US3512393A - Gas sampling analyzing system - Google Patents

Description

E. L. WEISS GAS SAMPLING ANALYZING SYSTEM May 19, 1970 Filed May 29, 1967 l 3 Sheets-Sheet 1 mud-U MM MUONE May 19, 1970 E. L. WEISS GAS SAMPLING ANALYZING SYSTEM 3 Sheets-Sheet 2 Filed May 29, 1967 May 19, 1970 Filed May 29, 1967 3 Sheets-Sheet 5 MmZZ 24m GONE 24mPm muqw mmk iu United States Patent 3,512,393 GAS SAMPLING ANALYZING SYSTEM Edward L. Weiss, Quakertown, Milford Township, Bucks County, Pa, assignor to Leeds & Northrup Company, Philadelphia, Pa., a corporation of Pennsylvania Filed May 29, 1967, Ser. No. 642,100 Int. Cl. G01m 31/00, 1/22 U.S. Cl. 73-23 9 Claims ABSTRACT OF THE DISCLOSURE A gas sampling analyzing system having provision for a reverse fiow cleansing cycle and including provision for preventing contamination of the gas sample with the cleansing fluid.

BACKGROUND OF THE INVENTION The invention relates to control, preferably automatic control, in the operation of processing apparatus wherein it is desirable to prevent build-up of solid or semisolid material at the entrance of a conduit or probe for gas analyzing apparatus. This invention was devised for use in sampling exhaust gases in the basic oxygen process of steel making. In the oxygen process of steel making, it is necessary periodically to analyze a sample of gas from the furnace accurately to control the constituents thereof. One of the readings that is necessary is that of the oxygen content and CO and CO To obtain these readings, the open end of a conduit, sometimes referred to as a probe, is inserted into a duct of the furnace and a gas sample is adapted to be drawn through the conduit from the duct by a sample pump. The opposite end of the conduit is connected to an analyzer for the gas sample. In order to prevent or remove a build-up of a solid or semi-solid material at the probe end of the conduit, a reverse flow of purging fluid is directed periodically through the conduit and out through the probe. A valve arrangement is connected in the conduit between the sample pump and the probe to prevent the purging fluid from entering the sample pump. The valve arrangements of prior art system however, have not included a provision for avoiding elfects of leaky valves. When leaks occur, the purging fluid is introduced into the gas sample, thereby causing errors in readings of the gas constituents.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a method and apparatus for a gas sampling analyzing system having provision for a reverse flow cleasing or purging cycle wherein the purging fluid is prevented from contaminating the gas sample by establishing a protective barrier of the gas sample under pressure between the purging fluid line and the valve means leading to the pump for drawing the as sample into the gas analyzer.

More specifically, Fn ere is provided a gas sampling analyzing system having provision for a reverse flow cleansing cycle including inlet means for obtaining a gas sample, a gas analyzer, and a flow passage connecting the inlet means and the gas analyzer. A pump having inlet and outlet connections is positioned in the flow passage between the inlet means and the analyzer to draw a gas sample into the inlet means for delivery to the analyzer. Valve means is positioned in the flow passage between the pump inlet and the inlet means and a purging fluid line is connected to the valve means. The valve means includes means adjustable to a first position for blocking gas flow from the inlet means to the pump while admitting purging fluid to the flow passage from the purging fluid line to provide a reverse flow to the inlet means and the adjustable means is adjustable to a second position for blocking the reverse flow to M 3,512,393 c Patented M y 0 the inlet means while admitting gas flow from the inlet means to the pump. A feedback flow passage is connected at one end between the pump outlet and the analyzer and at' the other end to the valve means at a location between the purging fluid line and the pump inlet for establishing a protective barrier of the gas sample under pressure from the pump outlet between the purging fluid line and the pump inlet when the valve means is adjusted to the second position.

In one form of the invention, the valve means comprises a rotary valve having guard grooves surrounding the ports thereof, the guard grooves being so constructed and arranged as to communicate with a pressure port which is pressurized with sample .gas from the feedback flow passage.

In another form of the invention, the valve means comprises a plurality of valves, one of which is in normally open position and two of which are in normally closed position, the valves being concurrently adjustable to their other positions and a check valve in the feedback flow passage.

