Guide
Two questions tell you if your trolley wheels are open, plugged, shielded or sealed: is there a welsh plug on the I-beam side, and is there a shield or seal on the bracket side?
Before you start
You need a flashlight and a spare trolley. Lock out and tag out the conveyor before you inspect.
Start here · wheel design
Retainer or full ball?
If you can see the balls, look for a steel cage between them, or count them.
Fig. 1 · Retainer (left) and full ball (right) trolley wheels.
| CAGEDRetainerSteel cage separates the balls. Lowest friction. Up to 325°F. | FULL COMPLEMENTFull ballNo cage, more balls. Heavy load and contamination. Up to 500°F. |
Count the balls
| Wheel | Retainer | Full ball |
|---|---|---|
| 3 in | 7 balls | 11 balls |
| 4 in | 8 balls | 13 balls |
| 6 in | 8 balls | 13 balls |
The configurations
Seven catalog codes. Four configurations.
Fig. 2 · Catalog codes 0 to 6, retainer type. Shaded blue marks the part that changes.
| Configuration | Code | What you see |
|---|---|---|
| Open / open | 0 | Nothing on either side. |
| Welsh plug, no shield | 1 | Plug on the I-beam side only. |
| Shield, no welsh plug | 2 | Shield on the bracket side only. |
| Sealed | 3 to 6 | Welsh plug plus a seal on the bracket side. Four seal types. |
Drawings and codes from the Frost product catalog, page 9 (retainer type). Full ball wheels use the same plugs, shields and seals.
Know the two sides
Every wheel has two sides.
The I-beam side faces the beam. The bracket side faces the trolley bracket. The welsh plug caps the I-beam side. A shield or seal covers the ball gap on the bracket side.
Fig. 3 · Frost product catalog, page 10, Figure 1: a sealed wheel with a welsh plug.
Question 01 · I-beam side
Is there a welsh plug?
Look at the side of the wheel that faces the I-beam.
Fig. 4 · Yes: a smooth, dished steel cap covers the face. No: you can see the balls and the end of the bracket hub.
Easier off the track
The I-beam side is hard to see on a running line. Check a spare trolley or one removed for maintenance.
Question 02 · Bracket side
Is there a shield or seal?
Look at the bracket side, at the ring between the bracket hub and the tread.
Fig. 5 · Yes: a steel ring covers the balls. No: you can see the balls around the bracket hub.
Cross-check
A seal always comes with a welsh plug on the I-beam side. A shield alone does not.
Your configuration
Put the two answers together.
| Shield or seal? No | Shield or seal? Yes | |
|---|---|---|
| Welsh plug? No | Open / openCODE 0 | Shield, no welsh plugCODE 2 |
| Welsh plug? Yes | Welsh plug, no shieldCODE 1 | SealedCODES 3 TO 6 |
Why it matters
Open trolleys must be lubricated in operation by automatic oilers. Fully closed trolleys ship grease packed.
Sealed wheels
Shielded vs sealed: four ways Frost seals a wheel.
| Code | Seal | What it does |
|---|---|---|
| 3 | Triple labyrinth | The conveyor industry standard. Retains lubrication and keeps contaminants out. |
| 4 | Splashproof® | A Frost design that acts as a double triple labyrinth, for severe dirt and liquid. |
| 5 | Splashproof® with wiper | Adds a wiper seal, so the bearing can be relubricated or purged without seal damage. |
| 6 | Contact lip seal | Stays under pressure against the mating surface as it wears. Standard to 275°F continuous, high temperature to 400°F continuous. |
Common questions
Questions we hear a lot.
What is a welsh plug on a trolley wheel?
A welsh plug is a smooth, dished steel cap on the I-beam side of the wheel. It closes off the bearing on that face.
What is the difference between a shielded and a sealed trolley wheel?
A shielded wheel has a shield on the bracket side only (code 2). A sealed wheel has a welsh plug on the I-beam side plus a seal on the bracket side (codes 3 to 6).
How many balls are in a full ball trolley wheel?
A full ball wheel has 11 balls in the 3 in size and 13 in the 4 and 6 in sizes. Retainer wheels have 7 balls (3 in) or 8 balls (4 and 6 in).
Which trolley wheels need lubrication in operation?
Open trolleys must be lubricated in operation by automatic oilers. Fully closed trolleys ship grease packed.
Talk with our team
Send us two photos. We’ll identify the wheel.
Send a photo of the I-beam side, a photo of the bracket side, the part number if you have it, and your application.
616.453.7781 · frost.sales@frostinc.com
Want a copy for the shop floor? Download the printable guide (PDF). Replacing trolleys too? See how to measure trolley drop.
Related Guides
Guide
How to Measure Trolley Drop
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