US2622122A

US2622122A - Conservator for liquid-immersed apparatus

Info

Publication number: US2622122A
Application number: US153174A
Authority: US
Inventors: Thomas C Lennox
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1950-03-31
Filing date: 1950-03-31
Publication date: 1952-12-16
Anticipated expiration: 1969-12-16

Description

Dec. 16, 1952 T C. LENNOX 2,622,122

CONSERVATOR FOR LIQUID-IMMERSED APPARATU S Filed March 31. 1950 Fig.1.

Inventor: Thomas C. Lennox,

His Attorney.

Patented Dec. 16, 1952 CONSERVATOR FOR- LIQUID-IMMERSED APPARATUS Thomas C. Lennox, Pittsfield, Mass assignor to General Electric Company, a corporation of New York Application March 31, 1950, Serial No. 153,174

3 Claims. 1

This invention relates to liquid-immersed electrical apparatus, and more particularly to expansion devices for the insulating liquid in which such apparatus is immersed.

It is common practice to immerse certain types of electrical apparatus, such as electrical transformers, in an insulating liquid which partly or wholly fills .the container for the electrical apparatus, such as a transformer tank. Since such insulating liquid expands and contracts with changes in temperature of the electrical apparatus, it is necessary to provide expansion space for the liquid. This expansion space may be provided when the container for the electrical apparatus is normally only partially filled with the insulating liquid by making the container sufficiently large to accommodate the expansion of the liquid, an alternative which is undesirable since it adds considerably to thecost of the apparatus, as well as unduly increasing its size.

The conventional means which has been used in the prior art for providing for the expansion of the insulating liquid has been to use an auxiliary tank, commonly referred to as a conservator, which is mounted above thecontainer for the apparatus, such as a transformer tank, and feeds the insulating liquid to the tank by gravity. When the insulating liquid in the main tank expands, it pushes a column of liquid up into the conservator or expansion tank, which is made sufficiently large to accommodate the anticipated expansion.

There are several undesirable features about the use of an expansion or conservator tank mounted above the main tank in which the apparatus is contained, although, so far as I know, this is the usual way in which conservator tanks have been mounted in the prior art. One serious objection is that such an arrangement increases the overall height of the electrical apparatus. A second objection when the insulating liquid is oil or some other inflammable liquid is that this arrangement increases somewhat the fire hazard in the event that there should be an explosion of the electrical apparatus, since the gravity feed from the conservator tank would continually add more fuel to the fire.

It is an object of this invention to provide a new and improved liquid expansion tank construction for use with liquid-immersed electrical apparatus.

It is a further object of thisinvention to provide a liquid expansion tank for use'with liquidimmersed electrical apparatus which will reduce the necessary overall height of the apparatus.

In accordance with these objectives, this invention provides an expansion tank which is mounted on the side of the containing tank for the electrical apparatus, and maintains the oil within the main tank at a substantially constant level by utilizing the heating and cooling cycle of the electrical apparatus to produce the necessary motion of the insulating liquid to and. from the expansion tank.

Hereinafter in this specification I shall use a transformer by way of example as the type of liquid-immersed electrical apparatus to which my invention is applied. However, it will be understood that my invention applies equally well to any type of tank-enclosed liquid-immersed apparatus. Furthermore, in referring to the insulating liquid which surrounds the electrical apparatus, I shall hereinafter use oil by way of example as the insulating liquid used although it will be understood that any other suitable insulating liquid may be used.

The features of this invention which I believe to be novel are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and use, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawing in which Fig. 1 is a form of my invention utilizing a side-mounted expansion tank, with the transformer tank and expansion tank both being sealed against the admission of air from the atmosphere; while Fig. 2 is a modification of the structure shown in Fig. 1 in which the connecting duct between the main transformer tank and the expansion tank is placed below the top of the main transformer tank.

There is shown in Fig. 1 a form of my invention in which the complete transformer tank and expansion tank system is sealed and is not open to the atmosphere, and in which the transformer tank is completely filled with oil. There is shown in Fig. 1 a transformer tank 20 of conventional design having a duct 2| communicating with the inside of the transformer tank and mounted above the cover of the tank. The duct 2| extends radially outwardly beyond the outer periphery of the tank 20 and is connected by a pipe 22, which extends parallel to the axis of tank 20, to an expansion chamber 23 which is mounted on-the side, of tank 20. The system is filled with. oil

through a suitable valve (not shown) in the bottom of tank 20 until tank 20 is full and sufiicient oil has flowed through duct 2! and pipe 22 to fill expansion tank 23 to the normal oil level which 3 it is desired to maintain in expansion tank 23 at the temperature of filling, such as the oil level indicated by the dotted line 24, for example. Sufficient air, or preferably nitrogen, should be forced into the top of the expansion tank 23 above the oil level so that When the minimum operating temperature is reached, the pressure inside the expansion tank will still be slightly above atmospheric. As the oil in the transformer tank expands under high temperature conditions, it will force oil through the duct 2| and conduit 22 into expansion chamber 23. Any

