mobilisation, operation and shift management, metering and usage management, redundancy and failure management, demobilisation and return, scope and exclusions.
• Commercial: hire or buy, long-term hire, own the base, rent the peak, how to brief us.

Hire kit checklist by job

Most hire problems are not the compressor. They are a missing manifold, a hose one size too small, wet air at a paint gun or a diesel tank with no bund. Use this table to check that the whole kit is in the quote before the hire is confirmed. Hose sizes are inside diameters and are starting points; confirm them with the pressure-drop check in the next section.

Two rules apply to every job. Every hose’s rated working pressure must be above the compressor’s maximum, including the safety-valve setting. And every claw coupling needs its locking pin and a whip check, because a hose that parts under pressure flails with enough force to injure. For the detail on hose layouts see hoses, manifolds and distribution; for refuelling and bunding see fuel supply and refuelling.

On bunding, the usual rule is a bund holding at least 110% of the largest tank inside it: a 1,000 litre fuel bowser needs a bund of at least 1,100 litres. To size the fuel run, take the full-load consumption from the machine’s data sheet. If it shows 22 litres per hour (an illustrative figure) and the machine averages 70% load, a 12-hour shift uses roughly 22 × 0.70 × 12 = 185 litres. Diesel use does not fall in strict proportion to load, so use the maker’s part-load figure where the data sheet gives one.

How much pressure will the hose lose? A worked check

A widely used formula for pressure drop in a smooth line carrying compressed air is:

Δp = 450 × q^1.85 × L ÷ (d⁵ × p)

Here Δp is the drop in bar, q is the free air flow in litres per second, L is the length in metres, d is the inside diameter in millimetres and p is the starting pressure in bar(a). Two things stand out. The drop rises with the fifth power of the diameter, so one size smaller makes a large difference. And the drop is in proportion to length.

Worked example (illustrative). A 400 cfm compressor at 7 bar(g) feeds a work area 60 m away.

• Flow: 400 cfm ÷ 2.1189 = 188.8 l/s; 188.8^1.85 = 16,237.
• Starting pressure: 7 + 1.013 = 8.013 bar(a).
• 38 mm (1½ in) hose: d⁵ = 79,235,168. Δp = 450 × 16,237 × 60 ÷ (79,235,168 × 8.013) = 0.69 bar.
• 51 mm (2 in) hose: d⁵ = 345,025,251. Δp = 450 × 16,237 × 60 ÷ (345,025,251 × 8.013) = 0.16 bar.

Hoses add couplings, bends and a rougher bore than steel pipe, so multiply the result by about 1.5 for a hose run with several joints. That gives about 1.0 bar on the 38 mm hose and about 0.24 bar on the 51 mm hose. A good target is a hose drop of no more than about 0.3–0.5 bar at full flow, so the 51 mm hose is the right choice here.

The table shows the formula result for 60 m of line before the hose factor. The drop is in proportion to length, so 120 m of the same hose loses twice the figure shown. Where a run is longer, or flow is higher, run two hoses in parallel or move the compressor closer.

Sandblasting hire: from nozzle size to compressor size

For sandblasting equipment for rent, the nozzle sets everything. Air flow through a blast nozzle rises with the square of its bore and roughly in proportion to absolute pressure. The figures below are the widely used planning values for a new venturi nozzle at 100 psig (No. 3 to No. 8: 59, 105, 165, 240, 326 and 427 cfm), scaled by absolute pressure to 7 bar(g) (101.5 psig), a factor of 116.2 ÷ 114.7 = 1.013.

The last column sizes for the nozzle worn one size larger, plus about 15 cfm of helmet air and 10%; for the ½ in nozzle it assumes wear to 9/16 in.

Worked example (illustrative). One blaster with a 9.5 mm (⅜ in) nozzle and an air-fed helmet.

1. New nozzle: about 243 cfm.
2. Nozzles wear. They are normally changed when worn about 1.6 mm (1/16 in) over size, and by then a ⅜ in nozzle uses the air of a 7/16 in nozzle: about 330 cfm. Size for the worn nozzle.
3. Helmet air through a breathing-air filter: allow about 15 cfm, or the respirator maker’s figure.
4. Add 10% for leaks and the blast pot: (330 + 15) × 1.10 = 380 cfm.

