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Quotes - Engineering - SalesCompressed Air Dryers for Packaging Lines
A packaging line is a long chain of small pneumatic actions: the case erector's vacuum cups and folding cylinders, the cartoner's tuckers, the labeler's tamp pad and blow-on jet, the form-fill-seal machine's jaw cylinders and film clamps, the checkweigher's reject blast, the case sealer's tape heads, the stretch wrapper's clamp and cutter, and the palletizer's gripper. Add hot-melt tanks pressurized with air and the venturi generators behind every vacuum cup, and a single line draws 30 to 80 SCFM, while a hall with four lines on a 40 hp screw runs 170 to 180 SCFM.
Water in that air attacks the cheapest parts first. Valve manifolds corrode from the inside and stick, cylinder seals wash out and the actuator drags, and a reject blast that sprays condensate onto a carton wets the flap the glue is about to land on. Vacuum cups lose grip as their venturis scale. Where the air touches the package or the product, as it does on a blow-on labeler or a bagger, oil aerosol from a lubricated compressor is the contaminant a food or pharmaceutical customer's audit will find.
A refrigerated dryer holding a 38°F pressure dew point covers a packaging hall at normal room temperature, since nothing on the line runs colder than the room. It sits in the compressor room after the receiver and is sized to the compressor: a 40 hp screw at 175 SCFM takes the 185 or 200 SCFM dryer, a 20 hp screw at 90 SCFM the 105 size, and a 10 hp piston unit without an aftercooler takes a high-inlet-temperature dryer that accepts its 180°F discharge. The 0.01 micron oil-removal afterfilter goes behind the dryer, with an activated carbon filter after it where the air touches food.
Packaging lines are the textbook case for a cycling dryer. They stop for changeovers, run in batches, wait on upstream production and sit idle on the night shift while the compressor holds the header up, so the load on the dryer averages 30 to 50 percent of the compressor's output. A thermal-mass TMC Series or an NXC Series cycling dryer shuts its refrigeration compressor off through those gaps and returns most of its premium in the first year.
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Average dryer load on a batch packaging lineWith the load averaging 30 to 50% of compressor output across changeovers and idle shifts, a cycling dryer spends long stretches with its refrigeration compressor off.
What wet air does on a packaging line
Where the downtime comes from
- Solenoid valve manifolds corroding and sticking, one station at a time
- Cylinder seals washed of lubricant, actuators dragging and missing their timing window
- Reject jets and blow-on labelers spraying condensate onto cartons and film
- Vacuum cups losing grip as venturi generators scale and clog
The dryer specification for a packaging hall
What to put on the requisition
- 38°F pressure dew point, ISO 8573-1 class 4, sized to the compressor rather than to the line count
- Cycling dryer for batch and single-shift duty; non-cycling where the lines run three shifts flat out
- 1 micron prefilter, 0.01 micron oil-removal afterfilter, activated carbon where the air touches food
- A high-inlet-temperature dryer where the compressor is a piston unit with no aftercooler
Dryers that fit a packaging line
Ratings at 100 psig and 100°F inlet. A single line on a 10 to 20 hp compressor uses the 30 to 105 SCFM sizes; a multi-line hall on a 40 to 60 hp screw the 185 to 265 SCFM sizes.
| SERIES | TYPE | FLOW RANGE | MAX INLET | MAX PRESSURE |
| TMC Series | Thermal Mass Cycling | 30 to 635 SCFM | 140°F | 210 psig |
| NXC Series | Cycling | 20 to 2,000 SCFM | 158°F | 232 psig |
| HPRB Series | Non-Cycling | 7 to 50 SCFM | 120°F | 200 psig |
| DXR Series | Non-Cycling | 10 to 4,200 SCFM | 131°F | 203 psig |
| HTR Series | High Inlet Temperature | 25 to 125 SCFM | 180°F | 232 psig |
| GFN Series Filters | Compressed Air Filter | 6 to 1,500 SCFM | — | 232 psig |
| NGF Series Filters | Compressed Air Filter | 20 to 1,500 SCFM | — | 250 psig |
| ND Series Zero-Loss Drains | Condensate Drain | Call for sizing | — | 290 psig |
Put these three items on the packaging line requisition.
- Cycling dryer sized to the compressor, not to the number of lines
- Zero-loss drains on receiver, dryer and every filter bowl
- Carbon stage behind the coalescer wherever air reaches food
Timer drains cost a packaging line more than the dryer does
A timed solenoid drain opens on a schedule whether there is condensate to discharge or not, and a 5-second blow every 2 minutes on the receiver, the dryer and two filter bowls adds up to several SCFM of compressed air wasted around the clock. On a 40 hp compressor that is a few percent of the output bought and thrown away, and on a packaging line that idles half the time, a larger share still. A zero-loss drain opens only when its float or level sensor sees liquid, so nothing but water leaves the system.
