US3660593A

US3660593A - Pressure vessel power lead-through

Info

Publication number: US3660593A
Application number: US100652A
Authority: US
Inventors: Arnold Gordon Bowles
Original assignee: National Forge Co
Current assignee: National Forge Co
Priority date: 1970-12-22
Filing date: 1970-12-22
Publication date: 1972-05-02
Anticipated expiration: 1989-05-02
Also published as: BE774611A; FR2119318A5; SE384945B; GB1365946A; DE2154184A1

Abstract

An electrode for use in supplying power to equipment within a sealed vessel capable of containing fluid under pressure wherein an electrically conductive rod encased in an insulating material passes through the vessel wall to the interior of the vessel and has a boss member fitted upon its interior end. The boss member bears the outward load caused by the pressurized fluid and is supported by the inner surface of the vessel wall. The boss member is electrically insulated from the vessel wall by an insulating disc. The boss is made of conducting material and has an electrical terminal affixed to it. The boss member is substantially larger in cross-sectional area than the crosssectional area of the conducting rod. Concentric with the disc and between the vessel wall and the boss member is an O-ring seal to prevent the escape of the pressurized fluid through the conducting rod passage in the vessel wall. In some embodiments a second boss member is interposed between the insulating disc and the vessel wall inner surface to prevent any flexing motions of the vessel wall from being transmitted to the insulating disc.

Description

United States Patent Bowles 51 May 2,1972

[ PRESSURE VESSEL POWER LEAD- THROUGH [5 7] ABSTRACT An electrode for use in supplying power to equipment within a sealed vessel capable of containing fluid under pressure wherein an electrically conductive rod encased in an insulating material passes through the vessel wall to the interior of the vessel and has a boss member fitted upon its interior end. The boss member bears the outward load caused by the pressurized fluid and is supported by the inner surface of the vessel wall. The boss member is electrically insulated from the vessel wall by an insulating disc. The boss is made of conducting [52] US. Cl. ..174/152 R, [74/18 [51] Int CL l I h l l I "H0", 17/26 material and has an electrical terminal affixed to it. The boss [58] new 0 Search I II I 174/18, 50.56 151 152 R member is substantially larger in cross-sectional area than the 174/152 E 153 R; 339/94 A 126 R 126 J, 126 RS cross-sectional area of the conducting rod. Concentric with 214 R 214 C the disc and between the vessel wall and the boss member is an O-ring seal to prevent the escape of the pressurized fluid 56] References Cited through the conducting rod passage in the vessel wall.

UNITED STATES PATENTS In some embodiments a second boss member is interposed between the insulating disc and the vessel wall inner surface to 2,0l9,059 l0/l935 Sherman ..174/152 RUX prevent any flexing motions of the vessel wall from being 2,65 l ,672 9/1953 Ivanoff... 174/152 R transmitted to the insulating disc. 2,838,596 6/1958 Foord ..174/152R 2.897.472 7/1959 OBrien ..174/153 R 4 Claims, 2 Drawing Figures Primary Examiner-Laramie E. Askin Att0rne \'Philip M. Shaw, Jr.

PRESSURE ATMO SPHERE Patented May 2, 1972 3,660,593

PRESSURE ATMOSPHERE ATMOS PHERE.

PRESSURE VESSEL POWER LEAD-THROUGH BACKGROUND OF THE INVENTION The present invention relates to electrodes for use with pressure vessels and particularly to electrodes which pass through pressure vessel walls or covers.

There are many applications where electrical power has to be supplied to heaters or some other electrical device within a sealed pressure vessel. Generally the power is passed through a conductive rod which passes through the pressure vessel wall or through the pressure vessel cover. Such electrodes must meet the following requirements:

a. they must be sealed against the high pressure fluid, either liquid or gas, within the vessel;

b. they must be electrically insulated from the vessel;

c. they must resist the force of the pressure within the vessel pushing the electrode out of the vessel;

d. and they must resist breakdown due to heating in the conductive portion of the electrode during the transmission of electrical power through the electrode.

Sme prior pressure vessel electrodes employ the sealing method commonly used in sealing piston rods, valve stems, plunger pumps, and alike. Specifically a packing is squeezed wall or cover to make a seal. The gripping of the rod also produces a frictional effect which prevents the rod from being pushed out of the pressure vessel wall or cover by the end force due to the pressurized fluid. For applications using fluid under high pressure the length of the packing need be considerable to exert a sufficient frictional restraining force on the rod. In all applications such packing must be resilient and unaffected by the high temperatures generated in the electrode when it conducts electrical power.

