LEVEL MEASUREMENT SYSTEM

• US 20100257931A1
• Filed: 11/13/2008
• Published: 10/14/2010
• Est. Priority Date: 11/13/2007
• Status: Active Grant

• Current Assignee: Tracerco Ltd.
• Original Assignee: Johnson Matthey PLC
• Inventors: Featonby, Paul David, James, Kenneth, Jackson, Peter, Partington, Thomas John
• Granted Patent: US 8,495,913 B2
• Time in Patent Office: Days
• US Class Current: 73/290.V
• CPC Class Codes: G01F 22/00 Methods or apparatus for measuring volume of fluids or fluent solid material, not otherwise provided for
• CPC Class Codes: G01F 23/2961 for discrete levels G01F23/2962 - G01F23/2968 take precedence
• CPC Class Codes: G01F 23/2962 Measuring transit time of reflected waves

Abstract

An apparatus and method for the identification of different phases (11-20) in a multi-phase medium comprises at least two arrays (26A, 26B) of ultrasound transducers capable of transmitting and receiving ultrasound through the medium separating them. The method and apparatus is useful for the location of phase interfaces in vessels such as oil separators.

Claims

1. A method of determining the location of an interface between two materials within a vessel comprising:

(a) providing a plurality of first ultrasound transducers capable of transmitting ultrasound through at least one of said two materials, said first ultrasound transducers being located within a first elongate housing, spaced apart from one another along a longitudinal axis of the housing;

(b) providing a plurality of second ultrasound transducers capable of receiving ultrasound transmitted by said first ultrasound transducers and generating an electrical signal in response thereto, said second ultrasound transducers being located within a second elongate housing, spaced apart from one another along a longitudinal axis of the housing,

(c) each one of said first ultrasound transducers being associated with a respective one of said second ultrasound transducers to form a transmitter-receiver pair, such that ultrasound emitted by one member of said pair may be received by and generate an electric signal in the other member of said pair,

(d) locating the first and second housings within the vessel such that the ultrasound transmitted by at least one of the first transducers is capable of being detected by at least one respective second transducer and that the first and second housings containing the transducers are at least partially immersed in at least one of the materials contained in the vessel,

(e) transmitting ultrasound from more than one of said first ultrasound transducers to respective second ultrasound transducers and monitoring the signal generated by each of said second ultrasound transducers in response to the ultrasound transmitted by said first ultrasound transducers,

(f) comparing the signal generated by the receiving second ultrasound transducer or a parameter calculated from said signal with the signal generated by a different receiving ultrasound transducer or a parameter calculated from said signal to determine whether the acoustic characteristics of the material located between the first housing and the second housing changes between the compared receiving transducers.

2. A method according to claim 1, wherein the first transducer transmits a pulse of ultrasound towards the respective second transducer, which, upon receipt of the pulse is stimulated to transmit back to the initiating first transducer.

3. A method according to claim 2, wherein a pulse generator provides to each transmitting transducer a coded sequence of pulses and further wherein the pulse coding of adjacent transmitting transducers is different.

4. A method according to claim 1, wherein adjacent transmitting transducers are stimulated to transmit at different times.

5. A method according to claim 1, wherein the time of flight of the ultrasonic energy between a first transmitter-receiver pair is compared with the time of flight of ultrasonic energy between an adjacent transmitter-receiver pair.

6. A method according to claim 1, wherein the attenuation of the ultrasonic energy between a first transmitter-receiver pair is compared with the attenuation of ultrasonic energy between an adjacent transmitter-receiver pair.

7. A method according to claim 6, wherein said first ultrasound transducers comprises a linear array of ultrasound transmitters T_n-T_n+x, where n is an integer from 1 to x and x is the number of transmitters in the array, said second ultrasound transducers comprise a linear array of ultrasound receivers R_n-R_n+x, said transmitters and receivers forming a plurality of transmitter-receiver pairs TR_n, and both first and second housings are placed in a vessel aligned with and parallel to each other, oriented such that the housings extend towards the bottom of the vessel, T₁ and R₁ being nearest the bottom of the vessel, and wherein step (f) comprises:

i. measuring the amplitude of the signal A_n received by the receiving transducer R_n;

ii. comparing A_n with a predetermined amplitude A_L;

iii. if A_n>

A_L then measuring TOF_n where TOF_n is the time of flight of the sound between T_n and R_n;

iv. if A_n<

A_L then recording TR_n as located within a material phase having high sound attenuation properties;

v. repeating steps i-iv for each TR_n until n=x;

vi. comparing TOF_n with TOF_n+1;

vii. if TOF_n+1>

TOF_n+P % then recording that a material phase boundary lies between TR_n and TR_n+1 where P is a predetermined value representing a significance factor.

