RESOURCES
Resources
Straight answers to procurement questions, not generic content.
Practical reference material for technical buyers — the classifications, ratings and documentation that decide whether a component is the right one. Everything here is a summary for orientation. Always work to the current standard and the manufacturer’s documentation for your application.
Hazardous area quick reference
Getting an Ex component wrong is expensive and, in the wrong place, dangerous. Four things have to line up: the zone, the gas or dust group, the temperature class, and the protection concept.
Zones — gas and dust
| Zone | Where an explosive atmosphere is… | Equipment category |
|---|---|---|
| Zone 0 | Present continuously, or for long periods, or frequently | Category 1G |
| Zone 1 | Likely to occur in normal operation occasionally | Category 2G |
| Zone 2 | Not likely in normal operation, and only for a short period if it does | Category 3G |
| Zone 20 | Combustible dust cloud present continuously, for long periods or frequently | Category 1D |
| Zone 21 | Dust cloud likely in normal operation occasionally | Category 2D |
| Zone 22 | Dust cloud not likely in normal operation, and short-lived if it occurs | Category 3D |
Equipment certified for a lower-numbered zone may be used in a higher-numbered one of the same type. The reverse is never true.
Gas groups and temperature classes
Group I covers mining. Group II covers surface industry and subdivides by how easily the gas ignites:
| Group | Representative gas | Notes |
|---|---|---|
| IIA | Propane | Least easily ignited of the three |
| IIB | Ethylene | Covers IIA |
| IIC | Hydrogen and acetylene | Most onerous; covers IIA and IIB |
Dust equipment uses Group III: IIIA combustible flyings, IIIB non-conductive dust, IIIC conductive dust.
The temperature class is the maximum surface temperature the equipment can reach. It must sit below the auto-ignition temperature of the substance present.
| Class | Max surface temperature |
|---|---|
| T1 | 450 °C |
| T2 | 300 °C |
| T3 | 200 °C |
| T4 | 135 °C |
| T5 | 100 °C |
| T6 | 85 °C |
T6 is the most restrictive. Equipment rated to a lower temperature class satisfies the classes above it.
Protection concepts you will see in a marking
| Marking | Concept | In short |
|---|---|---|
| Ex d | Flameproof enclosure | Contains an internal explosion and stops it propagating |
| Ex e | Increased safety | Extra measures so arcs and hot surfaces do not occur |
| Ex ia / ib / ic | Intrinsic safety | Energy limited below what can ignite the atmosphere |
| Ex p | Pressurisation | Clean air or inert gas keeps the atmosphere out |
| Ex m | Encapsulation | Live parts sealed in compound |
| Ex n / Ex ec | Non-sparking | Zone 2 only |
| Ex o / Ex q | Oil immersion / powder filling | Arcs isolated by the surrounding medium |
A full marking also carries the equipment protection level — Ga, Gb or Gc for gas, Da, Db or Dc for dust.
ATEX certification applies in the EU. IECEx is the international scheme. Since Brexit, equipment placed on the market in Great Britain needs UKCA marking under the UK regulations, while the EU and Northern Ireland routes differ again. Check which market the equipment is going to before you order.
IP and IK ratings
An IP rating has two digits: the first is protection against solid objects and dust, the second against water. A rating is not a general promise of ruggedness — IP68 says nothing about impact, and IPX9K says nothing about dust.
IP first digit — solids and dust
| Digit | Protection against |
|---|---|
| 0 | No protection |
| 1 | Solid objects over 50 mm — a hand |
| 2 | Solid objects over 12.5 mm — a finger |
| 3 | Solid objects over 2.5 mm — a tool |
| 4 | Solid objects over 1 mm — a wire |
| 5 | Dust protected — limited ingress, no harmful effect |
| 6 | Dust tight — no ingress |
IP second digit — water
| Digit | Protection against |
|---|---|
| 0 | No protection |
| 1 | Vertically dripping water |
| 2 | Dripping water, enclosure tilted up to 15° |
| 3 | Spraying water up to 60° from vertical |
| 4 | Splashing water from any direction |
| 5 | Water jets from any direction |
| 6 | Powerful water jets |
| 7 | Temporary immersion |
| 8 | Continuous immersion, conditions agreed with the manufacturer |
| 9 / 9K | High-pressure, high-temperature jets |
IK — impact resistance
IK ratings run from IK00 to IK10 and describe the impact energy an enclosure withstands. IK08 is 5 joules; IK10 is 20 joules. Lighting, cameras and enclosures in exposed or public areas are the usual places you will see one specified.
When a component is obsolete
Discontinued does not mean unobtainable, but the routes differ in cost, lead time and risk. There are usually five:
- Remaining original stock — distributor shelf stock, manufacturer run-out or new old stock. Cleanest option where it exists. Check date codes and storage conditions on anything with electrolytics, seals or batteries.
- Surplus and secondary market — genuine parts from plant clearances, cancelled projects and specialist stockists. Provenance is what matters here, and it is where counterfeit risk concentrates.
- Repair or refurbishment — often the fastest route for drives, PCBs and motors, particularly through the original manufacturer’s service arm.
- Manufacturer’s recommended replacement — the successor part. Usually fits and functions, but check terminal layout, footprint, firmware and configuration tooling before assuming a drop-in.
- Form, fit and function equivalent — a different manufacturer’s part matched against the specification. Needs the original data to compare against, and someone to own the decision that it is suitable.
If you are carrying a known obsolescence risk on a critical asset, tell us before it becomes urgent. Options are far wider when the machine is still running.
Certification and documentation
Documentation has to be specified before an order, not asked for afterwards. These are the ones that come up most often:
Common documents, and what they actually tell you
| Document | What it is |
|---|---|
| Declaration of Conformity | The manufacturer’s statement that the product meets the relevant directives or UK regulations. Product-level, not batch-level. |
| Certificate of Conformity (CoC) | A supplier statement that the goods supplied conform to the order and specification. |
| Certificate of Analysis / test certificate | Results from testing performed on the product or its material. |
| EN 10204 2.1 | Declaration of compliance with the order, no test results. |
| EN 10204 2.2 | Test report based on non-specific inspection. |
| EN 10204 3.1 | Inspection certificate with specific test results, validated by the manufacturer’s authorised representative independent of the manufacturing department. |
| EN 10204 3.2 | As 3.1, but countersigned by the purchaser’s representative or an independent inspector. |
| ATEX / IECEx certificate | The notified or certification body’s certificate for the equipment, referenced by number in the marking. |
| Certificate of origin | Country of manufacture, for customs and for contracts that restrict origin. |
Certification travels with the part number and often with the revision. A functionally identical component from a different plant or a later revision may carry different documentation.
What to send with a sourcing request
The quality of a quote follows the quality of the enquiry. In order of usefulness:
- Manufacturer and full part number, including any suffix. Suffixes usually carry voltage, connection type or certification.
- Quantity, and whether a partial delivery is acceptable.
- Where it is going and by when — the delivery point changes both price and lead time.
- The application, if certification or environment matters: zone and gas group, IP rating, classification society, ambient and process temperature.
- What it replaces — a photograph of the rating plate is often faster than a part number, and settles ambiguity when labels have been overpainted.
- Documentation required — say so up front, especially for hazardous area or marine equipment.
- Whether an equivalent is acceptable, and who signs it off. This single line is often the difference between a two-day answer and a two-week one.
Have a requirement in the meantime?
Send us a part number, a datasheet, or a description of what you need.