In accordance with a further aspect of the invention, there is provided a programmer for automatic blow-back of the purging fluid at predetermined intervals.

For further objects and advantages of the invention and for more detailed description thereof, reference is to be had to the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of a gas sampling analyzing system having provision for a reverse flow cleansing cycle embodying the present invention;

FIG. 1A is a fractional view showing the rotary sample valve of FIG. 1 rotated through an angle of FIG. 2 is a front elevational view of a rotary sample valve which was diagrammatically illustrated in FIGS.

1 and 1A;

FIG. 3 is a top plan view of FIG. 2;

FIG. 4 is a perspective view of the rotary valve element of FIGS. 2 and 3 and diagrammatically illustrated in FIGS. 1 and 1A, and

FIG. 5 is a modified gas sampling analyzing system having provision for a reverse flow cleansing cycle in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is illustrated a gas sampling analyzing system 10 having provision for a reverse flow cleansing cycle in accordance with the present invention. A conduit 11 is provided with an open end or probe end 11a which is adapted to extend through the wall 12 of a duct through which the gas to be analyzed passes. The probe end 11a of the conduit 11 preferably is provided with a magnetic particle trap 13 to attract the magnetic particles in the gas and prevent their entry into the conduit 11 or a porous filter means of heat resistant material. The conduit 11 is also provided with a filter 14 positioned outside of the duct 12. The filter 14 preferably is of the cartridge type and is adapted to prevent the solid particles in the gas sample from passing into the gas sampling analyzing system. A gas sample pump P is adapted to provide suction to the conduit 11 and draw the gas sample from conduit 11 through a valve device V as later to be described, and into a gas sample analyzer 15. The pump P is connected in a conduit or flow passage 16, one end of which connects to the valve device V and the other end of which is connected to a feedback flow passage or conduit 17 which also connects to the valve device V A conduit or line 18 connects the gas analyzer 15 to the junction between the conduits 16 and 17. A purging fluid line 20 has one end connected to the valve device V and the other end is connected by way of a solenoid valve V to a source of purging fluid. Any suitable source of purging fluid may be utilized, one example of which being air. A bleed line 21 is also connected to the valve device V to bleed off any leakage of the purging fluid through the valve device V The entire sampling system is adapted to be heated to prevent condensation and to prevent taking in liquid water at those times when particuluate water from the cooling sprays is entrained in the exhaust gases. This has been diagrammatically illustrated in FIG. 1 by the steam jackets 23, 24 and 25. The jacket 24 provides heat for the purging fluid and the jacket 25 is adapted to heat the suction pump. The jacket 24 prevents the purging fluid from cooling the system during the purging or cleaning operation in the blow-back cycle.

During normal gas sampling operation of the system 10, sample gas is drawn into the open end of the probe 11a and through conduct 11, due to the suction created by pump P. The valve device V includes a rotary element R as further described and illustrated in connection with FIGS. 2-4. As may be seen in FIG. 4, the rotary element R is provided with a pair of parallel main grooves G and G The main grooves G and G are relatively deep and respectively are surrounded by guard grooves g and 82 With the rotary element R of valve device V in the position illustrated in FIG. 1, the inlet conduit 11 is connected to one end of groove G and the opposite end of this groove is connected to conduit 16. Thus it will be seen that the sample pump P is adapted to draw a gas sample through conduit 11, thence through the groove G into conduit 16 and the inlet and outlet connections of pump P after which the gas sample passes through conduit 18 into the gas sample analyzer 15. The gas sample analyzer may be of any known type and preferably includes provision for recording the analysis of the gas sample. The feedback conduit 17 is connected from the pressure side of the pump to the guard groove g whlch surrounds the ports of conduits 11 and 16 connected to the main groove G This arrangement provides protective barrier of the sample gas under pressure around the valve ports leading to the inlet of suction pump P and prevents the gas sample from being contaminated by any leakage in the valve device V The purging fluid line 20 is connected to one end of the groove G and the guard groove g connects with the bleed line 21 which connects to atmosphere.

