The Castair 4BG is the OEM steel belt guard for the Castair C2 air compressor. Dimensions are 40 x 20 x 5 inches — the same footprint as the 4BG7 but with a 5-inch depth that matches the C2's belt and pulley stack, which is narrower than the C3 or G30. If your C2's factory guard is damaged, missing, or failed an inspection, the 4BG is the direct OEM replacement. It bolts on to the existing C2 frame mounting points without modification.
Safety and Compliance
- OSHA 29 CFR 1910.219 compliance: Federal law requires guarding on all exposed belt and pulley drives during operation. A missing or damaged belt guard on the C2 is a citable violation — and more importantly, a genuine injury risk to anyone working near the compressor.
- OEM fit vs. aftermarket: Generic belt guards are sized to fit a range of machines. The 4BG is sized to fit the C2. The 5-inch depth is specific to the C2 drive geometry — a guard with a different depth will leave the pulley face partially or fully exposed, which is not compliant and not safe.
- Insurance documentation: When a shop uses OEM replacement parts, it demonstrates that the equipment is being maintained to manufacturer specifications. An aftermarket guard of unknown origin and fit does not carry the same documentation value if a belt-related incident ever goes to a liability review.
- Reciprocating compressor belt hazards: V-belt drives on reciprocating compressors are high-RPM, high-tension systems. They will catch fabric, hair, or fingers without warning. The 4BG eliminates access to the belt and pulleys entirely when installed correctly.
Construction and Specifications
- Material: Steel frame — welded and formed construction. Steel is the correct material for a belt guard in a working shop environment. It handles vibration, impacts, and temperature cycling that would crack plastic or composite guards over time.
- Dimensions: 40 inches wide x 20 inches tall x 5 inches deep. The 5-inch depth is the critical measurement that distinguishes the 4BG from the 4BG7 (7-inch depth). Do not substitute based on width and height alone.
- Finish: Protective coating to resist the shop environment — oil mist, humidity, and cleaning agents.
- Mounting: OEM bolt pattern for the C2 frame. Installs to existing mounting points.
Model Compatibility
- Castair C2: The 4BG is the correct and only OEM belt guard for the C2. It is designed to the C2 belt drive dimensions and mounts to the C2 frame.
- Not compatible with C1, D3, G11: Those models use the 3BG (32x20x5). The width difference — 32 inches vs 40 inches — means the 4BG will not mount correctly on a C1, D3, or G11 frame.
- Not compatible with C3 or G30: Those models need the 4BG7 (40x20x7). Same width and height as the 4BG, but the 7-inch depth is required for the wider belt stack on the C3 and G30. The 4BG's 5-inch depth will leave the pulley face exposed on those models.
- Model identification: Find your model number on the compressor nameplate — typically on the crankcase near the oil fill port. If the nameplate is damaged or missing, the frame dimensions and pump configuration can help identify the model. Call us at 866-217-0063 if you need help confirming compatibility.
Installation
- Lock out / tag out before starting: The C2 must be fully de-energized before removing or installing the belt guard. Disconnect power at the breaker, lock it out, and tag it. Do not rely on the pressure switch — lock out the electrical source.
- Bolt-on replacement: The 4BG attaches to the C2 frame mounting points. Remove the fasteners from the old guard, position the 4BG, and install. No drilling or modification is required on the correct model.
- While the guard is off: Inspect the belt for wear (cracking, glazing, fraying, stretching), check pulley alignment, and look for any signs of bearing issues (noise, wobble, heat discoloration). If the belt is marginal, replace it now — the compressor is already locked out and the drive is accessible.
- Verify full coverage before restart: Once the 4BG is installed and fasteners are secure, confirm the guard fully covers the belt and both pulleys with no gaps at the edges. Then restore power.
- Part number matters: The 4BG, 4BG7, and 3BG look similar at a glance. Confirm you have the right SKU for your C2 before ordering. If the guard does not align with the frame mounting holes, stop — call 866-217-0063 before attempting any modification.
Why Buy From Air Compressor Factory Direct?
- Genuine Castair OEM parts: The 4BG is the factory guard for the C2 — the same part Castair installs at the factory. Not an approximation, not a generic steel fabrication.
- Specialist since 2016: Air compressor parts and service is our specialty. We know the Castair model lineup and can confirm which guard matches your compressor before you order.
- Free shipping: No handling or freight surcharges on standard orders.
- Free technical support: Call 866-217-0063. We can verify compatibility from your model and serial number and confirm you are ordering the correct guard for your C2.
- Full manufacturer warranty: Genuine Castair OEM parts carry full manufacturer warranty coverage. Third-party substitutes typically do not.
Call 866-217-0063 for quick answers and help!
