Skip the Usual Fix: Quoting Ex d to End the Argument
The reflex on an overseas pump package is to price a flameproof (Ex d) motor for every Class 1 Div 2 or Zone 2 location because the client "expects explosion proof" and nobody wants a hold point at FAT. It works, in the sense that the shipment clears inspection. It fails as engineering for three reasons: you pay for a cast, machined flame-path enclosure the area does not require; you inherit flame-path maintenance (gap inspection, no paint or sealant in the joint, torque on every bolt) for the life of the plant; and you have taught the client that the minimum in the standard is negotiable, so the next package gets the same treatment on cable glands, junction boxes and instruments.
The opposite reflex, quoting Ex nA because "that is all the code needs" and arguing later, fails just as reliably. The client rejects it, the schedule slips, and the motor is re-ordered anyway. Get it running, then fix it properly: work the checks below before the quotation goes out, not after the motor lands on the dock.
Check 1: Identify Which Classification System the Site Actually Uses
Reading to take: the area classification drawing title block and the project electrical design basis. Look for the governing code named there, not the client's nationality.
Why it matters: the phrase "Class 1 Div 2 Group IIB" mixes two systems. A drawing that says Div 2 with Group IIB has been written by someone straddling both systems, and the certificate you buy has to match one of them.
- Drawing says Class/Division with Groups A–D: the motor needs a Division listing (UL, CSA or FM) or a zone certificate the AHJ has agreed to accept. Go to Check 2 using Division terminology.
- Drawing says Zone with Groups IIA/IIB/IIC: an IECEx or ATEX certificate is the native document. Go to Check 2 using Zone terminology.
- Drawing mixes them, or the country has no national standard and borrows another region's (China adopting European practice is a common case): stop and get the design basis corrected in writing before quoting. A mixed classification cannot be certified against.
Check 2: Read the Zone or Division and Gas Group Off the Drawing
Reading to take: the zone/division boundary that encloses the pump motor location, the gas group, and the temperature class (T-rating) of the released material.
Mechanism: the protection concept is chosen against the probability of an explosive atmosphere being present, not against how nasty the gas is. Zone 2 (and Division 2) means the atmosphere is not expected in normal operation and, if it occurs, exists only for a short time. That is why the standards permit protection concepts for Zone 2 that rely on the equipment simply not being an ignition source in normal operation: non-sparking (Ex nA), increased safety (Ex e), and also the concepts qualified for the more onerous Zone 1 and Zone 0. Ex d is permitted in Zone 2 because anything good enough for Zone 1 is good enough for Zone 2; it is not required.
- Location is Zone 2 / Div 2: minimum compliant concept for a motor is Ex nA (or Ex e). Go to Check 3.
- Location is Zone 1 / Div 1: Ex nA is not acceptable. Ex d or Ex e (with the additional design limits that entails for a motor) is the starting point. Go to Check 3 with that as the floor.
- Gas group is IIC (or NEC Group A/B) with Ex d: the enclosure design tightens; confirm the vendor offers the motor frame in that group before it goes on the quote.
- T-class on the drawing is lower (hotter-permitted) than the motor's surface temperature marking: the motor is rejected regardless of protection concept. Read the T-rating on the certificate, not the datasheet.
Check 3: Find the Real Reason the Client Wants Ex d
Reading to take: the client's specification wording and their own reason, in their words, for rejecting Ex nA. The reason determines whether you argue, comply, or re-quote.
| What the client says | What is usually behind it | Correct response |
|---|---|---|
| "All our Ex equipment is Ex d" | Site standardisation: interchangeable spares, one maintenance procedure, one inspection routine | Legitimate. Comply, but get it written into the spec so it is a paid requirement. |
| "The pump might move to Zone 1 later" | Future flexibility; relocation without re-certifying | Legitimate. Comply and note it in the spec. |
| "We don't accept self-declared certificates" | Under ATEX, Ex n equipment can be manufacturer self-certified without third-party testing; some clients refuse this | Offer Ex nA with a voluntary third-party certificate (IECEx or notified-body ATEX) before escalating to Ex d. |
| "Ex d is stronger" | Mechanical: thick cast enclosure survives impact and abuse an Ex nA frame will not | Legitimate for pump skids in traffic areas. Comply if written in. |
| "We want the lowest ignition probability" | Risk appetite: of the Zone 2 concepts, Ex n has the highest ignition probability because it relies on no fault occurring | Legitimate risk decision; the client owns it. Comply and record it. |
Outcome routing: first row only, go to Check 4 and prepare the code argument. Any other row, go to Check 5 and treat Ex d (or Ex e) as a specification requirement, not a code requirement.
Check 4: Verify the Certificate Route and Marking Before Arguing
Reading to take: the actual certificate for the Ex nA motor you intend to offer. Read the issuing body, the marking string, the gas group, the T-class, and the standard edition listed.
Three things trip up an otherwise correct Ex nA offer:
- Self-declaration. An ATEX Ex nA certificate issued by the manufacturer alone is valid, but a client who has been burned by one will not accept it. An IECEx certificate is always third-party and is the easier document to defend overseas.
- Marking edition. Later editions of the increased-safety standard fold non-sparking motors into the
Ex ecmarking. A client's spec that lists only "Ex nA" and a motor marked "Ex ec" produces a paperwork rejection even though the protection is the same. Match the marking on the certificate to the marking in the spec, or add both to the spec. - Ancillaries. Terminal box, anti-condensation heater, encoder, thermistor circuit and cable glands each carry their own concept. A non-sparking motor with an Ex e terminal box and Ex d glands is normal; the client sees three different markings and assumes an error. List every component and its marking in the submittal.
