Measuring and testing – Gas analysis – Odor
Reexamination Certificate
1999-02-03
2001-03-06
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
Odor
Reexamination Certificate
active
06196051
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to apparatus for determining odor levels in odorized gas streams.
2. Description of the Related Art
Federal and state regulations require that combustible gases (e.g., natural gas) in transmission lines be odorized to provide a quick and easy means for detecting the presence of gases. Odorization involves adding small amounts of a chemical with a distinctive odor to the gas stream. This odor facilitates leak detection and provides an early warning of potentially unsafe conditions.
The odor must be readily detectable by a person with a normal sense of smell when gas is present at a given concentration in air. The concentration is typically specified as a certain percentage of the lower explosive limit (LEL) of the gas.
Federal and state odorizing regulations require gas operators to conduct periodic sampling at distribution sites to assure proper odor levels. Portable instruments, sometimes referred to as odorometers, have been devised to determine gas odor levels using olfactory testing. These instruments are available from a number of manufacturers including Bacharach, Inc. and Heath Consultants, Inc.
In one known device, gas to be analyzed enters the instrument through a gas intake port. The gas passes through a low pressure regulator and then a flow adjustment valve, which is operated by a user. The gas then enters a sensor chamber, which measures gas flow. A signal from the sensor chamber is processed, converted to a digital signal and fed to a liquid crystal display (LCD). The gas from the sensor chamber is then mixed with air drawn in by an air blower. The air-gas mixture then exits the device through an exhaust port, where it can be sniffed by a user.
One test that is commonly performed with such a device is known as a threshold odorant test (TOT). This test is used to determine a threshold gas-air concentration at which odor is barely detectable. In this use, the operator slowly opens the flow adjustment valve, allowing the gas sample to enter the instrument, while at the same time breathing normally with his or her nose placed close to the exhaust port. When odor in the sample is detected, the operator depresses a read button to observe a reading on the LCD corresponding to gas flow. A look-up chart is then used to convert the reading into a percent gas concentration, which is then hand-written somewhere for recordation.
Another use of the device is to determine odor characteristics at given gas-air concentrations. In this use, a gas/air mixture at a preset concentration is sniffed by various persons who then categorize the odor level as “absent,” “barely detectable,” “readily detectable,” “strong” or “obnoxious.”
A significant problem with these known devices it that they fail to provide accurate and repeatable gas concentration readings. Except for the LCD output, the instruments are substantially analog devices and lack adequate control means to ensure steady operation. For instance, the fans or blowers used to draw air through the devices cannot be sufficiently controlled to ensure constant speed, which is critical in determining gas concentration.
Furthermore, the known devices fail to provide adequate mixing of the sample gas and air. Consequently, the gas-air mixtures are not uniformly mixed, resulting in testing inaccuracies.
In addition, known devices are not equipped with recording means for storing and/or analyzing test data. Consequently, users must hand-write the data somewhere and use a look-up table to cross-reference data with gas concentration values. This is a potential source for further errors.
BRIEF SUMMARY OF THE INVENTION
Thus, a primary object of the invention is to provide a device for determining odor levels in gas streams that produces highly accurate and repeatable results.
Another object of the invention is to provide a device for determining odor levels that is microprocessor based.
A further object of the invention is to provide a device for determining odor levels that thoroughly mixes the gas sample to be tested with air.
Yet another object of the invention is to provide a device that automatically records test data and is thereby substantially “paper-free.”
A further object of the invention is to provide a device that analyzes test data, obviating the need for look-up tables and data interpretation.
A further object of the invention is to provide a device that can download test data stored therein to a personal computer (PC) for analysis, report preparation and storage in a main database.
Still another object of the invention is to provide a device that can be linked to a printer to print data stored in the device.
Yet another object of the invention is to provide a device that can be uploaded with data such as test location and technician information from a PC.
These and other objects are accomplished by utilizing a microprocessor-based odorometer for correlating odor levels in gas streams with gas in air concentrations in accordance with the invention. The device includes a mixing chamber for mixing gas from a gas supply to be tested with air to form a gas-air mixture. The mixing chamber includes a gas inlet port through which the gas is received, an air intake port through which the air is received, and an outlet port through which the gas-air mixture exits the mixing chamber. A static mixing element is located at the air intake port to cause turbulence in incoming air flow to promote thorough mixing of the air and gas. The device includes a flow control valve that is connected to the gas supply to enable a user to selectively adjust the flow rate of the gas entering the device. A mass flow sensor is positioned between the flow control valve and the gas inlet port of the mixing chamber for accurately measuring the mass flow rate of the gas flowing into the mixing chamber. A motorized fan is positioned in a hose connected to outlet port of the mixing chamber for drawing the gas-air mixture out of the mixing chamber and moving it to a sniff chamber, where it can be sniffed by the user to detect odor.
The device is equipped with a microprocessor controller including a tachometer for determining the rotational speed of the motorized fan. The microprocessor controller is responsive to signals from a fan speed sensor for controlling the rotational speed of the motorized fan such that it is maintained at a substantially constant speed. Consequently, there is substantially constant air flow into the device.
A rechargeable lead-acid battery is provided for powering the instrument.
The device includes memory for storing test data. It is equipped with a keypad and an LCD display for user interface.
The device displays test results in actual air/gas percentages, eliminating the need for look-up charts.
The device records complete test results electronically. It can also record any comments by technicians relating to a given test such as, e.g., information on weather conditions at a test site. In addition, test records are stamped with date/time information as well as information on device calibration.
The apparatus can be linked to a PC to enable test and device data to be exchanged between the PC and the apparatus. A software package is provided for the PC to generate reports, graphs, and data archives from data read from the device. The device thus eliminates the need to manually write test reports. In addition, critical test data recorded by the device cannot be altered using the device. This feature substantially reduces the risk of test data being falsified by technicians.
Test data downloaded from the device to a PC can also be exported to third-party developed applications for further processing.
In addition, the software package allows user, test location and calibration information to be easily uploaded from the PC to the device. This feature eliminates the need for technicians to prepare forms and perform repetitive data entry.
The device also includes a user authentication feature. Each user is required to enter an identification and correspondin
Marshall Stephen Edward
Selman Glenn Scott
Skubis Christopher Lee
Politzer Jay L.
Williams Hezron
YZ Systems, Inc.
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