After a predeterminel time, the valve device V s adapted to be actuated so that the rotary element R 1s rotated through an angle of 90 or revolution to the position shown in FIG. 1A. Since the main groove G and its guard groove g are identical to the groove G and its guard groove g it will be apparent that the element R may be rotated in either direction. However, for purposes of explanation, it will be assumed that the element R is rotated in a counter-clockwise direction from FIG. 1 to FIG. 1A. Referring to FIG. 1A it will be seen that the inlet conduit 11 is now connected to a port at. one end from the main groove G and the port at the opposite end of groove G is connected to the purging fluid line Similarly, the conduit 16 leading to the suction pump P is connected to the main groove G to which there is no other connection. The feedback conduit 17 is not connected to any of the grooves in the rotary element R.

When the rotary element R of the valve device V has been rotated to the position illustrated in FIG. 1A, the solenoid valve V is adapted to be operated from its normally closed position to its open position thereby permitting the purging fluid to pass from the source through the valve V and the heater 24, the groove G and through the conduit 11, filter 14 and out through the probe end 11a. This reverse flow of purging fluid is adapted to clean the proble end and avoid build-up of solid particles thereon.

As pointed out above the rotary element R of the valve device V is adapted to be actuated at a predetermined time. This may be accomplished in various ways. While the valve device V may be operated manually it is preferably operated automatically from a programmer 26 which in turn controls a motor M for rotating the element R of the valve device V The solenoid valve V may be controlled manually however it also is preferably operated automatically from a programmer 26. The programmer 26 may be periodically operated by a signal from a timer to initiate the blow-back or reverse flow cleansing cycle. The programmer 26 may receive a signal based on the duct temperature for controlling the blow-back cycle or the programmer 26 may receive a signal based on the pressure differential in the probe for initiating the blowback cycle.

After the blow-back cycle has been completed and the probe has been cleaned by the purging fluid the rotary element R of the valve device V is adapted to be rotated through 90 to bring the grooves again into position with the respective conduits as illustrated in FIG. 1. This rotation is preferably accomplished by the motor M under the control of the programmer 26. It will of course be understood that prior to rotation of the rotary element R the solenoid valve V is actuated to closed position and thereby shutting off the purging fluid entering the line 20. When the rotary element R is returned to the position shown in FIG. 1 should there be any leakage of the purging fluid through valve V into line 20 and should there be any leakage of the purging fluid out of the groove G the guard groove g will vent such leakage of purging fluid to atmosphere by way of the vent line 21.

Referring to FIGS. 2 and 3 there is illustrated the valve device V which includes the rotary element R of FIG. 4. As may be seen in FIG. 2 the rotary element R is positioned inside of a drive cup 30 which is rotatably mounted within a valve mounting block 31 supported on a bracket 32. The bracket 32 also supports the motor M, the shaft 33 of which is adapted to drive through a shaft assembly 34 and pin 35 the cup 30 and the rotatable element R. The upper surface of the rotary element R in which the grooves G g G g are contained engages flat surface on a valve block 37 into which gas conducting ports are drilled. The arrangement of the gas conducting ports and associated passages and flow connections 11, 16, 17, 20 and 21 are best seen in FIG. 3. It will be noted that these are the flow connections previously described and diagrammatically illustrated in connection with FIG. 1.

When the motor M is energized it is adapted to drive through suitable reduction gearing to rotate the drive cup 30 which in turn rotates the rotary element R. As shown in FIG. 2 the shaft 33 of the motor M is provided with a cam 40 which is adapted to be engaged by an actuator 41 of a switch 42, FIG. 3. The switch 42 is adapted to control the position of the valve in response to valve motion commands from the purge cycle programmer 26, FIG. 1.

Referring to FIG. 5 there is illustrated a modification of the present invention. For purposes of clarity corresponding parts have been provided with the same reference characters. The gas sampling analyzing system it) of FIG. 5 operates in a substantially similar manner to system 10 of FIG. 1 however the rotary valve device V has been replaced by a pair of solenoid valves V and V During a gas sample analyzing operation the valve V is normally open and the valves V and V are normally closed. The gas sample is drawn by section pump P into the probe end 11a through the conduit 11 and filter 14 and normally open valve V to the inlet of pump P. From the outletor pressure side of the pump P the gas sample is directed through the conduit 18 to the analyzer 15 with part of the gas sample flow passing through the feedback line 17 and the check valve located therein. The return end of the feedback line 17 is connected to the purging fluid line 20 between the normally closed valves V and V The bleed line 21 preferably is provided with a needle valve 51 for controlling the amount of sample gas passing through line 21.