Another type of prior art electrode employs a tapered conductive rod which fits into a gland piece within the vessel wall or cover. Insulation is interposed between the rod and the gland. The taper is designed to prevent the rod from being forced out by the fluid when the vesel is pressurized. One disadvantage of this design is that theinsulation must resist both the high pressure from the fluid and the high temperature generated in the electrode. The insulation commonly breaks down in service and occasionally such electrodes, being made of too soft a material, are extruded out of the pressure vessel like bullets out ofa gun.

In either type of prior art electrode discussed above the conductive rod must be strong enough at the operating temperature to resist the high pressure within the vessel. Pure copper, which has the highest conductivity of the generally available materials, cannot be used in most cases since its strength falls off very rapidly with an increase in temperature. Thus necessitates the use of an electrode of a less conductive material and having a large cross-sectional area relative to a copper electrode of the same electrical power conducting capability. Generally this substitute material, for example beryllium copper, is also more expensive than non-alloyed copper.

SUMMARY OF THE INVENTION The first boss member is solid and has a substantially larger cross-sectional area than the conductive rod. Concentric with the rod, and between the first boss member nd the interior vessel surface is generally disc shaped insulating means. Concentrically encompassing the insulating means is a first sealing means to prevent the escape of the pressurized fluid through the rod passage and more importantly to prevent the buildup of fluid pressure between the first boss member and the interiorly projecting end of the conductive rod. The first sealing means is not directly exposed to the high temperature of the rod during the transmission of electric power.

The purpose of the first boss member is to distribute the outwardly directed force generated by the pressurized fluid against the vessel wall rather than against the inwardly projecting end of the rod. Thus substantially no end load is exerted against the rod. The first boss member is adapted to receive an electrical lead from the equipment to be supplied with power inside the vessel. The outer end of the conductive rod is adapted to receive an external electrical lead.

In some embodiments a second boss member is provided between the insulating means and the interior surface of the vessel. The second boss member has an annular restriction in its diameter at the point where it contacts the interior surface of the vessel. A second sealing means circumferentially encompasses the annular restriction to prevent the escape of the pressurized fluid through the conducting rod passage. The purpose of this annular restriction is to prevent the transmission of bending effects in the vessel wall or cover due to the high pressure within the vessel to the insulating member and the first boss member. In such high pressure applications, the insulating member is made of a generally inflexible material, such as ceramic, and the bending forces exerted upon it should be minimized.

Thus it is an object of the invention to provide an electrode for use with a pressure vessel wherein the electrically conductive portion of the electrode passing through the vessel wall or the vessel cover is not directly subjected to the outward pressure within the vessel but rather is shielded from the interior pressure by a boss member having a substantially large crosssectional area relative to the cross-sectional area of the conducting portion of the electrode.

It is a further object of the invention to provide an electrode for use with a pressure vessel wherein the means for sealing the electrode passage in the pressure vessel is not subjected to the high temperatures generated by the conduction of electrical power through the electrode.

The foregoing and other objectives, features, and advantages of the invention will be more readily understood upon consideration of the following detailed description of certain preferred embodiments of the invention, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of one embodiment of the invention shown mounted in a portion of a pressure vessel wall or a pressure vessel cover;

FIG. 2 is a vertical sectional view of a second embodiment of the invention shown mounted in a portion of a pressure vessel wall or a pressure vessel cover.

DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS Referring now more particularly to FIG. 1 there is shown a portion of the pressure vessel 10 which may be either a portion of the vessel wall or a portion of the cover on the vessel.

Hereinafter the term wall" as used in this description shall be construed to mean a portion of either the pressure vessel wall or the pressure vessel cover. A rod 12 of conducting material extends through a passage 14 in the vessel wall 10 to the interi-' or of the vessel. The rod projects beyond the interior surface 16 of the vessel wall 10. A sleeve 18 encases the rod 12 and electrically insulates it from the vessel wall 10.

The interiorly projecting end 20 of the rod is threaded into a circular boss or solid reinforcing member 22 made of a high strength, electrically conductive material such as steel, which has a cross-sectional area substantially larger than the crosssectional area of the rod 12. By substantially larger is meant nine to 16 times a large (i.e., having a diameter three to four times the diameter of the rod).

The boss member has a threaded projection 24 adapted to receive a lead 26 from equipment (not shown) which is to be supplied with power within the pressure vessel.

