Witt made changes to the material used for this new product to extend its area of application to include oxygen. In contrast to the existing gas filter 77, the filter insert of the new model is made from bronze instead of chromium-nickel-steel. New approved elastomers are also used. The filter with bronze element was tested by BAM and is approved for use with oxygen up to 40 bar maximum operating overpressure. For other gases Witt specifies a maximum pressure of as much as 50 bar.
The filter is used to keep out tiny mechanical impurities in many industrial gases. A special feature of the model is that the filter can be replaced easily without dismantling the product. The condensate filtered out of the gas is removed via a drain outlet.
The weight of model 77 with bronze or chromium-nickel-steel filter insert starts at 2.8 kg, depending on the connection. The fitting, which is compact given its performance, has a diameter of only 72 mm and a length of 205 mm. It is designed to be installed in pipes with thread or flange and is part of a product series that also includes models to build into outlet manifolds.