Derwent Water Services Limited supplies an extensive range of valves which are used in water pre-treatment plant from a variety of manufacturers:
- Air-operated valves
- Pneumatically-operated valves
- Air-actuated valves
- Solonoid valves
- Butterfly valves
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Typical uses of these valves in water treatment plant applications are:
- Base/exchange softening: controlling the 5-cycle softening plant operation, i.e. sequencing of the valves for normal service condition, backwash, regenerant draw, slow-rinse and fast-rinse cycles
- Demineralisation: non-corrodible valves for plant sequencing and operation
- Filter operation: sequencing of fast-rinse and backwash cycles
Typically, these valves can be mounted on a structured front manifold in front of the ion exchange vessels, and the sequencing of the valves is controlled by a valve stager or selection of solonoid valves.
The valves are of the diaphragm and butterfly type. The valve operation is typically with clean air as the motive force at around 5 bar pressure. However, some valves can be operated by clean low dissolved solids water as the motive force.
The valve bodies and diaphragms are of various materials, e.g. neoprene, Teflon, EPDM, thermoplastic materials for the diaphragm and PVC, PVDF, PP materials for the valve bodies. This range of materials allows high working pressures, high working temperatures and long life.