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.
Technical Specifications
| Body Material | Plastic, Brass, Aluminum alloy, Stainless steel |
|---|---|
| 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 with standard glass and seal |
| High-Temperature Option | Up to 180°C with safety glass, or up to 280°C for selected Tempax/borosilicate designs |
| Typical Working Pressure | Up to 4 bar for standard models |
| Reinforced Models | Up to 10 bar, subject to size, glass thickness, seal, and body design |
| Seal Material | NBR, FKM, PTFE, or copper |
- Standard and custom specifications are available.
- Drawing and sample-based customization is supported.
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
Standard Sizes
BSP Thread Sizes
The following consolidated table is suitable for your website. It removes the original supplier’s product codes and uses clearer dimension names.
| 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.
CUSTOM MANUFACTURING
Need a Custom Size or Specification?
Send your drawing, sample, dimensions, material requirements, operating temperature, pressure and process medium. We will review the application and confirm the suitable product specification before production.
Standard products and OEM/ODM solutions available.
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