Explosion-Proof Junction Boxes
Flameproof and increased-safety junction boxes for terminating and looping cables in Zone 1 and Zone 2 areas — available in aluminium, GRP and 316L stainless steel.
Typical range
- Ex e junction box, 4–48 terminals
- Ex d (flameproof) junction box
- Ex e increased-safety enclosure with cable entries
- Custom entry configurations to drawing
Indicative specification
- Protection: Ex e / Ex d IIC T6
- Ingress protection: IP66
- Materials: die-cast aluminium, GRP, 316L stainless steel
- Entries: M20 / M25 / G / NPT
- Ambient: -40 to +55 °C
Applications
Field junction and looping, instrumentation and control circuits, lighting circuits, tank farms and loading areas.
Part of the explosion-proof electrical apparatus range. Request a quote with your terminal count and cable sizes.
How to specify an explosion-proof junction box
A junction box is usually the least expensive item on a hazardous-area drawing, and the most common cause of an inspection finding. The enclosure itself is rarely the problem — the entries, the terminals and the plugs used to close unused ways are. Six decisions drive the specification:
- Zone and gas group. Zone 1 needs a certified enclosure (Ex d or Ex e); Zone 2 also accepts Ex nA or Ex ec. The group (IIA, IIB or IIC) sets the minimum marking the box must carry.
- Protection concept. Increased safety (Ex e) is the normal choice for terminating and looping, because it keeps the interior free of arcs and sparks. Flameproof (Ex d) is used where the box contains devices that make or break a circuit, or where a higher group is called for.
- Material. Die-cast aluminium for standard weight and cost; GRP where corrosion resistance or weight matter more; 316L stainless steel for offshore, chloride-rich and frequent wash-down areas.
- Entries and glands. Count the incoming and outgoing cables, record the outside diameter of each, and fix one thread standard for the whole box.
- Terminals. Terminal count follows the number of cores to be terminated, not the number of cables.
- Certification market. Tell us where the plant is being built — the marking that satisfies one market is not automatically the marking another inspector expects.
Ex d or Ex e — which enclosure for a junction box?
Both concepts are certified and both are used in Zone 1. The choice follows from what is inside the enclosure.
| Concept | What it relies on | Usual choice when |
|---|---|---|
| Ex e — increased safety | No arcs or sparks in normal service, generous creepage and clearance, rated terminals, defined maximum dissipation | The box only terminates and loops conductors, and the circuits are instrument, control or lighting circuits |
| Ex d — flameproof | An internal explosion is contained and the flame is quenched before it can leave the enclosure through the joint faces | The box contains switching or protective devices, or the project standard calls for flameproof enclosures |
| Ex nA / Ex ec — non-sparking | No sparking contacts in normal operation, without the design margin of Ex e | Zone 2 only, where the area classification permits it |
Materials and entries
Die-cast aluminium
The default for most onshore installations: light, dimensionally stable and available with the full range of entry configurations. In coastal or chloride-rich atmospheres it needs a sound surface treatment, and it should not be specified where it will be washed down with aggressive chemicals.
GRP (glass-reinforced polyester)
Chosen where weight and corrosion resistance outrank mechanical toughness — for example on structures where the enclosure is supported by light steelwork. Entry fittings still have to be certified as part of the assembly.
316L stainless steel
The safe answer for offshore platforms, desalination areas and plants that hose down equipment. Heavier and more expensive, and it needs care when it is bolted to carbon steel to avoid galvanic corrosion.
Threads: metric, G and NPT
Metric (ISO 965) and G (ISO 228) threads are parallel and seal on a washer or a face; NPT (ASME B1.20.1) is tapered and seals on the threads themselves. Mixing standards on one box is possible with adapters, but every conversion adds a joint that has to be checked. Decide the standard once, at the drawing stage, and keep glands, reducers, stopping plugs and breathers on the same thread.
Terminals and how to count them
Our Ex e junction boxes take 4 to 48 terminals, with entry configurations built to drawing. When counting, include every core that has to be terminated — including screens and spares — and leave room for later additions, because a box that is full on day one is usually rebuilt within a year. If the cables arrive from different directions, say so: the entry layout, not the terminal count, is often what turns a standard box into a built-to-drawing one.
Frequently asked questions
Can a Zone 2 junction box be used in Zone 1?
No. The marking on the box has to be suitable for the zone in which it is installed. A box certified for Zone 2 only cannot be upgraded by adding a better gland.
Do I need flameproof boxes for instrument signals?
Usually not. Instrument and control circuits that neither arc nor spark are normally terminated in Ex e enclosures. Ex d becomes necessary when the box contains devices that switch the circuit.
What is the difference between IP66 and flameproof?
They answer different questions. IP66 is an ingress-protection rating against dust and water; flameproof (Ex d) is a protection concept against ignition. A box can be flameproof without being IP66, and IP66 without being flameproof.
Can the entries be changed after installation?
Entries can be added only in the way the certification allows — normally by drilling to a certified pattern and fitting certified entries. Unused entries must be closed with certified stopping plugs, not with ordinary bolts.
Can you build boxes to our drawing?
Yes. Custom entry configurations and non-standard terminal arrangements are built to drawing. Send the drawing with the cable schedule and we will confirm feasibility together with the closest certified enclosure size.
What to send us for a quote
- Zone and gas group of the installation, and the country the plant is being built in
- Terminal count and the cross-section of each core
- Number of entries, cable outside diameters, and the thread standard
- Material and any surface-treatment requirement
- Quantity and required delivery date
Send those five points to our team and we will come back with an indicative specification and the exact Ex marking. Request a quote.
Assembly and internal wiring of Ex enclosures and control stations is shown in our factory videos.
Explosion-Proof Junction Boxes: Frequently Asked Questions
Choosing between flameproof and increased-safety junction boxes, and specifying entries correctly.
Should I choose an Ex e or an Ex d junction box?
Choose Ex e (increased safety) when the box only carries terminals and splices, with no switching device and no component that can produce a spark, and when the rated voltage and terminal arrangement can be kept within increased-safety limits. Choose Ex d (flameproof) when the enclosure has to contain an internal fault, or when the box will hold devices such as relays, contactors or fuses. Mixed installations commonly use an Ex e enclosure with Ex d components inside, marked Ex de.
Which materials and IP ratings do you offer?
Die-cast aluminium alloy for light weight and good heat dissipation, galvanized carbon steel and cast steel for heavier industrial duty, and 304 or 316 stainless steel for offshore, coastal and chemical environments. Standard sealing is IP66; IP67 versions are supplied for washdown and areas subject to temporary submersion.
Can the number and position of cable entries be customised?
Yes. We produce junction boxes with custom entry quantity, entry size and entry placement, in metric, PG or NPT thread, based on your drawing or a simple sketch showing the conduit routing. Sending terminal count, conductor cross-section and required entries with the enquiry keeps the quotation accurate on the first pass.
What documentation comes with an explosion-proof junction box?
Each shipment includes the nameplate data matching your order, the installation and torque instructions, and the ATEX documentation for the certified model, plus a declaration of conformity with the standard the enclosure is designed and tested to, IEC 60079. Where a customer needs a model that is not in our certified list, we build it to the ATEX / IECEx design requirements rather than implying a certificate that does not exist.
Question not answered here? Send it to our engineering team — we answer hazardous-area selection questions with the relevant standard referenced.
Related: explosion-proof electrical apparatus, distribution boxes, conduit fittings and cable glands.
