Product Overview
Borosilicate tubular sight glass (also known as tubular gage glass, sight glass tube, or tubular sight gauge) is a precisely cut cylinder. It lets you see liquids and gases directly. You can find it in boilers, reactors, pipelines, and industrial vessels. We make our sight tubes from high-grade, extra-hard borosilicate. They offer clear optics and strong resistance to thermal shock and common chemicals. This makes them ideal for tough industrial use.
Key Selling Points
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Material & Optical Performance: Extra-hard borosilicate glass lets over 90% of visible light through. This ensures clear viewing with low distortion.
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Thermal & Chemical Resistance: Stays stable at working temperatures up to 450 °C, based on how it’s used. It resists common acids, alkalis, and solvents.
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Standard borosilicate sight tubes have a pressure rating of up to 20 bar (2.0 MPa) in typical mounting setups. You can reach higher ratings with thicker walls and reinforced housings. Always verify these limits for each application.
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Surface & Cut Quality: Ends are precision-cut with chamfered or ground faces to meet customer specs. An optional polished finish reduces light scattering.
- Customization & Turnkey Supply:
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Cut-to-length
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Diameter
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Wall thickness
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End prep (flat, beveled)
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Batch pressure testing is available.
The quote provides MOQ and lead time.
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Materials & Manufacturing
We source extra-hard borosilicate (industrial grade, boric oxide ≥ 5%). Then, we process sight tubes. This includes controlled cutting, annealing, and finishing steps to reduce internal stress. Our in-house QA performs:
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Visual inspection for inclusions and bubbles.
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Dimensional tolerance checks (OD/ID/length);
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Hydrostatic or pneumatic pressure tests on sample batches.
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Thermal shock testing protocol (sample-based).
Experience & Expertise: Our production team follows clear SOPs for cutting, annealing, and surface finishing. This ensures consistent optical and mechanical performance. You can request third-party test reports and material certificates. They help with procurement compliance and EHS reviews.
Typical Applications
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Boiler water level sight windows and boiler auxiliary equipment.
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Chemical reactor sight ports and process vessel monitoring.
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Pipeline flow visual inspection (sampling & bypass assemblies).
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Equipment that requires clear visual confirmation for petrochemical and refining processes.
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Pharmaceutical pilot plants and lab process equipment must borosilicate chemical resistance.
Technical Specifications
Notes: Values are typical industry ranges. Final ratings depend on tube OD, wall thickness, mounting method and operating conditions. Request our specific application review for safety-critical installations.
| Parameter | Borosilicate Tubular Sight Glass |
|---|---|
| Material | Extra-hard borosilicate glass (boric oxide ≥ 5%) |
| Optical transmissivity (visible) | ≥ 90% |
| Typical OD range | 12 mm — 100 mm |
| Typical ID range | OD minus wall thickness (see wall thickness) |
| Typical wall thickness | 1.5 mm — 8.0 mm (dependent on OD & pressure rating) |
| Standard lengths (cut-to-length) | 50 mm — 1200 mm (custom lengths available) |
| Working temperature (typical) | up to 450 °C (application dependent) |
| Thermal shock resistance | ≥ 160 °C (typical) |
| Bending strength (typical) | ≈ 60–80 MPa (material dependent) |
| Working pressure (standard mounting) | up to 20 bar (2.0 MPa); thicker tubes / reinforced housings increase rating |
| Surface finish | Cut & chamfered / end-polished / side-polished (option) |
| Inspection & testing | Visual, dimensional, hydrostatic/pneumatic sampling, thermal-shock sampling |
| Certifications (available) | Material certificates on request; test reports available on application |
Ordering & Safety Notes
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Ordering information should include: OD, ID or wall thickness, required length, end preparation (bevel/flat), required working pressure, operating temperature, and mounting type.
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For pressure-retaining service, specify the fitting/housing type and request a joint design check. Do not assume tube pressure rating without confirming the full assembly and gasket/holder configuration.
Standard Sizes / Common SKU Table
Common diameters and lengths frequently stocked. All sizes can be manufactured to order. Click the download link to get the full printable size matrix (CSV / PDF).
Common Sizes
| SKU | OD (mm) | Wall (mm) | ID (mm) | Standard Lengths (mm) |
|---|---|---|---|---|
| BT-12-2.0 | 12 | 2.0 | 8.0 | 50, 100, 150, 200 |
| BT-20-2.5 | 20 | 2.5 | 15.0 | 100, 200, 300 |
| BT-25-3.0 | 25 | 3.0 | 19.0 | 100, 200, 300, 500 |
| BT-38-3.5 | 38 | 3.5 | 31.0 | 100, 300, 500 |
| BT-50-5.0 | 50 | 5.0 | 40.0 | 200, 500, 1000 |
| BT-76-6.0 | 76 | 6.0 | 64.0 | 300, 600, 1200 |
| BT-100-8.0 | 100 | 8.0 | 84.0 | 500, 1000, 1200 |
Specification Sheet & Test Reports
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Product spec sheet (PDF): detailed mechanical properties, recommended mounting notes and handling instructions.
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Test certificate & batch trace: provided with orders on request.
Installation & Handling Guidance
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Always inspect for chips or cracks before installation.
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Use compatible mounting housings that spread loads evenly. Avoid putting point loads on glass ends.
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For pressure service, use the right gasket type. Also, check clamp torque following the housing manufacturer’s instructions.
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Avoid direct impact. If polishing or finishing is needed, use proper protective packaging.
Customization & Manufacturing Lead Times
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Customization: diameter, wall thickness, length, end finish (flat, beveled), polishing, and batch testing.
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Lead time (typical):
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Stock items: 3–7 business days.
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Custom cuts and testing: 7–21 business days, based on order size and finish.
(Provide final ETA in formal quotation.)
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Experience, expertise, authority, trust.
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Experience: Production uses set processes for cutting, annealing, and visual/pressure inspection. This helps reduce stress and maintain consistent optical quality.
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Expertise: Our engineering team reviews applications. If the installation is pressure-critical, we conduct engineering checks and sample testing protocols.
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Authoritativeness: You can request batch material certificates and sample test reports. These support procurement, QA, and regulatory records.
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Trustworthiness: All sight tubes come in protective, labeled cartons. You can select sample inspection and third-party testing options. These include hydrostatic and thermal shock tests, which are available before full production.
FAQ
Q — Can you supply Pyrex®-branded tubes?
A — We provide industrial borosilicate with similar properties. If you need a specific brand, please mention it in your RFQ, and we’ll let you know about availability and cost.
Q — What is the maximum safe pressure?
A — Safe working pressure depends on OD, wall thickness, and mounting. Standard unreinforced borosilicate tubes can typically handle up to 20 bar (2.0 MPa) in regular housings. For higher pressures, please ask for an engineering review.
Q — Do you offer pre-assembly into sight gauge housings?
A — Yes — we can provide glass and compatible holders. We can also suggest housings. Just specify the flange type and pipe interface in your RFQ.
How to Order / Request a Quotation
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Prepare the following:
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OD
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Wall thickness (or ID)
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Required length
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End finish
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Expected operating temperature and pressure
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Quantity
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Submit RFQ via email or contact form with photos or sketches, if available.
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We’ll provide:
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a commercial quote
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recommended mounting notes
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estimated lead time
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available test certificates.
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Samples are available on request (sample fee may apply, refundable on bulk order).
Contact & Sales
Aohong Group — Sight Glass Division
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Email: info@hsahglass.com
WhatsApp: 8618632879676
Website: www.hsahglass.com
