Intrinsic Safety Barriers

Enicstra stocks intrinsic safety (IS) barriers used to limit energy in field circuits entering ATEX, IECEx, and Class I Division 1/2 hazardous areas. Inventory covers passive Zener barriers (simpler, require quality plant ground), galvanic isolating barriers (active, isolation without ground dependency), and multi-channel barrier racks. Barriers are required by code for any electrical circuit entering a classified hazardous area unless the field device has its own explosion-proof or other protection method.

Brands carried include Pepperl+Fuchs K-System and HiD2000, MTL (Eaton), R. Stahl, Phoenix Contact MACX Safety, Stahl ISpac, GM International, Turck IM-series, and PR electronics 9100/9000 series. Obsolete IS barriers — discontinued MTL 7000-series first generations, retired K-System codes, end-of-life HiD2000 — are sourced through our supplier network. Each barrier is bench-tested for limiting behavior and ships with a 12-month functional warranty on the device.

For an obsolete IS barrier, send the OEM part number for a quote within 1–2 business days.

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Intrinsic Safety Barriers

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Buying guide

Choosing Intrinsic Safety Barriers components

IS barrier selection is dictated by the signal type, the hazardous-area zone classification, the simple-apparatus parameters of the field device, and the control-room equipment connected on the safe side. IS barriers are part of a system safety case — substituting a barrier changes the entity parameters and may require revalidation.

Specs to confirm before ordering:

Signal type: 4–20 mA analog (loop-powered or with supply on safe side), digital input from switch contact or Namur, digital output to solenoid or alarm, RTD or thermocouple temperature, frequency/pulse
Number of channels and isolation between them
Zone classification: Zone 0/1/2 (gas), Zone 20/21/22 (dust), Class I Div 1/2, Class II Div 1/2
Approval scheme: ATEX, IECEx, FM (US), CSA (Canada)
Barrier type: Zener (passive, requires high-quality plant ground) or galvanic isolating (active, no ground dependency)
Entity parameters: Uo (maximum output voltage), Io (maximum output current), Po (maximum power), Co (allowed external capacitance), Lo (allowed external inductance) — must envelope the field device's Ci, Li, and accept its Ui, Ii, Pi
Mounting: DIN-rail, IM-series bracket, or 19" rack
Diagnostic features: line-fault detection (open/short on field circuit), LED indicators, fieldbus diagnostics

Common gotchas: Zener barriers require excellent plant equipotential bonding ground because they shunt fault current to ground; in plants with substandard ground, Zener barriers may not protect properly and galvanic isolators are required. Entity parameter matching is mandatory — a barrier with Uo=28 V cannot be used with a field device rated Ui=24 V; the math is in IEC/ISA standards and must be documented. Multi-channel barriers in a single housing have isolation between channels that may not match the application requirement — verify channel-to-channel isolation rating. Replacing a barrier model with one having different entity parameters can invalidate the loop's safety calculations.

Typical applications: Profibus PA and Foundation Fieldbus signals into hazardous areas, 4–20 mA process transmitters in Zone 1, solenoid valves in classified areas, and switch inputs from Namur position monitors. On legacy installations, exact-OEM IS barrier replacement preserves the loop's safety documentation.

For obsolete IS barriers, send the OEM part number for a sourcing quote.

Related categories Frequently asked questions

Do you stock obsolete MTL and Pepperl+Fuchs IS barriers?

Yes. Discontinued MTL 7000-series first generations, retired Pepperl+Fuchs K-System and HiD2000 codes, end-of-life R. Stahl ISpac, and earlier Turck IM-series are sourced through our supplier network.

Zener barrier vs. galvanic isolator — which do I need?

Galvanic isolator is the safer default — no ground-quality dependency, isolation between safe and hazardous sides. Zener is cheaper but only works in installations with low-impedance equipotential bonding ground. New designs almost always use galvanic isolators.

How do I check entity parameter matching?

Compare barrier output parameters (Uo, Io, Po) against field device input ratings (Ui, Ii, Pi); barrier output must be less than or equal to field device input. Cable capacitance/inductance plus device Ci/Li must be less than barrier Co/Lo. This calculation must be documented for the loop.

Is the certification preserved on surplus barriers?

Yes — the OEM certification (ATEX, IECEx, FM, CSA) is the property of the unit when manufactured. Surplus units retain certification provided they have not been physically modified.

Can I substitute a barrier with different entity parameters?

Only if the new entity parameters still envelope the field device and stay within the barrier's certified limits — and the safety documentation is updated. Substituting silently can invalidate the loop's safety case.

What is the warranty?

12-month functional warranty on the device. The loop's intrinsic safety status remains the integrator's responsibility, independent of the device warranty.