What are the standard dimensions for a DIN7081 sight glass?

DIN7081 describes the form commonly used for long, rectangular sight glasses and level-gauge plates. In practice, manufacturers produce a set of industry-preferred sizes that fit most clamp and gasket systems. Below we summarize those commonly produced dimensions, give realistic tolerance ranges, and provide practical guidance so you can measure, order and install DIN7081 sight glasses with confidence.

Typical DIN7081 plate sizes

The table below lists frequently manufactured lengths and the most common width/thickness combinations used for DIN7081 style plates. These are the sizes you will most often find in supplier catalogs or in stock inventories.

Code	Common length (l) mm	Common width (b) mm	Common thickness (t) mm
A	115	30 / 34	17
B	140	30 / 34	17
C	165	30 / 34	17
D	190	30 / 34	17
E	220	30 / 34	17
F	250	30 / 34	17
G	280	30 / 34	17
H	320	30 / 34	17
I	340	30 / 34	17
J	370	30 / 34	17
K	400	30 / 34	17

Note: supplier catalogs sometimes label these with internal product codes; the table above summarizes the most common metric sizes you will encounter. If your application demands heavier duty, manufacturers can offer thicker plates or custom lengths.

---

Typical manufacturing tolerances

In real-world procurement you should expect tolerances rather than absolute exactness. Typical tolerance ranges used by many producers are:

• Length (l): commonly around +0 / −1.0 to −1.5 mm

• Width (b): for 34 mm nominal, expect about +0.2 / −0.6 to −0.8 mm

• Thickness (t): for 17 mm nominal, expect about +0 / −0.8 to −1.0 mm

• Flatness / parallelism: small values (hundredths of a millimetre), demanded for higher-pressure use

These ranges are practical rules of thumb to help you compare quotes and check incoming goods. Always request the exact tolerance statement and dimensional report from the supplier for critical applications.

How to measure and select the correct DIN7081 sight glass

Follow this short practical workflow before you order:

1. Measure the seat, not just the visible glass. Measure the gasket channel depth and the clamping space so you know the required overall and visible lengths.

2. Confirm width (30 vs 34 mm). The gasket profile and clamp design drive which width fits — don’t guess.

3. Pick the nearest standard length. Suppliers prefer standard lengths; choose the closest one that fits the seat. If none match, request a custom size.

4. Decide thickness by duty. 17 mm is common; if your application has higher pressure or thermal shock, specify a thicker plate and request rated P–T data.

5. Ask for tolerance & test certificates. For pressurized or safety-critical vessels, insist on dimensional certificates and batch traceability.

6. Verify sealing hardware. Ensure your gasket and clamp assembly match the glass width and seat geometry.

Material & performance notes

• Material: borosilicate glass is the common choice for DIN7081 plates because of thermal and chemical resistance. For special optical or vacuum needs, other glasses (fused silica, sapphire) may be used.

• Surface condition: check for edge finish and lapped faces for even seating.

• Operating limits: request the supplier’s pressure/temperature curves for the chosen size; these vary by thickness and treatment.

Installation and field checks

• Dry-fit and visually inspect before final assembly.

• Use correct torque sequence on clamps; uneven compression can crack a plate.

• Reject plates with chips on sealing edges — even small chips can propagate under cyclic loads.

• Record supplier batch numbers on the equipment log for traceability and future maintenance.

Handy imperial conversions

When communicating with stakeholders used to imperial units, you can use these approximate conversions:

• 140 mm ≈ 5.51 in

• 190 mm ≈ 7.48 in

• 280 mm ≈ 11.02 in
  (Always order and specify in metric for DIN parts — imperial sizes are only approximate.)

Short procurement checklist

• Measure seat depth and visible length ✔

• Confirm width (30 or 34 mm) ✔

• Choose nearest standard length ✔

• Specify thickness (17 mm typical; increase for heavy duty) ✔

• Request tolerance & batch certificates ✔

• Verify gasket/clamp compatibility ✔

Need help matching your level gauge or clamp to the correct DIN7081 sight glass? Send us your seat dimensions and photos — we’ll recommend the right standard size or a custom solution and provide material and tolerance certificates. Contact lumistar@188.com or visit our product pages for datasheets.