8. A method according to claim 7, wherein steps i-iv are carried out for each TR_n in sequence starting from TR₁.

9. A method according to claim 7, further comprising:

viii. comparing TOF_n with TOF_n+2 and optionally TOF_n+3, and

ix. if each of TOF_n+1, TOF_n+2 and optionally TOF_n+3>

TOF_n+P % then recording that a material phase boundary lies between TR_n and TR_n+1.

10. A method according to claim 7, wherein A_n and TOF_n are calculated as average values of A and TOF values measured at intervals over a period of time.

11. A method according to claim 7, further comprising compiling a phase profile of the material within the vessel from the location of each TR_n and the TOF_n and A_n measurements.

12. A method according to claim 1, wherein at least one of the transducers generates a signal in response to the detection of its own emissions reflected back from the internal wall of the housing and wherein said signal is processed to provide information about the acoustic coupling between the external wall of the housing and the material external and immediately adjacent to it.

13. A method according to claim 1, wherein the time of flight of the ultrasonic energy between the members of a transmitter-receiver pair in one direction is compared with time of flight in the other direction such that the rate and direction of fluid flow may be estimated.

14. A method according to claim 1, wherein at least some of the transducers are periodically stimulated to emit sound waves of a frequency suitable to induce cavitation of the fluid at the surface of the transducer and housing.

15. An apparatus adapted to be used to carry out the method according to claim 1 comprising:

(a) a plurality of first ultrasound transducers capable of transmitting ultrasound through at least one of said materials, said first transducers being located within a first elongate housing, arranged as a linear array, spaced apart from one another along a longitudinal axis of the housing;

(b) a plurality of second ultrasound transducers capable of receiving ultrasound transmitted by said first ultrasound transducers and generating an electrical signal in response thereto, said second transducers being located within a second elongate housing, arranged as a linear array, spaced apart from one another along a longitudinal axis of the housing,

(c) each one of said first ultrasound transducers being associated with a respective one of said second ultrasound transducers to form a transmitter-receiver pair, such that ultrasound emitted by one member of said pair may be received by and generate an electric signal in the other member of said pair,

(d) mounting means for said first and second housings, said mounting means being capable of maintaining said first and second housings in a position relative to each other such that each one of a transmitter-receiver pair is aligned with the other one of the transmitter-receiver pair and that ultrasound transmitted by at least one of the first transducers is capable of being detected by at least one respective second transducer,

(e) mounting means for mounting the first and second housings within a vessel such that at least a part of the first and second housings containing the transducers may be immersed in at least one of the materials contained in the vessel, and

(f) signal processing means capable of comparing signals generated by the second ultrasound transducers or a parameter calculated from said signals to determine whether the acoustic characteristics of any material located between the first housing and the second housing changes between any of the transmitter-receiver pairs.

16. An apparatus according to claim 15, wherein the housings are formed from a titanium-containing metal alloy.

17. An apparatus according to claim 15, wherein the housings contain an acoustic coupling medium.

18. An apparatus according to claim 15, wherein each housing is coated on at least one of its internal and external walls with an acoustically coupling coating.

19. An apparatus according to claim 15, further comprising a plurality of third transducers capable of transmitting sonic energy through at least one of said materials and a plurality of fourth transducers capable of receiving sonic energy transmitted by said third ultrasound transducers and generating an electrical signal in response thereto each one of said third transducers being associated with a respective one of said fourth transducers to form a transmitter-receiver pair, such that ultrasound emitted by one member of said pair may be received by and generate an electric signal in the other member of said pair.

20. An apparatus according to claim 19, wherein said plurality of third and fourth transducers are adapted to transmit and receive sonic energy of a different frequency from said first and second transducers.

21. A method according to claim 1, wherein the time of flight of the ultrasonic energy between a first transmitter-receiver pair is compared with the time of flight of ultrasonic energy between an adjacent transmitter-receiver pair and further wherein the attenuation of the ultrasonic energy between a first transmitter-receiver pair is compared with the attenuation of ultrasonic energy between an adjacent transmitter-receiver pair.