Sandwiched between the boss member 22 and the vessel wall interior surface 16 is an insulating member 28 in the form of a disc. The conducting rod 12 and the sleeve 18 pass through a hole 29 in the insulating disc 28. Mounted co-axially about the insulating disc 28 is an O-ring seal 30 which is also sandwiched between the vessel wall interior surface 16 and the boss member 22. The sealing ring 30 prevents the escape of the pressurized fluid through the passage 14 and the buildup of fluid pressure between the boss member 22 and the end of the rod.

As the vessel is pressurized, the fluid exerts an outward force against the boss member 22 which is distributed through the insulating disc 28 against the vessel wall 10. Because the conducting rod 12 is not substantially restrained in moving in the passage 14, no compressive load is placed upon it by the pressurized fluid; the boss member 22 absorbs all of the outward force. This allows the rod to be made of a good electrical conductor, such as copper, and have a smaller cross-sectional area relative to prior art electrodes of the type which must withstand the outward pressure of the fluid.

The exterior end 32 of the rod 12 is threaded to receive an external power lead 34. The insulating disc 28 may be made of a high strength plastic for embodiments where the pressure is significantly less than 20,000 pounds per square inch. For applications involving higher pressures the insulating disc is made of a ceramic.

The use of a ceramic insulating disc requires a modification in the design of the embodiment of FIG. 1 to prevent bending of the ceramic disc due to flexing of the vessel wall 10 when the fluid is pressurized.

Referring now more particularly to FIG. 2 a second embodiment in the invention is shown as comprising an electrical power lead 34 threaded upon the external end of a conducting rod 36. The conducting rod 36 is encased in an insulating sleeve 38 and passes through an aperture 14 in the vessel wall 10'. The conducting rod 36 and sleeve 38 project into the vessel a predetermined distance beyond the vessel wall interior surface 16'. A first boss member 40 is threaded on the interiorly projecting end 42 of the rod. This first boss member 40 has a threaded projection 44 adapted to receive an electrode from the equipment to be supplied with power.

Between the first boss member 40 and the vessel wall interior surface 16' is second boss member 46. Between the

boss members

40 and 46 is an insulating member 48 made ofa nonresilient, high pressure resistant material such as ceramic. The insulating member 48 is generally in the shape ofa disc and is mounted co-axially about the interiorly projecting portion of the rod 36 and the sleeve 38. Co-axially encompassing the disc 48 and between the

boss members

40 and 46 is an O-ring seal 50. The opposed surfaces of the

boss members

40 and 46 on either side of the disc 48 and the O-ring seal 50 are ground smooth to evenly distribute forces applied by the boss members to the disc and seal.

The boss member 46 has an annular restriction or reduction 52 in its diameter where it contacts the vessel wall interior surface 16'. Co-axially encompassing this reduction 52 is an O- ring seal 54. The O-

ring seals

50 and 54 prevent the escape of the pressurized fluid through the passage 14'.

The purpose of the annular restriction 52 in the diameter of the boss member 46 is to minimize the transmission of any flexing movement of the vessel wall 10' when the vessel is pressurized to the disc member 48 to prevent it from being cracked and thus becoming an imperfect insulator. It is also designed to prevent these bending moments from being applied to the conducting rod 36.

While in the above embodiments the boss members are described as being threaded upon the conducting rod, it should be obvious that other means of attaching the conducting rod to the boss member could be substituted, provided the interiorly projecting end of the conducting rod is not exposed to the pressurized fluid.

In both of the above embodiments the outward force of the pressurized fluid is not applied directly to the interiorly projecting end of the rod but instead is applied to a rigid reinforcing boss member made of a high strength material. Thus the conducting rod may be made of a low-strength material which is also a good electrical conductor.

Furthermore the sealing means about the aperture in the vessel wall, while subjected to high pressures, is not subjected to the high temperatures generated by the passage of electrical power through the conducting rod. This allows a greater variety and economy in the use of sealing materials. The temperatures generated in the rod would commonly run about 500 F. while the temperature at the seal would be 300 F. or whatever temperature at which the fluid within the vessel is maintained. O-ring seals are generally available with temperature ranges up to 450 F.

The terms and expressions which have been employed here are used as terms of description and not of limitation and there is no intention, in the use of such terms and expressions, of excluding equivalents of the features shown and described, or portions thereof, it being recognized that various modifications are possible within the scope of the invention claimed.

