Compressed-air demand management and load profiling

Demand management versus demand assessment

A demand assessment answers “how much air do we use?” and is usually carried out before choosing a compressor. Demand management goes further: it asks which parts of that demand are necessary, which can be reduced, and which can be moved, stored or served differently. It is an ongoing practice, not a one-off survey.

The reason it matters is simple. Every cubic metre of compressed air is expensive energy. If a plant buys a bigger compressor to supply leaks, open blowing and over-pressure, it pays twice: once for the machine and again every month in electricity. Reducing demand first is almost always the cheapest capacity a plant can find. For the measurement method itself, see our demand assessment and load profiling page.

What makes up your compressed-air demand?

Break the total demand into components. Each has a different cause and a different fix.

Peaks, duration and repetition

Average demand is useful for energy calculations, but pressure stability is decided by peaks. How a peak is handled depends on its character:

• Duration. An event lasting a few seconds is a storage problem. One lasting an hour is a compressor capacity problem.
• Repetition. A receiver may cover one event, but if events repeat faster than the compressor can recharge it, pressure will drift down.
• Rate of change. A sudden step, such as a large valve opening, can cause a dip even when total compressor capacity is adequate, because the next machine takes time to start and load.
• Location. A large intermittent user at the end of a long header is often best served by a local receiver close to it.

Plotting demand against time, with production states marked on the same chart, shows which events cause pressure problems and which do not. Our receivers and storage page covers how to size storage for a specific event.

Leakage: the largest controllable load

In most plants we visit, leakage is the largest single source of wasted air, and it runs 24 hours a day. It hides in quick couplings, worn hoses, drain valves stuck open, threaded joints, cylinder seals, FRL units and old branches no one uses any more.

A practical leak programme follows a cycle:

1. Measure the baseline: flow or compressor loaded time with production stopped.
2. Survey with an ultrasonic leak detector during a quiet period.
3. Tag each leak, estimate its size and record it in a register.
4. Repair, starting with the largest and easiest.
5. Measure the baseline again to verify the reduction.
6. Repeat at regular intervals, because new leaks appear constantly.

Our leak detection and leak repair register pages explain the method in more detail. Without step five, leak repair is a hope rather than a result.

Pressure: the hidden demand multiplier

Higher pressure increases demand in two ways. The compressor needs about 7% more power for each extra bar it generates, and every unregulated user and every leak consumes more air at higher pressure. This extra consumption is called artificial demand.

Many plants run 1–2 bar (14.5–29 psi) higher than any process really needs, because pressure was once raised to cure a problem at one machine. The better fix is usually to find and correct the cause: an undersized pipe, a blocked filter, a dryer with high pressure drop, or a single high-pressure user that needs a small booster or a dedicated compressor.

• Find the user that genuinely needs the highest pressure.
• Measure pressure drop from compressor to that user and remove avoidable losses.
• Regulate users at their point of use to the pressure they need.
• Lower the compressor setpoint in small steps, confirming production at each step.
• Consider reducing pressure, or isolating sections, during nights and weekends.

See our pressure optimisation and artificial demand page for the full method.

Inappropriate uses and their alternatives

Compressed air is one of the most expensive forms of energy in a factory, so it should not be used where a cheaper method works. Common examples:

Shaping demand by time, zone and pressure

Once waste is removed, the remaining demand can often be shaped so that it is easier and cheaper to supply.

• Isolate by zone. Fit isolation valves, manual or automatic, so non-working areas can be shut off at night and at weekends.
• Separate high-pressure users. A small dedicated compressor or booster for one high-pressure user can allow the whole plant to run lower.
• Separate air-quality needs. Only the users that need low dew point or oil-free air should receive it; treating all air to the highest standard wastes energy.
• Stagger large events. Where possible, avoid starting several large users at the same moment.
• Use storage. A receiver near a large intermittent user can supply its peak and recharge between cycles.
• Plan temporary demand. Shutdown cleaning, pipe testing or projects can be supplied by a rental compressor rather than oversizing the permanent plant.

