Permissible Operating Conditions
The permissible operating temperature and pressure cannot be considered independently. Thermal stress resulting from the temperature differences between the inner and outer surfaces of the glass is superimposed by stress caused by the the working pressure.
The higher the stress the lower the permissible working pressure. Thermal insulation is reducing the thermal stress and can become a requirement in certain circumstances.
Permissible Operating Temperature
Borosilicate glass can only be deformed at temperatures close to its transformation temperature (approximately 525ºC).
Provided that no sudden temperature shock arises borosilicate glass 3.3 may be used up to temperatures of about 300°C. Considering the gasket material operating temperatures up to 200°C are recommended.
At sub-zero temperatures tensile strength tends to increase. Therefore borosilicate glass 3.3 can be used safely at temperatures until down to -80ºC.
During operation rapid temperature changes across the glass wall should be avoided. Rapid temperature variations are effecting thermal stress in the glass which has an impact on the permissible operating pressure.
As a general guideline based on practical experience the maximum permissible thermal shock is 120K.
Permissible Operating Pressure
Components made of borosilicate glass 3.3 (cylindical, sherical, domed) in all nominal sizes can be operated under full vacuum (-1barg).
The maximum permissible operating pressures (ps) shown in the tables below are dependent on the nominal size DN respectively diameter D of the glass component.
Depending on their shape higher internal pressures are possible. In such cases the glass component is specially marked on in accordance with EN1595.
Summary Operating Data
- Maximum operating temperature = 200°C
- Minimum operating temperature = -80°C
- Maximum temperature difference (product/ambient) = 180K
- Maximum permissible thermal shock = 120K
- All components are suitable for full vacuum ps = -1barg
- Maximum pressure as per following tables:
Cylindrical glass components:
Our valves are designed for the operation in the same working condition range as the cylindrical glass components with the identical nominal diameter.