Hot liquid asphalt is applied to road and other surfaces in a variety of paving applications. Upon cooling, asphalt material becomes more viscous and eventually "freeze". Hot asphalt is typically applied by vehicular spraying apparatuses commonly known as asphalt distributors. Asphalt distributors conventionally comprise a pump delivering hot liquid asphalt from tank to a spray bar. The tank, pump and spraybar may either be supported by a truck or pulled behind the truck as a detachable trailer.
Before asphalt distributors can be stored, residual asphalt remaining in the spray bar and associated plumbing network must be removed to prevent asphalt from freezing therein, which could otherwise plug the distributor during the next startup. An older more traditional method of removing the remaining asphalt is to flush the asphalt out of the network and spray bar with a suitable solvent, such as diesel or flushing oil for example. However, this method has the drawbacks of requiring a large quantity of solvent and wasting the asphalt remaining in the network and spray bar. This method also creates a large quantity of asphalt-solvent waste product which must be disposed of in an environmentally sound manner, which is also costly.
To reduce the amount of asphalt remaining in the network and the amount of solvent needed to flush the distributor, many asphalt distributors have a bidirectional pump which can operate in reverse or "suckback mode" to suck asphalt from the network and spray bar back into the tank. After much of the asphalt is sucked back, the distributor is then typically flushed with solvent to remove any remaining asphalt in the network and spray bar. Although the "suckback mode" reduces the quantity of asphalt remaining in the distributor, significant quantities of asphalt still remain in various low collection points or sumps in the network after suckback mode. To prevent asphalt from freezing in these low points, significant quantities of flushing solvent is conventionally used to remove the remaining asphalt from these low collection points. However, using significant quantities of solvent is undesirable for the reasons outlined above and for space and convenience reasons. One significant and problematic low collection point is in the asphalt strainers of asphalt distributors. Asphalt strainers are typically connected between the tank and the pump of the distributor for removing frozen chunks of asphalt and other large impurities from the asphalt during spraying and other operations to ensure smooth operation of the distributor and to prevent clogging of nozzles in the spray bar. Due to the conventional large box like structure of prior asphalt strainers, a low point or sump is inherent therein.