V-Belt Cross Sections & Identification

What it is

A V-belt is identified by its cross section (the shape and size of the trapezoid) and its length. North American industrial belts fall into three families, each covered by its own ARPM (formerly RMA) standard:

• Classical — A, B, C, D and E sections (ARPM IP-20). Multiple-belt industrial drives.
• Narrow — 3V, 5V and 8V sections (ARPM IP-22). Deeper, narrower belts that carry more power in less space.
• Light-duty / FHP — 2L, 3L, 4L and 5L sections (ARPM IP-23). Single-belt fractional-horsepower drives such as blowers, shop tools and lawn equipment.

Cogged ("X," as in AX, BX, 3VX, 5VX), banded and double-V (AA, BB, CC) versions are variations on these sections.

How to identify

Read the part number on the belt back. The letters give the section, the numbers give the length:

• Classical (A, B, C…): e.g. B60 — B section, length number 60. The number is a nominal length code in inches; inside, pitch and outside lengths differ, so compare like with like.
• Narrow (3V, 5V, 8V): e.g. 5V1000 — 5V section, effective outside length 100.0 in (the number is in tenths of an inch).
• FHP (2L–5L): e.g. 4L360 — 4L section, outside length 36.0 in (tenths of an inch). The digit before "L" is the top width in eighths of an inch (4L = 4/8 = 1/2 in).

If the print is gone, measure the top width and depth with a belt gauge or calipers and compare with the table.

Section comparison

Key points

• A and 4L have the same nominal top width, as do B and 5L, but they are not interchangeable in every drive. FHP belts are built for light single-belt duty; classical belts are built for industrial multi-belt drives. A classical belt is often accepted on an FHP drive; an FHP belt on an industrial drive usually fails early.
• Narrow sections need narrow-section (3V/5V/8V) sheaves. Classical belts in narrow sheaves, or the reverse, ride wrong and wear quickly.
• Replace multi-belt drives as a matched set so all belts share the load.
• Cogged belts run cooler and bend around smaller sheaves; they usually replace the plain belt of the same section and length.
• Metric belts (SPZ, SPA, SPB, SPC, and classical Z, A, B, C to ISO 4184) are close to, but not the same as, North American sections. Confirm before cross-referencing.

Common mistakes

• Replacing a B-section belt with a 5L because the top width matches.
• Comparing an inside length on one belt with an outside length on another.
• Replacing one belt in a matched set.
• Putting a classical belt on narrow-groove sheaves.

Governing standards: ARPM IP-20 (classical multiple V-belts); ARPM IP-22 (narrow multiple V-belts); ARPM IP-23 (single V-belts, light-duty); ISO 4184 (classical and narrow V-belt lengths). Belt maker's interchange and drive design manuals.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.