Flow system with pressure level responsive air admission control

摘要

A vacuum operated sewerage system includes a static pressure sensor establishing a trigger signal at selected first level in a standpipe. The sensor is connected upstream of a discharge control valve and actuates a timer at the selected sensed pressure. The timer is connected to actuate the discharge control valve after a suitable time delay to prevent transient signal actuation, and establish flow for a predetermined period. An air admission valve is connected in series with the sensor to the timer to actuate the timer if the system vacuum drops below a selected level in the same manner as an increased hydrostatic pressure. The sensor can be eliminated for separate air admission control directly in response to the vacuum condition of the line.