Air Knife Drying in Parts Washers: A Simple Guide
Last updated: November 12, 2026
After parts are washed, they come out wet. If they stay wet, they can rust, leave water marks or cause problems in the next step of production. This guide explains, in plain English, how an industrial parts washer dries parts with air knives. It also covers the different drying options and what to check when parts come out wet.
Who this is for: anyone who buys, runs or looks after a production parts washer, including people who are not engineers.
Quick Answer: What Is Air Knife Drying?
Air knife drying means blowing a fast, flat stream of air across a wet part so the water is pushed off, a bit like a squeegee made of air. In an industrial parts washer, a blower feeds air to air knives and nozzles inside a dry zone. The parts pass through on a conveyor and leave dry enough for the next step.
Key Observations
- Most parts dry well with fast, unheated air. Heat is only added when a part needs it.
- Thin, light parts and fast lines are the usual reasons to add heated air.
- Tall parts that sit far from the air knives can use recirculated, heated air.
- Most Inline washers do not need compressed air. The dry zone is fed by a blower.
- Wet parts at the exit usually point to air knife position, a dirty filter or knife, or the blower.
Drying options at a glance:
| Drying option | When it is used | In simple terms |
|---|---|---|
| Fast ambient (unheated) air | Most parts | Blows the water off. Uses the least energy. |
| Fast heated air | Very thin or light parts, fast lines | Blows the water off and warms the part so the last film of water dries quickly. |
| Recirculated heated air | Tall parts far from the air knives | Moves a lot of warm air around the part so water blows off and also evaporates. |
Not sure which drying setup your parts need? Inline Cleaning Systems reviews your part and process details and recommends a configuration. Get a Free Quote or call +1 574-722-3714.
In this guide
- Quick answer
- Why parts need drying
- How an air knife works
- Blower or compressed air
- The three ways Inline dries parts
- What decides how well parts dry
- Hard-to-dry parts
- Why parts are still wet
- Keeping the dry zone working
- FAQ
- Next step
Why Do Parts Need to Be Dried After Washing?
Parts need to be dried after washing because water left on a part can cause corrosion, and the next step in production usually needs a clean, dry part. That next step might be painting or coating, assembly, packaging or shipping.
Inline Cleaning Systems says drying is often the hardest part of washer design. It gets harder when parts have complex shapes, blind holes (holes that do not go all the way through) or when the line runs fast. Getting parts dry without wasting energy requires taking a careful look at the part shape and how the line runs.
How Does an Air Knife Dry a Part?
An air knife dries a part by aiming a thin, even sheet of fast-moving air at its surface. The air pushes the water off the part instead of waiting for it to evaporate. Think of it as wiping the part with air.
In a conveyor parts washer, the dry zone is the last section of the machine. Parts ride through on the conveyor belt, and air knives and nozzles are placed above, below and sometimes on either side. Inline uses a mix of air knives and nozzles depending on the shape of the part.
- Air knife: a long, narrow outlet that gives a flat curtain of air across the width of the conveyor.
- Air nozzle: a smaller outlet that aims air at one spot, such as a pocket or a hole.
- Blower: the fan unit that supplies the air.
The conveyor itself matters too. Inline’s stainless steel flat wire belt has the most open area of any belt it uses, which helps air reach the underside of parts. For long parts, powered rollers leave open space between them so the bottom surface dries well.
Does Air Knife Drying Use a Blower or Compressed Air?
On Inline Cleaning Systems washers, the air knives are fed by a blower. Most Inline washers do not need compressed air at all. Compressed air is only used when a machine needs it for automated loading and unloading, or for custom washers with spray nozzles that move.
That matters when you plan utilities. A typical Inline washer needs electrical power, water, a drain and exhaust ventilation, and Inline confirms the exact list on the installation drawings.
What Are the Three Ways Inline Dries Parts?
Inline Cleaning Systems chooses one of three drying setups based on the parts and how the line runs. The goal is to dry the part fully while using no more energy than needed.
1. Fast ambient air (the most common choice)
This is the setup most parts use. It works on a wide range of parts and uses the least energy. Air knives or nozzles blow the water off at high speed, typically 30,000 feet per minute (about 340 miles per hour, or 150 meters per second). No heater is involved.
2. Fast heated air (for thin or light parts)
Some parts are so thin or light that they do not hold enough heat to dry on their own after they leave the dry zone. For these, electric heaters warm the air before it reaches the air knives. The air is heated to a programmed temperature and may or may not be recirculated. Fast line speeds can also call for heated air.
3. Recirculated heated air (for tall parts)
Tall parts can sit far away from the air knives, so a fast, narrow stream of air loses its punch before it reaches them. For these parts, Inline moves a larger volume of slower, warm air. The water is both blown off and evaporated. The air goes around through the blower again, which reduces the energy needed to heat it.
The temperature can be controlled with an inline heater, or the blower’s closed loop alone can heat the air up to 185 F (85 C) as the air is compressed over and over. Heating the air without a heater needs a specific type of blower, so Inline chooses the setup job by job.
| Setup | Air speed | Heat | Best for |
|---|---|---|---|
| Fast ambient air | High, typically 30,000 ft/min or more | None | Most parts |
| Fast heated air | High | Electric inline heaters | Very thin or light parts, fast lines |
| Recirculated heated air | Lower, but a larger volume | Up to 185 F (85 C) through the blower loop, or higher with a heater | Tall parts far from the air knives |
What Decides How Well Parts Dry?