A machine of about 400 cfm is the right hire; two ⅜ in nozzles need about 760 cfm. On pressure, aim for 7 bar(g) at the nozzle and allow about 1 bar for the pot, valves and hoses, so set the compressor to about 8–8.5 bar(g). Check the real nozzle pressure with a needle gauge at the nozzle holder, because a pressure drop you have not measured shows up as slow, uneven blasting. In monsoon months the aftercooler and separator matter: wet air makes abrasive bridge in the pot. More detail is on the sandblasting compressor hire guide.

Paint spraying hire: flow, pressure and clean air

For paint compressor rental, flow is modest and air quality is everything. Conventional spray guns typically use about 8–15 cfm each, and HVLP guns more, at lower pressure at the cap. Air-operated airless and air-assisted pumps can use 20–60 cfm depending on stroke rate; read it from the pump’s air-consumption curve.

Worked example (illustrative). Four conventional guns at 12 cfm each, one air-operated pump at 40 cfm, and two supplied-air hoods at 8 cfm each.

• Guns: 4 × 12 = 48 cfm, with about 75% in use at once: 48 × 0.75 = 36 cfm.
• Total: 36 + 40 + (2 × 8) = 92 cfm.
• With a 20% margin for leaks and filter losses: 92 × 1.20 = 110 cfm.

A machine in the 125–185 cfm class covers this job. The air must pass through an aftercooler, a refrigerated dryer at about +3 °C pressure dew point, a coalescing filter and an activated-carbon filter at the booth, or come from an oil-free machine; see oil-free air hire. Never place a diesel compressor where its exhaust can reach its own intake or a breathing-air line, because carbon monoxide passes straight through ordinary filters.

Checks to make when the hired compressor arrives

Fifteen minutes of checks at handover prevents most first-day problems. Record the results on the delivery note.

1. Placement. Level ground, at least 1 m clear on all sides, cooling air not recirculating, exhaust away from doors, intakes and people.
2. Hour meter and fuel. Note the hour reading and fuel level at handover; both are needed for service intervals and the hire record.
3. Fluids. Compressor oil and, on diesel units, engine oil and coolant at the correct level, with no fresh leaks under the machine.
4. Electrical (electric units). Earth connected, cable and protection sized for the motor, rotation direction checked before loading.
5. Hoses and couplings. Pressure rating marked, locking pins fitted, whip checks at every joint, no cuts or bulges.
6. Safety valve and gauges. Safety valve intact and not tampered with, gauges reading zero when vented.
7. Load test. Run up, load and unload, and confirm the set pressures. After 15–20 minutes, check the discharge temperature on the controller against the maker’s range.
8. Treatment. Drains discharge, the dryer reaches its dew point, and condensate goes to a separator, not onto the ground.

The fuller site procedure is in commissioning and acceptance.

How Reddy Compressors helps

We treat every hire as an engineering job. We ask about the duty, the reason for the hire and the site before we choose the machine. We then prepare the compressor in our own workshop, with treatment, hoses and power or fuel arrangements that match.

Our team of over 20 service engineers and technicians services hire machines every 300 running hours and attends faults on them. We provide operators where you want us to run the machine. Because we also sell, service and supply spares for ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other brands, we can help in two ways during a breakdown hire. The rental keeps you running, and our service team can work on your own compressor. Our breakdown diagnostics and AMC services pick up from there.

Reddy Compressors, Srinilayam, 12-13-200, First Floor, Street No. 1, Tarnaka, Secunderabad 500017. Phone +91 99590 60718 or +91 92468 88812, WhatsApp +91 99590 60718, email reddycompressors@gmail.com.

What to send us

• Why you need the air (breakdown, shutdown, project, peak) and the dates or expected duration.
• Flow in cfm or m³/min and the minimum pressure at the user, in bar or psig.
• Air quality needed: tools only, dry air, oil-free, instrument or process air.
• Diesel or electric; if electric, the available supply.
• Site location, access and distance from the compressor position to the tie-in or work face.
• Hours per day, and whether you need our operators.
• For a breakdown: make, model and nameplate photo of the failed compressor.

Frequently asked questions

What sizes of air compressor can I hire from Reddy Compressors?

