Behaviour of deepwell handpumps with PVC rising mains

When handpumps with PVC rising mains are used at greater depths, fracturing of the rising mains and the pump rods occur and pump yields decrease. Investigations to solve these problems were carried out in a testing site in the Netherlands. Three Dutch handpumps were tested: the SWN 81, the Volanta and a hybrid in which the SWN 81 superstructure was joined to the base of the Volanta. The elasticity of PVC rising mains governs pump behaviour because: 1. it reduces the effective piston stroke, resulting in lower volumetric efficiencies and 2. it reduces the resonance frequencies, so that resonance occurs at normal pumping frequencies. Pressure waves in the water column in the rising main are the main cause for these resonances. The resulting increased pressure fluctuations may lead to increased stresses. The valve dynamics are not important for this type of pump. Fatigue was the main cause of fractured PVC rising mains and steel pump rods. Factors contributing to fatigue are frequent stress fluctuations (more than 10 million pump cycles), corrosive water, notches in the PVC, and stress concentrations in the joints of the rising mains and pump rods. Design modifications such as the reduction of the ratio of the piston diameter/rising main diameter and wall thickness, can increase fatigue lifetime and pump efficiencies. Finally the report explains origins and effects of buckling, swinging and 'snaking', and the consequences of creep and cylinder support.