Conveyor Belt Specifications: EP 800/4 6+2 X Decoded

Conveyor belt specifications get written as one line — 1000 EP 800/4 6+2 X — and the most expensive mistake in that line is reading the 800 as the width. It is not the width. It is strength, in newtons per millimetre, and a buyer who confuses the two either accepts a belt that cannot carry the load or pays for one twice as strong as the job needs.

Here is the whole string decoded, field by field, with the document that governs each number — plus the three specs that never appear in the string and still decide whether the belt survives its first month.

Conveyor belt specifications: every field in the string

A conveyor belt specification is a single ordered string that states belt width, carcass material, full-thickness tensile strength, ply count, top and bottom cover thickness, and cover grade — for example 1000 EP 800/4 6+2 X.

Position	Example	Field	What it commits you to	Governed by
1	DIN 22102	Standard	The rulebook every other field is measured against	DIN 22102 / ISO 14890
2	1000	Nominal belt width, mm	The width on the order, plus a tolerance most buyers never read	ISO 251
3	EP	Carcass material	E = polyester yarns lengthwise, P = polyamide (nylon) crosswise	ISO 14890
4	800	Full-thickness tensile strength, N/mm	Minimum breaking strength per millimetre of belt width	ISO 14890
5	/4	Number of plies	How many fabric layers make up the carcass	ISO 14890
6	6+2	Cover thickness, mm	6 mm rubber on the carrying side, 2 mm on the pulley side	DIN 22102
7	X	Cover grade	The abrasion / cut / gouge class of the rubber	DIN 22102, ISO 10247

Written out in full, a fabric belt line reads DIN 22102 AB 1000 EP 800/4 6+2 X, where AB is the manufacturer's own acronym. A steel cord belt swaps the carcass block for DIN 22131 AB 1200 St 1600 7T/5 X — St for steel cords, 1600 N/mm breaking strength, 7 mm top cover, T for additional reinforcement, 5 mm bottom cover.

The number after EP is not the width

N/mm is the same thing as kN/m. An 800 N/mm belt at 1000 mm wide has a nominal full-thickness breaking strength of 800 kN across the belt. That is a breaking figure, not a working one — the tension the conveyor is actually designed around is a fraction of it, set by the conveyor calculation, not by the belt line.

Two consequences follow, and both cost money. Quote a wider belt at the same strength number and you have bought more total strength than you priced for. Quote the same width at a higher strength number and you have usually bought more plies, a thicker carcass, and — as the next section shows — bigger pulleys you may not have.

Width: ISO 251 lets a 1 200 mm belt arrive at 1 188 mm

ISO 251 specifies the nominal widths of conveyor belts with a textile carcass and the tolerance permitted on each. Nominal widths run from 300 mm to 3 200 mm, and the tolerance is ±1 % of nominal width with a flat ±5 mm floor below 500 mm.

Nominal width (mm)	Tolerance (mm)	Acceptable delivered width (mm)
300	±5	295–305
400	±5	395–405
500	±5	495–505
600	±6	594–606
650	±6.5	643.5–656.5
800	±8	792–808
1 000	±10	990–1 010
1 200	±12	1 188–1 212
1 400	±14	1 386–1 414
1 600	±16	1 584–1 616
1 800	±18	1 782–1 818
2 000	±20	1 980–2 020
2 200	±22	2 178–2 222
2 400	±24	2 376–2 424
2 600	±26	2 574–2 626
2 800	±28	2 772–2 828
3 000	±30	2 970–3 030
3 200	±32	3 168–3 232

A nominal 1 200 mm belt is inside ISO 251 anywhere between 1 188 mm and 1 212 mm — a 24 mm spread that no purchase order ever writes down, and the reason a receiving inspector's tape measure and a supplier's certificate can both be right.

Lengths are a separate matter: ISO 251 states plainly that the lengths of conveyor belts are not standardised. It sets tolerances only. An endless belt up to 15 m is allowed ±50 mm; over 15 m and up to 20 m, ±75 mm; over 20 m, ±0.5 % of the length. An open-ended belt delivered as a single length may run up to 2.5 % long and may not run short at all.

That asymmetry is deliberate and worth knowing before you argue about it. A belt delivered long can be cut. A belt delivered short is scrap.

Cover grades: the letter means nothing without the standard

Two systems classify belt covers, and they do not share letters. DIN 22102 uses W, X and Y. ISO 10247 uses H, D and L. Both classify on abrasion loss, tensile strength and elongation at break.

Letter	Standard	Written for
W	DIN 22102	Particularly high levels of abrasive wear
X	DIN 22102	Abrasive wear plus cutting, impact from high drop heights, and gouging
Y	DIN 22102	Normal service conditions
H	ISO 10247	Severe cut and gouge service
D	ISO 10247	Severe abrasion service
L	ISO 10247	Moderate service

Say the quiet part: a quote that names a grade letter without naming the standard it was graded against has committed to nothing. "Grade X" is a DIN answer. If the enquiry asked for an ISO classification, X is not one of the three answers available, and somebody is going to discover that at the arbitration stage.

Alongside the abrasion letters sit the special-property letters, which are added when the service condition demands them: E for antistatic, K and S for antistatic and flame retardant, T for high temperature, R for low temperature, G for oil and fat resistance, and C for chemical resistance.

The cover is also what wears out. Abrasion resistance of the rubber cover is the biggest single influence on how long the belt lasts — which makes the grade letter a more consequential argument than the extra millimetre of cover thickness buyers usually spend the call on.

