Threaded Sight Glass Window

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.

METAGLAS® – Threaded Sightglass – NPT-Thread

Threaded Sight Glass Window Dimensional Drawing

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