1-805-484-2992
Quotes - Engineering - SalesWhy the compressor sizes the dryer
The dryer sits between the compressor and everything else, so the most air it can ever see is what the compressor delivers, and it sees all of it every time the compressor loads. The plant's average consumption is irrelevant to the dryer size; it only decides how many hours a day the dryer works hard. Read delivered flow off the compressor data sheet as ACFM or CFM free air and use it as SCFM. Where the sheet is gone, a rotary screw at 100 to 125 psig makes 4.3 to 4.6 SCFM per horsepower and a piston compressor 3.5 to 4.
Screw, piston, or a room full of both
Rotary screw compressors come with an aftercooler, so they hand the dryer 100 to 115°F air at a steady rate for most of the shift; that section is split by horsepower, and each page reads across to a flow band and the series in it. Reciprocating compressors pulse, load intermittently and, with no aftercooler, discharge air at 180 to 200°F, which is the duty the high-inlet-temperature series were built for. The point-of-use pages size a dryer to one machine, one paint booth or one lab rather than to the whole compressor, and the central plant pages cover several compressors on a common header, dryers mounted on the receiver and temporary rental flows.
The corrections that move the answer
Inlet temperature, ambient temperature and line pressure each carry a factor: 110°F inlet 0.80, 120°F 0.65; 110°F ambient 0.88; 80 psig 0.92, 125 psig 1.08. Divide delivered flow by the product of the factors and pick the first model at or above the result. A 30 hp screw delivering 135 SCFM into a 110°F compressor room, with 110°F air leaving its aftercooler, is a 135 / (0.80 x 0.88) = 192 SCFM duty: the 200 SCFM dryer, not the 150. The sizing pages carry the full tables and a worked method.
What we need to quote a dryer
Compressor type and horsepower, or better the delivered SCFM and discharge pressure; whether it has an aftercooler; the hottest the compressor room gets in summer; hours loaded per day; and the dew point the process needs. Call 1-805-484-2992, 8am to 5pm, or send the nameplate through the quote form and we return a model number sized for those conditions, with the prefilter, afterfilter and drain that go with it.
Four things on the compressor that pick the dryer
Type, horsepower, aftercooler, duty cycle
A refrigerated dryer is rated in SCFM at 100 psig, 100°F inlet air and 100°F ambient. The compressor decides how far the real duty sits from that point: a screw and a piston of the same horsepower deliver different flows at different temperatures, and a compressor that loads for a third of the day wants a different dryer from one that never unloads.
Compressor type
- Rotary screw: 4 to 5 SCFM per hp, steady flow through an aftercooler
- Reciprocating: 3.5 to 4 SCFM per hp, pulsing, often no aftercooler
- Two compressors on one header: add the flows that can run together
Horsepower to SCFM
- 25 hp screw: 108 to 115 SCFM, the 125 SCFM dryer
- 10 hp piston: 35 to 40 SCFM, the 42 or 50 SCFM dryer
- Delivered flow on the data sheet beats any rule of thumb
Aftercooler and inlet temperature
- Aftercooled screw: room temperature plus 15 to 20°F
- Piston with no aftercooler: 180 to 200°F at the discharge
- 110°F inlet derates a standard dryer to 80 percent, 120°F to 65
Duty cycle
- Loaded 60 percent of the shift or more: non-cycling
- Nights and weekends idle: cycling saves 50 to 80 percent of dryer power
- Variable-speed compressor: cycling dryer, still sized for full output
The pages most sizing questions land on
Every current dryer series
Fifteen series from 7 to 12,500 SCFM; each card opens the series page with its part numbers
HPRB Series: Current small non-cycling dryer, 7 to 50 SCFM, with low-GWP R513A refrigerant, a 3-in-1 heat exchanger and a built-in separator on the larger sizes.
7 to 50 SCFM · Non-Cycling · 200 psig max inlet · 120°F max inlet
DXR Series: Direct-expansion non-cycling dryer in 27 sizes from 10 to 4,200 SCFM; the widest single range on the site, with a full data sheet behind every model.
10 to 4,200 SCFM · Non-Cycling · 203 psig max inlet · 131°F max inlet
HPRplus Series: Large non-cycling dryer for 2,500 and 3,000 SCFM central plants with digital controls and a low-pressure-drop exchanger.
2,500 to 3,000 SCFM · Non-Cycling · 232 psig max inlet · 120°F max inlet
FLXA Series: Current cycling dryer, 75 to 2,000 SCFM, air- or water-cooled, with low-GWP refrigerants and a heat-transfer cycling control that follows the load.
75 to 2,000 SCFM · Cycling · 120°F max inlet · R513A (75-550 scfm), R454C (800-2000 scfm)
FLX Series: Modular water-cooled cycling dryer skid for 3,000 to 12,000 SCFM, built from paired 1,500 and 2,000 SCFM modules.
3,000 to 12,000 SCFM · Cycling · 225 psig max inlet · 120°F max inlet
HES Series: Energy-saving digital-scroll dryer from 2,500 to 12,500 SCFM for central plants, modular above 3,750 SCFM.
2,500 to 12,500 SCFM · Digital Scroll Cycling · 232 psig max inlet · 130°F max inlet
TMC Series: Thermal-mass cycling dryer from 30 to 635 SCFM; stores cold in a thermal mass so the refrigeration compressor rests when air demand drops.
30 to 635 SCFM · Thermal Mass Cycling · 210 psig max inlet · 140°F max inlet
NXC Series: Cycling dryer in 19 sizes from 20 to 2,000 SCFM with a dry thermal mass and up to 80 percent power savings at part load.
20 to 2,000 SCFM · Cycling · 232 psig max inlet · 158°F max inlet
AES Series: Digital-scroll cycling dryer from 600 to 10,000 SCFM in air- and water-cooled builds, matching refrigeration capacity to demand continuously.
600 to 10,000 SCFM · Digital Scroll Cycling · 232 psig max inlet · 120°F max inlet
VDR Series: Variable-speed dryer from 2,600 to 8,450 SCFM whose inverter-driven compressor tracks plant load; air- and water-cooled versions.
2,600 to 8,450 SCFM · Variable Speed Cycling · 203 psig max inlet · 158°F max inlet
HRHT Series: Current high-inlet-temperature dryer, 25 to 100 SCFM, rated for 200°F inlet air from reciprocating compressors with no aftercooler.
25 to 100 SCFM · High Inlet Temperature · 200°F max inlet · R513A
HTR Series: High-temperature direct-expansion dryer, 25 to 125 SCFM, for 180°F inlet air from piston compressors on shop and service-bay duty.
25 to 125 SCFM · High Inlet Temperature · 232 psig max inlet · 180°F max inlet
HHPR Series: Current high-pressure dryer rated 680 psig for PET blow molding and high-pressure process air, 115 to 2,400 SCFM.
115 to 2,410 SCFM · High Pressure · 680 psig max inlet · 120°F max inlet
APET Series: High-pressure dryer built for 500 and 725 psig PET and process lines, 45 to 1,000 SCFM.
45 to 1,000 SCFM · High Pressure · 725 psig max inlet · 120°F max inlet
AXHP Series: Ultra-high-pressure dryer in four pressure ratings to 6,000 psig, 20 to 275 SCFM, for high-pressure test, breathing-air and process systems.
20 to 275 SCFM · Ultra-High Pressure · 6,000 psig max inlet · 120°F max inlet
