This guide is for a field screen, not a final belt-drive design. It helps you organize the visible clues: sheave outside diameter, belt top width, center distance, stamped codes, bushing style, expected RPM, observed RPM, and motor-current prompts.
The companion calculator runs the local arithmetic and source-boundary checks. Current ARPM/MPTA standards, manufacturer catalogs, OEM limits, pump or fan curves, guarding, lockout/tagout, and qualified review still control running, ordering, installation, and repair decisions.
Start With What Changed
Belt drives that ran quietly for years usually change behavior for a reason. Start by separating observations from conclusions.
- Speed changed: a smaller driven sheave or larger driver sheave can raise driven RPM.
- Motor changed: a different pole count or VFD setting can shift driver speed.
- Belt section changed: similar top widths can ride differently in the groove.
- Groove condition changed: worn grooves, bottoming belts, or mismatched sheaves can reduce grip.
- Bushing or installation changed: reused bushings, wrong bore, wrong keyway, or torque errors need manufacturer data.
Use expected and observed RPM as a first-pass comparison, then verify with a strobe tach, motor nameplate, catalog pitch diameters, and equipment records.
Identify Belt Section Without Turning It Into Approval
Top width is a useful clue, but it is not a full belt identification. Measure only after the machine is isolated under the site procedure. Calipers are better than a tape rule; worn belts and worn grooves can mislead either method.
The calculator maps local top-width prompts to common A, B, C, D, E, 3V, 5V, 8V, and fractional-HP families. Treat the result as a confidence label. Confirm the actual belt series, length, construction, matched-set condition, and sheave groove profile against current catalog data before replacement.
Decode Part Numbers As Search Context
Many sheave and bushing markings encode groove count, belt family, diameter, or bushing family. That makes them useful for a search, but not enough for ordering or installation.
Taper-Lock 4-digit codes
Local fixtures such as 1610, 2517, 3525, 3535, 4030, and 4535 are checked against a Martin taper-bushing source pointer. The table is intentionally small and source bounded.
| Code | Local max-bore prompt | Local length prompt |
|---|---|---|
| 1610 | 1.625 in | 1.000 in |
| 2517 | 2.500 in | 1.750 in |
| 3525 | 3.500 in | 2.500 in |
| 3535 | 3.500 in | 3.500 in |
Verify the exact bore, keyway, hardware, torque, fit, material, and installation instructions in the current manufacturer catalog. The app is not a catalog substitute.
QD and split-taper clues
Letter codes and bolt placement can point to likely QD or split-taper families, but exact interchangeability depends on the manufacturer, hub, bore, keyway, shaft condition, and application loads.
Bushing Clues To Record
Document the visible details before you loosen anything:
- Bolts on the face of the hub can indicate a QD-style bushing.
- Bolts or screws on the flange edge can indicate a Taper-Lock-style bushing.
- Set screws with no pull-up bolts can indicate a fixed-bore sheave.
- A longitudinal split and stamped family code are stronger clues than general shape.
Do not use visual classification as installation approval. Manufacturer instructions control screw positions, torque, jackscrew use, key fit, anti-seize restrictions, and removal steps.
Affinity Laws Are A Source Prompt
For centrifugal pumps and fans, a speed change can increase load faster than expected. The local prompt uses the common relationships: flow varies with speed, head or static pressure varies with speed squared, and power varies with speed cubed.
That math is useful for screening, but actual acceptance requires current pump or fan curves, system curve, static head, NPSH or stall margin, pressure limits, motor/VFD/starter data, bearing and shaft limits, and qualified review. Present motor current should be treated as a direct current-state warning, not as a number to multiply by the speed ratio.
Symptoms Are Prompts, Not Repair Instructions
Common symptoms can point the next measurement:
- Black dust or squeal: check tension, alignment, groove wear, and overload.
- Belt rides low or polished groove bottom: check groove wear and belt section.
- One belt hotter than others: check matched-set condition and tension balance.
- Higher amps after a sheave change: verify driven speed, motor current, pump/fan curve, and original ratio.
- Seal or bearing trouble after a speed change: verify equipment RPM limits, pressure/head change, NPSH, overhung load, and OEM data.
Lockout/tagout, guarding, stored energy, hot surfaces, rotating parts, and employer safety procedures are outside the calculator and must be handled before inspection or service.
When To Stop And Pull Source Data
Stop treating the output as a field screen and pull current source data when any of these apply:
- High speed, unknown sheave material, or possible rim-speed/balance issue.
- Overhung load, long shaft, worn bearings, or changed hub geometry.
- Pump, fan, compressor, crusher, hammer mill, or other high-consequence service.
- PSM, ammonia, refinery, chemical, confined-space, guarded-machine, or other regulated context.
- Ordering parts, approving installation, removing guards, changing speed, or returning equipment to service.
The app should leave you with a better source checklist, not a final answer.
Sheave & Belt Source-Aware Field Screen
Screen sheave OD, belt section, wrap angle, rim speed, bushing clues, and pump/fan speed-change prompts with catalog, guarding, and OEM gaps visible.