Castair Belt Guard for C3U & C4U Compressors — 48x32x7.5" Steel Frame (Part# 5BG)
If you run a Castair C3U or C4U industrial compressor, this is the belt guard that fits it. The 5BG is a 48x32x7.5-inch steel frame belt guard, sized specifically for the larger belt-drive arrangements on these heavy-duty two-stage pump models. It is not a universal fit — it is engineered for these pumps and it installs correctly the first time.
Belt guards are not glamorous, but they matter. OSHA machine guarding standards require that rotating components — including belts and pulleys on air compressors — be guarded. Running a belt drive without a guard in a commercial shop is a liability issue and an inspection problem. Beyond compliance, a belt guard protects the belt itself from accidental contact, keeps oil and debris off the drive, and gives you a clean place to hang a warning label or maintenance tag.
The C3U and C4U are Castair's larger industrial pump platforms — slow-RPM, all cast iron, oil-lubricated, built for continuous shop use. The belt and pulley arrangement on these pumps is proportionally large, which is why this guard is the biggest in the Castair lineup at 48 inches long, 32 inches tall, and 7.5 inches deep. The 7.5-inch depth accommodates the belt travel and pulley profile without the guard riding tight against moving parts.
Specifications
- Part Number: 5BG
- Dimensions: 48" x 32" x 7.5"
- Material: Steel frame construction
- Compatible Models: Castair C3U and C4U compressor pumps
- Application: Belt and pulley guard for belt-drive compressor systems
Compatible Castair Belt Guards — Which One Do You Need?
Castair makes five steel frame belt guards, each sized to a specific pump or group of pumps. Do not guess — use the model of your pump to identify the right guard:
- Part# 2BG (24x16x5): A2, A3, A4, and A8 pumps
- Part# 3BG (32x20x5): C1, D3, and G11 pumps
- Part# 4BG (40x20x5): C2 pump
- Part# 4BG7 (40x20x7): C3 and G30 pumps
- Part# 5BG (48x32x7.5): C3U and C4U pumps — this guard
Note the difference between the C3 and C3U: the C3 uses the 4BG7 (40x20x7), while the C3U requires this larger 5BG (48x32x7.5). The U models are configured differently and use a bigger belt drive. Ordering the wrong guard is a common mistake — double-check your pump model plate before ordering.
When You Need to Replace a Belt Guard
- Guard is damaged or bent: A guard that has been hit by shop traffic or a fallen tool will not seat correctly and will vibrate. Replace it rather than bending it back into shape.
- Replacing the belt or pulley: Any time you open the belt drive, the guard comes off. If it is cracked or the mounting points are stripped, replace it while the compressor is already down.
- Compliance inspection upcoming: If your shop is due for an OSHA or insurance inspection and your belt guard is missing or damaged, this is a straightforward fix.
- New compressor build or motor swap: If you are building a C3U or C4U unit from components or swapping a motor, the 5BG is the correct guard for the finished assembly.
Installation Notes
The 5BG mounts to the compressor frame or base plate using the existing guard mounting hardware on the C3U and C4U platforms. Castair uses a consistent bolt pattern across their industrial line, so if you are replacing a damaged guard on an existing machine, the new guard should align to the same holes. If you are installing on a new build or a machine that has never had a guard mounted, contact us at 866-217-0063 and we can confirm the hardware requirements for your specific configuration.
The guard covers both the motor pulley and the pump flywheel — the full belt path from drive to driven. This is the correct coverage for compliance purposes. A guard that only covers one side of the belt run does not meet machine guarding requirements.
Pricing and Availability
The 5BG is a stock part at Air Compressor Factory Direct. At $389.62, it is priced as an OEM Castair replacement component. This is not an aftermarket guard — it is the factory part for these pumps.
Why Buy From Air Compressor Factory Direct?
- Castair specialist: We stock the full Castair accessory line, including all five belt guard sizes, so you get the right part the first time.
- Free shipping on qualifying orders.
- Free technical support: Call 866-217-0063 if you need to confirm fitment on your specific pump model or configuration.
- OEM parts only: We do not substitute aftermarket components for Castair OEM parts.
- Honest guidance: If you're not sure which guard your pump needs, we'll look it up with you — we'd rather you order the right part than have to return the wrong one.
Call 866-217-0063 for quick answers and help!
