Infrared leak detector

• US 6,791,088 B1
• Filed: 05/03/2002
• Issued: 09/14/2004
• Est. Priority Date: 05/04/2001
• Status: Expired due to Fees

• Current Assignee: Twin Rivers Engineering Incorporated
• Original Assignee: Twin Rivers Engineering Incorporated
• Inventors: Williams, William J. II, Dejong, Glenn A.
• Primary Examiner(s): Hannaher, Constantine
• Assistant Examiner(s): Gabor, Otilia
• Application Number:
  US10/138,399
• Time in Patent Office: 865 Days
• Field of Search: 250/343, 250/345, 250/338.5, 73/40, 73/407, 73/491, 73/492, 340/605, 340/539, 340/632, 340/491.6, 340/693.5, 340/635, 340/363, 340/464, 340/455, 356/437, 356/414
• US Class Current: 250/343
• CPC Class Codes: G01M 3/047 with photo-electrical detection means, e.g. using optical fibres
• CPC Class Codes: G01N 21/11 Filling or emptying of cuvettes
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis
• CPC Class Codes: G01N 2201/0221 Portable; cableless; compact; hand-held

Abstract

A leak detector using an infrared emitter and pyroelectric sensor to form an instrument for identifying the presence and concentration of a selected material type gas compound, such as a refrigerant gas compound within a given sample, such as a sample of ambient air. For the detection, a radiation flux coming from an infrared emitter penetrates the sample, which is analyzed spectrally, and results in a wave length-specific signal being generated at the output of the detector. By controlling the type of optical filter, the radiation energy is controlled at a selected wavelength, to ensure coverage of all selected compounds. For refrigerants, the selected wavelength can be between approximately 8 to approximately 10 microns in the wavelength range. This selected wavelength obscures other signals, thus minimizing false alarms. By not chopping or pulsing the emitter, the leak detector has a faster response time with no adverse impacts on the accuracy of the compound material being detected. To further minimize false alarms and to ensure that the emitter does not come in contact with the sample gas, an additional filter can be positioned in the optical path. For refrigerant compounds, the filter can block out signals below approximately 6 microns. For detecting refrigerants, two filters can be used: 1) a broadband filter to allow detection of all refrigerants currently on the market, and 2) a narrowband filter to limit detection only to R134_a which possesses a narrow wavelength, so that detection of other compounds (or contaminants) can be minimized.

Claims

1. A portable handheld infrared (IR) refrigerant gas leak detector, comprising in combination:

an infrared (IR) chamber;

means to solely draw a gas sample from a gas leak emanating from a single pressurized refrigerant gas source into the chamber;

means for detecting a selected compound from the sample in the chamber; and

a handheld housing for supporting the chamber, the drawing means and the detecting means so that the detector is portable and is carryable in a single hand, wherein the detector detects whether there is a leak in the single pressurized gas source without introducing or mixing a secondary tracer gas within the device.

2. The portable detector of claim 1, wherein the IR chamber includes:

an IR emitter for emitting an IR beam;

an IR filter in the path of the beam; and

an IR sensor for receiving the emitted beam; and

and a reaction tube where the sample interacts with the IR beam.

3. The portable detector of claim 2, wherein the filter includes:

a broadband filter for passing wavelengths between approximately 8 to approximately 10 microns therethrough, and the sample is refrigerant.

4. The portable detector of claim 2, wherein the IR filter includes:

a narrowband filter which limits detection to (HFC) Hydrogenated Fluorocarbon compound refrigerants.

5. The portable detector of claim 2, wherein the IR filter includes:

a first broad band filter for filtering the beam before the beam passes into the chamber for removing portions of gas constituents from being selected for leak detection; and

a narrow broad band filter for filtering the beam after the beam passes through the chamber and into the IR sensor.

6. The portable detector of claim 5, wherein the first broadband filter and the second broadband filter each pass in-band IR energy within the range of approximately 8 to approximately 10 microns.

7. The portable detector of claim 2, further comprising:

an audio output to the detector for emitting an audio signal from a detected leak, the audio output having a zero control setting having a substantially constant approximately 1 Hz chirp signal, the audio output digitally shifting to a 2 Hz chirp rate upon detection of the gas leak, and the audio output increasing the chirp rate above approximately 2 Hz in proportion to size of the gas leak being detected.

8. The portable detector of claim 2, further comprising:

a signal detection accumulator with a forward biased detector circuit; and

a zero circuit referenced to approximately a circuit ground instead of referenced between supply rails.

9. The portable detector of claim 2, further comprising:

a window adjacent to the emitter which reduces convection noise and increases in-band IR radiation signal strength.

10. The portable detector of claim 1, wherein the drawing means includes:

an air pump having a continuous sampling rate of approximately hundreds of cc/min so that the detector does not have to be within approximately 0.635 centimeters (approximately 0.25 inch) of a refrigerant leak source, and the sample includes an air sample that includes the refrigerant leak source.

11. The portable detector of claim 1, wherein the IR leak detector includes:

a pyroelectric sensor.

12. The portable detector of claim 11, wherein the sensor is selected from at least one of:

a pair of back to back piezo capacitor elements.

13. The portable detector of claim 1, further comprising:

an elongated continuously cylindrical and detachable needle probe extension for attaching adjacent to the drawing means for allowing the detector to take the sample in tight spaces, the needle probe extension having an inlet opening adjacent to and not at a tip end of the needle probe extension.

14. The portable detector of claim 1, wherein the IR chamber includes:

a gold plated plastic infrared (IR) optical chamber.