Method and system for measurement of liquid level in a tank

• US 4,736,329 A
• Filed: 06/16/1986
• Issued: 04/05/1988
• Est. Priority Date: 10/25/1984
• Status: Expired due to Fees

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Ferretti, Michael D., Weiss, Thomas S. Sr., Gabel, Brian L., Horton, James A.
• Primary Examiner(s): YASICH, DANIEL
• Application Number:
  US06/853,825
• Time in Patent Office: 659 Days
• Field of Search: 73/304 R, 73/301, 73/299, 73/291, 364/509, 364/575, 364/581
• US Class Current: 700/281
• CPC Class Codes: G01F 23/16 Indicating, recording, or alarm devices being actuated by mechanical or fluid means, e.g. using gas, mercury, or a diaphragm as transmitting element, or by a column of liquid

Abstract

The computer based remote tank telemetry system uses a method for updating a prior collected average level of substance in a tank. It continuously determines values of differential pressure within the tank and in accordance with the values of differential pressure determines the instantaneous level of substance within the tank. A prior collected average level is stored and is compared with each of the instantaneous values of level thus obtained. On the basis of this comparison a relative weighing factor is determined which weighs the relative contribution of the collected and instantaneous values in determining a new collected value. The new collected average is compared against a predetermined setpoint to determine whether the level of substance in the tank is too low. The results of this comparison can be displayed locally, and using a modem, communicated to a remote display. The method for determining the relative weighing factor has three tiers. The selection of the required tier is done in accordance with the levels compared.

Claims

1. A method for determining when to deliver further substance from a remote location to a tank containing substance at a user location in accordance with the level of substance in the tank comprising the steps of:

(a) comparing a first substance level with a first predetermined set point to determine a first time when the level falls below the first set point;

(b) comparing a second substance level with a second predetermined set point to determine a second time when the level falls below the second predetermined threshold;

(c) determining the rate of substance usage between the first and second times;

(d) transmitting the rate to the remote location in response to the occurrence of the second determination; and

(e) dispatching to the user location a vehicle containing the further substance in response to the transmission.

2. The method of claim 1 in which steps (a) and (b) include determining the substance level using a time weighted averager.

3. The method of claim 1 in which step (c) includes:

determining the level difference between the first and second substance levels;

determining the time difference between the first and second times; and

dividing the level difference by the time difference.

4. The method of claim 1 in which step (d) includes transmitting through a modem and telephone lines.

5. A method for measuring the level of substance in a tank in which the level is subject to changes and updating a prior collected average level of the substance comprising the steps of:

(a) continuously determining values of differential pressure from within the tank;

(b) determining the instantaneous level of substance within the tank in response to the determined values of differential pressure;

(c) determining a difference relationship between the prior collected average level and the instantaneous level;

(d) determining a relative weighting factor for the prior collected average level and the instantaneous level which weighting factor varies in accordance with the difference relationship;

(e) determining a new collected average in response to the relative weighting factor;

(f) determining the rate of substance depletion in response to the new collected average; and

(g) repeating steps (b) through (f) in which the new collected average becomes the prior collected average in step (c).

6. A method for determining when to deliver further substance from a remote location to a tank containing substance at a user location in accordance with the level of substance in the tank in which the level is subject to changes comprising the steps of:

(a) continuously determining values of differential pressure from within the tank;

(b) determining the instantaneous level of substance within the tank in response to the determined values of differential pressure;

(c) determining a difference relationship between the prior collected average level and the instantaneous level;

(d) determining a relative weighting factor for the prior collected average level and the instantaneous level which weighting factor varies in accordance with the difference relationship;

(e) determining a new collected average in response to the relative weighting factor;

(f) comparing the new collected average with a first predetermined set point and transmitting a first signal to the remote location when the new collected average is below the first predetermined set point;

(g) comparing the new collected average with a second predetermined set point and transmitting a second signal to the remote location when the new collected average is below the second predetermined set point; and

(h) dispatching to the user location a vehicle containing the further substance in response to a transmission; and

(i) repeating steps (b) through (g) in which the new collected average becomes the prior collected average in step (c).

7. A method for measuring the level of substance in a tank in which the level is subject to changes and updating a prior collected average level of the substance comprising the steps of:

(a) continuously determining values of differential pressure from within the tank;

(b) determining the instantaneous level of substance within the tank in response to the determined values of differential pressure;

(c) determining a difference relationship between the prior collected average level and the instantaneous level;

(d) determining a relative weighting factor for the prior collected average level and the instantaneous level which weighting factor varies in accordance with the difference relationship;

(e) determining a new collected average in response to the relative weighting factor;

(f) determining maximum and minimum pressures within the tank and providing a signal to a remote display representative of the maximum and minimum pressures; and

(g) repeating steps (b) through (f) in which the new collected average becomes the prior collected average in step (c).

8. A method for measuring the level of substance in a tank in which the level is subject to changes and updating a prior collected average level of the substance comprising the steps of:

(a) continuously determining values of differential pressure from within the tank;

(b) determining the instantaneous level of substance within the tank in response to the determined values of differential pressure;

(c) determining a difference relationship between the prior collected average level and the instantaneous level;

(d) determining a relative weighting factor for the prior collected average level and the instantaneous level which weighting factor varies in accordance with the difference relationship;

(e) determining a new collected average in response to the relative weighting factor;

(f) comparing the new collected average with a predetermined setpoint and providing a signal when the new collected averge is below the setpoint;

(g) telecommunicating with placing a phone call to a remote station in response to the signal and periodically repeating the phone call until the phone call is answered; and

(h) repeating steps (b) through (g) in which the new collected average becomes the prior collected average in step (c).

9. A method for measuring the level of substance in a tank in which the level is subject to changes and updating a prior collected average level of the substance comprising the steps of:

(a) continuously determining values of differential pressure from within the tank including analog to digital converting of a differential pressure signal;

(b) determining whether the converting is operating and providing a signal to a remote display in response to the converting determination;

(c) determining the instantaneous level of substance within the tank in response to the converted values of differential pressure;

(d) determining a difference relationship between the prior collected average level and the instantaneous level;

(e) determining a relative weighting factor for the prior collected average level and the instantaneous level which weighting factor varies in accordance with the difference relationship;

(f) determining a new collected average in response to the relative weighting factor; and

(g) repeating steps (b) through (f) in which the new collected average becomes the prior collected average in step (d).

10. A method for measuring the level of substance in each tank of a plurality of tanks in which the level is subject to changes and updating a prior collected average level of substance in each tank comprising the steps of:

(a) continuously determining values of differential pressure from within each tank;

(b) determining the instantaneous level of substance within each tank in response to the determined values of differential pressure;

(c) determining a difference relationship between the prior collected average level and the instantaneous level of each tank;

(d) determining a relative weighting factor for the prior collected average level and the instantaneous level for each tank which weighting factor varies in accordance with the difference relationship of each tank;

(e) determining a new collected average for each tank in response to the relative weighting factor of each tank; and

(f) repeating steps (b) through (e) in which the new collected average becomes the prior collected average in step (c).