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Quotes - Engineering - SalesDrying only the air that needs it
Most plants that need -40°F air need it in one place: an instrument panel, a laser cutter, an outdoor bulk-bag station, a lab bench. A point-of-use dryer sits on that branch, downstream of the refrigerated dryer that already serves the rest of the system, and is sized for the branch flow alone. Purge, price and footprint all scale down with it.
Because the refrigerated dryer has already brought the air down to about 38°F, the point-of-use unit removes only the vapor that is left. That is how a desiccant dryer not much bigger than a filter housing, or a membrane module with no power supply, holds -40°F on a branch day after day. Fed saturated air straight from a receiver, the same unit would be overwhelmed.
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Modular heatless, membrane or single tower
Three ways to reach a low dew point on a small flow, from the unit that regenerates itself to the one you recharge by hand.
Modular Heatless: A compact heatless dryer built from aluminum columns, for labs, machines and tight spaces: 11 models from 3 to 177 SCFM. It ships with a coalescing prefilter and a particulate afterfilter, uses non-lubricated soft-seat valves and carries CSA/UL listing. -40°F on an 8-minute cycle -94°F, class 1, on a 4-minute cycle with 86°F inlet Energy management controller option from 24 SCFM
3 to 177 SCFM · PHDM Series
Membrane: Hollow-fiber membranes pass water vapor through the fiber wall into a sweep stream, so there is no desiccant, no condensate and no moving parts. Three lines: a fixed sweep unit with no electrics, a version whose digital control matches sweep to demand, and a compact line that mounts in any orientation. 0.53 to 46.2 SCFM inlet at -40°F Up to 200 psig and 150°F inlet 304 stainless housings for corrosive sites
to 46 SCFM · SSM, HMM, HMD Series
Single Tower: A non-regenerative column of silica gel with a color indicator that turns from blue to white as the charge is used up. Built for HVLP spray guns and small tools, it needs no power and mounts inline; when the indicator says so, the charge is replaced. 5 to 30 SCFM at 100 psig As low as -40°F; to 200 psig and 125°F Built-in 15 micron dust filter
5 to 30 SCFM · HDF Series
Class 1 from a modular heatless unitReached on the 4-minute cycle with inlet air held to 86°F, from a dryer that mounts beside the machine it serves.
Three point-of-use technologies compared
Figures at 100 psig and 100°F inlet unless the cell says otherwise.
| COMPARED | MODULAR HEATLESS | MEMBRANE | SINGLE TOWER |
| Flow range | 3 to 177 SCFM | 0.53 to 46.2 SCFM inlet at -40°F | 5 to 30 SCFM |
| Dew point | -40°F; -94°F with 86°F inlet | +50°F to -40°F, set by flow | As low as -40°F while the gel is fresh |
| Power | Needed for valves and controls | None, or a solenoid on the demand sweep version | None |
| What it consumes | Purge air every cycle | Sweep air: inlet minus outlet flow | Silica gel charge, 1 to 6 lb |
| Filtration | Coalescing pre and particulate after, standard | Coalescing prefilter; heavier package for dirty air | 15 micron dust filter built in; coalescing prefilter optional |
Sizing a point-of-use dryer
Membrane capacity depends heavily on the dew point you ask for. The largest demand sweep module takes in 138.1 SCFM and delivers 119.3 SCFM at a +40°F dew point, yet at -40°F it delivers 27.4 SCFM from 46.2 SCFM in. Size a membrane on outlet flow at the target dew point, and size the compressor for the inlet.
Single tower units are sized on flow at line pressure: the smallest passes 4 SCFM at 80 psig and 7 SCFM at 150 psig. Modular heatless capacity is corrected for pressure between 50 and 150 psig with a published factor.
Call and talk it through with an engineer: 1-805-484-2992
Putting a dryer on one branch
At minus 40°F, a modular heatless unit is usually the better buy at 20 SCFM; a membrane earns the job only where there is no power or the dryer must hide in an enclosure. The inline membrane that delivers 20.9 SCFM at that dew point needs 29.1 SCFM from the compressor, so more than a quarter of the air leaves as sweep. The 24 SCFM modular size covers the branch at 100 psig, its rating pressure, with both filters included. If plus 40°F is enough for the instruments, the comparison flips, and one membrane module carries the flow with plenty in hand.
Indoors, at the point where the branch leaves the heated header, before the pipe runs anywhere cold. A dryer mounted out at the bulk-bag station or the loading dock puts its prefilter drain in the same cold that froze the line in the first place. Everything downstream of the dryer should be clean pipe: old steel that has carried wet air sheds dry rust flakes once dry air runs through it, and they end up in the tool. Leave the filter bowls and the dryer status lights where someone walking past will actually see them.
Yes, if it is sized on the flow those machines draw at the same moment, at the pressure the dryer actually sees. Find the worst realistic overlap, such as two cells cycling together or a blow-off running while a press indexes, and size for that peak rather than for the average. A membrane handles overload poorly: its outlet dew point loosens as soon as flow passes the figure it was selected for. A single tower gel unit tops out at 30 SCFM and a modular heatless unit at 177 SCFM; a branch that grows past those is a twin tower duty.
