TL;DR

Walk the system with a sonic leak detector at every joint, fitting, and drain. Prioritize leaks by flow rate. A 3 mm orifice leak at 7 bar wastes roughly 60 SCFM continuously.

What you might see

audible hissing near fittings or hoses
pressure decay after compressor stops
compressor runs more than expected for the load
higher energy cost per unit of compressed air

Likely causes

Tap to mark as ruled out

Degraded compression fittings, push-to-connect joints, or threaded NPT fittings with dried sealant
Cracked or perished flexible hoses at connection points
Automatic drain valve stuck closed or cracked body allowing continuous air bleed
Safety valve weeping at less than the set pressure from seat contamination or a weak spring

Required tools

Sonic leak detector
PTFE tape and anaerobic thread sealant
Replacement push-to-connect fittings
LOTO kit
Numbered leak tags for tracking

Safety first

Depressurize and lock out the section being repaired before opening any fitting. Compressed air at pressure can cause serious eye and tissue injury.
Do not use open flame or hot tools near compressed air fittings.

Procedure

7 steps · ~60 min

1
Use a calibrated sonic leak detector to survey all fittings, valves, hoses, and manifold joints in the distribution system. Mark each leak with a numbered tag.
2
Estimate the leak rate at each tag point. Prioritize any leak audible from 1 meter away, these are typically greater than 10 SCFM losses.[1]
3
Schedule repairs during the next planned downtime. Lock out and depressurize the affected section before opening any fitting.
4
Replace all plastic push-to-connect fittings more than 5 years old. Replace the entire fitting, not just the collet insert.
5
Re-seal threaded NPT joints with fresh thread sealant (PTFE tape plus anaerobic thread compound). Do not re-use old PTFE tape.
6
Test each auto drain valve: activate the manual test button and verify it opens and closes fully. Replace any drain that does not cycle completely.[1]
7
After repairs, repeat the sonic survey. Document the total estimated leak reduction in SCFM and the expected energy savings per year.

Sources

Atlas Copco GA VSD+ Air Compressor User Manual, Atlas Copco
Atlas Copco GA VSD+ IOM, distribution system leak detection and drain valve maintenance procedures (general)
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