| 摘要 |
<p>Drains, sewers etc. are cleaned by vacuum suction of clearings into a receiver which has an inlet for clearings and a connection to a source of vacuum, as well as mechanical means for discharging settled sludge from the bottom of the receiver; the liquid in the receiver is kept down to a chosen level by a pump having its intake set at that level and fitted with a non-return valve in its delivery line so that air cannot be drawn through the pump into the receiver. Redn. of level can take place concurrently with sewer cleaning, settlement and sludge discharge, so that cleaning is not interrupted to empty the receiver.</p> |
