Inline air filters — grades & order

Particulate (P) filters catch dust and rust. Coalescing (C) filters merge oil/water aerosols so they drain out. Activated carbon (AC) adsorbs oil vapor. Stages get finer downstream and pressure drop adds up.

• General purpose (P)1–5 µm particulate, 0.1 ppm oil
• Coalescing (C)0.01 µm / 0.008 ppm oil — pre-desiccant grade
• High-efficiency coalescing0.01 µm / 0.001 ppm — ISO 8573 Class 1 oil
• Activated carbon (AC)≤ 0.003 ppm oil vapor — instrument/breathing prep

• Size by ACFM at minimum operating pressure — not nominal pipe size.
• Use next size up if downstream demand is intermittent (avoids high ΔP during peaks).
• Plan total ΔP across train ≤ 5 psid clean.

• Recommended order (compressor → use): aftercooler → separator → P (general) → refrigerated dryer → C (coalescing) → AC (only if needed) → final P.
• For desiccant dryer: aftercooler → separator → general P → high-efficiency C → desiccant → particulate after-filter.
• Mount vertical, drain down. Allow clearance to drop bowl for element change.
• Install differential-pressure gauge on every coalescing or carbon stage.

• Coalescing/carbon: replace element annually OR at 7 psid ΔP, whichever first. Carbon also has time limit (~6 mo continuous).
• Particulate: replace at 10 psid or per OEM.
• Verify auto-drain on filter bowl operating every cycle.
• Log ΔP monthly — rising ΔP is the only reliable filter-life indicator.