Fit zero-loss drains on the receiver, the dryer's separator and every filter bowl, and check them monthly with the test button rather than by listening for a discharge you may never hear.
- Replace timer drains with zero-loss drains on the receiver, dryer and filters
- Test each drain monthly; a stuck float shows up as water at the line, not at the drain
- Pipe drain discharge to an oil-water separator where compressor oil is present
Where the dryer and filters go
Compressor, aftercooler, receiver, 1 micron prefilter, dryer, 0.01 micron afterfilter and then the header, with the carbon filter as the last stage on lines that need it. Packaging halls are often at the far end of a plant from the compressor room, fed by a long main through a warehouse that is not heated in winter. Air dried to 38°F and then chilled to 30°F in that pipe condenses, so either insulate the main or fit a small point-of-use dryer at the hall and let the central dryer carry the rest of the plant. A drip leg and drain at the end of the main is the minimum.
Sizing for a batch load
Size the dryer to the compressor's full delivery even though the line averages half of it, because the dryer sees the full flow whenever the compressor is loaded. The averaging is what the cycling dryer exploits, not a reason to buy a smaller unit. A 30 hp screw delivering 130 SCFM into a 100°F compressor room takes the 130 SCFM cycling dryer; the same compressor in a 110°F mezzanine takes the 170. The flow and SCFM page has the method.
Piston compressors on a single line
A stand-alone packaging line in a small plant often runs on a 7.5 or 10 hp two-stage piston compressor with no aftercooler, which discharges 180°F air that a standard refrigerated dryer cannot take. The HTR Series and HRHT Series are built for that inlet, with the separator and zero-loss drain inside, and deliver a 50°F pressure dew point (ISO 8573-1 class 6) that is still 20°F below a 70°F packaging hall. Pair one with a GHTN high-temperature prefilter if the compressor runs hard, and pipe the compressor discharge to it by the shortest route.
Food and pharmaceutical lines
Where the air touches product or primary packaging, the customer audit will look for ISO 8573-1 class 1 oil and often a stated particle class. A lubricated screw meets that with the 0.01 micron coalescing afterfilter and an activated carbon filter downstream of the dryer, plus a point-of-use filter at the machine. The food packaging page goes further into the classes.
Getting a packaging line's air right
Several SCFM, continuously, once the receiver, the dryer and two filter bowls each blow for 5 seconds every 2 minutes. On a 40 hp compressor that is a few percent of the output, and on a line that idles half the time the share is larger again, because the drains keep venting while nothing else is drawing air. Zero-loss drains open only on liquid. Test them monthly with the button, since you may never hear one discharge.
Each station's valve sees water once the dryer falls behind, and those at the low points or the ends of the header see it first. Condensate washes lubricant from spools and seals and leaves corrosion inside the manifold body, so a station sticks now and then, fails outright, and the next one follows weeks later. Replacing valves station by station chases the damage; checking the dryer outlet dew point and the drains finds the cause.
Only if it has no aftercooler, which is common on two-stage units of that size. Its 180°F discharge is far beyond a standard dryer's inlet rating, so a high-inlet-temperature dryer with its separator and zero-loss drain built in is the right match, with a high-temperature prefilter ahead of it on a compressor that runs hard. The 50°F pressure dew point it delivers still sits well below a 70°F hall, so the line's pneumatics see no condensate.
To the compressor, at its full delivery and corrected for the compressor room, even when the lines average about half of it. Whenever the compressor loads, the dryer sees its entire output, and a dryer chosen for the average floods during every full-load stretch. The averaging is what makes a cycling dryer worthwhile, not a reason to buy smaller. A 30 hp screw at 130 SCFM in a 110°F mezzanine, for example, takes the 170 SCFM cycling dryer.
Where the label goes on food or pharmaceutical packaging, yes. The blow-on jet fires air directly at the package, so oil aerosol from a lubricated compressor lands exactly where a customer audit will look for it. A point-of-use filter at the labeler, behind the plant's 0.01 micron coalescer and an activated carbon stage, brings that air to class 1 oil. Case erectors and palletizers that never touch the product can stay on coalesced plant air.
More on drying packaging-line air
Cycling versus non-cycling dryers for a batch load
How a 40 percent average load turns into a real power saving, with the worked figures.
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PET Blow Molding
The mold is cooled with 40 to 55°F chilled water so the bottle sets before ejection.
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Injection Molding
Molding plants run three shifts with the compressor loaded most of the time, so the non-cycling DXR Series is the usual choice.
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