US3943775A
Expired / Lapsed
US
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Method and apparatus for predicting the explosiveness of a volume containing inert gas and hydrocarbon vapors when mixed with air
Assignee: Chevron USA Inc
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Filing: 1975-03-24
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Granted: 1976-03-16
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Expires: 1995-03-24
Abstract
Abstract A method is disclosed for changing the inert gaseous content of a volume including hydrocarbon vapors to air without producing an explosive mixture. First a sample is obtained from the volume and then mixed with air to form a gas mixture. During the mixing, the mixture is monitored for values including percentage in tenths of lower explosive limit and percentage of oxygen. Then the values are evaluated to see if the mixture forms an explosive mixture; and, if so, the volume is purged with an inert gas prior to ventilating the volume with air to remove the inert gaseous content including hydrocarbon vapors from the volume without producing an explosive mixture of the hydrocarbon vapors and air. Apparatus is also disclosed for use with the method. A sampling hose is located in a gaseous sample volume of inert gas and hydrocarbon vapors. It is connected to a valve to regulate the flow of gas through it. A second valve is connected to a source of air. These valves are also connected to respective sides of a tee so that the sample volume and air begin to mix in it as the mixture passes to a catalytic combustion indicator. The indicator reads percent oxygen and the percent (as a decimal) of the lower explosive limit. The results may be recorded graphically or may be displayed on digital means by using two analog-to-digital converters, a summer and a digital display. One converter emits a unit pulse series for each tenth of the lower explosive limit; the other emits a unit pulse series for each percent of oxygen. These pulses are added in the summer and displayed on a digital display.
Inventors
- 👤 Bruce De Baun
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:32
CPC Classifications
G; G01; G01N; G01N25/00; G01N25/50; G01N25/54; Y; Y10; Y10T; Y10T137/00; Y10T137/0318
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
136 words
A method of changing the inert gaseous content of a volume containing an inert gas mixture including hydrocarbon vapors to air without producing an explosive mixture of hydrocarbon vapors and air in said volume, comprising: obtaining a sample of inert gas including hydrocarbon vapors from a volume having an inert gaseous content including hydrocarbon vapors; mixing said sample with air to form a mixture; monitoring said mixture as it is being mixed for values including tenths of lower explosive limit and percentage of oxygen; determining from said values if said gaseous content of said volume and air can form an explosive mixture and, if so, purging said volume with inert gas prior to ventilating said volume with air to displace the inert gas from said volume without producing an explosive mixture of hydrocarbon vapors and air.
Claim 2
Independent Claim
136 words
A method of changing the inert gaseous content of a volume containing an inert gas mixture including hydrocarbon vapors to air without producing an explosive mixture of hydrocarbon vapors and air in said volume, comprising: obtaining a sample of inert gas including hydrocarbon vapors from a volume having an inert gaseous content including hydrocarbon vapors; mixing said sample with air to form a mixture; monitoring said mixture as it is being mixed for values including tenths of lower explosive limit and percentage of oxygen; determining from said values if said gaseous content of said volume and air can form an explosive mixture and, if so, purging said volume with inert gas prior to ventilating said volume with air to displace the inert gas from said volume without producing an explosive mixture of hydrocarbon vapors and air.
Claim 3
Dependent Claim
65 words
The method of claim 1 further characterized by converting said values to whole numbers and, if the summed said whole numbers exceed 21, purging said volume with an inert gas; monitoring said volume until the summed whole numbers are 21 and less; and ventilating said volume with air to displace the inert gas from said volume when the summed whole numbers are 21 and less.
Claim 4
Dependent Claim
74 words
The method of claim 1 further characterized by monitoring said volume while said volume is being ventilated with air for new values including tenths of lower explosive limit and percentage of oxygen; determining from said new values if said gaseous content of said volume and air can form an explosive mixture; if so, purging said volume with inert gas prior to ventilating said volume with air to displace the inert gas from said volume.