With the valve arrangement illustrated in FIG. 5 it will be seen that if there is any leakage of purging fluid through normally closed valve V the protective barrier of the gas sample under pressure in feedback line 17 will prevent entry of such purging fluid into the stream of gas sample being directed by the pump P to the analyzer 15. Thus it will be seen that the system of FIG. 5 operates in the same manner as the system 10 previously illustrated and described in connection with FIG. 1.

During a reverse flow cleansing cycle the programmer 26 operates the solenoid valves V V and V to their reverse positions at which time valve V is closed and valves V and V are open. The purging fluid will pass through the valves V and V into line 11 through the filter 14 and out through the probe end 11a thereby removing the solid particles from the inlet conduit 11. The valve V now being in closed position and the check valve 50 prevent the purging fluid from entering the pump P and the analyzer 15.

The programmer 26 in FIG. 5 is adapted to be operated in the same manner as previously described in connection with the system of FIG. 1. From the foregoing description it will be seen that in both systems 10 and 10' the valve connections to the suction pump P are provided with a protective barrier of the gas sample under pressure to prevent contamination of the gas sample being directed to the analyzer 15. In FIG. 5 if there is any leakage through the normally closed valve V such leakage would only be sample gas from the feedback line 17 and thus not introduce any contamination, into the gas sample. In the embodiment illustrated in FIG. 1 the guard groove g establishes a protective barrier of gas sam le under pressure around the main groove G thereby preventing contamination of the gas sample.

It will be apparent from FIG. 5 that the function of the check valve 50 and the function of the valve V may be combined in a single three-way valve. It will also be apparent that the present invention is applicable to multiprobe installations. In such installations the blow-back will be accomplished in sequence from the programmer for the various probes so as not to interfere with operation of the system.

While preferred embodiments of the invention have been described and illustrated herein it is to be understood that further modifications thereof may be made within the scope of the appended claims.

What is claimed is:

1. A gas sampling analyzing system having provision for a reverse flow cleansing cycle comprising:

inlet means for obtaining a gas sample,

a gas analyzer,

a flow passage connecting said inlet means and said gas analyzer,

a pump having inlet and outlet connections in said flow passage between said inlet means and said analyzer to draw a gas sample into said inlet means for delivery to said analyzer,

valve means in said flow passage between said pump inlet and said inlet means,

a purging fluid line connected to said valve means, said valve means including means adjustable to a first position for blocking gas flow from said inlet means to said pump while admitting purging fluid to said flow passage from said purging fluid line to provide a reverse flow to said inlet means and adjustable to a second position for blocking the reverse flow to said inlet means while admitting gas flow from said inlet means to said pump, and

a feedback flow passage connected at one end between said pump outlet and said analyzer and at the other end to a location between said purging fluid line and said valve means for establishing a protective barrier of the gas sample under pressure from said pump outlet between said purging fluid line and said valve means when said valve means is adjusted to said second position.

2. A gas sampling analyzing system according to claim 1 wherein said valve means comprises a plurality of valves one of which is in normally open position and two of which are in normally closed position said valves being concurrently adjustable to their other positions, and a check valve in said feedback flow passage.

3. In a gas sampling analyzing system according to claim 1 including heating means associated with said purging fluid line for heating the purging fluid prior to entry thereof into said flow passage leading to said inlet means.

4. In a gas sampling analyzing system according to claim 3 including heating means associated with said inlet means and said pump.

5. A gas sampling analyzing system according to claim 1 including automatic programmer means for operating said adjustable means of said valve means between said first and second positions.

6. In a gas sampling analyzing system having provislon for a reverse flow cleansing cycle having:

inlet means for obtaining a gas sample,

a gas analyzer,

a flow passage connecting the inlet means and the gas analyzer,

a pump having inlet and outlet connections in the flow passage between the inlet means and the analyzer to draw a gas sample into the inlet means for delivery to the analyzer, the improvement comprising:

valve means in the flow passage between the pump inlet and the inlet means,

a purging fluid line connected to said valve means, said valve means including means adjustable to a first position for blocking gas flow from the inlet means to the pump while admitting purging fluid flow passage from said purging fluid line to provide a reverse flow to the inlet means and adjustable to a second position for blocking the reverse flow to the inlet means while admitting gas flow from the inlet means to the pump, and

a feedback flow passage connected at one end between the pump outlet and the analyzer and at the other end to a location between said purging fluid line and said valve means for establishing a protective barrier of the gas sample under pressure from the pump outlet between said purging fluid line and said valve means when said valve means is adjusted to said second position.