What is claimed is:

1. An electrode for use with an apertured pressure vessel comprising an electrically conductive rod fitted within the aperture in the pressure vessel and projecting into the interior of the pressure vessel, an insulating sleeve encompassing the rod to prevent it from being in electrical contact with the pressure vessel, reinforcing means fitted upon the interiorly projecting end of the rod for preventing the application of an outwardly directed end load to the rod by the pressurized fluid within the vessel, the reinforcing means being electrically conductive and in electrical contact with the interiorly projecting end of the rod, insulating means between the reinforcing means and the interior surface of the vessel to prevent the reinforcing means from being in electrical contact with the interior surface of the vessel and for relieving the insulating sleeve of any outwardly directed force due to the pressurized fluid, and sealing means encircling the insulating means for preventing the pressurized fluid within the vessel from contacting the insulating sleeve and from escaping between the rod and the vessel aperture.

2. An electrode for supplying power to electrical equipment within a vessel filled with pressurized fluid comprising an electrically conductive rod, an insulating sheath encompassing the rod, the sheath and the rod projecting through an aperture in the vessel and extending a predetermined distance into the interior of the vessel, a reinforcing member fitted upon the interiorly projecting end of the rod for transmitting the outwardly directed force of the pressurized fluid to the vessel wall, the reinforcing member having a substantially larger.

cross-sectional area than the cross-sectional area of the rod, the reinforcing member being made of an electrically conductive material and being in electrical contact with the-rod, insulating means co-axial with the rod and insulating sheath for electrically insulating the reinforcing member from the interior surface of the vessel, sealing means including an O-ring seal, encompassing the insulating means to prevent the escape of pressurized fluid through the aperture in the vessel wall.

3. An electrode for use in supplying electrical power to equipment within a vessel containing pressurized fluid comprising an electrically conductive rod, an insulating sheath encompassing the rod, the sheath and rod being fitted through an aperture in the vessel to project a predetermined distance into the interior of the vessel, a first boss member being fitted upon the interiorly projecting end of the rod, the first boss member being made of electrically conductive material and being in electrical contact with the rod, a second boss member mounted co-axially about the rod and the insulating sheath and interposed between the first boss member and the interior surface of the vessel, the second boss member having an annular restriction in its diameter at the point where it comes in contact with the interior surface of the vessel, an insulating member co-axial with the rod and interposed between the first 4. An electrode as recited in claim 3 wherein the annular restriction in the diameter of the second boss member is sufficient tosubstantially prevent the transmission of flexing movement in the wall of the pressure vessel to the insulating member.

Claims

2. An electrode for supplying power to electrical equipment within a vessel filled with pressurized fluid comprising an electrically conductive rod, an insulating sheath encompassing the rod, the sheath and the rod projecting through an aperture in the vessel and extending a predetermined distance into the interior of the vessel, a reinforcing member fitted upon the interiorly projecting end of the rod for transmitting the outwardly directed force of the pressurized fluid to the vessel wall, the reinforcing member having a substantially larger cross-sectional area than the cross-sectional area of the rod, the reinforcing member being made of an electrically conductive material and being in electrical contact with the rod, insulating means co-axial with the rod and insulating sheath for electrically insulating the reinforcing member from the interior surface of the vessel, sealing means including an O-ring seal, encompassing the insulating means to prevent the escape of pressurized fluid through the aperture in the vessel wall.

3. An electrode for use in supplying electrical power to equipment within a vessel containing pressurized fluid comprising an electrically conductive rod, an insulating sheath encompassing the rod, the sheath and rod being fitted through an aperture in the vessel to project a predetermined distance into the interior of the vessel, a first boss member being fitted upon the interiorly projecting end of the rod, the first boss member being made of electrically conductive material and being in electrical contact with the rod, a second boss member mounted co-axially about the rod and the insulating sheath and interposed between the first boss member and the interior surface of the vessel, the second boss member having an annular restriction in its diameter at the point where it comes in contact with the interior surface of the vessel, an insulating member co-axial with the rod and interposed between the first and the second boss members to prevent them from being in electrical contact with each other, a first sealing means encompassing the insulating member to prevent the escape of the pressurized fluid from the rod aperture in the vessel, and a second sealing means co-axially encompassing the annular restriction to prevent the escape of the pressurized fluid through the rod aperture.

4. An electrode as recited in claim 3 wherein the annular restriction in the diameter of the second boss member is sufficient to substantially prevent the transmission of flexing movement in the wall of the pressure vessel to the insulating member.