Troubleshooting: Wet Air in the Lines

Water in the air lines is the most common air-quality call you will get. Nine times out of ten the fix is something that drains or dries, and it is already installed. Start there before you quote a new dryer.

Symptoms the customer will describe

• Water spits out of blow guns or tool exhausts
• Filter bowls fill up fast
• Rust or scale in pipe, tools, or valves
• Paint defects: spotting, blushing, poor adhesion
• Sluggish tools or sticking solenoid valves
• Lines or valves freezing in cold weather

Likely causes, most common first

1. Drains not working. A receiver, dryer, filter, or drip-leg drain is stuck, plugged, or manual and nobody opens it. Water backs up and gets carried downstream.
2. Dryer off, bypassed, or failed. Someone opened the bypass during a repair and never closed it. Or a refrigerated dryer has a dirty condenser or a refrigeration fault. Or a desiccant dryer’s desiccant is spent.
3. Dryer overloaded. More flow, hotter inlet air, or a hotter room than the dryer is rated for. Common after a compressor was added, or in summer.
4. Dew point too high for the piping. A refrigerated dryer’s pressure dew point is roughly 35 to 39°F. Any pipe colder than that, like outdoor runs in winter, will still condense water.
5. Piping layout. Drops come off the bottom of the header, no drip legs at low points, or water pooling in sags.
6. No dryer at all. An aftercooler and tank alone will not get air dry enough for most uses.

Quick checks a rep can do on the phone

1. “Is the water everywhere, or at one machine?” One machine points to that drop or its point-of-use filter. Everywhere points to the compressor room.
2. “When did you last see the tank and dryer drains discharge?” Ask them to press the test button on each electronic drain.
3. “Is the dryer running? Is the bypass valve closed?”
4. “On a refrigerated dryer, is the outlet pipe cool to the touch?” Warm outlet pipe on a running dryer suggests it is not cooling.
5. “Did anything change? New compressor, more machines, hot weather?”
6. “Do any lines run outdoors or through a cold area?”

Fixes

• Repair or replace failed drains. Convert manual drains to automatic.
• Close the bypass. Get the dryer serviced if it is not cooling or regenerating.
• If demand or conditions outgrew the dryer, size a new one to the real flow, inlet temperature, and room temperature. Dryers are rated at set conditions listed on the data sheet; hotter conditions cut capacity.
• For cold or outdoor lines, move to a lower dew point (desiccant) on the lines that need it.
• Fix the piping: drops off the top, drip legs with drains at low points.
• Add point-of-use filters with automatic drains as a last line of defense, not the main fix.

What to quote

• Electronic or zero-loss condensate drains
• Refrigerated dryer, or desiccant dryer for sub-freezing dew point needs
• Coalescing pre-filters and particulate after-filters for the dryer
• Point-of-use filters and filter-regulators with auto drains
• Drip-leg drains and piping components
• Oil-water separator for condensate from lubricated compressors. Condensate from these compressors carries oil and may not be legal to dump down the drain. Check local rules.

When to escalate

Paint lines, food contact, instruments, and breathing air have specific purity requirements. Get the required ISO 8573-1 class in writing and size the treatment to it.

Sources

1. DOE/Compressed Air Challenge, Improving Compressed Air System Performance, 3rd ed. (refrigerated dryer pressure dew point 35 to 39°F; desiccant dryer -40°F; condensate drains and condensate treatment; drops from top of header).
2. ISO 8573-1:2010, Compressed air: Part 1: Contaminants and purity classes (water class definitions by pressure dew point).
3. Dryer derating with inlet temperature, ambient, and pressure: dryer maker data sheets and correction tables. Use the specific maker’s table when sizing.