Vacuum pump

Abstract

A multi stage vacuum pump for pumping corrosive fluid with a first flow section of material less resistant to corrosion than the material of a second flow section downstream of the first flow section.

1 . A vacuum pump for pumping corrosive fluid, the pump comprising: a pumping mechanism comprising a plurality of pumping stages along a fluid flow path between an inlet for fluid at high vacuum and an outlet for fluid at low vacuum, and wherein the material of the pumping mechanism at a first section of said flow path is less resistant to corrosion than the material of the pumping mechanism at a second section of said flow path downstream of said first section. 
     
     
         2 . A vacuum pump as claimed in  claim 1 , wherein the respective materials of the first section and the second section are such that build-up of corrosive deposits at the first section is less than or equal to build-up of corrosive deposits at the second section. 
     
     
         3 . A vacuum pump as claimed in  claim 1  or  2 , wherein said first section and said second section are defined by a respective plurality of said pumping stages. 
     
     
         4 . A vacuum pump as claimed in any preceding claim, wherein said first section is adjacent to said second section along said fluid flow path. 
     
     
         5 . A vacuum pump as claimed in any preceding claim, wherein each of said pumping stages comprises a stator and a rotor. 
     
     
         6 . A vacuum pump as claimed in any preceding claim, wherein the or each pumping stage of the second section comprises components made from a Nickel rich iron. 
     
     
         7 . A vacuum pump as claimed in any preceding claim, wherein the or each pumping stage of the first section comprises components made from Spheroidal graphite iron. 
     
     
         8 . A vacuum pump as claimed in any preceding claim, wherein the components of said pumping stages are fabricated from selected materials such that the build-up of corrosion deposits in each stage during pumping of corrosive gas is generally equal one stage to another stage. 
     
     
         9 . A vacuum pump as claimed in any preceding claim, wherein pumping stages comprise a roots pumping mechanism or a claw pumping mechanism.