Product
Threaded Oil Level Sight Glasses
Threaded oil level sight glasses provide quick, direct observation of oil level and condition in gearboxes, reservoirs, pumps, compressors, and hydraulic equipment.
Specifications
| Product Type | Oil Level Sight Glass |
|---|---|
| Body Material | Brass, aluminum alloy, stainless steel or Plastic |
| Window Material | Float glass, tempered glass, or borosilicate glass |
| Thread Options | BSP (G), NPT, or metric |
| Seal Options | NBR, FKM, PTFE, or copper gasket |
- Clear, direct oil-level inspection without opening the equipment.
- Standard and custom specifications are available.
- BSP, NPT, and metric thread options are available.
Oil Level Indicator
Product Description
Threaded Oil Level Sight Glasses, also known as oil sight glass plugs, bull’s-eye oil level indicators, or threaded sight windows, provide a simple and reliable way to observe the oil level inside industrial equipment.
The sight glass is installed directly into a threaded port on a gearbox, oil reservoir, hydraulic tank, pump, compressor, bearing housing, or lubrication system. When correctly positioned, the visible oil line allows operators to check whether the lubricant is at the required level without opening the equipment or interrupting operation.
The transparent window also helps identify changes in oil condition, including discoloration, foam, water contamination, or suspended particles. This makes the product useful for routine inspection and preventive maintenance.
The metal body provides mechanical strength, while the glass window offers good transparency and scratch resistance. Depending on the application, the unit can be supplied with brass, aluminum, carbon-steel, or stainless-steel bodies. Window options include float glass, tempered safety glass, and heat-resistant borosilicate glass.
BSP, NPT, and metric threads are available for compatibility with different equipment standards. Optional reflectors can be added behind the window to improve the visibility of clear or light-colored oil.
Technical Specifications
| Parameter | Specification |
| Body Material | Brass, aluminum alloy, stainless steel, Plastic |
| Window Material | Float glass, tempered glass, or borosilicate glass |
| Thread Standard | BSP parallel thread, NPT tapered thread, or metric thread |
| Typical Temperature | Up to 100–120°C (Depends on glass and sealing material) |
| High-Temperature Option | Up to 180°C with safety glass, or up to 280°C for selected Tempax/borosilicate designs （Depends on glass and sealing material） |
| Typical Working Pressure | Up to 4 bar (Depends on size, glass thickness, seal and body design) |
| Reinforced Models | Up to 10 bar, subject to size, glass thickness, seal, and body design |
| Seal Material | NBR, FKM, PTFE, or copper |
| Reflector | Available with or without an internal contrast reflector |
| Installation | Male-threaded connection |
| Suitable Media | Lubricating oil, hydraulic oil, gear oil, and other compatible fluids |
Standard Sizes
BSP Thread Sizes
| Thread Size | Viewing Diameter V | Body/Wrench Size D | Overall Length L |
|---|---|---|---|
| G1/4 | 8 mm | 17 mm | 17–19 mm |
| G3/8 | 8–9 mm | 19–22 mm | 17–18 mm |
| G1/2 | 9–12 mm | 27 mm | 19–20 mm |
| G3/4 | 11–12 mm | 32 mm | 20–23 mm |
| G1 | 10–14 mm | 40 mm | 22–23 mm |
| G1¼ | 12–14 mm | 50 mm | 23–27 mm |
| G1½ | 13–17 mm | 55 mm | 25–26 mm |
| G2 | 17 mm | 70 mm | Approx. 27 mm |
Metric Thread Sizes
| Thread Size | Viewing Diameter V | Body/Wrench Size D | Overall Length L |
|---|---|---|---|
| M14 × 1.5 | 8 mm | 17 mm | 17–19 mm |
| M16 × 1.5 | 9 mm | 22 mm | 18–21 mm |
| M18 × 1.5 | 8–9 mm | 21–22 mm | 18–21 mm |
| M20 × 1.5 | 7.5–10 mm | 24 mm | 19.5–21 mm |
| M22 × 1.5 | 7.5–9 mm | 24–27 mm | 20–21 mm |
| M24 × 1.5 | 11 mm | 30 mm | Approx. 24 mm |
| M24 × 2 | 11 mm | 30 mm | 23–24 mm |
| M30 × 2 | 11 mm | 36 mm | Approx. 23 mm |
| M40 × 1.5 | 10 mm | 42 mm | Approx. 27 mm |
Other metric, BSP, and NPT thread sizes can be manufactured according to drawings or samples.
GET IN TOUCH
KUNYO Industrial Components Co.,Ltd.
Send us your product specifications, dimensions or drawings. Our team will review your requirements and respond within 24 hours.
PHONE
ADDRESS
No. 555 Longxing Road, High-tech Zone, Hengshui City, Hebei Province, China 053000
Inquire About: Threaded Oil Level Sight Glasses
Complete the form below and our team will get back to you within 24 hours.