METHOD AND APPARATUS FOR DETERMINING THE SUPERCOMPRESSIBILITY FACTOR OF NATURAL GAS

• US 3,701,280 A
• Filed: 03/18/1970
• Issued: 10/31/1972
• Est. Priority Date: 03/18/1970
• Status: Expired due to Term

• Current Assignee: Larry J. Stroman
• Original Assignee: Larry J. Stroman
• Inventors: Stroman, Larry J.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Smollar, Marvin
• Application Number:
  US05/020,606
• Time in Patent Office: 958 Days
• Field of Search: 73/194M,231M,23,30
• US Class Current: 73/861.02
• CPC Class Codes: G01F 15/043 using electrical means

Abstract

In one exemplar embodiment, an electrical circuit for deriving an electrical signal representative of the square of the supercompressibility factor of natural gas by providing means for measuring the static pressure of the gas, multiplying the static pressure measurement by predetermined functions of pressure, temperature and specific gravity for a preselected range of operation and adding a predetermined constant factor, approaching unity, to the product of the pressure and functions of pressure, temperature and specific gravity.

Claims

1. In apparatus for continuously determining the quantity of natural gas flowing in a pipeline over a preselected range of specific gravity, pressure and temperature utilizing a gas flow computer, the improvement therein for continuously correcting for the supercompressibility of the gas comprising measuring means for continuously measuring the static pressure of the gas and generating a first electrical signal in response thereto, a first multiplying circuit for receiving said first electrical signal and multiplying said signal by predetermined functions of pressure and specific gravity for generating a second electrical signal representative of the product of said static pressure and said predetermined functions of pressure and specific gravity, a second multiplying circuit for receiving said second electrical signal and multiplying said signal by a predetermined function of temperature and generating a third electrical signal representative of the product of said static pressure and said predetermined functions of pressure, specific gravity and temperature, means for producing a fourth electrical signal representative of a first predetermined constant, adding means for receiving said third and fourth electrical signals and summing said signals for producing a fifth electrical signal representative of the squared supercompressibility factor of the gas, means for producing a sixth electrical signal representative of barometric pressure, adding means for receiving and summing said first and sixth electrical signals representative of static pressure and barometric pressure and producing a seventh signal representative of absolute pressure, and a third multiplying circuit for receiving said fifth and seventh signals representative of the squared supercompressibility factor and absolute pressure, multiplying said signals and generating an eighth electrical signal representative of the product of said absolute pressure and squared supercompressibility factor for application to the gas flow computer.

2. The apparatus as described in claim 1, wherein said first multiplying circuit includes an input voltage divider circuit for receiving said first electrical signal and including a first manual potentiometer, said first manual potentiometer adjustable for causing a voltage drop across said potentiometer representative of the average specific gravity of the natural gas over the preselected range of specific gravity, and an amplifier circuit connected to said input voltage divider and receiving said first electrical signal, said voltage divider and amplifier circuits cooperating to multiply said first electrical signal by said preselected functions of pressure and gravity and generating said second signal.

3. The apparatus as described in claim 2, wherein said voltage divider has a division ratio equal to a second preselected constant multiplied by said preselected function of pressure.

4. The apparatus as described in claim 2, wherein said amplifier circuit has a gain equal to a third preselected constant multiplied by said preselected function of pressure.

5. The apparatus as described in claim 2, wherein said preselected function of specific gravity is equal to said seCond preselected constant multiplied by said average specific gravity value entered in said manual potentiometer plus said third preselected constant.

6. The apparatus as described in claim 1, wherein said second multiplying circuit includes an amplifier circuit having a gain varying in direct response to said predetermined function of temperature obtained by a temperature transducer circuit continuously monitoring the temperature of the gas flowing in the pipeline.

7. The apparatus as described in claim 1, wherein said adding means comprises a summing amplifier circuit.

8. The apparatus as described in claim 1, wherein said means for receiving and summing said first and sixth electrical signals representative of static pressure and barometric pressure comprises an input voltage divider network and a summing amplifier circuit.

9. A method of continuously determining a function of the supercompressibility factor of natural gas flowing in a pipeline over a preselected range of specific gravity, pressure and temperature, comprising the steps of measuring the continuous static pressure of the gas and generating an electrical signal representative thereof, deriving predetermined functions of pressure, temperature and specific gravity over the preselected range of operation, multiplying said signal representative of the static pressure of the gas by said predetermined functions of pressure, temperature and specific gravity for generating an electrical signal representative of the product PSF(P)F(G)F(T), generating an electrical signal representative of a predetermined constant factor valid for the preselected range of pressure, temperature and specific gravity, and deriving an electrical signal representative of the squared supercompressibility factor of the gas equal to the signal representing the product PSF(P)F(G)F(T) plus the electrical signal representative of said derived predetermined constant.

10. The method as described in claim 9, including the further steps of generating an electrical signal representative of barometric pressure, deriving an electrical signal representative of absolute pressure of the gas by summing said electrical signals representative of static pressure and barometric pressure, and deriving an electrical signal representative of the product of said squared supercompressibility factor and said absolute pressure.

11. A method of continuously determining the value of the squared supercompressibility factor of natural gas flowing in a pipeline over a preselected range of specific gravity, pressure and temperature, comprising the steps of continuously measuring the static pressure of the flowing gas and generating a signal representative thereof, deriving functions of pressure, temperature and specific gravity over the preselected range of operation, multiplying said signal representative of the static pressure of the gas by said derived functions of pressure, temperature and specific gravity for generating a signal representative of the product PsF(P)F(G)F(T), deriving a constant factor related to the value of the squared supercompressibility factor of the gas at the average of the preselected range of specific gravity, pressure and temperature represented by the equation K1 Fpv2 - PsF(P)F(G)F(T) and generating a signal representative thereof, and deriving a signal representative of the squared supercompressibility factor of the gas equal to the sum of the signal representing said product PsF(P)F(G)F(T) and the signal representing said constant factor.

