US2041058A - Method and apparatus for determining the physical characteristics of metals - Google Patents

Description

May 19, 1936. F. FOSSAT] 2,041,058

.METHOD AND APPARATUS FOR DETERMINING THE PHYSICAL CHARACTERISTICS OF METALS Filed Jan. 22, 1934 //0 VAC.

In 0 ant or Franc/s lV/ChO/BS Fossaf/ Aiiorney Patented M... 19, 1936 UNITED STATES METHOD AND APPARATUS FOR DETERMIN- ING THE PHYSICAL CHARACTERISTIC OF METALS Francis Nicholas Fossati, Richmond, Calif., as-

signor to Standard Oil Company oi! Calif ornia,

San Francisco, Calii., a corporation of Delaware Application January 22, 1934, Serial No.'707,859

, 2 Claims.

This invention relates to a method and apparatus for determining the physical characteristics of alloys. v

The present method and apparatus are pari ticularly. but not necessarily, adapted for determining the physical characteristics of non-magnetic or-substantially non-magnetic alloys. The present invention is based on the discovery that the magnetic permeability of alloys increases proportionally as such alloys deterioratein use.

The reason for this increase or change in magnetic permeability of such alloys is not clear except -to the extent that the magnetic permeability is now known to vary as such alloys deteriorate 5 in use and that this variation can be determined by surface measurement. It is here proposed to employ this discovery especially for determining the physical characteristics or change in physical characteristics due to deterioration in 0 use of non-magnetic or substantially non-magnetic materials.

The present method and apparatus are particularly desirable for determining periodically the physical characteristics of chromium alloy :5 tubes used in high pressure stills such as that" type of pressure stills used in the process of cracking hydrocarbon products. These alloy tubes may be 18% chromium, 8% nickel and the remainder substantially iron, with not over 0.07% to carbon and are usually heat-treated so that they are substantially non-magnetic when new, but as they deteriorate in use their magnetic permeability increases proportionally. The deterioration of these high pressure still tubes may be for a great part due to the workings of the tube material during expansion and contraction in response to varied temperature to which they are subjected and due to the difference in expansion and contraction of adjacent integral portions ofthe L0 tube both laterally and longitudinally in response to the several different temperatures towhich I diiferent portions of the tubes are subjected. It is a frequent occurrence that this working of the tubes from the expansion and contraction of different portions of the tube in greater or less de grees, one portion from the other, results in cracking the tube or otherwise impairing or reducing the ductility of the tube. The cracks formed are usually parallel to the axis of the tube.

Up to the present time no satisfactory method of determining the characteristics of these alloy tubes has been developed without resorting to the removal of the tubes from the furnace and cutting samples therefrom for testing to strengthand ductility. This shortens the tubes and renders them unsuitable for use except in a shorter furnace. Furthermore, the weakened portions may be in the middle of the tube, in which case the samples from the ends give no indication of the true condition. It can be appreciated that should one of the tubes in a high pressure still give way under pressure and spray a volatile medium such as a hydrocarbon product into the combustion chamber,'the damage due to fire, explosion and the probable loss of life may be tremendous. In order to preclude such a disaster it has heretofore been the practice to periodically remove all of the tubes from the still and install new tubes, in spite of the fact that' a great number of the discarded tubes may he possessed of suflicient strength and ductility to be continued in use for a much longer time. In this regard it is here mentioned that these tubes range in price from two to four hundred dollars each andfor some installations may cost as high as six to eight hundred dollars each. This is an important factor to an industry that uses thousands of such tubes annually. In addition to the above the present invention may be employed for determining the physical characteristics of other alloys regardless of the particular shape of such alloys.

It is one object of this invention .to provide a method and apparatus for determining the physical characteristics of alloys.

Another object is to provide a method and apparatus for determining the physical characteristics of non-magnetic or substantially non-magnetic alloys.

Another object is to provide a novel method and apparatus for determining the magnetic permeability of alloys.

Another object is to provide a method and apparatus for determining the increase in magnetic permeability of alloys due to deterioration in physical properties, such as ductility and homogeneity, caused by the conditions of use of such alloys.

Another object is to provide a method and apparatus for determining the physical characteristics of alloys by surface measurements.

Another object is to provide a method and apparatus for determining the physical characteristics of alloys so long as access is had to one surface of such alloys.

Another object is to provide a method and apparatiis for determining the suitability of chromium alloy pressure still tubes for further service after a period of use; without damaging thetubes or removing them from their position in the fur.-

nace.

Another object is to provide a method and apparatus for determining the physical characteristics of chromium nickel alloys by a measure-- ment of their magnetic permeability.

A further object is to provide a method and apparatus having the above characteristics that shall be simple and durable in structure, positive and eflicient in operation, and that shall be comparatively cheap to manufacture.

