Improving reliability and functional sustainability of groundwater handpumps by coating the rubber piston seals with diamond-like carbon

Abstract

In many rural communities, handpumps are essential in order to provide access to safe drinking water from groundwater sources. The functional sustainability of handpumps is poor, however, and most maintenance issues in handpumps are caused by wear of the nitrile rubber piston seals. This study identified handpump problems faced by a rural community in southern Uganda, specifically related to wear of piston seals. We investigated a novel surface-engineering approach to improve the wear resistance of piston seals by depositing diamond-like carbon (DLC), and silicon (Si) doped DLC onto the seals. Wear mechanisms for the coated seals were determined using a piston seal wear test rig. Tests were undertaken with clean normal water, and water seeded with sand particles. Wear mechanisms identified included adhesion, abrasion, and fatigue. For the DLC and Si-DLC coated piston seals the dominant wear mechanism was abrasion, with minimal fatigue wear. Adhesive wear on the coated piston seals is explained by the generation and transfer of a tribo-layer, which increases wear resistance and functional sustainability of the piston seal. Wear resistant seals could significantly reduce the maintenance costs of existing handpump designs, and improve their functional sustainability.