Patented seal shroud combats leaks in water pumps

A unique design of seal shroud solves the problem of leaking seals and consequent bearing failure in automotive water pumps. Dean Palmer reports

A patented design of seal shroud has been developed that eliminates leaking seals in automotive water pumps, a costly source of warranty claims on engine manufacturers. Birmingham-based company Concentric Pumps' new design features a shroud, normally of pressed steel, inserted into the water pump housing to form a pressure chamber around the seal. The unique part of the development is a number of apertures around the periphery of the shroud which enable relatively high pump outlet pressure within the chamber. The space between the shroud and the pump shaft is designed to ensure even distribution of the coolant flow over the seal, while maintaining pressure. The design provides a more stable environment for the seal, reducing silicate formation and the hence the risk of failure. It also reduces the cost of both the housing and the seal, which together with large warranty savings represent a major advance for automotive OEMs. According to Concentric, its unique design is the first to address the problem of localised 'boiling' of the coolant at the sealing faces, which leads to the formation of silicates that can progressively degrade the seal faces. But, by raising the pressure around the seal - and hence the boiling point of the coolant - this can be avoided. At 6,000rpm, the new shroud will increase coolant boiling point by around 25°C. The new design also helps to avoid the problem of dry running, which occurs when low pressures cause the coolant to vaporise. The resulting high temperature leads to 'thermal rotation' or distortion of the primary sealing ring, again encouraging silicates to form an abrasive film on the seal faces. Concentric says its shroud is suitable for volume manufacturing and "will allow the use of a less expensive seal". It can also form the pump location diameter, therefore reducing the cost of manufacturing the housing and offsetting the on-cost of the shroud itself.