Wernert pumps successful

Eight Wernert pumps were supplied by AxFlow Ltd and installed when the wet chemical scrubber plant at Northumbrian Water’s (NW) Howdon sewage treatment works entered service in 1998. The recirculated liquor pumps handle Sodium Hydroxide (caustic) 25% dilution and Sodium Hypochlorite (Hypo) 17% dilution. The plant was designed to remove H2s and sulphur-based compounds through the use of a recirculated liquor made up of softened water. The Wernert NEPO pumps return the liquor from ground level to a height of around 4m to allow the liquor to dose the odorous air before it leaves the vessel stack. The chemicals are dosed directly into the liquors and are controlled and monitored using Prominent control technology. Certified to ATEX 100a, the Wernert NEPO has thick-walled casing parts made from plastic, as well as the completely metal enclosure and together these ensure that the pump is safe for pressure rating PN16. The choice of plastic depends on the chemical, thermal, mechanical and abrasive loads. In the case of the pumps supplied to NW, the pumps use an ultra-high molecular weight low pressure polyethylene. The pump design allows a quick exchange of the hydraulic side of the pump, without detaching the flanges or dismounting of the electric motor. AxFlow reports that other than regular conditioning monitoring, the eight pumps used in the scrubber circulation application have performed well since installation. In fact it has only been on four or five occasions that remedial work has been undertaken.
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