Custom Quartz Gauge, Sight & Vacuum Tubes

Quartz Glass builds quartz sight and gauge tubes for liquid-level viewing and vacuum-line inspection, and vacuum tube sections with the end connections needed to seal into your system.

Main tube dimensions, end connection position, overall length, and weld distortion are one assembly chain, not independent specs — a flange or joint position shifts if the overall length changes, so confirm all of them together.

Available Quartz Gauge, Sight & Vacuum Tubes Configurations

• Liquid-level gauge tubes — a clear viewing section mounted between two connections to show fluid level in a tank or vessel
• Sight tubes — a clear section built into a vacuum or process line purely for visual inspection, not for level reading
• Vacuum line sections — plain tubing with end connections sized to seal into an existing vacuum system

End connections are usually a ground flange for an O-ring seal, a ground joint, or an adapter that transitions from quartz to a metal fitting. Tell us which interface your equipment uses — the connection has to match what it's sealing against, not just the tube dimensions.

Replacing an existing gauge or sight tube? Send the equipment model and, if you have it, the old part or its drawing. At minimum we need OD/ID and wall, visible length, overall length, and the end connection type — a worn part is often enough for us to work from directly.

Quartz Gauge, Sight & Vacuum Tubes Factory Standard & Assembly Limit

The table above covers what's repeatable without added lead time. Tighter overall-length tolerance or a non-standard flange face usually pushes into custom territory — flag either on the RFQ rather than assuming the standard figures cover it.

Fabrication is cutting to length, end treatment, and welding the flange or joint onto the tube; branch ports, if needed, are welded in before the end connections. Before shipment we check the visible zone, wall thickness, port dimensions if present, coaxiality, sealing-surface condition, weld seams, and appearance.

10–80 mmTypical Gauge OD

1–5 mmTypical Gauge Wall

3,000 mmGeneral Length Envelope

±0.15–2.00 mm by ODDrawn Stock OD Tolerance

≥99.99%Natural SiO₂ · synthetic ≥99.999%

≤1100 °CContinuous Service Guideline

Specifications

Gauge, Sight & Vacuum Tube Specifications

Parameter	Reference Capability / Requirement
OD / ID	Defined with the mating gland, seal and required wall section
Wall Thickness	1–5 mm typical gauge series; other transparent stock wall sections by drawing
Visible Length	Clear observation zone dimensioned separately from the overall length
Overall Length	5–3,000 mm general fabrication envelope
End Connection	Plain / threaded adapter / ground joint / quartz flange / metal-gland interface
Pressure / Vacuum Duty	Not assigned as a universal rating; reviewed from OD, wall, temperature and connection design
End Finish	Ground square / fire-polished / machined sealing diameter
Material	High-purity transparent fused quartz

Standard Series

Gauge & Sight-Tube Configuration Series

Configuration	Controlled Dimensions	Interface	Typical Use
Plain sight tube	OD / ID / visible length	Compression gland	Liquid and gas observation
Boiler gauge tube	OD / wall / seal length	Equipment-specific gland	Water-level indication
Flanged sight tube	Face-to-face / seal OD	Quartz flange	Process vessels and reactors
Ground-end tube	Ground OD / end flatness	O-ring or gasket	Vacuum and high-purity systems
Ported vacuum tube	Port position / branch OD	Welded quartz port	Pumping and instrumentation
Closed-end sight tube	Visible depth / end form	Single-ended assembly	Probe and level-monitoring housings

Configurations

Gauge, Sight & Vacuum Tube Configurations

Plain Gauge TubeTransparent tube for level and process observation

Boiler Water-Level TubeSeal-length and guard geometry matched to the gauge assembly

Vacuum Sight TubeGround mating sections for evacuated equipment

Flanged View TubeQuartz flange or face-to-face process interface

Ground Joint TubeTapered or cylindrical ground connection

Ported Vacuum SectionSide connection for pumping, sensing or gas handling

Closed-End Indicator TubeSingle-ended transparent probe or level housing

Custom Joined AssemblyQuartz tube welded to branches, adapters or chambers

Material Selection

Transparent Quartz Grades for Observation & Vacuum Use

Electric-Fused QuartzGrade-specific UV cut-offOH 5–150 ppm; heat treatment can adjust OH. General-purpose continuously drawn stock. Confirm UV boundary by grade datasheet.

Flame-Fused Quartz · JGS2220–2500 nmOH 120–260 ppm; UV-visible optical components.

