US2827542A - Stress relief - Google Patents

Description

United States Patent STRESS RELIEF Frank K. Fellows and David A. Bell, Killen, Tex.

Application November 10, 1955, Serial No. 546,122

4 Claims. (Cl. 219-50) This invention relates to a method of and apparatus for relieving or overcoming stress in pipe, vessels, towers, manifolds, and the like.

The object of the invention is to provide a method of and-apparatus for removing stresses or brittleness in metal members while the metal members are in situ.

Another object of the invention is to provide a method of and apparatus for relieving stress in various metal members whereby the operation can be accomplished without the necessity of removing the member from its normal or service position, the method utilizing an introduction of power from welding machines so that stress or brittleness can be relieved in the members with a minimum cost and minimum time loss for the equipment.

A further object of the invention is to provide a method of and apparatus for relieving stress in various metal members which is extremely simple and inexpensive to manufacture and operate.

Other objects and advantages will be apparent during the course of the following description.

In the accompanying drawings, forming a part of this application, and in which like numerals are used to designate like parts throughout the same.

Figure 1 is an elevational view illustrating a metal member such as a vessel or tower and illustrating the present invention applied thereto.

Figure 2 is an elevational view illustrating the use of the present invention for annealing for removing stress in Welded pipe, tubing or the like, and with parts broken away and in sections.

Figure 3 is a diagram illustrating the temperature and time for accomplishing the annealing.

Figure 4 is a side elevational view of one of the insulated support members for the wires.

Figure 5 is a top plan view of the support member of Figure 4.

Figure 6 is a fragmentary view illustrating the insulated bead or body members mounted on a conductor wire.

Figure 7 is a plan view illustrating one of the insulated blocks with the buss bars mounted therein.

Figure 8 is a sectional View taken on the line 8-8 of Figure 7.

Referring in detail to the drawings, the numeral 10 designates a tower, vessel, manifold or the like which is adapted to be treated by the method of and apparatus of the present invention. It is to be understood that the method of the present invention can be used on other equipment besides the tower 10, as for example, the present invention can be used to relieve stress in welded pipes of tubings indicated by the numeral 11, in Figure 2. In Figure 2 the numeral 12 designates the welded joints between the pipes or tubes 11.

The present invention utilizes a plurality of insulated blocks which are each indicated by the numeral 14, Figure 8, and the blocks 14 may be made of any suitable material such as porcelain. Each of the blocks 14 includes a body portion 15 which is provided with a pair of spaced parallel longitudinally extending recesses or channels 16 which define therebetween a partition 17. A conductive buss bar 18 is secured within each of the recesses 16, and extending outwardly from each of the bars 18 is a plurality of terminals or bolts 19. Those terminals at the ends of the bars 18 are indicated by the numeral 20.

There is further provided a plurality of conductors 21 which are adapted to be trained or wrapped around the member 10 or 11 being heat treated, and the conductors 21 have their ends connected to the terminals 19. A plurality of insulated beads or body members 22 are mounted on the conductors 21, and the body members 22 may be provided with apertures or openings 23 for the projection therethrough of the conductors 21. The body members 22 serve to insulate or maintain the con ductors 21 out of electrical contact with the metal member 10 or 11 being treated.

Certain of the terminals 19 on the bars 18 may be interconnected together by bridge wires 24, Figure 7.

There is further provided a means for maintaining a record of the temperature of the member 10 or 11 being treated, and this means comprises contacts or terminals 25 which are arranged contiguous to the member 10 or 11 and these contacts 25 may be secured in place by any suitable manner and may be of conventional construction. Wires 26 lead from the contacts 25 to a suitable conventional thermocouple pyrometer. Thus, an accurate recording of the temperature of the member 10 or 11 will be provided. Wires 27 lead from the end terminals 20 on the bars 18, and the wires 27 are adapted to be connected to a conventional welding machine. Thus, when the welding machine is actuated or energized, electrical current will flow from the wires 27 through the bars 18 and then the Wires 21 will be heated or caused to glow due to the electrical energy passing therethrough and this heat from the wires 21 will heat the member 10 or 11 being treated so that the stress in the metal will be relieved or overcome. The stress in the members 10 and 11 usually result after the members have been in service for long periods or active periods of time.