7. In a gas sampling analyzing system having provision for a reverse flow cleansing cycle including:

inlet means for obtaining a gas sample,

a gas analyzer,

a flow passage connecting the inlet means and the gas analyzer,

a pump having inlet and outlet connections in the flow passage between the inlet means and the analyzer to draw a gas sample into the inlet means for delivery to the analyzer,

valve means in the flow passage between the pump inlet and the inlet means,

a purging fluid line connected to the valve means, the valve means including means adjustable to a first position for blocking gas flow from the inlet means to the pump while admitting purging fluid to the flow passage from the purging fluid line to provide a reverse flow to the inlet means and adjustable to a second position for blocking the reverse flow to the inlet means while admitting gas flow from the inlet means to the pump,

the improved method of preventing contamination of the gas sample with the purging fluid comprising the step of establishing a protective barrier of the gas sample under pressure from the pump outlet be- 7 tween the purging fluid line and the valve means when the valve means is adjusted to the second position.

8. A gas sampling analyzing system having provision for a reverse flow cleansing cycle comprising:

inlet means for obtaining a gas sample,

a gas analyzer,

a flow passage connecting said inlet means and said gas analyzer,

a pump in said flow passage between said inlet means and said analyzer to draw a gas sample into said in let for delivery to said analyzer,

valve means in said flow passage between said pump and said inlet means,

a purging fluid line connected to said valve means, said valve means including means adjustable to a first position for blocking gas flow from said inlet means to said pump while admitting purging fluid to said flow passage from said purging fluid line to provide a reverse flow to said inlet means and adjustable to a second position for blocking the reverse flow to said inlet means while admitting gas flow from said inlet means to said pump,

a feedback flow passage connected at one end between said pump and said analyzer and at the other end to said valve means for establishing a protective barrier of the gas sample under pressure from said pump between said purging fluid line and said valve means when said valve means is adjusted to said second position,

said valve means including a first normally open valve positioned in said flow passage between said inlet means and said pump,

second and third normally closed valves serially connected in said purging fluid line,

a bleed valve connected in a flow passage connected intermediate said second and third valves, and

check valve means connected in said feedback flow passage one end of which is connected between said pump and said analyzer and the other end of which is connected between said second valve and said flow passage leading to said bleed valve.

9. A gas sampling analyzing system having provision for a reverse flow cleansing cycle comprising:

inlet means for obtaining a gas sample,

a gas analyzer,

a flow passage connecting said inlet means and said gas analyzer,

a pump in said flow passage between said inlet means and said analyzer to draw a gas sample into said inlet for delivery to said analyzer,

valve means in said flow passage between said pump and said inlet means,

a purging fluid line connected to said valve means, said valve means including means adjustable to a first position for blocking gas flow from said inlet means to said pump while admitting purging fluid to said flow passage from said purging fluid line to provide a reverse flow to said inlet means and adjustable to a second position for blocking the reverse flow to said inlet means While admitting gas flow from said inlet means to said pump,

a feedback flow passage connected at one end between said pump and said analyzer and at the other end to said valve means for establishing a protective barrier of the gas sample under pressure from said pump between said purging fluid line and said valve means when said valve means is adjusted to said second position,

said valve means including a first normally open solenoid valve positioned in said flow passage between said inlet means and said pump,

second and third normally closed solenoid valves serially connected in said purging fluid line,

a bleed valve connected in a flow passage connected intermediate said second and third valves, check valve means connected in said feedback flow passage one end of which is connected between said pump and said analyzer and the other end of which is connected between said second valve and said flow passage leading to said bleed valve, and programmer means for concurrently operating said valves between their open and closed positions.

References Cited UNITED STATES PATENTS RICHARD C. QUEISSER, Primary Examiner J. WHALEN, Assistant Examiner US. Cl. X.R.

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