Compressed air for packaging machines

Where does a packaging machine use compressed air?

Almost every packaging format relies on air somewhere in the cycle. Form-fill-seal machines use cylinders to drive sealing jaws and film cutters. Cartoners use air to open cartons, push product and fold flaps. Case erectors, case packers and palletisers clamp, transfer and reject. Labellers use air blasts to apply labels and vacuum to hold them. Cappers and fillers use pneumatic valves, and blister and thermoforming machines use air for forming and ejecting.

These uses fall into four groups that behave very differently on the compressor side:

• Actuators such as cylinders, rotary actuators and grippers consume a fixed volume each stroke, so their demand rises with machine speed.
• Vacuum ejectors (venturi generators) consume air all the time they are switched on, whether or not a part is being held.
• Blow-off and air jets for cleaning, drying, ejecting rejects or separating film are continuous or long-pulse flows, and they are often the largest single users on a line.
• Purge and process air, such as gas flushing, nozzle purging or product-contact blowing, which sets the air-quality requirement for the whole machine.

A machine can use very little air across a shift and still need a large short pulse during a jaw close or a reject blast. Equally, a small continuous blow-off left running can account for most of its daily consumption. One average figure cannot describe both, which is why the cycle has to be broken down.

How to work out the air demand of a packaging machine

The most reliable method combines the machine’s pneumatic schedule with a short measurement at the machine inlet. Work through these steps:

1. Define the product and the cycle. Note the product, pack size, format tooling and recipe. Define one cycle from an observable control event, for example index to index, and note how many saleable packs one cycle produces.
2. List every pneumatic consumer. For each cylinder record bore, stroke, rod diameter, single or double acting and strokes per cycle. For each ejector and nozzle record its rated consumption at the supply pressure and how long it is on per cycle.
3. Calculate free-air volume per cycle. For a cylinder, swept volume multiplied by the absolute pressure ratio, (gauge pressure + 1.013) ÷ 1.013, gives free air per stroke. Add hose and valve dead volume, which can be significant on small, fast cylinders.
4. Multiply by cycle rate to get average actuator demand, then add the continuous users (ejectors, blow-off, purge) at their duty time.
5. Identify the peak. Find the moment in the cycle when the most consumers fire together. That instantaneous flow, not the average, is what the local supply and regulator must deliver without pressure collapse.
6. Measure to confirm. Log flow and pressure at the inlet over complete cycles at production speed, including stops, restarts and reject events, and compare with the calculation.

Keep cycles, attempted packs and accepted packs as separate counts. A machine set to 60 cycles per minute that rejects some packs uses air for every cycle, so air per accepted pack is the honest figure for comparing recipes or machines.

Worked example: a horizontal flow-wrapper

The figures below are illustrative to show the method, not data for any particular machine.

At 60 cycles per minute the actuators need roughly 90 l/min of free air, while the continuous blow-off adds 200 l/min. The machine averages about 290 l/min (around 10 cfm), and two-thirds of that is blow-off. Switching the nozzles off with the machine, or replacing them with engineered low-flow nozzles, would change the result more than any cylinder resizing.

Pressure: what the machine really needs at its inlet

Most packaging machines are designed for 5–6 bar (72.5–87 psig) at the machine, with the plant header typically at 6.5–7 bar (94.3–101.5 psig). The figure that matters is dynamic pressure at the machine inlet while the machine and its neighbours are running, not the static reading when the line is idle.

Common causes of low dynamic pressure at packaging machines include:

• undersized drop lines or quick couplings that restrict flow during peak events;
• a clogged inlet filter element or an undersized filter-regulator (FRL) unit;
• long, small-bore tubing between the valve island and the cylinders;
• several machines on one branch firing at the same moment;
• a header pressure that sags when the compressor reaches its load set point.

Raising the compressor pressure to cover a restriction downstream is an expensive fix. As a rule of thumb, each extra bar of generation pressure costs about 7% more compressor power. Fixing the drop, the FRL or the tubing is usually cheaper. A small local receiver at the machine, sized for the peak event, can also hold inlet pressure during short high-flow pulses without raising the header set point.

Air quality for packaging: product contact decides

Air that only drives cylinders through a valve island needs clean, dry air to protect seals and valves. Air that touches the product, its primary packaging or the inside of a container is a different matter. Blowing out cartons, drying bottles, flushing pouches and ejecting food packs can all bring air into contact with the product.

These are typical starting points only. The food, pharma or packaging-material specification and the plant’s own risk assessment set the final class. Where a reliable supply of oil-free air matters, an oil-free compressor removes the main source of oil contamination, although dryers and filters are still required.

Common packaging air problems and their causes

Telangana and Andhra Pradesh summers, with ambient temperatures of 40–45 °C, push compressor discharge and dryer inlet temperatures up. A refrigerated dryer sized at a mild reference condition can be overloaded in May, and water reaches the packaging hall precisely when the line runs hardest. Correct dryer sizing at site conditions and working automatic drains prevent most of these complaints.

