Explosion proof radar level gauge

Patent metadata

Field	Value
Publication number	US-10480985-B2
Application number	US-201715720031-A
Country	US
Kind code	B2
Filing date	Sep 29, 2017
Priority date	Sep 29, 2017
Publication date	Nov 19, 2019
Grant date	Nov 19, 2019

Abstract

A radar level gauge comprising a housing enclosing a compartment providing explosion proof protection, RLG circuitry located inside compartment, which circuitry is incompatible with intrinsic safety requirements, and a signal propagation device located outside the compartment. The housing has an explosion proof first signal passage providing a transmission line for the microwave transmit signal, and an explosion proof second signal passage in providing a two-wire interface for electrically conductively connecting the radar level gauge to an intrinsically safe system located externally of the radar level gauge. Further, the RLG includes an electrical barrier connected between the RLG circuitry and the two-wire interface, the electrical barrier preventing energy and/or thermal energy in the RLG circuitry from compromising the intrinsic safety of an intrinsically safe system connected to the two-wire interface.

First claim

What is claimed is:

1. A radar level gauge for determining the filling level of product in a tank, said gauge comprising:
a housing with a housing wall enclosing a compartment providing explosion proof protection;
RLG circuitry located inside compartment, said circuitry in use having an available electrical and/or thermal energy incompatible with intrinsic safety requirements;
a signal propagation device located outside said compartment, said signal propagation device being adapted to direct a microwave transmit signal toward said product and return reflections thereof from a surface of said product;
an explosion proof first signal passage in said housing wall, said first signal passage providing a transmission line for said microwave transmit signal between said RLG circuitry and said signal propagation device;
an explosion proof second signal passage in said housing wall, said second signal passage providing a two-wire interface for electrically conductively connecting said radar level gauge to an intrinsically safe system located externally of said radar level gauge, to provide at least one of: communication between said radar level gauge and said intrinsically safe system, and power supply to said RLG circuitry; and
an electrical barrier connected between said RLG circuitry and the two-wire interface, said electrical barrier preventing energy or voltages in said RLG circuitry from compromising the intrinsic safety of an intrinsically safe system connected to the two-wire interface.

2. The radar level gauge according to claim 1 , wherein said RLG circuitry includes at least one energy store having an energy storage capacity which is incompatible with IS requirements at a voltage applied to the storage capacity.

3. The radar level gauge according to claim 1 , wherein said RLG circuitry includes at least one energy store having an energy storage capacity greater than 600 μJ.

4. The radar level gauge according to claim 1 , wherein said RLG circuitry includes one of:
a capacitance of at least 100 μF with a voltage across the capacitance of at least 5 V,
a capacitance of at least 25 μF with a voltage across the capacitance of at least 6.5 V,
a capacitance of at least 10 μF with a voltage across the capacitance of at least 8 V,
a capacitance of at least 2 μF with a voltage across the capacitance of at least 12 V, and
a capacitance of at least 0.5 μF with a voltage across the capacitance of at least 16 V.

5. The radar level gauge according to claim 1 , wherein the electrical barrier includes at least one first diode connected in series between the RLG circuitry and the two-wire interface, thereby preventing energy from said RLG circuitry from reaching an intrinsically safe system connected the two-wire interface.

6. The radar level gauge according to claim 5 , wherein the electrical barrier includes at least one fuse and/or one resistor limiting a current and/or a power said at least one first diode is subjected to.

7. The radar level gauge according to claim 1 , wherein the electrical barrier includes at least one second diode connected in parallel between lines of the two-wire interface, thereby preventing negative voltages at the two-wire interface.

8. The radar level gauge according to claim 7 , wherein the electrical barrier includes at least one fuse and/or one resistor limiting a current and/or a power said at least one second diode is subjected to.

9. The radar level gauge according to claim 1 , wherein said first explosion proof passage is adapted to ensure that high frequency energy transmitted through the first passage comply with requirements defined in clause 6.6.1 of IEC 60079-0.

10. The radar level gauge according to claim 1 , wherein said compartment and said first and second passages comply with the Ex-d requirements of IEC 60079-1.

11. The radar level gauge according to claim 1 , wherein said intrinsically safe system complies with the Ex-ia requirements of IEC 60079-11.

12. The radar level gauge according to claim 1 , wherein said signal propagation device is a directional antenna.

13. The radar level gauge according to claim 12 , wherein said first signal passage includes a waveguide with a dielectric filling member made of a structurally strong and temperature resistant material.

14. The radar level gauge according to claim 1 , wherein said signal propagation device is a transmission line probe.

15. The radar level gauge according to claim 14 , wherein said first signal passage includes an electrical filter circuit having an input coupled to the RLG circuitry and an output coupled to the transmission line probe, the electrical filter circuit exhibiting a series capacitance for non-conductively coupling the RLG circuitry to the transmission line probe.

16. The radar level gauge according to claim 1 , wherein the transmit signal has a frequency greater than 1 GHz.

17. The radar level gauge according to claim 1 , wherein said RLG circuitry includes:
transceiver circuitry configured to generate and transmit an electromagnetic transmit signal S T and receive an electromagnetic return signal reflected from the tank,
processing circuitry configured to determine the distance between a reference position and the surface of the product based on a relationship between the transmit signal and the return signal, and
signal/power circuitry configured to receive operating power and communicate measurement data.

Assignees

• Rosemount Tank Radar Ab

Inventors

• Kleman Mikael
• Nilsson Leif

Classifications

• G01S13/08

  Systems for measuring distance only (indirect measurement G01S13/46) · CPC title

• G01S7/003

  Transmission of data between radar, sonar or lidar systems and remote stations · CPC title

• G01S13/88

  Radar or analogous systems specially adapted for specific applications (electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00) · CPC title

• G01S7/032

  Constructional details for solid-state radar subsystems · CPC title

• G01S7/02

  of systems according to group G01S13/00 · CPC title