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Quotes - Engineering - SalesRefrigerated Air Dryers for Pharmaceutical Plants
A pharmaceutical plant runs two compressed air systems inside one set of pipes. Utility air drives the cylinders on blister and cartoning lines, the actuators on process valves, the instrument loops on autoclaves and the packaging hall's robots and labelers. Process air touches the product: the atomizing air on a tablet coater, the spray nozzles and filter pulse-jets on a fluid-bed granulator, the vacuum break on a sterilizer, the transfer air in a capsule filler and the overpressure in an isolator. Water in utility air is the ordinary story of sticking valves and drifting instruments. Water in process air is a deviation: organisms from a wet pipe on a coated tablet, moisture in a hygroscopic granulation, condensate in a sterile vacuum break.
The refrigerated dryer is the plant's utility-air dryer and the first stage of its process air. Utility air is specified at ISO 8573-1 class 2.4.2 or 1.4.1, a 38°F pressure dew point with coalescing filtration, which the refrigerated dryer delivers. Product-contact air is commonly specified at class 1.2.1 with microbiological monitoring: a –40°F dew point from a desiccant stage fed by the refrigerated dryer, oil to 0.01 mg per cubic meter and a sterile filter at the point of use.
A solid-dose plant runs on a 50 to 100 hp oil-free screw, 220 to 450 SCFM, and a large site on 150 hp and more. A 75 hp screw at 320 to 340 SCFM is the 400 SCFM dryer, with the desiccant stage on the process branch sized for its 50 to 100 SCFM alone. Oil-free compressors remove the oil question at the source, but their air is saturated all the same, so the dryer, separator and drains are unchanged.
Pharmaceutical plants run steady, validated schedules with the compressor loaded through the week, which is the non-cycling case; the DXR series or, above 600 SCFM, the AES digital-scroll dryers fit. Sites with one-shift packaging and idle weekends save with the FLXA cycling series.
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Contact-air class most pharma specs nameProduct-contact air at 1.2.1 needs desiccant drying to -40°F with oil held to 0.01 mg per cubic meter, so it leaves the utility header through a stage of its own.
What water does in a pharmaceutical plant
Utility air and process air
- Process valve actuators and instrument positioners sticking or drifting on condensate
- Organisms from a wet pipe reaching coated tablets, granulations and sterile vacuum breaks
- Moisture in atomizing and pulse-jet air wetting hygroscopic powders in the granulator
- Deviations, investigations and lost batches when a monitored air point fails its class
The two specifications a pharma plant writes
Utility air and product-contact air
- Utility air, class 2.4.2 or 1.4.1: 38°F pressure dew point from a refrigerated dryer with 0.01 micron coalescing
- Process air, class 1.2.1: desiccant stage fed by the refrigerated dryer, oil to 0.01 mg per cubic meter, sterile filter at the point of use
- Dew point, particle, oil and microbiological monitoring at defined points on a defined schedule
- Dryer, filters and monitor documented in the qualification package with their alarms
Dryers that fit a pharmaceutical plant
Rated at 100 psig and 100°F inlet air. A site on a 50 to 100 hp oil-free screw uses the 250 to 500 SCFM sizes; larger sites use 600 to 1,250 SCFM. The PDM dew point monitor gives the outlet reading the qualification package needs.
| SERIES | TYPE | FLOW RANGE | MAX INLET | MAX PRESSURE |
| DXR Series | Non-Cycling | 10 to 4,200 SCFM | 131°F | 203 psig |
| AES Series | Digital Scroll Cycling | 600 to 10,000 SCFM | 120°F | 232 psig |
| FLXA Series | Cycling | 75 to 2,000 SCFM | 120°F | — |
| NXC Series | Cycling | 20 to 2,000 SCFM | 158°F | 232 psig |
| HF Series Filters | Compressed Air Filter | 20 to 21,250 SCFM | — | 300 psig |
| GFN Series Filters | Compressed Air Filter | 6 to 1,500 SCFM | — | 232 psig |
| ND Series Zero-Loss Drains | Condensate Drain | Call for sizing | — | 290 psig |
| PDM Dew Point Monitor | Dew Point Monitor | Call for sizing | — | 145 psig |
Before qualification, confirm the air plant shows this.