Claim 5
Independent Claim
189 words
A method of changing the inert gaseous content of a volume containing an inert gas mixture including hydrocarbon vapors to air without producing an explosive mixture of hydrocarbon vapors and air in said volume, comprising: obtaining a sample of inert gas including hydrocarbon vapors from a volume having an inert gaseous content including hydrocarbon vapors; mixing said sample with air to form a mixture; monitoring said mixture as it is being mixed for values including tenths of lower explosive limit and percentage of oxygen; providing a graph having the tenths of the lower explosive limit of the volume plotted along one edge of the graph and the percent oxygen of the volume along another edge of the graph; finding the point on the graph which corresponds with coordinates representing the values of tenths of lower explosive limit and percent oxygen of said volume; and adding inert gas to said volume for a period of time if the point is above the critical dilution line prior to ventilating said volume with air to remove the inert gas from said volume without producing an explosive mixture of hydrocarbon vapors and air.
Claim 6
Independent Claim
189 words
A method of changing the inert gaseous content of a volume containing an inert gas mixture including hydrocarbon vapors to air without producing an explosive mixture of hydrocarbon vapors and air in said volume, comprising: obtaining a sample of inert gas including hydrocarbon vapors from a volume having an inert gaseous content including hydrocarbon vapors; mixing said sample with air to form a mixture; monitoring said mixture as it is being mixed for values including tenths of lower explosive limit and percentage of oxygen; providing a graph having the tenths of the lower explosive limit of the volume plotted along one edge of the graph and the percent oxygen of the volume along another edge of the graph; finding the point on the graph which corresponds with coordinates representing the values of tenths of lower explosive limit and percent oxygen of said volume; and adding inert gas to said volume for a period of time if the point is above the critical dilution line prior to ventilating said volume with air to remove the inert gas from said volume without producing an explosive mixture of hydrocarbon vapors and air.
Claim 7
Dependent Claim
131 words
The method of claim 4 further characterized by monitoring said volume while said volume is being ventilated with air for new values including tenths of lower explosive limit and percentage of oxygen; finding a point on the graph which corresponds with coordinates representing said new values; finding a point on the graph representing 0.0 lower explosive limit and 21% oxygen; drawing a straight line through each of said points; determining if said line crosses a vertical line representing the lower explosive limit of said volume; and adding inert gas to said volume for a period of time if the point is above the critical dilution line prior to ventilating said volume with air to remove the inert gas from said volume without producing an explosive mixture of hydrocarbon vapors and air.
Claim 8
Dependent Claim
48 words
The method of claim 4 further characterized by varying the sample being monitored; monitoring said varied sample for new values; finding a new point on the graph which corresponds with coordinates representing said new values; and determining if said new point is on the straight line previously drawn.
Claim 9
Independent Claim
229 words
A method of changing the inert gaseous content of a volume containing an inert gas mixture including hydrocarbon vapors to air without producing an explosive mixture of hydrocarbon vapors and air in said volume, comprising: obtaining a sample of inert gas including hydrocarbon vapors from a volume having an inert gaseous content including hydrocarbon vapors; mixing said sample with air to form a mixture; monitoring said mixture as it is being mixed for values including tenths of lower explosive limit and percentage of oxygen; providing a graph having the tenths of the lower explosive limit of the volume plotted along one edge of the graph and the percent oxygen of the volume along another edge of the graph; finding a first point on the graph which corresponds with coordinates representing the values of the tenths of lower explosive limit and percent oxygen of said volume; finding a second point on the graph representing 0.0 lower explosive limit and 21% oxygen; drawing a straight line through said first point and said second point; determining if said straight line crosses a vertical line representing the lower explosive limit of said volume; adding inert gas to said volume, and if said straight line intersects said vertical line prior to ventilating said volume with air to remove the inert gas from said volume without producing an explosive mixture of hydrocarbon vapors and air.
