High-volume temporary air stations

When does a site need a high-volume air station?

A single portable covers most construction jobs. A station of several machines is needed when demand is large, continuous or critical:

Representative images of machine types we sell, service and rent. Models and capacities are confirmed against your duty.

• a plant’s main compressor house is down for overhaul, replacement or a long breakdown;
• a production expansion runs ahead of the permanent compressor installation;
• a project needs large flows for pipeline drying, multiple drill rigs, several blasting crews or lift-irrigation work;
• seasonal peaks exceed the installed plant;
• the air is critical enough that one machine is not acceptable, because its failure would stop the site.

Our rental fleet runs from 50 to 2,000 cfm per machine, so a station can be built from several mid-sized portables, a few large units, electric machines tied into a plant header, or a mix of these.

Start with the demand profile, not the fleet

List every user and how it actually uses air. A good profile separates:

• Base load – the steady flow that runs all the time.
• Normal peak – the highest sustained flow during production.
• Transients – short surges such as blow-downs, start-up of a line or several tools at once.
• Minimum load – overnight or weekend demand, which affects how machines unload and cycle.
• Essential load – the users that must keep running if a machine fails.

Use the best evidence available: flow meter readings, the running and loading hours of the existing compressors, equipment data, or production records. Do not size a station from installed compressor nameplates – they show what the plant could make, not what it uses, and leaks are part of the demand until they are fixed.

Net capacity: what really reaches the header

Each step between the airend and your header takes something away. Work out net capacity like this:

1. Start with each machine’s rated free air delivery (FAD) at the pressure it will actually run.
2. Allow for site conditions: high summer ambient and dust reduce cooling margin, and machines may need derating or more space.
3. Subtract purge air if heatless desiccant dryers are used – they consume part of the dried air to regenerate.
4. Allow for pressure drop across aftercoolers, separators, filters, dryers, manifolds and hoses; set discharge pressure high enough to meet the minimum at the user, remembering roughly 7% more power for each extra bar.
5. Remove the largest machine from the total. What remains is the capacity you have during a single failure or service stop.

Measure delivery at the point where the commitment is made: the compressor outlet, after the dryer or at the customer’s header. These are different numbers and must not be mixed up in a quotation.

Standby: N, N+1 and protected demand

Many small machines give better turndown and smaller steps when one fails, but more items to fuel, service and control. A few large machines are simpler to manage, but each failure removes a big share of capacity. Choose the split from the demand profile, the essential load and the site’s ability to manage the fleet.

Shared equipment is a hidden single point of failure. If four compressors feed one dryer, one manifold and one hose to the header, the station is only as reliable as those. Consider bypasses, a second dryer or a split header where the air is critical.

Sequencing and control of several machines

Portable and rental machines each have their own load/unload or modulation control. Run together without a plan, they fight each other: several units part-loaded, pressure swinging, and fuel or power wasted.

• Set pressure bands in steps, so base-load machines stay loaded and trim machines follow demand.
• Use a central sequencer on electric stations where machines support it; on diesel fleets, set bands manually and check them under load.
• Use receivers to steady pressure and reduce cycling of the trim machine.
• Rotate duty between machines so running hours stay balanced for servicing.
• Make sure every machine can deliver into the common manifold without back-pressure tripping, and fit non-return valves on each outlet.

Treatment and distribution at volume

Large flows bring large amounts of water. At high ambient and humidity, especially in the Indian monsoon, a 1,000 cfm station can condense a great deal of water per day. Plan for:

• aftercoolers and separators on each machine or on the manifold;
• dryers sized for the total flow at the real inlet temperature – refrigerated (typical pressure dew point around +3 °C) or desiccant (typically −20 °C or −40 °C);
• filters to the ISO 8573-1 class the process requires, and oil-free machines where Class 0 air is specified;
• condensate collection and disposal that suits site rules, since oily condensate must be treated, not drained to ground;
• manifolds and hoses sized for the full flow and length, with isolation per machine so one can be serviced while others run.

Fuel, power and people

A diesel station running around the clock needs a fuelling plan: tank capacity, bowser access, refuelling times that do not leave machines starved, and spill control. An electric station needs feeders sized for all machines starting and running, with protection and someone authorised to switch. Mixed stations are common: electric machines on a plant feeder for base load, with diesel portables for peaks or for cover during electrical work.

