
The strongest, most secure sight glass elements available, Metaglas® mechanically prestressed windows, are available in a threaded design for process applications. Metaglas threaded sight glasses are compliant with the recently revised ASME (founded as the American Society of Mechanical Engineers) standard for electric boilers, Section I PEB-13, Water Gages. The revised ASME standard now allows manufacturers of boilers with a diameter of 16” or smaller to use a bull’s-eye-type fused sight glass window instead of the traditional tubular sight glass for observation of the water level in the boiler.
These sightglass are available in variety of thread type including NPT and metric straight threads. Described as offering the optics of glass and the strength of steel, these glass elements provide a level of safety, and a useful service life, well beyond that provided by conventional tempered glass or plastic in sterile service. Even at the most extreme temperatures (as high as 536° F) or in overpressure situations, sudden, total failure – that involving leakage or explosive shattering of the glass – essentially never occurs.
Resources
Datasheets
Threaded Metaglas
Metaglas® Line Overview
Webcasts
How to Ensure Sight Glass Safety
How to Select and Maintain Sight Glasses for Chemical and Pharmaceutical Applications
Manuals
Installation / Operation / Maintenance Manual
Sight Glass Strength – Compression vs. Fusion
Sight Glass Application Handbook
Step by Step Guide to Sight Glass Selection
Blog Posts
Why Metaglas® Is Considered the Safest Sight Glass in the World
METAGLAS® – Threaded Sightglass – NPT-Thread
d2 Thread | SW | d1 | d4 | l | l1 |
¼“ NPT | 21 | 9 | 9 | 17 | 11 |
3/8“ NPT | 24 | 10 | 12 | 20 | 13 |
½“ NPT | 27 | 14 | 16 | 25 | 15 |
¾“ NPT | 36 | 18 | 20 | 26 | 16 |
1“ NPT | 41 | 21 | 23 | 34 | 19 |
1 ¼“ NPT | 50 | 25 | 30 | 30 | 20 |
1 ½“ NPT | 55 | 30 | 36 | 36 | 24 |
2“ NPT | 70 | 35 | 44 | 40 | 25 |
3“ NPT | 100 | 50 | 60 | 55 | 30 |
Advantages:
- Very compact
- High pressure resistance
- Simple assembly
- Long working life
Operating conditions:
- Pressure: 100 bar
Materials:
- Ring material: Carbon Steel (1.0570), Stainless Steel (1.4462) Hastelloy
- Glass: Borosilicate to DIN 7080
Ring materials | Operating temperature |
Carbon steel 1.0570 | -10°C to +300°C |
Duplex stainless steel 1.4462 | -30°C to +280°C |
Hastelloy C22 (2.4602) | -60°C to +300°C |