The criteria for selection of the three elastomers commonly used are:
a) Natural Rubber
Ⅰ) Excellent erosion resistance for liners (against solids up to 15mm size), but limited to particles 5mm size for impeller
Ⅱ) Not suitable for very sharp solids
Ⅲ) Easily be damaged by oversized solid or trash
Ⅳ) Impeller peripheral speed should be less than 27.5 m/s, to avoid the thermal breakdown of the liner, adjacent to the outer edge of the impeller.
Ⅴ) Unsuitable to oils, solvents or strong acids
Ⅵ) Unsuitable for temperatures in excess of 77°C
Ⅰ) Used for pump side liners, where the peripheral speed of the impeller is higher than 27.5 m/s, ( and precluding the use for standard rubber) ad used for impeller where occasional trash may damage a rubber impeller.
Ⅱ) Erosion resistance is greater where erosion is of sliding bed type rather than one of direction impact.
Ⅲ) Has less erosion resistance to find solids than natural rubber. Has greater erosion resistance to coarse sharp edged particles than natural rubber.
Ⅳ) Unsuitable for temperatures exceeding 70°C and for concentrated acids and alkalies, ketone, esters, chlorinated and nitro hydrocarbons.
c) Synthetic Elastomers: Neoprene, Butyl, Hypalon, Viton and others
These are used in special chemical applications under the following conditions:
Ⅰ) Not as erosion resistance as natural rubber
Ⅱ) Have a greater chemical resistance than natural rubber or polyurethane
Ⅲ) Generally allows higher operation temperature than natural rubber or polyurethane