- Refrigerated dryer on the full flow, desiccant only on process air
- Sample ports after the filters, not inside the dryer
- Monitor alarms logged by the building monitoring system
Monitor the dew point where the class is claimed
A dryer's controller shows a dew point measured inside the dryer, which is useful for the technician and not what the qualification refers to. The class is claimed at the point of delivery, after the filters and the pipe, and that is where the monitoring point belongs: a sample port with a dew point sensor at the refrigerated dryer outlet for the utility header, and another after the desiccant stage for the process branch.
A portable monitor reading –148 to +68°F covers both, with a 4-20 mA output and alarm contacts so the building system logs it. A quarterly reading with the room temperature noted is the record most inspections expect, and a permanent sensor on the process branch is common practice.
- Sample port after the filters, not inside the dryer
- A single monitor serving both the utility header and the process branch
- Alarm contacts wired to the building monitoring system
Where the dryer and filters go
Compressor, aftercooler, receiver, 1 micron prefilter, refrigerated dryer, 0.01 micron coalescer, header for utility air. The process branch leaves the header through a desiccant dryer sized for the process points, then a 0.01 micron filter and a sterile filter at each point of use, with a sample port ahead of the sterile filter for the monitoring program. The refrigerated dryer stays in the utility room; only stainless pipe and the final filters enter the classified areas. The filter placement page shows the stages and where the drains sit.
Why the refrigerated dryer comes first
A desiccant dryer fed with saturated 100°F compressor air spends most of its purge or heater energy removing water that a refrigerated dryer removes for a fraction of the cost. Air arriving at the desiccant bed at a 38°F dew point carries about a tenth of the water, so the bed cycles less, a purge-saving control keeps the purge down, and the desiccant lasts years. The refrigerated versus desiccant page sets out the pairing.
Cycling or non-cycling for pharma
A validated plant runs a steady schedule, and the compressor is loaded most of the week; the non-cycling DXR series at full load costs no more to run than a cycling dryer and has fewer parts to qualify. Sites whose packaging runs one shift, or whose compressor is variable-speed and idles at night, spend enough hours at low load for the FLXA cycling series to pay back. Above 600 SCFM the AES digital-scroll dryers modulate refrigeration to the load, and the controller's dew point output can be wired to the plant's monitoring system.
Documenting the dew point
Under cGMP the dryer is a qualified utility: the user requirement specification states the class at each point, the qualification proves it, and the monitoring program keeps proving it. A dew point monitor at the refrigerated dryer outlet and another after the desiccant stage give logged readings against the class limits, with alarm contacts to the building system. The dew point and ISO classes page lists the class values the specification refers to.
Utility and process air for a cGMP plant
Treat it as a change to a qualified utility, so it goes through change control. The class for every delivery point is already written into the user requirements, and the replacement has to be shown to meet it: rating and room correction in the design review, piping order and drains in the installation check, then a run of dew point readings at the monitored points. A like-for-like size on unchanged piping usualy keeps that testing short.
Because the process points are a small slice of the plant's air. A solid-dose site on a 75 hp screw makes 320 to 340 SCFM, while the coater, granulator and isolators together may draw 50 to 100 SCFM. A desiccant unit sized for that branch, fed with air already at a 38°F dew point, regenerates less and holds a steady -40°F, whereas one sized for the whole compressor spends purge or heater energy drying air that only drives cylinders.
Downstream of the coalescer that follows the refrigerated dryer, on the utility header itself, not on the dryer's own controller. The class is claimed for the air as delivered, so the reading has to include whatever the filters and the first length of pipe add or fail to remove. On the process branch the port sits after the desiccant stage and ahead of the sterile filter, so the sample is drawn before the final element that guards the point of use.
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