Referring to Figures 4 and 5 of the drawings, there is shown an accessory which may be used for helping to maintain the wires 21 out of contact with the members 10 or 11. Thus, in Figures 4 and 5 the numeral 28 designates a support member which can be made of any suitable electrically insulated material such as porcelain, and the support member 28 may be provided with a plurality of spaced parallel notches or recesses 29 for receiving therein portions of the wires 21.

Fromthe foregoing, it is apparent that there has been provided a method of 'and apparatus for use in relieving stress in various members such as towers, vessels, manifolds, pipes and the like. In Figure l the apparatus is shown mounted on a tower or vessel 10 and in Figure 2 the apparatus is shown mounted on welded pipe or tubing 11. Thus, with the apparatus arranged as shown in Figure l, a plunality of the blocks 14 are arranged so that their longitudinal axis extends parallel to the longitudinal axis of the member 19 and these blocks 14 have their ends spaced slightly apart. The terminals 20 are adapted to be connected to a suitable source of electrical energy as for example to a conventional welding machine through the medium of the wires 27. The contacts 25 are mounted on the member 10 in any suitable manner, :and the wires 26 lead from the contacts 25 to a suitable conventional thermocouple pyrometer. Thus, when the welding machine is energized, the current will flow from the wires 27 to the terminals 20 and then to the bus bars 13. This current will then flow up through the terminals 19 and up through the wires 21. These wires 21 will thus be heated and the heat from the wires 21 will raise the temperature of the member 10 or memher 11 and by raising the temperature of these members to [the desired degree, brittleness will be removed and also any stress in the members will be relieved since the metal will be annealed. After a given section of the member or 11 has been treated, the blocks 14 can be moved to the next section to be treated so that the entire member 19 or 11 can be heat treated with the present invention. The blocks 14 are made of insulated material so that the bars 18 are electrically insulated from the member 10 or member ill. The wires or conductors 21 are also electrically insulated from the member 10 or 11 by means of the porcelain body members 22 and also by means of the support members 28 which may be made of electrically insulating material such as porcelain also. Thus, the support members 2@ may be interposed between portions of the wires 21 and the member 10 or 11. In Figure 3, there is shown a graph which illustrates the steps in heat treating the member 10 or 11 so as to effect the desired annealing. Thus, plotted along the vertical axis is the temperature in degrees, and plotted along the horizontal axis is the time that the heat is applied. It will be seen that there results on the scale or graph a recording of the temperatuire in degrees and time that the member is exposed to the heat, and this graph may result from the contacts which are electrically connected to the thermocouple pyrometer.

The welding machine supplies the electrical energy and heat whereby the wires 21 cause the member 1% or 11 to become annealed so that the stresses are relieved or overcome or removed.

In Figure 3 there is shown a typical graph wherein temperature it plotted against time on a recording instrument during the stress relief of a member treated by the process of the present invention. It is to be understood that the temperature and time of treatment will vary for diiferent types of materials being treated. The members are treated by progressive stages and the member which may be a tower, vessel, manifold or the like, is treated in situ so that it does not have to be moved from place to place, when being treated. This is specially suitable when large members which are often encountered, are to be treated. The treatment is performed in the field without removal of the object to be treated from its normal service position and the treatment uses welding machines for power. A plurality of welding machines can be used and after a given section of a tower or the like has been treated, the wires can be moved, to a fresh section to be treated and a desired amount of overlap in the treatment of the sections may be used. The wires 21 are arranged in parallel on the member being treated. The thermocouples 25 are staggered around the entire area being treated so that an accurate reading is brought about. If desired, additional insulation can be placed where needed and if desired the inside of the member 10 or 11 may also be insulated to increase the efiiciency of the operation. Also, small portions of a tower, vessel or the like which have become stressed may be treated for relief of the stressed area without treating the entire unit. Thus, the present invention will eliminate the costly process of annealing units in a furnace. The arrangement shown in Figure 6 provides a flexible arrangement for the wires 12 so that the wires can be readily wrapped around the member 10 or 11; The wires 24 serve as jumper wires so that there will be a continuous circuit for the electrical energy. The members are adapted to be heat treated in progressive stages. The members can be heat treated at a small cost and with a minimum time loss since it is not necessary to move the equipment to a furnace.

The members which are treated by the present invention may suffer stresses after they have been in service for a long period of time and :as for example when the members have been exposed to varying temperatures or adverse conditions. The arc welding machine or machines which apply the electrical energy may have a capacity of'300 amperes with a 40 or 50 volt capacity.

