Borosilicate, Quartz & Aluminosilicate glass tubes | Standard wall & Heavy wall options. Tubular sight glass provides a simple, continuous visual indication of liquid level, flow, and phase separation in atmospheric and pressurized systems. Material selection and proper wall thickness directly impact pressure rating, thermal endurance, and safety margin.
Tubular sight glass (glass tube level indicator) is a cylindrical transparent component used for quick, reliable visual monitoring of liquid levels in industrial tanks, chemical reactors, oil reservoirs, and water treatment systems. Unlike flat glass gauges, tubular designs offer 360° visibility and simple installation. The two most critical specification parameters are glass material (borosilicate, quartz, aluminosilicate) and wall thickness (standard or heavy wall). Correct pairing of material and wall thickness ensures pressure containment, resistance to thermal shock, and extended service life. This guide helps procurement and engineering teams select the optimal tubular sight glass for their operating environment.
Tubular sight glass consists of a transparent glass cylinder mounted between two end fittings (metal or plastic) with protective guards. It directly reveals liquid level, color, clarity, and movement inside a vessel. Common configurations include single-tube level indicators, by-pass level gauges, and sight flow indicators. Tubular design offers cost-effective level monitoring for pressures up to medium range, depending on glass diameter, material, and wall thickness. Buyers should specify outer diameter (OD), inner diameter (ID), length, material family, and wall thickness class to ensure safe operation.
Product Alias: glass tube level gauge, sight tube, water level tube, tubular level indicator, and transparent tube sight glass..
Standard wall (2–3mm) – suitable for low pressure (up to 6 bar) and temperatures to 200°C. Heavy wall (4–6mm) – recommended for pressures up to 15 bar and moderate mechanical stress. Excellent chemical resistance to most acids (except HF) and alkalis. Best value for general purpose water, oil, and mild chemical service.
Standard wall – withstands extreme temperatures up to 1000°C and thermal shock. Heavy wall quartz – provides higher mechanical strength while maintaining exceptional optical clarity. Perfect for high-temperature furnaces, solar thermal systems, and corrosive high-purity processes where borosilicate fails.
Heavy wall recommended – superior mechanical toughness (3-4x stronger than borosilicate). Standard wall also available for moderate vibration. Ideal for mobile equipment, compressor level gauges, and applications with pressure surges or frequent thermal cycling. Temperature range up to 450°C.
Thicker walls exponentially increase pressure rating but reduce thermal shock resilience slightly. For high pressure + high temperature, quartz heavy wall provides optimum safety. For standard industrial needs, borosilicate heavy wall offers proven reliability. Our engineering team calculates safe working pressure per DIN 7080 / ASTM E438.
Recommendation: Borosilicate heavy wall (4mm) – resistant to mild acids/solvents, moderate pressure 8-10 bar. Standard wall for open-top vessels.
Recommendation: Quartz tubing, standard or heavy wall based on pressure. Excellent thermal stability, no clouding at elevated temperatures.
Recommendation: Aluminosilicate heavy wall – withstands vibration, pressure spikes, and oil mist. Long service life without cracking.
Recommendation: Borosilicate heavy wall with protective guard – reliable for hot water level up to 200°C / 10 bar.
Recommendation: Quartz standard wall – high clarity, autoclavable, thermal shock resistance for frequent cleaning cycles.
Recommendation: Aluminosilicate standard/heavy wall – corrosion resistant, mechanical robustness against ship vibration and motion.
Below 200°C and ≤10 bar → borosilicate. Above 300°C or high thermal shock → quartz. Heavy vibration or frequent pressure cycles → aluminosilicate.
Standard wall (≤6 bar, low risk). Heavy wall (≥10 bar, safety critical). Our team provides burst pressure calculation.
Provide OD, ID, length, thread or flange connection type, and optional protective guard material (SS304/316).
Challenge: A specialty chemical plant needed to monitor level in a methyl ethyl ketone (MEK) tank at 95°C, 6 bar. Standard glass tubes showed surface etching after 4 months.
Solution: Borosilicate heavy wall tubing (5mm wall thickness) with enhanced chemical resistance, plus PTFE end seals.