excess air or gas in the top of the tank 20 is ex pelled in advance of the expulsion of the oil. When the temperature inside transformer tank 20 declines in value the pressure of the air or nitrogen above the oil level in expansion chamber 23 will force oil back up through pipe 22 and into tank 26. When this happens, the oil in the expansion chamber will diminish to a low level such as is indicated by the dotted line 25. Transformer tank 20 is maintained completely filled with oil at all times, with the thermal cycle of the transformer maintaining a flow of oil be.- tween the main tank and expansion tank in accordance with the expansion and contraction of the oil. An oillevel indicator or alarm 4| is provided in duct 2| to warn of loss of oil through leakage.

Since this transformer and expansion tank system is not open to the atmosphere, means should preferably be provided to prevent rupture of the main tank 20 in case of an excessive pressure condition in the transformer tank-expansion tank system. Since a simple pressure relief diaphragm on top of the main tank 20 would, if broken, permit the pressure of the air or nitrogen inside expansion tank 23 to force all the oil in expansion tank 23 out through the broken diaphragm, such an arrangement is unacceptable. In order to provide an adequate pressure relief, I provide a double. diaphragm arrangement, as shown in Fig. 1. These two diaphragms are indicated at .26 and 21, respectively. Diaphragms 26 and 2.1 are located in an extension of duct 2|, and are radially displaced from one another. It will be noted that due to their radial displacement along the. extension of duct 2|,

diaphragms

26 and 21 enclose a small space 23 which is connected' by a conduit 29 to the air or nitrogen space above the oil level in expansion tank 23. The space 28 is therefore at the same pressure as the space above the oil level inside expansion tank 23. In the event of a moderate increase in pressure beyond the allowable pressure limit inside expansion tank 23, radially outer diaphragm 21 will be caused to rupture, thereby relieving excess pressure. However, in the case of a. very sudden increase in pressure inside expansion tank 23 which could notbe relieved by the flow of oil through pipe 22 or ga through the conduit 29, both diaphragms 25 and 21 will rupture.

Preferably diaphragm 27 will be weaker than diaphragm 26. This is so that in the event of a moderate increase in pressure beyond the allowable pressure limit inside expansion tank 23, rupture of diaphragm 21 will relieve the excess pressure but diaphragm 26 will still be intact to prevent loss of the oil in duct 2 I.

A basket of silica gel 30 may be suspended in the upper part of expansion chamber 23 to absorb any residue of free moisture left in the system at installation.

Thereis shown in Fig. 2 a modificat n f the construction of Fig. 1 which permits the use of a small gas cushion in the top of the main transformer tank as a protection against sudden increases in pressure. In Fig. 2 there is shown a transformer tank 3| which is filled to an oil level 32 slightly below the top of the tank to permit a gas or air cushion 33 between the oil level 32 and the topof tank 3|. A duct 34 communicates with tank 3| at a level slightly below the top of the tank, the oil level in the duct being the same as in the tank. A pipe 35 parallel to the axis of tank 3 I. provided for oil flow between the transformer tank 3| and expansion tank 36 which is similar to expansion tank 23 shown in Fig. 1.

The systemisfilled with oil through a suitable valve in the bottom of tank 3| until the oil in tank 3| has reached a level slightly below the top of the tank, and suflicient oil has flowed through duct 34 and conduit 35 to fill expansion tank 36 to the normal oil level which it is desired to maintain in the expansion tank 36 at the temperature. of filling. Sufiicient air, or preferably nitrogen, should beforced into the top of expansion tank 36 above the oil. level, and into the space 3.3 above the oil level in transformer tank 3|, so that when the minimum operating temperature is reached the pressure inside the system will still be slightly above atmospheric. In order to provide adequate pressure relief, a double diaphragm arrangement imilar to that of Fig. 1 is provided. Diaphragms 31 and 38 are located in an extension of duct 34, and are radially displaced from one another. Due to their radial displacement from one another along the extension of duct 34,, diaphragms 31 and 33 enclose a small. space 39 which is connected by a conduit 40 to the air or nitrogen space above the oil level in expansion tank 36. The space 39 is therefore at the same pressure as the space above the oil level inside expansion'tank 35. In the event of a moderate increase in pressure beyond the allowable pressure limit, radially outer diaphragm 38 will. be caused to rupture, thereby relieving, the excessp'ressure. However, in case of a very sudden increase in pressure which could not be relieved by the flow of oil or gas through the

conduits

35 and 40, both diaphragms 31 and 38 will rupture.

