Sight Glasses

Toughened

Glass

Metaglas

Surface Damage

Damage to the toughened surface can cause unexpected catastrophic failure

Scratches or any other surface damage do not affect safety or life of Metaglas

Residual
Stress

Residual stress is created when bolting up. Re-bolting causes excessive residual stress which can lead to failure

Repeated re-bolting does not affect Metaglas strenght and integrity

Pressure

Lower resistance to pressure and catastrophic failure on overpressurisation

Higher pressure ratings for similar disc thickness

Impact

Impact (mechanical shock) causes catastrophic failure and the glass shatters into a multitude of small fragments

Metaglas has an extremely high resistance to impact. Very high impact may cause local pitting of the glass but this neither affects the the function or its leak tightness

Sensitivity

Toughened Glass is very sensitive to uneven torquing of sight port bolts

The glass surfaces must be entirely flat and smooth (within 0.07 mm) to aviod uneven torquing.

Extremely high tolerance to uneven torquing.

Uneven surfaces do not therefore result in glass damage.

Made of Failure

Uneven or over torquing results in the glass cracking right through

Metaglas cannot be overtorqued as you are torquing metal on metal. On reaching the limits of uneven torquing cracks will appear but the Metaglas will remain leak tight

Erosion

Erosion, particulary right through the glass toughened surface, results in significant weakening which can lead to catastrophic failure

Metaglas will remain leak tight to a high level of erosion

Cleaning

Glass must be replaced unless it can be cleaned in-situ

Metaglas lasts indefinitely regardless of how many times you remove, clean and replace it