Description
Quartz gauge and sight tubes use the clear tube bore itself as the viewing or liquid-level observation area. They are commonly supplied as replacement tubes for an existing gauge or sight-glass assembly, where the tube must match the installed center-to-center length, sealing faces, flange or threaded connection, and the operating condition of the complete assembly.
The main difference from general fused quartz tubing is therefore not the base OD / ID / wall range. It is the interface geometry and verified installed condition. Tube dimensions are selected from the general Quartz Glass Tubes range, while the final service rating must be assigned against the actual fittings, flanges, seals and gauge body used with the tube.
Viewing Area
| Feature |
Design Basis |
| Observation Area |
The full-length clear bore functions as the liquid-level or process viewing area |
| Tube OD |
Selected to fit the gauge body, supports, seals and existing interface |
| Wall Thickness |
Selected together with OD and the verified pressure / temperature condition of the complete assembly |
| Replacement Match |
Existing tube dimensions, sealing length and end geometry can be reproduced from a sample or dimensioned drawing |
Interface
| Interface Type |
Specification |
Notes |
| Flange Connection |
Gauge-body flange interface |
Reference patterns cited for installed systems include JB82-59 and HGJ-51-91, including DN20 convex-face configurations |
| Threaded Connection |
Threaded end or fitting interface |
Used where the existing gauge body is designed around threaded connections |
| Ground Tube Ends |
Both ends ground square |
Provides flat sealing faces for gasket, packing or fitting contact |
| Custom Replacement |
Matched to existing hardware |
End spacing, tube OD and sealing geometry are taken from the installed gauge assembly |
Where a flange standard or equipment drawing is available, the tube and mating geometry should be checked against that exact assembly rather than selected from a generic pressure-tube table.
Gauge Installation
| Center-to-Center Length |
Availability |
Use |
| 300 mm |
Standard measurement length |
Compact vessel and process-gauge installations |
| 500 mm |
Standard measurement length |
General level-gauge replacement |
| 800 mm |
Standard measurement length |
Medium viewing span |
| 1100 mm |
Standard measurement length |
Longer vessel-level measurement |
| 1400 mm |
Standard measurement length |
Extended gauge assemblies |
| 1700 mm |
Standard measurement length |
Long-span level observation |
| 2000 mm |
Standard measurement length |
Large vessel gauge installations |
| Custom |
Matched to installation |
Non-standard vessel spacing or direct replacement of an existing tube |
Operating Condition
Pressure and temperature figures for gauge products must be treated as assembly ratings, not as standalone ratings for a bare fused quartz tube. The allowable condition is determined by the tube dimensions together with the flange or fitting, seal material, compression method, support geometry and equipment design.
| Assembly Parameter |
Reference Values |
How to State It |
| Working Pressure |
1.6 / 2.5 / 4.0 / 6.4 / 10.0 MPa |
Only for a complete gauge assembly verified for the corresponding flange / fitting configuration |
| Operating Temperature |
Reference gauge-system figures cited up to 1450°C |
Do not apply this value to bare tube stock; verify the complete installed assembly and seal system |
| Bare Quartz Tube |
No standalone pressure / temperature rating stated on this page |
Tube stock is supplied by dimensions and material; service rating belongs to the validated assembly |
Rating note: a quartz tube alone must not be represented as a 10.0 MPa or 1450°C-rated pressure component. Those figures can only be used when the exact tube, fitting, flange, seal and gauge-body combination has been verified as a complete assembly.
Replacement Tube Matching
| Input |
What to Confirm |
| Existing Tube |
OD / ID or wall thickness / overall length / usable viewing length |
| Gauge Spacing |
Center-to-center distance between upper and lower connections |
| Interface |
Flanged, threaded, packing-gland or other installed connection |
| Sealing Faces |
Ground-end diameter, flatness requirement and gasket / packing contact area |
| Operating Medium |
Liquid or process fluid in contact with the quartz tube |
| Operating Condition |
Normal and maximum pressure / temperature of the complete gauge assembly |
Tube Selection
| Requirement |
Recommended Route |
| General clear quartz tube without a gauge interface |
Fused Quartz Tubes |
| Replacement liquid-level gauge tube |
Match tube dimensions, center-to-center length and installed sealing interface |
| Flanged sight / gauge tube |
Confirm flange pattern, sealing face and complete-assembly rating |
| Non-standard vessel spacing |
Supply center-to-center length and existing gauge-body dimensions |
| High-pressure / high-temperature assembly |
Rate only after the exact tube + flange / fitting + seal system is defined and verified |
For quotation: provide tube OD, ID or wall thickness, overall length, center-to-center length, end-interface drawing or gauge model, flange / thread details, operating medium, working pressure, working temperature, quantity, and photos or drawings of the existing assembly when the tube is a replacement part.