The pulley diameter your belt spec already chose

Most enquiries never mention pulleys, and the belt spec has already decided them. ISO 3684 gives the minimum pulley diameter as a simple product:

D = e × C, where e is the carcass thickness in millimetres and C is a factor fixed by carcass material.

Carcass material	Factor C
Cotton	80
Polyamide	90
Cotton / polyamide	90
Cotton / polyester	98
Polyester	108
Rayon	118
Steel cord	145

A polyester-carcass belt with a 5 mm carcass gives 108 × 5 = 540 mm, which is then rounded up to the next standard pulley diameter. Those diameters follow a preferred-number series: 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1 000, 1 250, (1 400), 1 600, (1 800) and 2 000 mm. So 540 becomes 630.

Not every pulley on the conveyor needs that figure. ISO 3684 splits pulleys into three duties: type A for drive pulleys and pulleys under high tension, type B for snub pulleys in the return run under lower tension, and type C for bend pulleys turning the belt through less than 30°. Type B may drop one step down the series; type C, two steps.

Two caveats the standard states about itself, and neither is optional. The values are minimums to use in the absence of information from the belt manufacturer. And the method does not apply to carcasses thicker than 20 mm, to heat-resistant belts carrying product above 100 °C, or to belts running below −40 °C.

Running a correctly specified belt on an undersized pulley is the quietest way to destroy it.

Where the spec and the shipment stop agreeing

Four failures account for most conveyor belt specification disputes, and all four are documentation failures rather than manufacturing ones.

One cover number instead of two. "8 mm of cover" is not a spec. 6+2 and 4+4 are both 8 mm and they are not the same belt; the second one puts only 4 mm of rubber over the carrying face instead of 6, a third less wear life where the wear actually happens.
Width without its tolerance. If the ISO 251 allowance is not written on the order, the receiving inspector treats nominal as exact and raises a claim over a belt that is in spec.
A grade letter with no standard. Covered above; it is the most common single line to go missing on a translated enquiry.
No pulley diameter in the enquiry at all. The supplier then picks a carcass that suits their stock, and the belt arrives needing pulleys the plant does not have.

There is a fifth, and it is the one that image files cause. A roll of black belt photographs identically at 400 N/mm and at 1 600 N/mm. Cover thickness, carcass count and width are invisible in a photograph, so the buyer forms an impression from a picture and the impression is worthless.

The fix is not a better photograph. It is putting the measured numbers onto the picture: snap each measurement to the actual edge of the belt in the frame, lock the width, the cover split and the carcass thickness onto the image where the buyer is already looking, and export the result at the size the enquiry platform accepts. Tools built for measured dimension annotation do this in a single pass over the photo, which is why it is worth doing on every belt line in the catalogue rather than only on the ones a buyer queries. The distinction matters more here than in most categories: an AI image generator will happily render a plausible-looking "1000 mm" onto a belt that is 800, because it is inventing a caption rather than measuring an object. The number has to come from a measurement.

That is the same discipline behind an industrial spec diagram attached to a quotation, and it is the same reason how to label metal product specifications treats the callout as part of the specification rather than decoration. If your belt line also carries a load figure, WLL vs MBL load rating labels covers the pair of numbers buyers most often read backwards.

Conveyor belt specification checklist before you send the quote

Nominal width in mm, with the ISO 251 tolerance written beside it
Carcass material named (EP, NN, ST), not just "fabric"
Full-thickness tensile strength in N/mm, labelled as strength — never left to be mistaken for width
Ply count stated separately from strength
Cover thickness as two numbers (6+2), never one total
Cover grade letter and the standard it is graded against
Smallest pulley diameter on the receiving conveyor, in mm
Belt length, and whether the belt is endless or open-ended
Special properties required: antistatic, flame retardant, heat, low temperature, oil, chemical
A dimensioned image of the belt cross-section attached to the quotation

FAQ

What does EP mean on a conveyor belt?

EP means the carcass fabric has polyester (E) yarns running lengthwise and polyamide — nylon — (P) yarns running crosswise. The combination gives low lengthwise stretch from the polyester and good transverse flexibility and impact absorption from the nylon, which is why EP is the default fabric carcass for general bulk handling.

Is the 800 in EP 800/4 the belt width?

No. It is the full-thickness tensile strength in newtons per millimetre of belt width, which is the same unit as kN/m. Belt width is a separate number written before the carcass code, as in 1000 EP 800/4. Reading the strength as the width is the single most common error on translated enquiries.

What does 6+2 mean in a conveyor belt specification?

It is the cover thickness split: 6 mm of rubber on the top, carrying side and 2 mm on the bottom, pulley side. Some suppliers write it 6/2. A single figure such as "8 mm cover" does not specify the belt, because the split determines how much wear life the carrying face actually has.

What is the difference between cover grade X and cover grade Y?

Both are DIN 22102 grades. Y is written for normal service conditions. X is the more versatile grade: on top of abrasive wear it is intended for cutting, impact from high drop heights, and gouging. W is the grade for particularly severe abrasive wear. ISO 10247 classifies the same property with different letters — H, D and L — so the letter alone is ambiguous unless the standard is stated.

How do I calculate the minimum pulley diameter for a conveyor belt?

Multiply the carcass thickness in millimetres by the ISO 3684 factor for the carcass material — 108 for polyester, 145 for steel cord, 90 for polyamide — then round up to the next standard pulley diameter in the series 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1 000, 1 250, 1 600, 2 000 mm. Snub pulleys in the return run may go one step smaller and bend pulleys turning less than 30° two steps smaller.

Conveyor Belt Specifications: What EP 800/4 6+2 X Locks In