Modular metering pump system

Abstract

A metering pump system for supplying an aqueous chemical to treat water includes first and second metering pumps connected to a common suction line and a common discharge line and operable to supply a desired chemical feed rate, an electronic flowrate sensor in communication with one of the common suction line and the common discharge line to measure an actual flowrate of the metering pump system, a controller in communication with the metering pumps and the electronic flowrate sensor, and a control loop implemented by the controller to operate one or more of the metering pumps to correct a deviation between the desired chemical feed rate and the actual flowrate measured by the electronic flowrate sensor.

What is claimed is: 
     
         1 . A method for controlling a chemical feed rate to a destination stock, the method comprising:
 using a metering pump system to supply an aqueous chemical at a desired feed rate through a system discharge, the metering pump system comprising:
 a first metering pump having a first discharge volume and a first theoretical feed rate corresponding to the first discharge volume times a first speed of the first metering pump; 
 a second metering pump having a second discharge volume and a second theoretical feed rate corresponding to the second discharge volume times a second speed of the second metering pump; 
 a system theoretical feed rate equal to a sum of the first theoretical feed rate and the second theoretical feed rate; 
 a system inlet connected to a supply of the aqueous chemical, the first metering pump and the second metering pump; 
 a system discharge connected to the first metering pump, the second metering pump and a water source to be treated by the aqueous chemical; 
 a flowrate sensor in one of the system inlet or the system discharge; and 
 a controller in communication with the first metering pump, the second metering pump, and the flowrate sensor; 
   operating the metering pump system at the system theoretical feed rate equal to the desired feed rate;   measuring an actual feed rate with the flowrate sensor;   determining a deviation between the actual feed rate and the desired feed rate; and   changing one or more of the first speed and the second speed to eliminate the deviation.   
     
     
         2 . The method of  claim 1 , wherein the changing is performed by the controller implementing a control loop comprising:
 combining a pump speed signal of the one or more of the first metering pump and the second metering pump and a feedback signal from the flowrate sensor; and   communicating a controlling output signal to the one or more of the first metering pump and the second metering pump.   
     
     
         3 . The method of  claim 1 , wherein the operating the metering pump system at the system theoretical feed rate consists of operating the first metering pump at the first theoretical feed rate equal to the system theoretical feed rate. 
     
     
         4 . The method of  claim 1 , wherein the operating the metering pump system at the system theoretical feed rate comprises simultaneously operating the first metering pump and the second metering pump. 
     
     
         5 . The method of  claim 1 , wherein:
 the operating the metering pump system at the system theoretical feed rate consists of operating the first metering pump at the first theoretical feed rate equal to the system theoretical feed rate; and   the changing consists of changing the first speed.   
     
     
         6 . The method of  claim 1 , wherein:
 the operating the metering pump system at the system theoretical feed rate consists of operating the first metering pump at the first theoretical feed rate equal to the system theoretical feed rate; and   the changing comprises switching operating the first metering pump to operating the second metering pump.   
     
     
         7 . The method of  claim 1 , wherein:
 the operating the metering pump system at the system theoretical feed rate consists of operating the first metering pump at the first theoretical feed rate equal to the system theoretical feed rate; and   the changing comprises continuing operating the first metering pump and begin operating the second metering pump.   
     
     
         8 . The method of  claim 1 , wherein:
 the operating the metering pump system at the system theoretical feed rate comprises simultaneously operating the first metering pump and the second metering pump; and   the changing comprises changing the first speed and the second speed.   
     
     
         9 . The method of  claim 1 , wherein:
 the operating the metering pump system at the system theoretical feed rate comprises simultaneously operating the first metering pump and the second metering pump; and   the changing comprises continuing operating the first metering pump and stop operating the second metering pump.   
     
     
         10 . The method of  claim 1 , wherein the deviation is a difference greater than a selected value between the actual feed rate and the desired feed rate. 
     
     
         11 . The method of  claim 1 , wherein the flowrate sensor is in the system inlet. 
     
     
         12 . The method of  claim 1 , wherein:
 the first metering pump and the second metering pump are peristaltic pumps; and   the operating the metering pump system at the system theoretical feed rate comprises simultaneously operating the first metering pump and the second metering pump.   
     
     
         13 . The method of  claim 12 , wherein the deviation is a difference greater than a selected value between the actual feed rate and the desired feed rate. 
     
     
         14 . The method of  claim 1 , wherein:
 the first metering pump and the second metering pump are peristaltic pumps;   the operating the metering pump system at the system theoretical feed rate consists of operating the first metering pump at the first theoretical feed rate equal to the system theoretical feed rate; and   the changing comprises switching operating the first metering pump to operating the second metering pump.   
     
     
         15 . The method of  claim 14 , wherein the deviation is a difference greater than a selected value between the actual feed rate and the desired feed rate. 
     
     
         16 . The method of  claim 1 , wherein:
 the first metering pump and the second metering pump are peristaltic pumps;   the operating the metering pump system at the system theoretical feed rate comprises simultaneously operating the first metering pump and the second metering pump; and   the changing comprises changing the first speed and the second speed.   
     
     
         17 . The method of  claim 16 , wherein the deviation is a difference greater than a selected value between the actual feed rate and the desired feed rate. 
     
     
         18 . The method of  claim 16 , wherein the flowrate sensor is in the system inlet. 
     
     
         19 . The method of  claim 1 , wherein:
 the first metering pump and the second metering pump are peristaltic pumps;   the operating the metering pump system at the system theoretical feed rate comprises simultaneously operating the first metering pump and the second metering pump; and   the changing comprises continuing operating the first metering pump and stop operating the second metering pump.   
     
     
         20 . The method of  claim 19 , wherein the deviation is a difference greater than a selected value between the actual feed rate and the desired feed rate.