Since duct 34 islocated below the top of transformer tank 3|, and the oil level in the duct is the same as the oil level in the tank 3|, if the diaphragms 31 and 38 were located at the same level as the oil, an excessive loss of oil would occur if both diaphragms 31 and 38 ruptured. In order to prevent such an excessive loss of oil, the radially outer portion of duct 34 containing diaphragms 31 and 38 is elevated above the oil lever 32. This assures that in the event of rupture of the. diaphragms 3'! and, 38 only oil above the level indicated by dotted line 32 will gene ally be'lost. through the diaphragms. Oil level indicator or alarm is provided to warn of decrease of oil level due to leakage or other causes.

While there, have been shown and described particular embodiments of my invention, it will be obviousto those skilled in the art that various changes and modifications can be made therein without departing fromthe invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters. Patent of the United States is:

1. In combination with liquid-immersed elecca a p ratus n a containing tank, expansion means for said liquid comprising an expansion tank mounted exteriorly adjacent said containing tank, substantially the greater portion of said expansion tank being lower than the uppermost surface of said containing tank, a duct positioned above the top surface of said containing tank and projecting radially outwardly from said containing tank, one end of said duct being connected to the interior of said containing tank, the other end of said duct being provided with pressure-relief means, said duct being connected intermediate its two ends to a conduit projecting into said expansion tank substantially to the bottom of said expansion tank, said containing tank normally being completely filled with said liquid, said containing tank and said expansion tank being sealed against entrance of air from the atmosphere, said expansion tank being filled above any liquid present therein with a gaseous medium at a minimum pressure in excess of atmospheric pressure, the normal heating and cooling cycle of said liquid-immersed electrical apparatus causing pressure differentials between said containing tank and said expansion tank which result in liquid flow between said two tanks, said pressure relief means comprising a first and a second frangible diaphragm positioned in said radially-projecting duct, said two diaphragms enclosing a space at the radially outer end of said duct, a conduit connecting said space between said diaphragms to the upper end of said expansion tank, excessive gas pressure interiorly of said expansion tank normally causing the radially outermost of said diaphragms to rupture before said radially inner diaphragm ruptures.

2. In combination with liquid-immersed electrical apparatus in a containing tank, expansion means for said liquid comprising an expansion tank mounted exteriorly adjacent said containing tank, substantially the greater portion of said expansion tank being lower than the uppermost surface of said containing tank, said containing tank being filled with said liquid to a level slightly below the top of said containing tank, a gaseous medium filling the space between the top level of said liquid and the top of said containing tank, a duct projecting radially outwardly from said containing tank, one end of said duct being connected to the interior of said containing tank, the other end of said duct being provided with pressure-relief means, said duct being connected intermediate its two ends to a conduit projecting into said expansion tank substantially to the bottom of said expansion tank, said containing tank and said expansion tank being sealed against entrance of air from the atmosphere, said expansion tank being filled above any liquid present therein with a gaseous medium at a minimum pressure in excess of atmospheric pressure, the normal heating and cooling cycle of said liquid-immersed electrical apparatus causing pressure differentials between said containing tank and said expansion tank which result in liquid flow between said two tanks, said pressure-relief means comprising a first and a second frangible diaphragm positioned in said radially projecting duct, said two diaphragms enclosing a space at the radially outer end of said duct, a conduit connecting said space between said diaphragms to the upper end of said expansion tank, excessive gas pressure interiorly of said expansion tank normally causing the radially outermost of said diaphragms to rupture before said radially inner diaphragm ruptures, the radially outer portion of said duct in which said diaphragms are contained being elevated above the normal liquid level present in said containing tank.

3. In combination with liquid-immersed electrical apparatus in a containing tank, expansion means for said liquid comprising an expansion tank mounted exteriorly adjacent said containing tank, substantially the greater portion of said expansion tank being lower than the uppermost surface of said containing tank, a duct having one end connected to the interior of said containing tank at the upper end thereof and projecting radially outwardly from said containing tank, the other end of said duct being provided with pressure-relief means, said duct being connected intermediate its two ends to a conduit projecting into said expansion tank substantially to the bottom of said expansion tank, said containing tank and said expansion tank being sealed against entrance of air from the atmosphere, said expansion tank being filled above any liquid present therein with a gaseous medium at a minimum pressure in excess of atmospheric pressure, the normal heating and cooling cycle of said liquidimmersed electrical apparatus causing pressure differentials between said containing tank and said expansion tank which result in liquid fiow between said two tanks, said pressure relief means comprising a first and a second frangible diaphragm positioned in said radially projecting duct, said two diaphragms enclosing a space at the radially outer end of said duct, a conduit connecting said space between said diaphragms to the upper end of said expansion tank, excessive gas pressure interiorly of said expansion tank normally causing the radially outermost of said diaphragms to rupture before said radially inner diaphragm ruptures.

THOMAS C. LENNOX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,584,523 Egbert May 11, 1926 1,693,265 Austin Nov. 27, 1928 1,693,430 Austin Nov. 27, 1928 1,697,141 Rodman et al. Jan. 1, 1929 1,712,765 Hill May 14, 1929 1,775,028 Hilliard Sept. 2, 1930