Matching compressors to the managed demand

After demand has been reduced and shaped, the compressors and controls should be revisited. A plant that has cut its leakage may now find a large base compressor running unloaded for long periods. That is the moment to re-assign base and trim roles, adjust sequencing or consider a VSD trim machine. Our controls and sequencing page covers this step.

Measure the result in a way that does not depend on production volume. The most useful indicator is energy per unit of air delivered, such as kWh per m³, or specific power in kW per m³/min. A second useful indicator is non-production demand as a share of the working-hours demand. Both should be tracked over months, not just once.

Sustaining the gains

Demand management fails when it is treated as a project with an end date. Leaks return, pressure creeps up after a complaint, and new machines arrive with their own blow-off nozzles. Simple habits keep the gains:

• A named person responsible for compressed air.
• Monthly review of compressor energy and loaded hours.
• Leak survey at a fixed interval, with a repair register.
• A rule that any pressure increase needs a recorded reason.
• A check of air use whenever a new machine or line is installed.

How Reddy Compressors helps

Reddy Compressors has worked with industrial compressed air since 2002 from Tarnaka, Secunderabad. As an independent multi-brand specialist, not tied to any manufacturer and not an authorised dealer, our interest is in getting your system right, whether that means fewer leaks, lower pressure or a different machine. We have tie-ups with all major and reputed brands.

We can log demand and pressure, carry out leak surveys and maintain a repair register, review pressure settings and point-of-use regulation, advise on zoning and storage, and re-tune compressor controls once demand has changed. Where new capacity is genuinely needed, we supply new and used compressors of brands including ELGi, Atlas Copco, Ingersoll Rand, KAESER and Chicago Pneumatic, and our own rental fleet can supply temporary loads. Our service teams cover all of Telangana and Andhra Pradesh, with equipment and spares supplied across India.

What to send us

• Nameplate photos of your compressors and dryers.
• Current pressure settings and the pressure your processes need.
• Monthly compressor electricity use, if available.
• A list of the main air users and any known open-blowing points.
• Your working hours, including nights, weekends and holidays.
• Any pressure complaints, with the time and place they occur.

Frequently asked questions

How can I reduce compressed-air consumption in my factory?

Start by measuring demand when production is stopped, which shows your leakage. Then repair leaks and verify the result, lower system pressure to what your highest real user needs, replace open blowing with engineered nozzles or blowers, isolate idle areas, and use point-of-use regulators. Once demand has fallen, review compressor controls so the machines match the smaller load.

What is artificial demand in compressed air?

Artificial demand is the extra air consumed because the system pressure is higher than users need. Unregulated tools, blow-offs and every leak use more air at higher pressure. The compressor also needs about 7% more power for each extra bar. Reducing pressure to the true requirement cuts both artificial demand and generation energy at the same time.

How much compressed air is typically lost to leaks?

It varies widely from plant to plant, so the only reliable answer is to measure your own. Log the flow, or the compressor’s loaded time, when production is completely stopped but the system remains pressurised. In plants without a regular leak programme, that non-production demand is often a large share of the working-day demand, which is why leak repair usually comes first.

Is it better to add a receiver or a bigger compressor for pressure dips?

It depends on the dip. If pressure falls briefly during short, repeated events, a receiver near the user is usually the better and cheaper answer. If pressure stays low for long periods because demand exceeds capacity, more compressor capacity is needed. Logging flow and pressure together with production events shows which situation you have.

Should compressed air be switched off at night?

Where nothing needs air at night, shutting off the compressors or isolating idle areas removes the leakage load entirely during those hours. Where some users must run, isolating the unused zones and lowering pressure helps. Check that nothing critical, such as instrument air or fire-protection equipment, depends on the supply before introducing a shut-off routine.

What is a good KPI for compressed-air efficiency?

The most useful is energy per unit of air delivered, such as kWh per m³ or specific power in kW per m³/min, because it does not depend on how much the plant produced that month. Track it together with non-production demand and average header pressure. Together these three show whether the system is improving or slipping back.

Related pages

• Leak detection and air-loss management
• Pressure optimisation and artificial demand
• Compressor controls and sequencing
• Compressed-air energy optimisation hub
• Air demand profiling
• Energy management and continuous improvement