These terms can often be confused though the distinction is fairly obvious. Submersible pumps are complete units, including the motor, and the whole can be totally submerged whereas immersible pumps are mounted in vertical position with the motor above the liquid and the pump end extended below the liquid level.
Submersible pumps are widely used for water and sewage handling applications, their compact dimensions and ease of use with integral float switches make them ideal for these situations. However, as they have standard carbon and ceramic mechanical seals and the materials of construction (generally cast iron or lower grade stainless steel) are limited, submersible pumps are unsuitable for use on liquids other than water, they are not designed for use with chemical or aggressive liquids.
On the other hand, immersible pumps can be designed and manufactured specifically for use in corrosive and aggressive situations and are made in a range of materials from 316 stainless steel up to engineered plastics such as polypropylene and PVDF. As the motor is above the pump it can be supplied in a specification to suit the environment, including ATEX Zones 1 and 2. Column lengths up to 6 metres can be supplied and even with shorter lengths (provided that the impeller is flooded at start up) the pump can still pump down to 6 metres.
Crest manufacture and supply a comprehensive range of immersible pumps for use in chemical and corrosive environments. Please contact our team for more information.