In use, the tower or other members are taken out of service and permitted to cool and then cleaned and the stress cracks are welded along with any other repairs that may be needed. The wires 21 are then wrapped on the tower and the plurality of wires 21 are arranged quite close together. The number of welding machines connected to the terminals 20 can be varied as desired and the member may be treated in only one operation or else it can be treated in progressive stages. After the windings are in place and secured and the thermocouples 25 are spaced over the area to be treated, insulation is placed over the area being treated and such insulation may be magnesium or asbestos and this asbestos which is placed over the apparatus has its joints sealed. If desired the inside of the tower may also be insulated. The thermocouples are connected to the recording instrument and the welding machines are started and amperage is adjusted so that the rise in temperature is 400 per hour in the metal being treated. This rise is continued until the temperature for annealing the type or metal being treated has been reached at which point the amperage of the welding machine is reduced to hold the annealing temperature for such time as specified in A. S. T. M. tables for processing this type of metal. At the end of this specified time, the amperage is further reduced so that there is a cooling rate of the metal of 200 per hour or to conform to the cooling rate set forth in the A. S. T. M. tables for this type of ,metal until the temperature drops to 300 at which point the machines may be stopped and removed from the line and the metal permitted to cool normally to a point where it is the same as that of the atmosphere surrounding it. This process gives a graph which may resemble the graph shown in Figure 3. If the vessel or area treated was not covered in its entirety with the one treatment, then the above procedure is repeated into the untreated area while allowing a three inch overlap of the Winding into the area already treated and when the end is reached the windings may be removed. With the present invention, the metal being treated may be annealed thoroughly and efliciently as though it had been removed and heat treated in a furnace. As above stated, with the present invention the object being treated need not be disturbed from its normal operating position.

I claim:

1. In combination, a metal member to be heat treated in situ, a plurality of insulated blocks arranged in end to end spaced apart relation with respect to each other and said blocks being arranged contiguous to the outer surface of said member, there being a pair of spaced parallel longitudinally extending recesses arranged in each of said blocks defining a longitudinally extending partition therebetween, bus bars secured within said recesses, terminals extending outwardly from said bus bars, certain of said terminals adapted to be connected to welding machines, conductors connected to the other of said terminals and trained around said member, and contacts arranged contiguous to the member being treated and adapted to be connected to a thermocouple pyrometer.

2. In combination, a plurality of insulated blocks arranged in end to end spaced apart relation with respect to each other, there being a pair of spaced parallel longitudinally extending recesses arranged in each of said blocks defining a longitudinally extending partition therebetween, bus bars secured within said recesses, terminals extending outwardly from said bus bars, certain of said terminals adapted to be connected to welding machines, conductors connected to the other of said terminals, and contacts adapted to be connected to a thermocouple pyrometer.

3. In combination, a plurality of insulated blocks arranged in end to end spaced apart relation with respect to each other, there being a pair of spaced parallel longi- 5 tudinally extending recesses arranged in each of said blocks defining a longitudinally extending partition therebetween, bus bars secured within said recesses, terminals extending outwardly from said bus bars, certain of said terminals adapted to be connected to welding machines, conductors connected to the other of said terminals, and contacts adapted to be connected to a thermocouple pyrometer, said conductors including wires, and a plurality of spherical body members mounted on said wires.

4. In combination, a plurality of insulated blocks ar- 10 ranged in end to end spaced apart relation with respect to each other, there being a pair of spaced parallel longitudinally extending recesses arranged in each of said blocks defining a longitudinally extending partition therebetween, bus bars secured within said recesses, terminals extending outwardly from said bus bars, certain of said terminals adapted to be connected to welding machines, conductors connected to the other of said terminals, and contacts adapted to be connected to a thermocouple pyrometer, said conductors including wires, and insulated support members provided with slots for receiving portions of said wires.

References Cited in the file of this patent UNITED STATES PATENTS 430,838 Dewey June 24, 1890 1,269,052 Clark et a1 June 11, 1918 2,044,734 Newhouse June 16, 1936 2,276,643 Bates Mar. 17, 1942 2,319,482 Tucker May 18, 1943 2,639,363 Brister et al May 19, 1953 FOREIGN PATENTS 135,315 Australia Nov. 15, 1949

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