Glass-metal connectionCladding tube
The highly transparent special glass of the cladding tube produced at NARVA’s own glassworks is made from raw materials which are low in iron to make it particularly transparent for light. The same special glass is used for vacuum tubes like for light sources at NARVA. It is evident that high quality light sources needs to be made from very transparent glass to ensure a high light output.
Although the glass used in the light sources is very transparent, the cladding tube additionally is coated with nano particles of silicon dioxide, both inside and outside. Afterwards the layers are sintered into the surfaces, which makes them smudge proof. This coating increases the transparency of the glass further, reaching the maximum glass transmission of 96%.
The highly transparent special glass of the cladding tube produced at NARVA’s own glassworks is made from raw materials which are low in iron to make it particularly transparent for light. The same special glass is used for vacuum tubes like for light sources at NARVA. It is evident that high quality light sources needs to be made from very transparent glass to ensure a high light output.
Although the glass used in the light sources is very transparent, the cladding tube additionally is coated with nano particles of silicon dioxide, both inside and outside. Afterwards the layers are sintered into the surfaces, which makes them smudge proof. This coating increases the transparency of the glass further, reaching the maximum glass transmission of 96%.
The coating on the cladding tube prevents the glass surface from weathering which can occur under unfavourable climatic conditions. It also stabilises the glass by sealing any micro-cracks.
The comparatively high wall thickness of the NARVA vacuum tubes and their coating gives the tubes a high level of hail resistance, tested by TÜV Rheinland in accordance with the EN 12975-2 hail resistance test by using an ice ball test. The cladding tubes are also 100% resistant to the impact of a 150 g heavy steel ball dropped from 40 cm and close to 80% resistant when dropped from 60 cm.
This surface treatment modifies the tubes so that they behave like safety glass in the event of a break under heavy force: the shards produced are relatively small and are not scattered all over.
The special glass of the vacuum tube also has a significantly lower permeability level for hydrogen and helium compared to the frequently used borosilicate glass. As a result, the vacuum properties of the tube last for 20 years.
The comparatively high wall thickness of the NARVA vacuum tubes and their coating gives the tubes a high level of hail resistance, tested by TÜV Rheinland in accordance with the EN 12975-2 hail resistance test by using an ice ball test. The cladding tubes are also 100% resistant to the impact of a 150 g heavy steel ball dropped from 40 cm and close to 80% resistant when dropped from 60 cm.
This surface treatment modifies the tubes so that they behave like safety glass in the event of a break under heavy force: the shards produced are relatively small and are not scattered all over.
The special glass of the vacuum tube also has a significantly lower permeability level for hydrogen and helium compared to the frequently used borosilicate glass. As a result, the vacuum properties of the tube last for 20 years.
Glass drawing plant.
Glass processing.