How well parts dry comes down to a handful of simple things. Inline looks at each one when it designs the dry zone.
- Part shape: flat parts shed water easily. Cups, pockets and blind holes trap it.
- Line speed: a faster line gives each part less time under the air. Inline works out the dry zone length from the number of air passes a part needs at the target speed.
- Air knife position: the height and angle of each knife decide where the air hits. Inline’s ClearView tunnel uses a Unistrut mounting system, so air knife position can be moved easily when parts change.
- Air knife distance: air knives work best within 1 inch (25 mm) of the part surface. Farther away, the air stream becomes turbulent and loses effectiveness. Air nozzles can extend the useful distance to 4 to 6 inches (100 to 150 mm).
- Conveyor: an open belt or rollers let air reach the underside of the part.
- Wash temperature: a part that comes out of a heated wash carries some of that heat into the dry zone. Heated washing helps both cleaning and drying.
How Are Hard-to-Dry Parts Handled?
Hard-to-dry parts are handled by moving the air, the part, or both, so the air reaches every surface. These examples come from machines Inline has built.
- Gear washer: air knives rotate a full 360 degrees around the outside of the part while a probe rises through the center hole to dry the inside.
- Tube washer: dries the entire inside length of long hydraulic cylinders.
- Tote and seed box washers: each box rotates through the blow-off, air knives blow off all sides, and extra dry zones can be added for faster drying.
- Valve plunger washer: small machined parts move through a dry stage and then a cooling stage before they are unloaded.
- 7-stage washer for automotive decorative panels: the last stage dries polished aluminum sheets with electrically heated air.
Example: Drying Deep Cavities in a Formed Sheet Metal Part
In one drying test, Inline worked with a formed sheet metal part that had several deep, V-shaped cavities the air knives could not reach well. The test ran at a conveyor speed of 15 ft/min after a 160 F (71 C) wash. Without extra help, water droplets stayed inside the cavities after the dry zone.
Inline then added an air nozzle that reached down into the cavity and blew the water out from the inside. With the nozzle in place, the cavities came out dry. The test showed exactly where the extra air was needed, which is why Inline uses a mix of air knives and nozzles and why sample parts are so useful before a dry zone is designed.
Have a part with pockets, blind holes or a tall shape? Send part drawings or sample parts and Inline will recommend a dry zone setup. Get a Free Quote.
Why Are Parts Still Wet When They Leave the Washer?
Parts are usually still wet because the air is not hitting them hard enough or in the right places. This table lists the common causes and what to check first.
| What you see | Likely cause | What to check |
|---|---|---|
| Water left on top surfaces or in pockets | Air knives at the wrong height or angle | Knife height and angle for the current part |
| Parts wetter than they used to be | Less air reaching the knives | Blower intake filter, air hose condition, blower drive belt tension |
| Weak or uneven air across the belt | Build-up inside the air knives or nozzles | Clean the knives and nozzles |
| Parts re-wetted near the exit | Air knives placed too close to the curtains | Move the air knives so the curtains cannot reach the air knives |
| Thin parts still damp just after the exit | Parts not holding enough heat to dry | Whether heated air is needed or working, heater wiring |
| New part shape will not dry | Dry zone set up for a different part | Move air knife brackets, review the number of passes at line speed |
How Do You Keep the Dry Zone Working?
You keep the dry zone working by making sure nothing blocks the air, and that the blower and air hoses are in good condition. These are the drying checks Inline includes in its preventive maintenance guidance.
- Check and replace the blower intake filter. Inline washers use a furnace-style filter to clean the air going into the blower.
- Check the air knives and nozzles for build-up that blocks the air.
- Check the blower drive belt tension and grease the lubrication points.
- If the air is electrically heated, inspect the heater wiring.
- When parts change, check that the air knives are at the right height and angle.
For the full checklist across the whole machine, see the parts washer maintenance guide in Related reading below.
Air Knife Drying FAQ
Yes. Drying is a standard stage in most conveyor parts washers. The dry zone is sized from the number of air passes a part needs at the target line speed.
Usually not. Most parts dry well with fast, unheated air, which uses the least energy. Heated air is used in three cases: very thin or light parts that do not hold enough heat to dry on their own, fast lines, and tall parts that sit far from the air knives.
Not on most Inline Cleaning Systems washers. The air knives are fed by a blower. Compressed air is only used for automated loading and unloading, or on custom washers with moving spray nozzles.
The dry zone length depends on how many air passes a part needs to dry at the target line speed. A faster line or a harder-to-dry part needs a longer dry zone.
Water left on a part can lead to corrosion. Drying removes that moisture. Some washers also add a rust-preventive chemical to the rinse to leave a thin layer of corrosion protection on the part.
Yes. Sample parts are welcome. They often help Inline confirm the right approach through cleaning and drying trials before the final design.
Next Step: Get a Drying Setup for Your Parts
The quickest way to get the drying right is to show the engineers your parts. Send Inline Cleaning Systems the part size, shape, material, target line speed and how dry the parts need to be. The team will recommend a washer and dry zone setup.
Get a Free Quote, call +1 574-722-3714, or see all parts washer features, including ambient and heated blowoff.
Related reading: aqueous parts washer guide, parts washer maintenance and how to choose an industrial parts washer.