US3490266A - Hot extraction hydrogen analyzer - Google Patents

Description

Jan. 20, 1970 E. L. BENNET ETAL 3,490,266

HOT EXTRACTION HYDROGEN ANALYZER Filed June 15, 1967 2 Sheets-Sheet 1 Z Jan. 20, 1970 E. L. BENNET ETAL' 3,490,266

HOT EXTRACTION HYDROGEN ANALYZER Filed June 15, 1967 2 Sheets-Sheet 2 WWW; am

United States Patent Ofiice 3,490,266 Patented Jan. 20, 1970 3,490,266 HOT EXTRACTION HYDROGEN ANALYZER Eugene L. Bennet and Robert N. Revesz, St. Joseph, Mich., assignors to Laboratory Equipment Corporation, v St. Joseph, Mich., a corporation of Michigan Filed June 15, 1967, Ser. No. 646,221 Int. Cl. G01n 7/16 US. Cl. 73-19 4 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for the determination of oceluded or entrapped hydrogen in steel which comprises the steps of and means for physically flooding a sample chamber and contained sample and an upwardly extending burette tube with mercury, draining the mercury from the burette and sample chamber without the entry of air, heating the sample so as to release the gas therefrom and flooding the apparatus again to expel the evolved gas into the burette, the apparatus having an open ended tube laterally opposite the burette which likewise is flooded at the time of the gas transfer to provide an ambient pressure reference for the burette.

BACKGROUND OF THE INVENTION Field of the invention Analytical apparatus for the determination of gases in metals.

Description of the prior art Interstitially held or occluded hydrogen in steel sample can be removed under the influence of heat or reduced pressure and thereafter easily measured. A combination of heat and reduced pressure accelerates the removal greatly. While apparatus has been developed which provides for this combination of effects, such apparatus has hitherto been expensive and fragile and unsuited for routine determinations in such on-site environments as foundries and the like.

SUMMARY OF THE INVENTION The purpose and object of this invention is the pro vision of a method and appropriate apparatus for the determination of gases in metals or more narrowly of hydrogen in steel which is simple, quick, accurate, and which permits the use of inexpensive simple and sturdy apparatus entirely free from any possibility of nonobvious malfunctioning. To this end, a sample holder is connected to the bottom of a burette and appropriately disposed for heating. A quantity of mercury is held below the sample holder in an appropriate reservoir and is displaceable up into the sample holder and the burette by a plunger so as to flood both these parts and expel air therefrom. Thereafter the mercury is drained from the burette and sample holder, establishing a near perfect vacuum in the system, and the sample is heated to expel its occluded gases. The mercury is then again raised by the plunger to flood the sample holder and the burette to the extent permitted by the expelled gas and the gas quantity read on the calibrations of the burette tube.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation of apparatus embodying the present invention;

FIG. 2 is an enlarged section taken along the line 22 of FIG. 1;

FIG. 3 is a section of the operating stopcock taken substantially along the line 33 of FIG. 1; and

FIG. 4 is a longitudinal section through an alternative form of gas exhaust outlet attachment.

DESCRIPTION OF A PREFERRED EMBODIMENT The illustrated embodiment of the apparatus of the present invention is mounted to a flat base 10. A collar 12 Welded to the base supports vertically an elongated cylinder 14. The sides of the cylinder are oppositely vertically slotted through about the lower third of its length as at 16, and a lever 18 extends through the opposite slots. The lever 18 is pivotally connected at one end 20 to one end of a link 22, and the other end of the link is pivotally connected to an upstanding ear 24 secured to the base plate 10. The end 26 of the lever remote from the pivotally connected end 20 lies on the opposite side of the cylinder 14 and constitutes a handle 26 and is releasably engageable on a pin 30 supported between two ears 32 which are secured along their bottom edges to the base plate.

That portion of the lever 18 which lies within the cylinder is pivotally connected by pin .34 to a guide piston 36 which fits closely but slidably within the cylinder 14. The piston has a split skirt so that the pin 34 may extend through an appropriate aperture in the lever and be received in appropriate holes in opposite skirt portions. A piston rod 40 is secured to the top surface of the guide piston 36 to extend upwardly within the cylinder and has secured to its upper end a main piston 42 which engages the walls of the cylinder in fluid-tight relationship. To permit easy reciprocation and, at the same time, maintain a fluid-tight seal, the piston incorporates polytetra-fluoroethylene sealing rings 44. The spacing of the piston 42 above the lever 18 as achieved by the piston rod 40 results in the piston 42 reciprocating only Within the upper, unslotted portion of the cylinder 14.