Claim 10
Independent Claim
229 words
A method of changing the inert gaseous content of a volume containing an inert gas mixture including hydrocarbon vapors to air without producing an explosive mixture of hydrocarbon vapors and air in said volume, comprising: obtaining a sample of inert gas including hydrocarbon vapors from a volume having an inert gaseous content including hydrocarbon vapors; mixing said sample with air to form a mixture; monitoring said mixture as it is being mixed for values including tenths of lower explosive limit and percentage of oxygen; providing a graph having the tenths of the lower explosive limit of the volume plotted along one edge of the graph and the percent oxygen of the volume along another edge of the graph; finding a first point on the graph which corresponds with coordinates representing the values of the tenths of lower explosive limit and percent oxygen of said volume; finding a second point on the graph representing 0.0 lower explosive limit and 21% oxygen; drawing a straight line through said first point and said second point; determining if said straight line crosses a vertical line representing the lower explosive limit of said volume; adding inert gas to said volume, and if said straight line intersects said vertical line prior to ventilating said volume with air to remove the inert gas from said volume without producing an explosive mixture of hydrocarbon vapors and air.
Claim 11
Dependent Claim
120 words
The method of claim 7 further characterized by monitoring said volume while said volume is being ventilated with air for new values including tenths of lower explosive limit and percentage of oxygen; finding a first point on the graph which corresponds to coordinates representing said new values; finding a second point on the graph representing 0.0 lower explosive limit and 21% oxygen. drawing a straight line through said first point and said second point; determining if said line crosses a vertical line representing the lower explosive limit of said volume; and adding inert gas to said volume if said straight line intersects said vertical line prior to ventilating said volume with air to remove the inert gas from said volume.
Claim 12
Dependent Claim
48 words
The method of claim 7 further characterized by varying the sample being monitored; monitoring said varied sample for new values; finding a new point on the graph which corresponds with coordinates representing said new values; and determining if said new point is on the straight line previously drawn.
Claim 13
Dependent Claim
143 words
Apparatus for predicting the potential explosiveness of a gaseous volume containing inert gas and hydrocarbon vapors when air is added or substituted for said inert gas in said volume, comprising: means for obtaining a gaseous sample of said inert gas and hydrocarbon vapors; means for mixing said sample with air to form a resultant mixture thereof; means for measuring the fraction of the lower explosive limit of the hydrocarbon vapors in said resultant mixture, said lower explosive limit being the unit minimum quantity of hydrocarbon vapors in a gas needed to support combustion; means for separately measuring the percentage of oxygen in said resultant mixture; and means for summing said measurements of said fraction of the lower explosive limit and the percentage of oxygen, said sum being an indication of the explosiveness of said inert gas and hydrocarbon vapors when mixed with air.
Claim 14
Dependent Claim
143 words
Apparatus for predicting the potential explosiveness of a gaseous volume containing inert gas and hydrocarbon vapors when air is added or substituted for said inert gas in said volume, comprising: means for obtaining a gaseous sample of said inert gas and hydrocarbon vapors; means for mixing said sample with air to form a resultant mixture thereof; means for measuring the fraction of the lower explosive limit of the hydrocarbon vapors in said resultant mixture, said lower explosive limit being the unit minimum quantity of hydrocarbon vapors in a gas needed to support combustion; means for separately measuring the percentage of oxygen in said resultant mixture; and means for summing said measurements of said fraction of the lower explosive limit and the percentage of oxygen, said sum being an indication of the explosiveness of said inert gas and hydrocarbon vapors when mixed with air.
Claim 15
Dependent Claim
117 words
The apparatus of claim 10 wherein said means for summing comprises: a first analog-to-digital converter connected to said means for separately measuring the percentage of oxygen so that said first analog-to-digital converter emits a unit pulse series for each percentage of oxygen; a second analog-to-digital converter connected to said means for measuring the fraction of the lower explosive limit of the hydrocarbon vapors so that said second analog-to-digital converter emits a unit pulse series for each fraction in tenths of the lower explosive limit; a summer connected to said first and second converters to add the unit pulse series of each to form a sum; and a digital display connected to said summer to display said sum.
Claim 16
Dependent Claim
182 words
The apparatus of claim 10 wherein said means for determining said sum comprises a graph having two axes wherein the percentage of oxygen is plotted along one axis and said fraction of the lower explosive limit is plotted along the other axis; said graph having a first line defining the lower explosive limit, said first line being straight and passing through a first point corresponding to 11% oxygen and the lower explosive limit, denoted as 1.0, and a second point corresponding to 21% oxygen and said lower explosive limit on said graph; whereby on said graph a second straight line is drawn through a first point whose coordinates represent the measured fraction of the lower explosive limit and the measured percentage of oxygen and a second point whose coordinates are 0.0 as the fraction of the lower explosive limit and an oxygen content of 21%; so that if said second line crosses the first line, more inert gas must be added to the volume, and if said second line does not intersect said first line, the volume may be vented with air.