If the certificate is third-party and the marking matches the spec, take the code argument to the client with the certificate and the 60079-14 selection table in hand. If the client still refuses, go to Check 5; you are now dealing with a preference, and preferences are handled by specification, not by standards.
Check 5: Decide Between Minimum Compliant and Specification-Driven
Reading to take: cost delta, delivery delta, and long-term maintenance burden for each concept at this location. Put the numbers in front of the client; the decision is theirs, but the consequences should be visible.
| Concept | Marking | Zones permitted | How it prevents ignition | Maintenance burden | Typical client objection |
|---|---|---|---|---|---|
| Non-sparking | Ex nA (Ex ec in later editions) | Zone 2 only | No arcs, sparks or hot surfaces in normal operation; standard frame with controlled clearances and surface temperature | Lowest: normal industrial motor care plus periodic Ex inspection | Self-certifiable; highest ignition probability of the Zone 2 options; lighter frame |
| Increased safety | Ex e | Zone 1 and 2 | Extra margin on creepage, clearance, temperature rise and locked-rotor time so a fault does not produce ignition | Moderate: locked-rotor (tE) time protection relay must be set and verified | Motor sizing penalty; relay coordination adds a step |
| Flameproof | Ex d | Zone 1 and 2 | Ignition may occur inside; enclosure contains the pressure and cools escaping gas through flame paths | Highest: flame-path gap inspection, no paint or sealant in joints, all fasteners present and torqued, certified glands and plugs only | Cost and weight; lead time in IIC |
- Client accepts the code argument: quote Ex nA (or Ex e) with third-party certification. Go to the procedure.
- Client insists but refuses to put it in writing: stop here. Escalate through your own project management to get the requirement onto a signed change or clarification before the purchase order is placed.
Lock the Protection Method Into the Specification and Verify It
The resolving branch, whichever concept was chosen, is the same procedure. Do it once, at quotation, so the night shift eighteen months from now can replace a motor from the spares list without reopening the argument.
- Record the governing classification system on the motor data sheet: NEC/CEC Division, or IEC/ATEX Zone. Never both.
- Record zone or division, gas group in that system's notation, temperature class and ambient range, copied from the area classification drawing revision number.
- State the accepted protection concepts explicitly, e.g. "Ex nA or Ex ec (IECEx or notified-body ATEX certified); Ex e and Ex d also accepted" or, where the client requires it, "Ex d only". Include both old and new markings where the standard edition has changed the designation.
- State the certificate route: IECEx, ATEX notified body, UL/CSA/FM Division listing. If self-declared ATEX Ex n is not acceptable, say so.
- List every ancillary and its required marking: terminal box, glands, heater, thermistor circuit, encoder, brake.
- For Ex e motors, add the requirement for a locked-rotor protection relay set to the certificate's tE time and a commissioning test record for it.
- For Ex d motors, add the requirement for a flame-path inspection record at receipt and a certified-gland schedule.
- Attach the vendor's certificate to the submittal and check the marking string, gas group and T-class against the data sheet line by line.
Verification before the motor leaves the vendor and again at site:
- Nameplate marking string matches the certificate and the data sheet exactly.
- Gas group on the nameplate covers the drawing's gas group (IIB certificate is not acceptable for a IIC area; a IIC certificate is acceptable for IIB).
- T-class on the nameplate is equal to or cooler than the drawing's T-class.
- Certificate number on the nameplate resolves on the issuing body's register.
- Every gland, plug and terminal box on the delivered motor carries its own marking; none are blank commercial parts.
Where to read the selection rules yourself: IEC/EN 60079-14 is the installation and selection part of the series and contains the permitted-concept-per-zone tables. The series runs to roughly twenty parts, most of which are construction standards for specific concepts and will not help with selection; buying the whole set sight unseen is expensive, and a library or standards subscription is the cheaper first look. Vendor selection wall charts (Pepperl+Fuchs publishes a widely used one) are a good desk reference but carry the vendor's product bias.
Stop here if the classification drawing cannot be reconciled to one system, if the country's adopted standard cannot be identified in writing, or if the client's AHJ will not confirm acceptance of the certificate route. Those are not vendor-selection problems. Escalate to the client's hazardous-area authority, the certifying body's technical desk, or the motor manufacturer's certification department with the drawing and certificate in hand.
FAQ
How do I tell whether a Class 1 Div 2 pump motor needs Ex d or Ex nA?
Read the area classification drawing: Division 2 and Zone 2 both permit non-sparking (Ex nA / Ex ec) and increased safety (Ex e) motors, so Ex d is not required by code. Ex d becomes required only where the client's specification demands it for standardisation, relocation, mechanical protection or certificate policy.
How do I handle a drawing that says "Div 2 Group IIB"?
Treat it as a defect: Division classification uses Groups A–D, Zone classification uses IIA/IIB/IIC. Get the design basis corrected to one system in writing before quoting, because no certificate can be matched to a mixed classification.
How do I answer a client who rejects Ex nA because ATEX Ex n can be self-certified?
Offer the same non-sparking motor with an IECEx certificate or a notified-body ATEX certificate, which are third-party by definition, before moving up to Ex e or Ex d. Write the certificate route into the specification so the requirement is contractual.
How do I know when to stop arguing and escalate?
Stop when the classification system cannot be reconciled, when the country's adopted standard is not documented, or when the client's authority will not confirm acceptance of the certificate route. Escalate to the client's hazardous-area authority, the certifying body, or the motor manufacturer's certification department with the drawing and certificate attached.