The cylinder terminates at its upper end in a dome 46 and a vertical aperture 48 extending upwardly from the center of the dome.

A tubular side arm 50 is mounted in a bore in the side wall of the cylinder 14 to extend horizontally outward therefrom and define a passage 52 into the upper end of the cylinder cavity immediately under the dome 46. The side arm 50 is adapted to have fitted thereover the open end 54 of a Y-shaped sample tube 56 in gastight relationship. To this end, sealing rings 58 are embedded in the outer surface of the side arm. Also, since the depth of insertion of the side arm into the open end 54 is somewhat critical, the side arm is provided with a collar 60 to determine exactly the depth of insertion. A spring clip 55 is contained in the outer end of the side arm to permit fluid passage thereby but block the passage of the sample to be tested and retain it in the sample tube 56.

The sample tube 56 is desirably formed of heat and thermal shock resistant tubing such as Vycor (a trademark of the Corning Glass Co.), a synthetic fused quartz. As stated, the sample tube is Y-shaped and the open end 54 may be considered the stem of the Y. The other two arms 62 and 64 have closed ends and make about a right angle with respect to each other. The shorter 62 of the two arms is a desiccant holder and incorporates a constriction 66 adjacent its mouth to retain a screen-enclosed capsule 68 of an appropriate desiccant material or a molecular sieve. The open end 54 extends at about a 60 angle from the plane of the right angle defined by the arms 62 and 64, and the projection of the open end on that plane lies about from each of the closed arms.

A burette 70 has a lower end fitting 72 contained in the aperture 48 in the top end of the cylinder. Sealing rings 74 are provided in the inside surface of the aperture so as to make a gas-tight seal on the received end fitting 72. The passage 76 of the fitting extends upwardly to a stopcock housing 78. Upwardly from the stopcock housing, a calibrated burette tube 80 and an open pressure balancing tube 82 extend in side-*by-side relation. The stopcock plug 84 (FIG. 4) has two passage systems therethrough at right angles to each other. One of them 86 pro-' vides a simple connection of the passage 76 of the fitting to the calibrated burette tube. The other 88 is Y- shaped and opens both the burette tube and the pressure balancing tube 82 to the passage 76.

The burette tube is calibrated as at 90 over only a portion of its length. Upwardly from the calibrated portion, a simple stopcock 92 is provided. The burette tube terminates upwardly of the stopcock 92 in an open, right-angle lateral bend 94. A drying tube 96 containing an appropriate desiccant may be coupled to the open upper end of the burette tube 94 by a sleve 98 or other appropriate structure. The pressure balancing tube 82 extends straight upward from the stopcock 78 and terminates in an open upper end above the level of the upper end of the burette tube 80.

The device is completed by a small, tubular, resistance furnace 100 having an interior cavity adapted to enclose the sample arm 64 of the sample tube 56. The heater will be carried on a table 102 which may be mounted on the exterior of the cylinder 16 as by a clamp 103 and arm 104.

The table should provide room enough to permit sliding the furnace off or on the sample arm.

The operation of the above described device is as follows. The cylinder 16 above the piston 42 is filled with mercury to a level somewhat below the side arm 50 when the piston is lowered. It will be understood that the ca-' pacity of the cylinder and the scope of movement of the piston 42 will be sufficient to accomplish the purposes to be described.

The mercury forms a part of the permanent equipment of the apparatus.

To start an analysis, the furnace 100 will be withdrawn from the sample arm and the sample tube disconnected from the apparatus for the deposit of a sample 106 therein. The sample as illustrated is about a quarter of an inch in diameter and three-quarters of an inch long and weighs about 5 grams. The desiccant arm will be filled with mercury to keep the desiccant from unnecessary contamination, as will be described later. It will be understood of course that the sample tube is freely rotatable on the side arm without breaking the gas-tight seal.

The sample tube is then reconnected to the side arm 50 and rotated so that both the desiccant arm and the sample arm are tilted downwardly with the sample arm desirably having a greater downward inclination. The open end or mouth 54 of the sample tube 56 is straight and about one inch long, and the telescoping attachment of the open end to the side arm 50 occupies entirely this straight portion. In other Words, with the sample tube oriented as described on the side arm, the spring clip 55 occupies a position over the steeply downwardly sloping floor of the sample arm.