Result: 18+ months service life without visible corrosion, reduced maintenance downtime by 60%.
Challenge: A plastics molding plant used a hot oil heater with a level tube that failed due to thermal stress after frequent startup/shutdown.
Solution: Quartz glass tubing (standard wall, but high-purity fused silica) capable of ΔT 1000°C.
Result: Zero thermal shock failures over 2 years; operator gained reliable level visibility even under rapid temperature changes.
Challenge: A mobile mining equipment hydraulic reservoir experienced frequent glass tube breakage due to vibration and pressure spikes (standard borosilicate wall).
Solution: Aluminosilicate heavy wall tubing (6mm wall thickness) with reinforced stainless steel guard.
Result: Breakage eliminated, mean time between failures increased from 3 months to over 24 months.
Challenge: Need clear, non-leaching level indication for WFI (water for injection) without contamination.
Solution: Borosilicate standard wall tube, smooth bore, polished ends. FDA-compliant.
Result: Meets USP Class VI requirements; simple visual inspection without electronic sensors.
We provide free technical datasheets with maximum working pressure (MWP) for each material & wall thickness combination. Safety factors comply with DIN 7080/ISO 3587.
| Material | Standard Wall Pressure* (6 bar typical) | Heavy Wall Pressure* (≤15 bar typical) | Max Temp (°C) | Thermal Shock ΔT | Mechanical Toughness |
|---|---|---|---|---|---|
| Borosilicate | Up to 6 bar | 8–15 bar (depending on OD/ID) | 280°C | ~150°C | Good |
| Quartz | Up to 10 bar (more brittle, but high temp) | 12–20 bar (large safety margin needed) | 1000°C | ~1100°C | Moderate (brittle) |
| Aluminosilicate | Up to 8 bar | 12–25 bar (strongest) | 450°C | ~250°C | Very high |
*Pressure ratings are indicative for 25mm OD tube; actual ratings depend on diameter and wall thickness. Our engineering team validates per application.
High-quality drawn or molded glass tubing with exact ID/OD tolerances, fire-polished ends, and consistent wall concentricity. No distortion, excellent clarity.
Borosilicate (DIN 7080), Quartz (fused silica), Aluminosilicate (technical glass). Stock and custom lengths from 100mm to 2000mm.
We assist with pressure calculations, gasket recommendations, and protective guard design. Fast turnaround for OEM, distributor, and EPC projects.
| Standard / Certification | Applicability | Buyer Note |
|---|---|---|
| DIN 7080 / 7082 | Tubular sight glass dimensions and test methods | European standard for level gauge tubes |
| ISO 3587 | Glass tubes for level gauges – general requirements | International interchangeability |
| ASTM E438 | Borosilicate glass classification | Used for material specification |
| HS Code (typical) | 7020.00 / 7017.10 | Laboratory/hygienic or industrial glassware; verify with customs broker |
Standard wall offers lower pressure rating (typically ≤6 bar) and lighter weight, suitable for atmospheric or low-pressure tanks. Heavy wall (≥4mm thickness) significantly increases pressure rating, mechanical strength, and safety margin for pressurized vessels or vibration-prone environments.
Yes, for low-pressure steam (up to 6 bar, 160°C) with proper safety guards. For higher pressure or superheated steam, consider aluminosilicate or quartz heavy wall.
Depends on deposit. Mild acid (acetic) removes mineral scale; solvents for oil residues. Avoid mechanical abrasives. Quartz can be cleaned with high-temperature firing. Borosilicate and aluminosilicate can be chemically cleaned per compatibility.
Please provide: material (borosilicate/quartz/aluminosilicate), desired outer diameter (OD) and inner diameter (ID) or wall thickness, length, max operating temperature & pressure, media type, and quantity.
Yes, we provide custom glass finishing: rounded or polished ends, grooved ends for specific level gauge fittings. Please share your assembly drawing.
Aluminosilicate heavy wall (≥5mm) provides superior impact and fatigue resistance, significantly reducing risk of fracture in compressors or vehicle-mounted tanks.
Share your operating conditions, required material, diameter and wall thickness. Our team provides expert selection and fast global delivery.