On continuous hire, operators matter. Our team has run a 450 cfm diesel unit on round-the-clock hire at a steel plant in Andhra Pradesh, with operators on 12-hour shifts and oil change and service every 300 running hours. For a lift irrigation project in Kurnool district we supplied three 450 cfm machines. The same disciplines – shift handover, logbooks, planned servicing – scale up to larger stations.

Acceptance: proving the station works

1. Check each machine individually: pressures, discharge temperature, safety shutdowns and leaks.
2. Bring the station up together and check that pressure bands share load as planned.
3. Measure pressure at the customer connection under real demand, and flow where a meter is fitted.
4. Check dew point after the dryer once it has stabilised.
5. Stop the largest machine deliberately and confirm that the protected demand is still met.
6. Record the baseline readings so later problems can be compared against them.

How Reddy Compressors helps

We plan and supply high-volume temporary air stations from our own fleet of diesel and electric compressors, oil-injected and oil-free, from 50 to 2,000 cfm and 2 to 30 bar. As an independent multi-brand specialist we rent, sell and service ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other machines, and we can supply brand-new compressors for long-term projects. We have supplied compressors on breakdown to leading pharmaceutical manufacturers in Hyderabad and Telangana, and to leading companies across sectors for long-term rental and breakdown cover.

• We help build the demand profile and set the standby philosophy with your team.
• We quote the full station: compressors, treatment, receivers, manifolds, hoses, transport, operators and servicing.
• Our 20-plus service engineers and technicians cover all of Telangana and Andhra Pradesh, and we supply across India with project-based site support where feasible.
• Temporary generators can be planned alongside through Reddy Generators, under the same management.

Visit or call us at Srinilayam, 12-13-200, First Floor, Street No. 1, Tarnaka, Secunderabad 500017; +91 99590 60718 or +91 92468 88812; reddycompressors@gmail.com.

What to send us

• Peak, normal and minimum air demand, with how they were measured
• Required pressure at the header and air quality class
• Which users are essential if a machine stops
• Duration and operating hours (shifts, days, months)
• Available power, fuel access and standing area
• Details of the existing compressor house or header connection point

Frequently asked questions

How do I size a temporary air station for my plant?

Start from what the plant actually uses, not the installed compressor ratings. Use flow meter data, compressor loading hours or equipment demand to find base load, peak and essential load. Then allow for site conditions, dryer purge and pressure drop, and check that the essential demand is still met with the largest machine out of service. We can work through these figures with your team.

Is it better to rent one large compressor or several smaller ones?

Several smaller machines give smaller capacity steps, better turndown at low demand and less impact when one fails. One large machine is simpler to fuel, service and control, but its failure removes most of your air. For critical plant air, a station of several machines with one spare is usually the safer choice; for a steady non-critical duty, fewer, larger units may be practical.

What does N+1 mean for rental compressors?

N+1 means you have enough machines to meet peak demand with any one machine stopped, whether for a fault or for its 300-hour service. It is the usual standard for production air and long shutdown cover. Where full N+1 is not justified, a station can be designed to keep only the essential users supplied during a fault.

How many cfm can you supply for a temporary air station?

Individual rental machines in our fleet range from 50 to 2,000 cfm, at 2 to 30 bar, and stations combine several of them. The practical size depends on the demand profile, pressure, air quality, available space, power or fuel, and duration. Send us your requirement and we will propose a fleet and standby arrangement to suit.

Can rental compressors connect to my existing plant air header?

Yes, usually through a temporary manifold, isolation valves and non-return valves into a tie-in point on the header or dryer outlet. The tie-in location, pressure settings and changeover sequence must be agreed with your maintenance team so the rental machines and any running plant compressors share load properly and the work area stays safely isolated.

Do multiple rental compressors need a dryer each?

Not always. Several machines can feed a common aftercooler, separator and dryer set sized for the total flow, which is simpler. But a single shared dryer becomes a single point of failure, so where the air is critical consider two dryers, a bypass or a split header. Dryers must be sized for the real summer inlet temperature and pressure.

Related pages

• Temporary air engineering centre
• Temporary air redundancy and failure management
• Temporary air hoses, manifolds and distribution
• Temporary air metering and usage management
• Peak demand rental
• Temporary air tie-in and changeover