Synthetic Fused Silica · JGS1185–2500 nmSiO₂ ≥99.999%; OH ≈1000 ppm. Selected for deep-UV transmission; strong OH absorption near 2730 nm.

Vacuum-Fused / Low-OH · JGS3Grade-specific UV–IR / 260–3500 nmVacuum-fused OH <3 ppm; JGS3-class OH ≤10 ppm. Use the lot certificate and transmission curve at the working thickness.

OH content varies by grade and batch; the lot certificate is authoritative. Compare material routes and typical transmission data.

Fabrication

Cutting, Grinding, Joining & Leak-Interface Preparation

• Precision CuttingOverall and visible lengths prepared from a common datum
• End GrindingSquare faces for glands, gaskets and axial seating
• OD / ID GrindingControlled sealing diameters for vacuum and pressure interfaces
• Fire PolishingSmooth non-sealing ends for safe handling and optical clarity
• Quartz WeldingPorts, flanges and adapters joined to the sight tube
• Final InspectionOD, wall, visible length, end geometry and interface features checked after processing

Applications

Gauge, Sight & Vacuum Applications

Boiler Water-Level GaugesTransparent tubes matched to gland and guard geometry

High-Temperature ReactorsObservation paths for thermal and corrosive processes

Vacuum EquipmentGround and flanged tubes for evacuated chambers and pumping lines

Process Sight GlassesVisible sections for fluid, gas and phase monitoring

Laboratory ApparatusQuartz view tubes for distillation, reaction and analysis

Semiconductor SystemsHigh-purity observation and vacuum components for process equipment

FAQ

Frequently Asked Questions

What pressure rating does a quartz sight tube have?

There is no universal rating for the product family. Allowable duty depends on OD, wall, unsupported length, temperature, surface condition and the end connection; the equipment designer should validate the final assembly.

What dimensions are needed for a replacement gauge tube?

Provide OD, ID or wall, overall length, visible length, seal length, end finish and the gland, flange or joint geometry.

Can the ends be ground for vacuum seals?

Yes. OD/ID and end faces can be ground for O-rings, gaskets, glands or custom vacuum interfaces.

Can side ports or quartz flanges be added?

Yes. Port and flange datums should be included on the drawing so the finished assembly can be inspected after welding.

Product Examples

Product Forms and Finished Components

Need a gauge, sight or vacuum quartz tube?Enter OD, ID, wall and length, then send the visible zone and end-interface drawing for review.

Open the Tube Configurator

Engineering Data

Grade-Qualified Material Purity

Electric-fused / flame-fused quartz: SiO₂ ≥99.99%; synthetic JGS1-grade fused silica: ≥99.999%. Grade and lot certificate govern supplied material.

Engineering Data

Service Temperature

Transparent quartz: continuous use ≤1100 °C; short-term excursions ≤1200 °C. Opaque / milky quartz: continuous use ≤1000 °C. Load, atmosphere, support span and thermal cycling determine the application limit.

Engineering Data

Transparent Stock Tolerances · Continuous Drawing

OD band (mm)	OD tolerance (mm)	Wall tolerance (mm)	Formed length tolerance (mm)	Max wall variation (mm)	Max ovality (mm)	Max bow
<10	±0.15	±0.10	±1.0	0.10	0.15	2‰
10–15	±0.20	±0.10	±1.0	0.12	0.20	2‰
15–20	±0.30	±0.15	±1.0	0.13	0.25	2‰
20–30	±0.40	±0.15	±1.0	0.15	0.30	2‰
30–40	±0.60	±0.15	±1.0	0.25	0.40	2‰
40–50	±0.80	±0.20	±1.0	0.30	0.50	2‰
50–65	±1.00	±0.20	±2.0	0.40	0.60	2.5‰
65–85	±1.20	±0.30	±2.0	0.50	0.80	2.5‰
85–100	±1.50	±0.30	±2.0	0.60	1.00	2.5‰
100–200	±1.50	±0.50	±2.0	0.65	1.10	3‰
200–350	±2.00	±0.60	±2.0	0.70	1.20	3‰

Formed stock and finished cut parts use different length tolerances. Continuously drawn transparent stock: ±1.0 mm at OD ≤50 mm / ±2.0 mm at OD >50 mm. Rotationally fused opaque stock: ±5.0 mm. Cold-cut finished parts: standard ±0.5 mm; precision ±0.1 mm only where agreed for the finished geometry.