Instrument installation often encounters challenging environments such as flammable or explosive atmospheres, high-dust areas, high-temperature and high-humidity locations, strong electromagnetic fields, or extremely cold regions.
In hazardous areas, improper installation may lead to ignition sources, equipment failure, or safety incidents.
Therefore, strict compliance with installation requirements is essential.
18 Core Requirements for Instrument Installation in Hazardous Locations
1. Routing of Instrument Electrical Cables
Electrical wiring should be routed in areas with lower explosion risk and away from potential leak or release sources.
If the flammable medium is heavier than air, cables should be installed higher or buried underground; for lighter-than-air gases, the routing should be lower.
Cable routes should remain outside the walls of hazardous buildings.
No intermediate joints are allowed in instrument cables.
2. Wall and Floor Penetration Sealing
Cable conduits passing through walls or floors must be tightly sealed with flame-retardant or non-combustible materials to prevent gas migration.
3. Avoiding Mechanical, Thermal, or Corrosive Damage
Electrical wiring must avoid exposure to vibration, heat sources, corrosion, or mechanical impact.
If unavoidable, proper protective measures must be taken.
4. Use of Certified Explosion-Proof Equipment
All instruments, electrical devices, and materials installed in hazardous zones must:
Meet explosion-proof certification standards
Be accompanied by valid Ex documentation and factory certificates
Have no external damage, cracks, or deformation
5. Threaded Connections of Protective Conduits
Threaded joints must use cylindrical pipe threads with at least six full threads engaged.
Apply conductive anti-rust grease and secure with locknuts.
Do not use hemp or lead oil.
Electrical continuity must be ensured across all connections.
6. Full Sealing of Protective Conduits
All conduits must be completely sealed to prevent gas ingress.
7. Proper Fixing of Conduits
Conduits must be firmly fixed with pipe clamps.
Welding is not permitted.
8. Routing Relative to Process Pipelines
Instrument electrical lines installed along process pipe racks must be routed on the side with lower explosion risk.
If the process medium is heavier than air, routes should be above the pipe rack; if lighter, below.
9. Explosion-Proof Junction and Terminal Boxes
Junction boxes and terminal boxes must be Ex-rated.
All terminations must be tight, reliable, and equipped with anti-loosening and anti-pull-out devices.
Cable entries must be fully sealed.
10. Positive-Pressure Instrument Enclosures
Where positive-pressure explosion-proof enclosures are used, the purge/ventilation line must remain unobstructed.
Shut-off valves are not allowed on purge lines.
11. Safety Warning Labels
Instrument panels, enclosures, and electrical devices in hazardous areas must display clear warnings such as:
“Do not open while energized.”
12. Separation of Intrinsically Safe and Non-Intrinsically Safe Circuits
IS (intrinsically safe) circuits and non-IS circuits:
Must not share the same cable
Must not be installed in the same conduit
13. Separation Between Different IS Circuits
When non-shielded cables are used, different IS systems must not share the same cable or conduit.
14. Insulation Testing of Intrinsically Safe Circuits
After installation, IS wiring must be tested with 50 Hz, 500 V AC for 1 minute.
No breakdown indicates acceptable insulation performance.
15. Conduit Material Requirements
Use galvanized steel water-gas pipes for conduit.
Electrical conduit or plastic conduit is not acceptable.
16. Grounding for Intrinsically Safe Instrument Systems
IS systems should:
Use an independent grounding electrode, or
Be grounded at the signal grounding point
Grounding resistance must meet design requirements.
17. Grounding of IS Circuits
IS circuits themselves must not be grounded.
If an instrument requires grounding for functional reasons, follow the manufacturer’s installation manual.
18. Explosion-Proof Flexible Metal Conduits
Flexible connections must use certified explosion-proof metal conduits and matching Ex-rated connectors.
Connector type must match the instrument and be specified when ordering.
Summary
Instrument installation in hazardous areas requires stringent control over cable routing, conduit sealing, explosion-proof certification, grounding, and the separation of intrinsically safe circuits.
Strict adherence to these requirements ensures operational safety, compliance with international standards, and long-term reliability of field instruments.