The accomplishments of the above and other objects will be apparentto those skilled in the art from the following description when taken in connection with the accompanying drawing,

' wherein like reference characters refer to like parts. It is to be expressly understood that the drawing is not a definition of the invention, but

' merely illustrates one formof a device by means of which the principles of the invention may b eftectuated.

In the drawing:

Figure 1 is an elevational view, partly in section, of a device embodying the invention.

Figure 2 is a schematic diagram illustrating one manner in which the present device may be electrically wired for carrying out the invention; and

Figure 3 is a fragmentalview, mostly diagrammatic, illustrating a detail embodying the invention.

In the form shown there is provided an exploring element represented in its entiretyby II, an indicating element represented in its entirety by I2, and a flexible cable III containing the wires for electrically connecting the elements I I and I2.

The exploring element II comprises an open core transformer l3 mounted in a carrier I4, the latter being provided with a handle I5, whereby the exploring element may be moved along the interior of an alloy tube I6 to be tested. The poles of the primary I1 and secondary I8 of. the transformer I3 are rounded as shown at I8 and 2| respectively for registering with and properly contacting the interior curved contour of the tube I6. The element II is also provided with an arcuate shaped spring 22 fixed to the carrier I4 and disposed on the opposite side of the element II from the poles I8 and2l. The spring 22 is employed for urging the transformer poles I9 and 2| into registering contact relation with the interior surface of the tube I6 being tested. The element II in its entirety is of a rugged durable structure sufi'icient to withstand the use to which it is intended and to prevent any relative move- I ment between the poles I9 and 2|.

within a suitable supporting frame 25, the latter being supported by and in fixed relation with member 23. The upper position of the frame 25 is employed to support a novel scale 26, the latter being graduated as at 21 in accordance with a selected unit later to be defined. The frame 25 is also provided with a shaft 28 positioned at one end thereof and disposed in transverse relation thereto, which position is adjacent to but above the pole 29 of the secondary 3| of transformer 24. The shaft 28 is employed to turnably support the lower end of an indicating handle 32, the latter being adapted for cooperating with the scale 26. The lower surface of the handle 32 is adapted to support in rigid fixed relation thereto, oneor more selected magnetic laminations or elements 33, the purpose of which will be later described. The lower end of the lamination 33 terminates in a plane passing through the longitudinal axis of the shaft 28, which plane lies at right angles to the plane of the lamination 33. The lamination 33 is here employed for regulating the magnetic conditions across the core opening of transformer 24, and the particular positioning of the lamination 33 is for the purpose of obtaining a better calibration on the scale 26. By terminating the lower end of the lamination 33 at to read by using a scale such as shown, which scale is constructed to have a greater longitudinal diameter than its vertical diameter. The range of the scale 26 may be increased by employing an additional lamination. The transformer 24 is also provided with a primary 30 having a pole 34 similar to theprimary I1 and pole I8 of transformer I3. The element or indicating part I2 of the device also includes a galvanometer 48, the latter being fixed to and carried by the opposite end of the supporting member 23 from the end on which the transformer 24 is mounted. The member 23 is further adapted to support the receptacle portion of a suitable plug 35- for receiving a cooperating plug portion carried by the cable I0 for operably connecting the element II and I2, and the receptacle portion 36 for receiving a cooperating plug portion for connecting the device to a source of electrical current.

The specific wiring here employed and the relation of the various elements can best be understood from the schematic diagram shown by Figure 2. The primaries I1 and 30 of the similar transformers I3 and 24 respectively, are connected in series as shown to a source of volt alternating current by means of conductors or wires 31. The secondaries I8 and 3| of the respective transformers I3 and 24 are connected in series with the galvanometer 40 by means of conductors or wires 38, but the secondaries I8 and 3| are wound to oppose one another. The field coil of the galvanometer may also be energized from the above source of current by means of a branch circuit comprising conductors or wires 4|. Any suitable galvanometer may be employed and the galvanometer movement here employed is the Leeds 8; Northrup #2375-A which-is provided with a laminated interior .core for use with alternating current. The field core of the present galvanometer is also constructed of laminations piled in the conventional manner, and the gal vanometer field coil consists of 900 turns of #19 D00 copper wire wound on a 1 x 1%," x 1%" form. a

Each of the. primary coils IT -and 38 of the transformers I3 and 24 respectively consists of 2000 turns of #28 enameled SCC magnet wire, while the respective secondary coils I8 and 3| consist of 1300 turns each of thesame size and type of wire used in the primary 'coils. All of .the transformer coils, both primaries and secondaries, are wound separately on a 1%" x 1%" x 1%" form, The transformer cores are formed from" U-shaped laminations which provide rigid assemblies, and precludes any relative movement between the poles.