Cutting air waste on a packaging line

Packaging halls are often the largest compressed-air users in food, pharma and consumer-goods plants, which makes them a good place to save energy without touching product quality.

• Interlock blow-off nozzles and vacuum ejectors with machine run signals so they stop when the machine stops.
• Use engineered air nozzles or air knives instead of open pipe ends, and check whether a low-pressure blower can do the job instead of 7 bar air.
• Fit ejectors with vacuum-hold (air-saving) functions that switch off supply once vacuum is reached.
• Regulate each machine to the lowest pressure that gives reliable seals and motion, not the header pressure.
• Survey for leaks at fittings, cylinder rod seals and valve exhausts, and record repairs.
• Shorten tubing and remove unnecessary dead volume on fast, small-bore cylinders.

Sizing the compressor and system for packaging lines

Once each machine’s average and peak demand is known, the plant figure is built up from all the machines, allowing for realistic diversity: not every machine peaks at the same moment, but all the continuous users do run together. Add an honest leak allowance from measurement, and future lines that are actually planned.

For packaging duty, a rotary screw compressor with a variable-speed drive or good modulation, a correctly sized air receiver and a refrigerated or desiccant dryer is the usual architecture. Where a single line is critical, a standby compressor or a rental machine on short notice protects output. The receiver smooths the short peaks that packaging cycles create, and good piping keeps pressure stable at the far end of the hall.

How Reddy Compressors helps

Reddy Compressors has served industry since 2002 from Tarnaka, Secunderabad, as an independent multi-brand specialist. We sell new and used or refurbished compressors, rent machines from our own fleet, and service and supply spares for ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other brands. We are not an authorised dealer of any of these brands. We have tie-ups with all major and reputed brands.

For packaging plants we can:

• log flow, pressure and dew point at the machine and at the compressor house to show where the demand and the pressure loss really are;
• recommend compressor, dryer, filtration and receiver arrangements, including oil-free compressors where product contact requires them;
• supply and commission compressors, dryers and filters, and provide service and AMC;
• supply rental compressors for breakdowns, shutdowns and line trials.

Our team of more than 20 service engineers and technicians covers the whole of Telangana and Andhra Pradesh, and we supply equipment, rentals and spares across India.

What to send us

• Machine type, maker and model, and the products and speeds it runs
• Pneumatic schedule or a list of cylinders, ejectors and nozzles if available
• Required pressure at the machine and any air-quality specification
• Present compressor, dryer and filter details, with nameplate photos
• The problem you see (seal faults, water on product, speed limits, high power) and when it occurs
• Site location and contact person

Frequently asked questions

How much compressed air does a packaging machine use?

It depends on the machine type, speed and especially the continuous users. Small labellers may use a few cfm, while cartoners and case packers with vacuum and blow-off can use tens of cfm. Calculate actuator air from bore, stroke, pressure and cycle rate, add ejectors and nozzles at their duty time, and confirm by logging flow at the inlet during production. The maker’s figure is a starting point, not a measured result.

What pressure does a packaging machine need?

Most packaging machines are designed to run at about 5–6 bar (72.5–87 psig) at the machine inlet, with the plant header typically at 6.5–7 bar (94.3–101.5 psig). The important figure is dynamic pressure during the heaviest event in the cycle with neighbouring machines running. If pressure collapses at that moment, fix the drop line, FRL or tubing before raising the compressor set point.

Do packaging machines need oil-free compressed air?

Not always. Air that only drives cylinders through valves needs clean, dry, filtered air. Air that touches food, medicines or the inside of primary packaging should meet the stricter class the product specification and risk assessment require, often ISO 8573-1 class 1 or better for oil. An oil-free compressor removes the main oil source, but dryers and point-of-use filters are still needed.

Why is my packaging machine getting water in the air lines?

Water usually means the dryer is overloaded, bypassed or not draining. In Telangana and Andhra Pradesh summers, high ambient and inlet temperatures push refrigerated dryers past their rating. Failed automatic drains, saturated coalescing filters and piping without drop legs also let condensate through. Check the dew point at the machine, test every drain, and confirm the dryer was sized for site conditions.

Why does my packaging machine fault only at high speed?

At higher speed, more pneumatic events overlap and peak flow rises. If the drop line, quick coupling, FRL or tubing cannot pass that flow, inlet pressure dips and cylinders slow, seals weaken or sensors time out. Log pressure at the machine at full and reduced speed. A larger drop, a higher-flow regulator or a small local receiver often cures it.

How can I reduce compressed air use on a packaging line?

Start with continuous users. Interlock blow-off nozzles and vacuum ejectors so they stop with the machine, replace open pipes with engineered nozzles, and fit air-saving ejectors. Regulate each machine to the lowest reliable pressure, repair leaks at fittings and cylinder seals, and consider a low-pressure blower for large drying or blowing duties instead of compressed air.

Related pages

• Printing, packaging and paper converting air
• Compressed air for robotics and end effectors
• Industrial vacuum pick and place systems
• End-use air preparation and FRL selection
• Food-grade compressed air
• Pneumatic application engineering centre