12. A method of continuously determining a function of the supercompressibility factor of natural gas flowing in a pipeline over a preselected range of specific gravity, pressure and temperature, comprising the steps of continuously measuring the static pressUre of the flowing gas and generating a signal representative thereof, deriving functions of pressure, temperature and specific gravity over the preselected range of operation, multiplying said signal representative of the static pressure of the gas by said derived functions of pressure, temperature and specific gravity for generating a signal representative of the product PsF(P)F(G)F(T), deriving a constant factor related to the value of the squared supercompressibility factor of the gas at the average of the preselected range of specific gravity, pressure and temperature represented by the equation K1 Fpv2 - PsF(P)F(G)F(T) and generating a signal representative thereof, deriving a signal representative of the squared supercompressibility factor of the gas equal to the sum of the signal representing said product PsF(P)F(G)F(T) and the signal representing said constant factor, continuously measuring barometric pressure and generating a signal representative thereof, deriving a signal representative of absolute pressure of the gas by summing said signals representative of static pressure of the gas and barometric pressure, and deriving a signal representative of the desired function of the supercompressibility factor by multiplying said signals representative of the squared supercompressibility factor and absolute pressure.

13. Apparatus for continuously determining a function of the supercompressibility factor of natural gas flowing in a pipeline over a preselected range of specific gravity, pressure and temperature, comprising means for continuously measuring the static pressure of the gas and generating a first signal in response thereto, means for continuously measuring the temperature of the gas and generating a second signal representative of a predetermined function of said measured temperature for the preselected ranges of specific gravity, pressure and temperature, first circuit means receiving said first and second signals and generating a third signal representative of the product of said first and second signals and predetermined functions of pressure and specific gravity for the preselected ranges of specific gravity, pressure and temperature, said third signal being representative of the product PsF(P)F(G)F(T), means for generating a fourth signal representative of a constant factor related to the squared value of the supercompressibility factor of the gas at the average of the preselected ranges of specific gravity, pressure and temperature represented by the equation K1 Fpv2 -PsF(P)F(G)F(T), and second circuit means for summing said third and fourth signals and generating a fifth signal representative of the desired function of the supercompressibility factor of the gas.

14. The apparatus as described in claim 13, wherein said first circuit means comprises an input voltage divider circuit for receiving said first signal and including a manual potentiometer, said potentiometer adjustable to a resistive value representative of the average specific gravity of the natural gas, said voltage divider having a division ratio equal to a first preselected constant multiplied by said preselected function of pressure, an amplifier circuit having a gain equal to a second preselected constant multiplied by said predetermined function of pressure, said voltage divider and amplifier circuits cooperating to multiply said first signal representative of static pressure by said preselected functions of pressure and gravity, and an amplifier circuit the gain of which varies in direct response to said second signal representative of said predetermined function of temperature.

15. Apparatus as described in claim 14, wherein said preselected function of gravity is equal to said first preselected constant multiplied by said average gravity resistive value entered in said manual potentIometer plus said second preselected constant.

16. The apparatus as described in claim 13, wherein said means for generating said fourth signal includes a source of positive dc voltage, and a manual potentiometer connected to said source of positive dc voltage for adjusting the voltage drop across the potentiometer to equal said constant factor.

17. The apparatus as described in claim 13, wherein said second circuit means comprises a summing amplifier for receiving and summing said third and fourth signals.

18. The apparatus as described in claim 13, further including means for continuously measuring barometric pressure and generating a sixth signal in response thereto, means for receiving said first and sixth signals representative of said static pressure of the gas and barometric pressure and summing said signals to produce a seventh signal representative of the absolute pressure of the gas, and third circuit means receiving said fifth and seventh signals and generating an eighth signal representative of the desired function of the squared supercompressibility factor obtained as a product of said fifth and seventh signals.

19. The apparatus as described in claim 18, wherein said means for receiving and summing said first and sixth electrical signals comprises a summing amplifier circuit.

20. Apparatus for continuously determining a function of the squared supercompressibility factor of natural gas flowing in a pipeline over a preselected range of specific gravity, pressure and temperature, comprising means for continuously measuring the static pressure of the gas and generating a first signal in response thereto, means for continuously measuring the temperature of the gas and generating a second signal representative of a predetermined function of said measured temperature for the preselected ranges of specific gravity, pressure and temperature, first circuit means receiving said first and second signals and generating a third signal representative of the product of said first and second signals and predetermined functions of pressure and specific gravity for the preselected ranges of specific gravity, pressure and temperature, said third signal being representative of the product PsF(P)F(G)F(T), means for generating a fourth signal representative of a constant factor related to the squared value of the supercompressibility factor of the gas at the average of the preselected ranges of specific gravity, pressure and temperature represented by the equation K1 Fpv2 -PsF(P)F(G)F(T), second circuit means for summing said third and fourth signals and generating a fifth signal representative of the squared supercompressibility factor of the gas, means for continuously measuring barometric pressure and generating a sixth signal in response thereto, means for receiving said first and sixth signals representative of said static pressure of the gas and barometric pressure and summing said signals to produce a seventh signal representative of the absolute pressure of the gas, and third circuit means receiving said fifth and seventh signals and generating an eighth signal representative of the desired function of the squared supercompressibility factor obtained as a product of said fifth and seventh signals.