US 4,297,081 AGranted

Liquid level control system

OwnerWilliam A. Irvininventor

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Abstract

A pump control system using a purge bubbler, a flat plate manometer having level sensing contacts therein, and control relays and alarms. The flat plate manometer includes a rectangular mercury column having calibration scales and a number of stainless steel contacts disposed along the column. The mercury closes a circuit between a common contact and the column contacts as the mercury rises. The manometer is fabricated from acrylic plastic to provide a light weight, low cost device. The input and output ports include microporous filters to prevent accidental loss of mercury. The input port is connected to a bubbler air pump and a standpipe in the vessel to be controlled. Pump start relays are connected to selected contacts of the manometer column to operate in accordance with the hydrostatic level of the liquid in the vessel. Interlocking relays are used in cooperation with the pump relays to allow pump start and pump stop levels to be independently selected. Contacts are also selected to operate high and low level alarms. Multiple pumps may be controlled from the manometer as required. A quick test system is included which switches the line from the vessel standpipe to a test valve that is open to the atmosphere. The operator can momentarily close the test valve causing the mercury column to rise and sequentially close each active contact. Indicator lamps are provided which show operation of each relay or pump associated with the active contacts and alarm devices will operate when the alarm contact are reached.

In a system for controlling the level of a liquid in a reservoir, said system having motor driven pumps for filling and emptying the reservoir, the pump control subsystem comprising:

an air pressure line having one end thereof disposed in said liquid;
air pump means for producing pressure in said air pressure line in which said pressure is proportional to the level of said liquid;
a mercury manometer utilizing a U-tube and having a pressure input to a first vertical mercury column connected to said air line and an outlet for a second vertical mercury column open to atmospheric pressure;
a common electrical contact disposed at the base of said U-tube and in conductive contact with said mercury columns;
a plurality of electrical pump-up control contacts disposed along said vertical mercury column below the zero pressure level of said mercury, said contacts adapted to be sequentially contacted as said mercury column rises in response to drops in said pressure and to thereby provide a conductive path from said column contact to each pump-up control contact contacted;
a plurality of electrical pump-down control contacts disposed along said second vertical mercury column above the zero pressure level of said mercury, said contacts to be sequentially contacted as said second mercury column rises in response to increases in said pressure and to thereby provide a conductive path from said common contact to each pump-down control contact contacted;
and
pump motor control means connected to selected ones of said pump-up and pump-down control contacts for providing a pump starting function when said mercury columns make contact with specific ones of said control contacts and a pump stopping function when said mercury columns breaks contact with other ones of said control contacts;
and
subsystem test means connected to said pump and said input to said first vertical mercury column for controlling said pressure to vary from a zero value to a predetermined maximum value to thereby cause said first mercury column to fall and said second mercury column to rise and to therefore sequentially contact each of said control contacts for testing of said pump starting and said pump stopping functions.

7 more elements

Abstract

Claims16