We hire compressors from 50 to 2,000 cfm and from 2 to 30 bar, which is about 30 to 435 psig. The fleet includes diesel portables, electric machines, high-pressure units for drilling and testing, and oil-free compressors for clean-air duty. Larger demands are met with several machines on a common manifold. For long-term projects we can supply brand-new machines to site.

Does compressor hire include hoses, dryers and an operator?

It can. We quote the complete air service, so hoses, couplings, manifolds, aftercoolers, moisture separators, dryers and filters are included where the duty needs them. Operators are available on shifts if you want us to run the machine. Fuel, site permits and work inside your own air network are normally your responsibility unless we agree otherwise in writing.

Who maintains a rental compressor during the hire?

We do. On our hire jobs the machine is serviced every 300 running hours, including the oil change, and our service engineers attend breakdowns on the hired compressor. On round-the-clock hires this works out at a service roughly every two weeks, so we plan it with your shift pattern. Your team should carry out daily checks and report any alarms.

Is it cheaper to rent or buy an air compressor?

For a few days to a few months, renting is usually cheaper because you avoid capital, storage and maintenance. For a permanent, continuous load, buying new or used usually costs less over the machine’s life. Many plants buy for the steady base load and rent for predictable peaks. We can help you compare both on your actual hours and duty.

Do you rent compressors outside Hyderabad?

Yes. Our office is at Tarnaka in Secunderabad, and our service teams cover the whole of Telangana and Andhra Pradesh. We supply rental compressors across India, and we provide project-based site support where it is feasible. Past hires include projects in Andhra Pradesh and Karnataka for contractors based across India, from steel and power plants to irrigation and gas development.

Should I hire a diesel or an electric compressor?

Choose diesel when the work moves, the site is remote or electrical power is uncertain, as in most construction, drilling and breakdown jobs. Choose electric when a suitable supply is available and the machine will stay in one place for a long time, which usually lowers running cost and noise. If an electric machine needs power, we can arrange a DG set through our sister business.

Do I need a receiver and manifold with a hired compressor?

It depends on the job. Breakers, rock drills and blasting normally run straight from the compressor through a distributor with valved outlets, so no receiver is needed. A receiver helps where demand comes in short bursts, such as paint booths, pulse filters and plant tie-ins, because it steadies pressure and stops the machine cycling. A manifold with a non-return valve on each inlet is needed whenever two or more compressors feed one line, so one machine cannot back-feed another. Ask for both on the quote if your job needs them.

What size compressor do I need to rent for sandblasting?

Start from the nozzle. At 7 bar(g), a new 6.4 mm (¼ in) nozzle uses about 106 cfm, a 7.9 mm (5/16 in) nozzle about 167 cfm and a 9.5 mm (⅜ in) nozzle about 243 cfm. Size for the nozzle when worn one size larger, add helmet air and about 10%. For one ⅜ in nozzle that comes to about 380 cfm, so hire a machine of about 400 cfm, set to 8–8.5 bar(g), with an aftercooler and moisture separator to keep the abrasive dry.

Can I rent a compressor for paint spraying near me?

Yes. Paint spraying needs modest flow but very clean, dry air. A small job with two or three guns often needs 50–100 cfm; a booth with several guns and an air-operated pump can need 110–185 cfm. The air should pass through a dryer, a coalescing filter and an activated-carbon filter, or come from an oil-free machine. We supply hire across Hyderabad, Secunderabad, Telangana and Andhra Pradesh. Send the number and type of guns, any pump model and the site location.

Can I hire a high-pressure compressor for water bore drilling?

Yes. Borewell and DTH drilling needs both high pressure and high flow: hammer pressure rises with depth and water head, and flow lifts the cuttings. Our hire range includes high-pressure units for drilling, with special DTH units up to 35 bar. Size by the hammer’s air curve, bore diameter, expected depth and water level, not by the depth alone. Hoses must be rated above the maximum machine pressure, with whip checks at every joint. See the borewell compressor hire guide for sizing.

Related pages

• Air compressor on rent in Hyderabad
• Typical compressor rental enquiries and how to brief us
• Temporary air for compressor breakdown
• Temporary air duty specification
• Temporary air: hire or buy
• Compressor annual maintenance contracts