Oil and gas pipelines use pigs (Pipeline Inspection Gauges) to clean or inspect the line. During pig firing (launch/receive) the launcher holds pressurized hydrocarbon and generates metallic friction sparks. A BTS-reported incident (2019) involved ignition while opening a pig receiver.
Pig Types
- Cleaning pig: removes solid paraffin with scraper cups
- Gauge pig: detects geometric anomalies
- Smart pig: MFL/ultrasonic corrosion mapping
- Sphere (top): liquid separation, gas line condensate
Launcher/Receiver Safety
- Isolation valve: double block + bleed
- Venting: safe location, flare or atmosphere
- Purge: N2 or methanol before launch
- Pressure gauge: verify 0 psi before opening
- Earthing: launcher body grounded - dissipate static
Metallic Spark Risk
- Pig metal part: worn scraper cups create friction sparks
- Iron sulfide (FeS): pyrophoric - ignites in air
- Water slug: accelerates pyrophoric reaction
- MIE methane: 0.24 mJ - very low
- Solution: N2-purge with pig, fill receiver with N2 first
API 1130 and NFPA 30
- API 1130: pipeline leak detection - computational monitoring
- NFPA 30: Class II/IIIA liquid pipework
- NFPA 70 Art 501: pig launcher Class I Div 2
- Foam monitor: deluge over launcher/receiver area
- PSSR: Pre-Startup Safety Review every pig campaign
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Sources & Further Reading
NFPA 30, API 1130, API RP 1165, ASME B31.4, B31.8, DOT 49 CFR Part 195. NFPA 30 Flammable Liquids standard.