Pressure compensated Venturi dispensing system
Systems, methods, and software program products for dispensing chemical solutions. A controller receives a signal from a pressure sensor indicative of a pressure of a diluent. The controller determines an expected flow rate of the diluent through an eductor based at least in part on the pressure of the diluent. The controller may further determine an expected concentration of a chemical product in the solution dispensed from a discharge port of the eductor. Based on the expected flow rated and concentration of the chemical product, the controller determines a duration of a dispense stage of a dispensing operation required to dispense a predetermined dose of the chemical product. The controller then causes the diluent to flow through the eductor for the determined duration of the dispense stage. A check valve on the output of the eductor prevents dissimilar chemicals from mixing and reduces a response time of the eductor.
1. A method of operating a chemical dispensing system using eductors, the method comprising:
obtaining, from a pressure sensor positioned at a fluid inlet of the chemical dispensing system, a first signal indicative of a pressure of a diluent;
determining, based at least in part on the pressure of the diluent and a desired dose of a chemical, a dispense duration that represents a duration of time to maintain a selector valve of the chemical dispensing system open in order to draw the desired dose of the chemical through an eductor at the pressure of the diluent;
controlling operation of the selector valve to cause the selector valve to open, thereby, causing the diluent to flow through the eductor, wherein the eductor includes an inlet port into which the diluent flows, a pickup port configured to draw the chemical into the eductor in response to the diluent flowing through the eductor, a discharge port, and a venturi fluidically coupled to the inlet port, the discharge port, and the pickup port; and
controlling operation of the selector valve to cause the selector valve to close after the selector valve has been opened for the dispense duration.
2. The method of claim 1 , further comprising determining a volume the chemical dispensed during the dispense duration based on a flow rate of the diluent.
3. The method of claim 2 , wherein the flow rate of the diluent is determined, at least in part, based on the pressure of the diluent.
4. The method of claim 1 , further comprising:
receiving a second signal from a second sensor positioned downstream of the discharge port of the eductor; and
determining, based at least in part on the second signal, that a solution including the diluent and the chemical was dispensed from the chemical dispensing system.
5. The method of claim 4 , wherein the second signal is indicative of a characteristic of the solution.
6. The method of claim 5 , wherein the characteristic comprises at least one of: a flow rate, a conductivity, an index of refraction, or a fluorescent property.
7. The method of claim 4 , further comprising:
receiving a third signal from a third sensor positioned upstream of the inlet port of the eductor; and
wherein determining that the solution including the diluent and the chemical was dispensed from the chemical dispensing system comprises determining, based on the second signal and the third signal, that the solution including the diluent and the chemical was dispensed from the chemical dispensing system.
8. The method of claim 1 , further comprising determining, based at least in part on the pressure of the diluent, a flush duration that represents a duration of time to maintain a flush valve of the chemical dispensing system open during a flush stage.
9. The method of claim 1 , further comprising:
determining a volume of a chemical solution dispensed during the dispense duration, the chemical solution including the chemical mixed with the diluent; and
determining, based at least in part on the pressure of the diluent and the volume of the chemical solution dispensed, a flush duration that represents a duration of time to maintain a flush valve of the chemical dispensing system open during a flush stage.
10. The method of claim 1 , wherein determining the dispense duration comprises using a table that maps flow rate of the chemical through the pickup port of the eductor to diluent pressure, or wherein determining the dispense duration comprises calculating a flow rate of the chemical through the pickup port of the eductor based on the diluent pressure.