The stopcock 84 will be oriented to permit How to both the pressure balancing tube 82 and the burette tube 80. The stopcock 92 will be opened and the lever 18 will be in its lowermost position. Upon raising the lever, mercury will be displaced from its reservoir in the cylinder 14, by the upward movement of the piston 42, out through the side arm to flood the sample tube entirely and upwardly through the burette and tube to a point above the stopcock 92. The lever will be held in that upper position while the stopcock 92 is closed and stopcock 84 turned to connect the burette 80 only. The lever is then lowered to permit the return of the mercury again to the reservoir in the cylinder 14. The sample tube will be rotated on th'e side arm 50 so that the two tubes each have an upward inclination and the mercury contained in them will drain into the reservoir. The spring clip 55, it will be appreciated, prevents the passage of the steel sample into the side arm either in the course of floating up on the received mercury 9r in the course of tilting the-sample tube up- 4 wardly so as to drain'it. In this fashion a high vacuum is established in the apparatus above the mercury level in the reservoir.

Although this evacuating principle is ideally near perfect, there are areas where minor entrapments of air may occur such that the vacuum isno't'as perfect as may be. Notably, the interstices between the particles in the desiccant tube may trap some bubbles, and the juncture between the sample tube and side arm provides a lodgement for an air bubble. Both of these constitute a very small proportion of the total volume, but might introduce an appreciable error, depending on the order of accuracy desired. It is therefore suggested that the evacuating procedure be repeated or twice repeated to improve the vacuum by the same multiple as the original evacuation procedure. The additional evacuation steps are the same as those described before except that the stopcock' 84 remains connected to the burette only and stopcock 92 remains closed until the mercury is in the burette.

After the apparatus has been successfully evacuated as described, the lever 18 is forced down and latched and the sample tube is turned on the side arm'so that the sample arm is in its lowermost position. Thereupon, the sample will drop to the bottom of the sample arm. Thereafter the sample tube is turned so that the sample arm is horizontal. Throughout the evacuation, the furnace 102 has, of course, been removed from interference with the movement of the sample tube.

After the sample tube has been turned to a horizontal position, the furnace is positioned over'itas illustrated in FIG. 2 and energized to bring the sample to a temperature of 600 to 1000 C. The hydrogen will be evolved from the sample and disseminated throughout the apparatus. After a suitable period of heating time, such'as 10 minutes for instance, the furnace is withdrawn and the sample arm permitted to cool. The sample tube will then be turned downward again to insure the flooding of both arms and the lever arm raised to flood the sample tube again and extend a column up into the burette tube. At this point, the stopcock plug 84 is turned so as to establish communication of the passage 76 with both the burette tube and the pressure balance tube 82. Thereafter, the level is manipulated by careful degrees so as to bring the level of mercury in the two tubes into equality, and the level in the burette tube then read, the gas above it being at atmospheric pressure. From this measurement the gas content of the steel sample can be readily computed. Following the reading the lower stopcock 84 is changed to its burette-only connection the top stopcock 92 is opened, and the lever 18 depressed to return the mercury to the cylinder 14. The sample tube is rotated so that the sample arm 64 inclines upwardly to drain but the desiccant arm remains downwardly inclined to retain its mercury. The tube is then removed and the sample withdrawn.

The apparatus illustrated in FIG. 4 is intended for use where highly accurate hydrogen determinations are wanted or where it is suspected that other gases may be present in the evolved hydrogen in sufiicient quantities to impair seriously the accuracy of the reading. Such an occurrence such as the latter is unlikely; tests have shown that to 95% of the gas collected by hot extraction is hydrogen and no further separation is necessary except when a very high order of accuracy is desired. To meet this need for high accuracy, however, there is shown a hydrogen elimination tube which, in essence, will be substituted for the drying tube 96 of FIG. 1. As illustrated, the upper horizontal end of the burette tube 94 is modified to provide a standard taper joint and the hydrogen elimination tube 110 possesses the matching joint part 114. The joint may be held together by springs 116 secured to a ring 118 on the upper end of the burette and hooked over horns 129 on the hydrogen elimination tube. The tube 110 is a simple, open-ended length of borosilicate glass tubing formed to constitute the abovementioned taper joint half and horns at one end and is connected at its other end to a closed length of palladium tubing 122 through the medium of a length of tubing 124 adapted for a glass-in-metal seal. A heating coil 126 or equivalent furnace will be associated with the palladium.

