Monitoring liquid level infed tank and flow rate of liquid therefrom to point of use

• US 4,856,343 A
• Filed: 11/24/1987
• Issued: 08/15/1989
• Est. Priority Date: 11/24/1987
• Status: Expired due to Fees

• Current Assignee: Exxonmobil Oil Corporation (Exxon Mobil Corporation)
• Original Assignee: Mobil Oil Corporation (Exxon Mobil Corporation)
• Inventors: Hon, Clarence C.
• Primary Examiner(s): Goldstein, Herbert
• Application Number:
  US07/124,638
• Time in Patent Office: 630 Days
• Field of Search: 73/168, 73/861, 73/223, 73/3, 73/291, 73/198
• US Class Current: 73/861
• CPC Class Codes: G01F 1/007 by measuring the level variations of storage tanks relative to the time
• CPC Class Codes: G01F 23/0046 with a stationary probe, where a liquid specimen is separated from the mean mass and measured by gauge glasses G01F23/02
• CPC Class Codes: G01F 23/02 by gauge glasses or other apparatus involving a window or transparent tube for directly observing the level to be measured or the level of a liquid column in free communication with the main body of the liquid

Abstract

The flow rate of liquid being fed to a point of use is continuously monitored as is the liquid level in the feed tank by detecting the level in a liquid gauge member at two successive locations while feed from the tank is blocked, so that such detected data can be employed in a computer to output the flow rate and tank level.

Claims

1. In a liquid feed system wherein liquid is withdrawn through an outlet at the bottom of a feed tank with a pump having an inlet which delivers the liquid to a use point and a constant cross-section liquid gauge member communicates with the interior of the tank such that a column of liquid is present in said gauge member to the same level as that in the tank, the gauge member further being in communication with the inlet of said pump, a method for checking the rate at which the pump is delivering liquid to the point of use, said method comprising

blocking the tank outlet at time T₀ so that the pump withdraws liquid only from the gauge member thereby reducing the level in the gauge member,

detecting the level of liquid in the gauge member at first and second reduced levels thereof and converting these detections to electrical signals indicative of times T₁, and T₂,

processing the time T₁ and T₂ electrical signals in a computer to provide the flow rate in said gauge member as a processed signal output indicative of the pump delivery flow rate to the point of use, and

further processing the flow rate, the T₁ electrical signal and data representative of time T₀ to compute the height of the level of the liquid column in the gauge member at time T₀.

2. The method of claim 1, wherein the pump is one of a reciprocating and centrifugal pump.

3. The method of claim 1 in which the computer is operated to generate a command signal for controlling the blocking of the tank outlet at time T₀.

4. The method of claim 3 in which the computer is operated to generate another command signal at time T₂ for controlling the unblocking of the tank outlet.

5. In a liquid feed system which includes a feed tank for holding a liquid and having a bottom outlet, a pump having an inlet operating to withdraw liquid from the tank through said outlet and deliver it to a point of use, and a constant cross-section liquid gauge member communicating with the interior of said tank such that a column of liquid is present in said gauge member to the same level as that in the tank, the gauge member further being in communication with the inlet of said pump, apparatus for checking the rate at which the pump is delivering liquid to the point of use, said apparatus comprising

a normally open power operated closure valve intervening the tank outlet and the pump,

means for power actuating said closure valve at time T₀ to move it to a closed position so that the pump withdraws liquid only from the gauge member thereby reducing the level of liquid in said gauge member,

first and second level detection means on said liquid gauge member positioned thereon at respective first and second vertically spaced locations and operable to detect level presence at such locations as times T₁ and T₂ values and output such detections as electrical signals, and

means for processing the time T₁ and T₂ electrical signals to provide the flow rate in said gauge member as a processed signal output indicative of the pump delivery flow rate to the point of use, said means for processing the electrical signals comprising a computer acquiring said signals, the computer being operable to generate a command signal at time T₀ to control the power actuation of the closure valve to closed position thereof, the computer being further operable to process the flow rate, the T₁ electrical signal and data representative of time T₀ to compute the height of the level of the liquid column in the gauge member at time T₀.

6. The apparatus of claim 5, wherein the pump is one of a reciprocating and centrifugal pump.

7. The apparatus of claim 5 in which the computer is operable to generate a command signal at time T₂ to control return of the closure valve to an open position.

8. The apparatus of claim 5 in which the liquid gauge member is an upright tube extending from adjacent the top of said feed tank to a point a distance below the bottom of said tank.

9. The apparatus of claim 8 in which the first level detection means is located on the gauge member proximate the bottom of said feed tank, the second level detection means being located on the gauge member below the tank bottom.

10. The apparatus of claim 9 further comprising a tank low level alarm means operatively coupled with said first level detection means, the computer being operable to inactivate said alarm means at times when said valve is in clsoed position.

11. The apparatus of claim 8 in which the liquid gauge member is a transparent sight glass.

12. The apparatus of claim 5 in which the closure valve is a solenoid control valve, energization of the solenoid moving the valve to closed position.

13. The apparatus of claim 5 in which the first and second level detection means each comprise non-contact level switches.

14. In a liquid feed system which includes a feed tank for holding a liquid and having a bottom outlet, a pump having an inlet operating to withdraw liquid from the tank through said outlet and deliver it to a point of use, and a constant cross-section liquid gauge member communicating with the interior of said tank such that a column of liquid is present in said gauge member to the same level as that in the tank, the gauge member further being in communication with the inlet of said pump, apparatus for checking the rate at which the pump is delivering liquid to the point of use, said apparatus comprising

a normally open power operated closure valve intervening the tank outlet and the pump,

means for power actuating said closure valve at time T₀ to move it to a closed position so that the pump withdraws liquid only from the gauge member thereby reducing the level of liquid in said gauge member,

first and second level detection means on said liquid gauge member positioned thereon at respective first and second vertically spaced locations and operable to detect level presence at such locations as times T₁ and T₂ values and output such detections as electrical signals, the liquid gauge member being an upright tube extending to a point a distance below the bottom of said tank, the first level detection means being located on the gauge member proximate the bottom of said feed tank, the second level detection means being located on the gauge member below the tank bottom, and

15. means for processing the electrical signals to provide the flow rate in said gauge member as a processed signal output indicative of the pump delivery flow rate to the point of use.