The Castair 4BG7 is the OEM steel belt guard for Castair C3 and G30 air compressors. At 40 x 20 x 7 inches, this is the largest of the Castair belt guard family — the 7-inch depth reflects the wider belt and pulley stack found on the C3 and G30 models, which are heavier-duty units than the C1/D3/G11 family. If you are running a C3 or G30 and the factory guard needs replacement, the 4BG7 is the correct part. Do not attempt to substitute the 3BG or 4BG — the depth dimension is not interchangeable.
Safety and Compliance
- OSHA 29 CFR 1910.219: All belt and pulley drives must be guarded during operation. The 4BG7 is the factory solution for the C3 and G30 — it covers the full belt run and pulley faces in compliance with federal rotating machinery guarding requirements.
- Why depth matters: The C3 and G30 use a wider drive assembly than smaller Castair models. A guard with insufficient depth — such as the 5-inch 3BG or 4BG — will not fully cover the pulley face. Partial coverage is a compliance failure, not a compliant installation. The 4BG7's 7-inch depth is engineered for the C3/G30 drive geometry.
- Insurance and liability: Operating heavy-duty shop equipment without correct guarding creates liability exposure. An OEM part number on your maintenance records demonstrates due diligence. A modified or ill-fitting aftermarket guard does not.
- High-RPM hazard: The C3 and G30 are higher-output compressors. The belt drives on these units move faster and carry more load than smaller reciprocating units. The exposed belt hazard is proportionally greater — the 4BG7 eliminates it when properly installed.
Construction and Specifications
- Frame material: Steel construction — welded and formed to match the C3 and G30 frame geometry. Steel resists the shop environment: oil mist, vibration, impact from carts and tooling.
- Dimensions: 40 inches wide x 20 inches tall x 7 inches deep. The 7-inch depth is the key differentiator from the 4BG (5-inch depth). Do not order based on width and height alone.
- Protective finish: Corrosion-resistant coating suitable for a working compressor bay environment.
- OEM bolt pattern: Mounts directly to C3 and G30 frame mounting points. No modification required on the correct model.
- Weight and durability: Steel construction at this size has real weight — the 4BG7 stays put under vibration and does not rattle loose over time the way lightweight aftermarket guards can.
Model Compatibility
- Castair C3: The 4BG7 is the correct belt guard for the C3. The C3 is a larger reciprocating compressor than the C1 or C2, and the wider belt drive is why the 7-inch depth is required.
- Castair G30: The G30 shares the same belt guard mounting requirements as the C3. Confirm your G30 is the belt-drive configuration — direct-drive variants do not use this guard.
- Not compatible with C1, C2, D3, G11: Those models use the 3BG (32x20x5) or 4BG (40x20x5). The depth difference is real and significant.
- Identifying your model: The model number is on the compressor nameplate, typically on the crankcase or tank. If the nameplate is worn, you can also identify the model from the original purchase documentation or the compressor's pump specification tag.
- When in doubt, call: 866-217-0063. Give us the model number and we will confirm which guard you need before you order.
Installation
- Lock out / tag out: The C3 and G30 are high-output units. De-energize, lock out, and tag out before removing or installing the belt guard. This is non-negotiable.
- Direct bolt-on: The 4BG7 mounts to the existing frame holes on the C3 and G30. Remove old guard hardware, position the 4BG7, reinstall hardware. No drilling or modification required if you have the correct model.
- Inspect drive components while the guard is off: With the guard removed and the unit locked out, inspect the V-belt condition (cracking, glazing, fraying), pulley alignment, and bearing condition. The cost to replace a belt during a scheduled guard swap is minimal compared to an emergency service call.
- Confirm guard seating before restart: The 4BG7 at 40x20x7 is a substantial component. Confirm all fasteners are secure and the guard is fully seated before restoring power.
- If the bolt pattern does not match: Stop. Do not drill new holes. Call 866-217-0063 — you may have the wrong part number for your specific C3 or G30 variant.
Why Buy From Air Compressor Factory Direct?
- Genuine OEM parts: The 4BG7 we ship is the factory Castair guard, not a generic steel fabrication that approximates the dimensions. OEM fit, OEM finish, OEM mounting pattern.
- Specialist since 2016: We focus on air compressor parts. We know the Castair lineup, including which guard goes on which model and why the depth dimensions matter.
- Free shipping: Standard orders ship free. No freight markup on heavy steel parts.
- Free technical support: Call 866-217-0063. If you are unsure whether your C3 or G30 variant takes the 4BG7 or a different configuration, we can verify from the model and serial number.
- Full manufacturer warranty: Genuine Castair parts carry manufacturer warranty. Aftermarket substitutes do not.
Call 866-217-0063 for quick answers and help!