Claim 17
Dependent Claim
192 words
The apparatus of claim 10 wherein said means comprises a graph having two axes whereon the fraction of the lower explosive limit is plotted as a decimal equivalent along one axis and the percentage of oxygen is plotted along the other axis; said graph having a critical dilution line constructed thereon, said line being a straight line passing through a point whose coordinates are 0.0 fraction of the lower explosive limit and 21% oxygen and a second point whose coordinates are the lower explosive limit, denoted as 1.0, and 11% oxygen; so that if a point corresponding to the readings of the fraction of lower explosive limit and percent oxygen of the mixture is on or below the critical dilution line, the volume from which said sample is obtained may be ventilated so as to gas-free the volume without producing an explosive mixture; and if the point is above the critical dilution line, said volume is purged with inert gas until a subsequent point whose coordinates correspond to subsequent monitored readings of the fraction of lower explosive limit and percent oxygen of said volume is on or below the critical dilution line.
Claim 18
Dependent Claim
212 words
Apparatus for predicting the explosiveness of a volume containing inert gas and hydrocarbon vapor when mixed with air, comprising: a sampling hose having one end locatable in a gaseous volume containing a mixture of inert gas and hydrocarbon vapors to which it is desirable to add air; at least a pair of valve means, one of said valve means being connectable to the other end of said sampling hose to regulate the flow of said gaseous mixture through said hose, the other valve means being connectable to a source of air to regulate the flow of oxygen therethrough; a tee having three innerjoined passages wherein the two passages are respectively connected to each of said pair of valve means; a catalytic combustion indicator having its inlet connected to the third passage of said tee so that a selectively combinable sample of said gaseous mixture and air may be regulated by said valves to flow to said indicator, said indicator including means to measure the fraction of the lower explosive limit and the percentage oxygen of the combined sample; and means for recording the sum of said measurements as an indication of the explosiveness of said volume containing said mixture of inert gas and hydrocarbon vapors if air were added to said volume.
Claim 19
Dependent Claim
212 words
Apparatus for predicting the explosiveness of a volume containing inert gas and hydrocarbon vapor when mixed with air, comprising: a sampling hose having one end locatable in a gaseous volume containing a mixture of inert gas and hydrocarbon vapors to which it is desirable to add air; at least a pair of valve means, one of said valve means being connectable to the other end of said sampling hose to regulate the flow of said gaseous mixture through said hose, the other valve means being connectable to a source of air to regulate the flow of oxygen therethrough; a tee having three innerjoined passages wherein the two passages are respectively connected to each of said pair of valve means; a catalytic combustion indicator having its inlet connected to the third passage of said tee so that a selectively combinable sample of said gaseous mixture and air may be regulated by said valves to flow to said indicator, said indicator including means to measure the fraction of the lower explosive limit and the percentage oxygen of the combined sample; and means for recording the sum of said measurements as an indication of the explosiveness of said volume containing said mixture of inert gas and hydrocarbon vapors if air were added to said volume.
Claim 20
Dependent Claim
119 words
The apparatus of claim 14 wherein said means for recording the sum comprises: a first analog-to-digital converter connected to said means for separately measuring the percentage of oxygen so that said first analog-to-digital converter emits a unit pulse series for each percentage of oxygen; a second analog-to-digital converter connected to said means for measuring the fraction of the lower explosive limit of the hydrocarbon vapors so that said second analog-to-digital converter emits a unit pulse series for each fraction in tenths of the lower explosive limit; a summer connected to said first and second converters to add the unit pulse series of each to form a sum; and a digital display connected to said summer to display said sum.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-03-16 | 1979-09-15 | 1980-03-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-03-16 | 1983-09-15 | 1984-03-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-03-16 | 1987-09-15 | 1988-03-16 | $7700.00 | Window Closed / Lapsed |