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Sintered Ware

BOROSIL® brand sintered glassware is used for the filtration of liquids and gases in the laboratory. It incorporates a porous glass disc as a filter media, which is non corrosive and reusable. It is also used for gas washing, dispersion and absorption.

Sintered disc is manufactured by crushing BOROSIL® brand glass, powdering, cleaning, separating into various mesh sizes and then fusing together in the form of a disc. The sintered disc is graded into 5 grades G1, G2, G3, G4, and G5. The grades are classified by maximum pore size which is obtained by measuring pressure at which the first air bubble breaks away from filter under certain conditions. The pressure differential is then used to calculate the equivalent capillary diameters in micron. The desired pore size is obtained by suitably controlling the grain size, firing time, temperature and the thickness of the disc. 'Each disc is test and graded individually.

The pore diameters are reasonably uniform, which ensures required flow rate through the filter. The flow rate further depends on pressure differential between the two sides of the disc, free area of the disc, viscosity of the fluid being filtered, etc. Between different discs of same size and grade, there is a fair amount of uniformity in pore size and hence the results from two or more discs of the same size and grade will be uniform. This ensures reproducible analytical results.

The discs have maximum surface hardness and hence glass powder does not get scraped off during cleaning or with chemicals. Filters do not shed particles during usage.The discs are sealed to tubing without blocking the pores. Then they are annealed properly in automatically controlled lehrs.

Porosity Grades

Chemical Durability

Operating Pressure

Thermal Limitations

Cleaning of Sintered Ware

Thermal Limitations

The resistance to thermal shock of sintered ware is comparatively less than that of standard BOROSIL® glassware. Therefore, articles of sintered ware should not be subjected to excessive temperature changes nor to direct flames.

BOROSIL® sintered crucibles are particularly suited for drying to constant weight. Dry sintered crucibles at room temperature can be placed directly into a drying oven at 150° C, although customary practice is to dry at 110° C. Sintered ware may safely be heated in a furnace to 500° C without ill effect, provided that the cycle of heating and cooling is gradual. It is advisable that rate of heating should not be more that 2° C /min. This prevents internal strains caused by excessive temperature differences between the surrounding glass vessel and the sintered disc which can lead to fracture of apparatus.

Sintered ware of porosity grades 4 and 5 when cold and damp should never be subjected to a sudden temperature change since the evolution of steam may set up sufficient pressure within the filter, to crack it.

Filtration Apparatus should be kept on its rim (stem upwards) in oven or sterilizer. A perforated support base is advantageous for air convection in case of pipeline filters. Care should be taken by use of heat insulating material such as asbestos to avoid premature heating near filter seal. Apparatus should remain in the oven or sterilizer during cooling to avoid too fast a cooling rate.

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