11. A dispensing system comprising:
an inlet manifold including a plurality of outlet ports and an inlet configured to couple to a source of a diluent;
a pressure sensor positioned to measure diluent pressure at an inlet end of the inlet manifold;
a flush manifold including a plurality of intake ports;
an eductor including an inlet port that is fluidically coupled to an outlet port of the inlet manifold, a pickup port fluidically coupled to a source of a chemical product, a discharge port fluidically coupled to an intake port of the flush manifold, and a venturi fluidically coupled to each of the inlet port, the pickup port, and the discharge port, the venturi being configured to draw the chemical product into the eductor in response to the diluent flowing through the inlet port such that the chemical product is mixed with the diluent to form a chemical solution;
a selector valve coupled between the inlet manifold and the eductor; and
a controller configured to perform operations comprising:
obtaining, from the pressure sensor, a first signal indicative of a pressure of the diluent;
determining, based at least in part on the pressure of the diluent and a desired dose of the chemical product, a dispense duration that represents a duration of time to maintain the selector valve open in order to draw the desired dose of the chemical through the eductor at the pressure of the diluent;
controlling operation of the selector valve to cause the selector valve to open, thereby, causing the diluent to flow through the eductor; and
controlling operation of the selector valve to cause the selector valve to close after the selector valve has been opened for the dispense duration.
12. The dispensing system of claim 11 , further comprising a second sensor positioned downstream of the discharge port of the eductor and configured to measure a characteristic of the chemical solution.
13. The dispensing system of claim 12 , further comprising a third sensor positioned upstream of the eductor inlet port and configured to measure a characteristic of the diluent.
14. The dispensing system of claim 11 , wherein the operations comprise determining a volume of the chemical dispensed during the dispense duration based on a flow rate of the diluent.
15. The dispensing system of claim 14 , wherein the flow rate of the diluent is determined, at least in part, based on the pressure of the diluent.
16. The dispensing system of claim 12 , wherein the operations comprise:
receiving a second signal from the second sensor; and
determining, based at least in part on the second signal, that a solution including the diluent and the chemical was dispensed from the chemical dispensing system.
17. The dispensing system of claim 16 , wherein the characteristic comprises at least one of: a flow rate, a conductivity, an index of refraction, or a fluorescent property.
18. The dispensing system of claim 13 , wherein the operations comprise:
receiving a second signal from the second sensor;
receiving a third signal from the third sensor; and
determining, based on the second signal and the third signal, that the solution including the diluent and the chemical was dispensed from the chemical dispensing system.
19. The dispensing system of claim 11 , wherein the operations comprise determining, based at least in part on the pressure of the diluent, a flush duration that represents a duration of time to maintain a flush valve of the chemical dispensing system open during a flush stage.
20. The dispensing system of claim 11 , wherein the operations comprise:
determining a volume of a chemical solution dispensed during the dispense duration, the chemical solution including the chemical mixed with the diluent; and
determining, based at least in part on the pressure of the diluent and the volume of the chemical solution dispensed, a flush duration that represents a duration of time to maintain a flush valve of the chemical dispensing system open during a flush stage.
21. The dispensing system of claim 11 , wherein determining the dispense duration comprises using a table that maps flow rate of the chemical through the pickup port of the eductor to diluent pressure.
22. The dispensing system of claim 11 , wherein determining the dispense duration comprises calculating a flow rate of the chemical through the pickup port of the eductor based on the diluent pressure.
23. A non-transitory computer readable media comprising instructions that, when executed by one or more processors, causes the one or more processors to perform operations comprising:
obtaining, from a pressure sensor positioned at a fluid inlet of a chemical dispensing system, a first signal indicative of a pressure of a diluent;
determining, based at least in part on the pressure of the diluent and a desired dose of a chemical, a dispense duration that represents a duration of time to maintain a selector valve of the chemical dispensing system open in order to draw the desired dose of the chemical through an eductor at the pressure of the diluent;
controlling operation of the selector valve to cause the selector valve to open, thereby, causing the diluent to flow through the eductor, wherein the eductor includes an inlet port into which the diluent flows, a pickup port configured to draw the chemical into the eductor in response to the diluent flowing through the eductor, a discharge port, and a venturi fluidically coupled to the inlet port, the discharge port, and the pickup port; and
controlling operation of the selector valve to cause the selector valve to close after the selector valve has been opened for the dispense duration.