It can now be understood that so long as the magnetic conditions existing across the openings of the two transformer cores are similar, that the voltage generated in the opposing secondaries I8 and 3| will be equal and opposite, and since the opposing secondaries are connected in series with the galvanometer 48, the latter will indicate a neutral or zero position. However, if the opening of the core of the transformer ,I3 is closed by some magnetic material, such as a deteriorated alloy -tube l6, then the voltage in secondary I8 will beraised accordingly and overcome the voltage in secondary 3| causing a current to flow in circuit 38 thereby causing the galvanometer to deflect from its neutral position. The voltage in secondary 3! may be raised to equal the voltage in secondary l8 by moving the handle 32 carrying the lamination 33 toward closed position until the magnetic conditions across the two core openings are again equal, at which time the galvanometer needle will again register zero.

It is now evident that the more magnetic the material across the core opening of the transformer IS, the more nearly must the core opening of transformer 24 be closed by the lamination 33. Thus the relative position of the handle 32 with the scale 26 asindicated by the graduations 21, may be used as a measure of the magnetic effect of the pipe l6 across the core opening of transformer I3. The magnetic effect here referred to is for the-most part permeability, although it may include'stray fields such as may be caused by eddy currents. Thus a non-magnetic material such as copper will cause a change in the reading. However, such efiects are beside the purpose here required.

For the purpose of choosing a unit of measurement of the magnetic mrmeability effect as regards this particular embodiment of the present device, the efiect of a #20 gauge iron wire positioned across the poles l9 and 2| of transformer I3 are represented by 10 divisions of the scale 26, the latter being graduated from to 110 divisions for one lamination and 0 to 290 for two laminations, the second lamination (not shown) being superimposed on the first said lamination when used. The laminations here used were soft transformer iron 1"- wide x 3 long and 28 gauge.

In practicing the present invention in connection with the'determining of the physical characteristics of chromium nickel iron alloy pipes used in high pressure stills, the pipe wall being /z" in thickness, it was found that good tubes were represented by 30 or less of the above scale divisions, questionable tubes 110 divisions orv less,

and that tubes having definite cracks therein were represented by 130 divisions. Therefore, one methodof carrying out the present invention may comprisesetting or positioning the handle 32 at a relative position with the scale 26, which position corresponds or substantially corresponds to a known alloy element, or for the particular embodiment here used, to a good tube, then in using the element II to explore the surface of a tube to be tested while observing the directional deflections of the galvanometer needle, from which the physical characteristics of the various portions of the tube may be readily observed. The present method may also include the original step of determining the magnetic permeability of a selected alloy element, .which element may be a pipe, tube, sheet of metal, or any other metallic member, and then in using the device to compare the physical characteristics or the magnetic permeability of like or similar elements or members with that of the selected element.

. The above teachings are thought to be sufiicient to enable one skilled in the art to make and use the present method and apparatus, or such equivalents as defined by the appended claims. vIt is to be understood that while the single form of the present device here illustrated and described is adaptable for use with a single surface of a metal, the device may be readily modified to utilize opposing surfaces of the metal being test ed, that is to say, the exploring transformer may be so constructed or provided with auxiliary means whereby the poles l9 and 2| of the transformer may contact the interior and exterior surfaces respectively of the pipe l6 or vice versa. Also, the scale 26 may be calibrated to include or cover any desired range. The lamination 33 may be of such magnetic characteristics as may be required to fulfill the particular oifice that various materials may require. Further, while it has been pointed out that the present method and apparatus is particularly adaptable for determining the physical characteristics of non-magnetic or substantially non-magnetic materials, they may also be employed for magnetic materials. The readings of the latter would, of course, be greater and possibly would require a moresensitive device, and the readings may or may not be as accurate as in the case of non-magnetic materials but would probably be sufficient for numerous requirements.

Accordingly, there is provided a novel method and apparatus for determining the physical characteristics of metals which method and apparatus are simple, efficient and practical. The apparatus is rugged and compact as well as portable.

Aside from the above, other changes, substitutions, modifications, additions and omissions may of said tube, and comparing the result with the claims. 40

magnetic permeability of a tube of known duc- 'tility and homogeneity.

2. An apparatus for exploring the magnetic properties of a substantially non-magnetic metal tube comprising twosimilar open core transformers, means for shunting the core .of the first of said transformers with a portion of the tube to be explored, a source of alternating current, the primaries of said transformers being connected in series and to said alternatingcurrent source, a galvanometer, the secondaries of said transformers being connected in series with said galvanometer and 'in opposition to each other, so that when the magnetic circuits of said transformers are equal in value no current will flow through said galvanometer, and a variable mag netic shunt for the core of said second tm former, said shunt including a manually operated lever, a magnetic element movable with said lever,

.and means for showing the relative podtion of said magnetic element with respect to said core.

FRANCIS NICHOLAS FOSSATL.

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