As is well known, hot palladium is permeable to hy drogen, but hydrogen only.

To use the hydrogen elimination tube 110, the apparatus, as stated, will lack the drying tube 96. Instead, the upper end of the burette tube will terminate in the open taper joint 112. The before-described analysis will be conducted to the point where a reading is taken in the calibrated portion 90 of the burette tube. At this point, the hydrogen elimination tube will be connected to the outlet of the burette tube and the heater 126 energized. At the time of connection, the hydrogen elimination tube and the portion of the burette tube above the stopcock 92 will hold air at ambient conditions of temperature and pressure. After the connection of the hydrogen elimination tube and the heating of the palladium portion thereof, the stopcock 92 will be opened and the hydrogen contained above the mercury column will diffuse into the air contained above the stopcock 92 and out through the palladium tube. After an appropriate time interval suflicient to eliminate all the hydrogen through the palladium tube, the heating will be stopped and the palladium tube permitted to return to ambient temperature. Thereafter, the two mercury tubes will again be balanced, and the difierences between the first and second readings will be the actual hydrogen present in the sample to a high degree of accuracy.

It will be appreciated that the method described above is an exemplification only and the apparatus is but a single embodiment of the invention herein.

We claim:

1. Apparatus for the determination of hydrogen in a metal sample which comprises a sample chamber, a burette connected to said sample chamber and extending upwardly therefrom, said burette having a valve at the top thereof, a reservoir having mercury therein below said sample chamber, means for displacing mercury from the reservoir to flood said sample chamber and said burette entirely, means for heating a sample in said sample chamber, a pressure balance tube aligned with said burette, and valve means interposed between the top of said sample chamber and the bottom of said burette and the bottom of said tube adapted optionally to permit fluid flow from said sample chamber ino the bottom of said burette only and into the bottom of said burette and the bottom of said tube altogether.

2. Apparatus for the determination of hydrogen in a metal sample which comprises a sample chamber, a burette connected to said sample chamber and extending upwardly therefrom, said burette having a valve at the top thereof, a reservoir having mercury therein below said sample chamber, means for displacing mercury from the reservoir to flood said sample chamber and said burette entirely, means for heating a sample in said sample chamber, said sample chamber having a bend and being connected to said burette to be rotatable with respect thereto to be optionally upwardly or downwardly inclined.

3. Apparatus for the determination of hydrogen in a metal sample which comprises a sample chamber, a burette connected to said sample chamber and extending upwardly therefrom, said burette having a valve at the top thereof, a reservoir having mercury therein below said sample chamber, means for displacing mercury from the reservoir to flood said sample chamber and said burette entirely, means for heating a sample in said sample chamber, a palladium tube connected to the upper end of said burette above said valve, and a heater for said palladium tube.

4. Apparatus for the determination of hydrogen in a metal sample which comprises a sample chamber, a burette connected to said sample chamber and extending upwardly therefrom, said burette having a valve at the top thereof, a reservoir having mercury therein below said sample chamber, means for displacing mercury from the reservoir to flood said sample chamber and said burette entirely, means for heating a sample in said sample chamber, said sample chamber incorporating a bend and being rotatable so as to be optionally upwardly or downwardly tilted.

References Cited UNITED STATES PATENTS 2,387,878 10/1945 Brown 73l9 2,361,844 10/1944 Homer 73-19 2,749,220 6/1956 Rochon 7319 3,176,500 4/1965 Coe 7319 3,177,700 4/1965 S1er 7319 CHARLES A. RUEHL, Primary Examiner 3 3 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,490,266 Dated January 20, 1970 Inventor(s) Eugene L. Bennet and Robert N. Revesz It is certified that error appears in the above-identified patent and that: said Letters Patent are hereby corrected as shown below:

Col. 4, line 42, "level" should be -lever--.

Col. 6, line 1, "inc" should be ---into---;

line 3, "altogether"should be "together-r.

SI'GNED AN'D SEALED JUL 1 41970 Attest:

mm n: W, m. Attcating Officer Gomissioner of Patents

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