US 3605795 A
Description (OCR text may contain errors)
Sept. 20, 1971 s. RAJAKOVICS SPINDLE VALVE Filed Jan. 2871969- llifl .ll/llllI/l ooo ooooo" /n van (or:
q "M w K G 0 10M 0M FM M A D United States Patent Oflice Patented Sept. 20, 1971 3,605,795 SPINDLE VALVE Gundolf Rajakovics, Kapfenberg, Austria, assignor to Gebr. Bohler & C0. Aktiengesellschaft, Kapfenberg,
Austria Filed Jan. 28, 1969, Ser. No. 794,537 Claims priority, application27Austria, Jan. 29, 1968,
Int. Cl. F16k 49/00 US. Cl. 137-338 Claims ABSTRACT OF THE DISCLOSURE A spindle valve for preventing the escape of an operating medium and resistant to extreme temperature differentials in said medium, the valve including a housing and an axially movable spindle having a closure means at one end adjacent a valve seat in the housing. A siphon surrounds the spindle and is spaced from the closure means, and a tube connects the closure means to the siphon. A siphon chamber exists between the siphon and the housing, and a narrow annulus exists between the tube and the housing. Cooling fins are connected to the housing adjacent the narrow annulus, and a heating means surrounds the siphon chamber.
This invention concerns spindle valves generally, and specifically a device for sealing spindles axially movable in a housing to prevent the escape of an operating medium, for example, liquid sodium for use in nuclear reactors. A siphon surrounds the spindle and a narrow radial gap, relative to its length, is provided between the housing and the spindle axially between the siphon and a valve disk.
The sealing of liquid valves represents a special problem when confronted with excessive temperatures, par ticularly if great nominal widths and strokes are required. Since the seal must be completely gas-tight, metal siphons are preferably used for sealing. At high temperatures the usual materials lose so much in strength that the loading capacity of siphons made therefrom is very low. in addition, the corrosion increases considerably in these materials, particularly at temperatures over 600 C., which can lead to premature failure of the sealing elements in view of the small wall thicknesses of metal siphons. Metal alloys, which show better strength properties at high temperatures, contain major portions of alloying elements, such as nickel, for example, which can be dissolved by liquid nickel at temperatures over 600 C., so that the sealing element may likewise fail.
It is logical to cool the area where the siphon is arranged so that it attains a lower temperature level than the operating medium in the valve. Such a solution has the disadvantage, however, that dissolved impurities of the liquid metals, particularly the oxides thereof, travel in the coldest spot of the valve, that spot being the siphon. The result is a concentration of alkali-metal oxide in the area of the siphon, which can lead to a very rapid destruction of the siphon by corrosion. Besides, there is a danger that when the valve is used at low temperatures, the temperature at the location of the siphon will drop down to the solidification point of the operating medium (particularly in the case of sodium) and the siphon is therefore mechanically destroyed when the valve is actuated, due to solidification of the operating medium.
The object of the present invention is to avoid the above-mentioned disadvantages and to keep the siphon at a substantially constant temperature of 300 C., for example, substantially independent of the temperature of the operating medium. This is achieved according to the invention by an apparatus of the above-mentioned type by providing a cooling gap having cooling fins provided on its outer wall, and the siphon chamber can be heated, for example, by means of an electric heating coil surrounding it.
Further details of the apparatus according to the invention will result from the following description of an embodiment of the invention which is represented schematically in the drawing, showing a valve for liquid sodium in a longitudinal section.
The inner limiting surface of a coolable gap 1 is defined by a tube-like siphon 8 consisting of a stainless chrome-nickel steel accordian portion having one end attached to valve housing 5, and the other end having a tube 2 sealingly connected with a valve disk 4. The gas space 3 existing between the siphon 8 and a valve spindle 3 is filled with a protective gas, for example, argon, which can be introduced through a nipple 11. The gas space 3' is sealed by a stuffing box which comprises a packing 13 and a gland 12. The outer limiting surface of a coolable gap 1 is defined by a cylindrical part 6 of the housing provided with cylindrical, preferably outwardly extending radially-arranged cooling fins 7. The longitudinal zone of part 6 adjacent the siphon and adjoining the cooling fins 7 is embraced by a heating coil 9 by means of which siphon 8 is electrically heated. The heating coil 9 is surrounded at its sides remote of the siphon by a heat-insulating layer 10. The part 6 with the cooling fins 7 can easily be so dimensioned that, with constant intensity of the electric current traversing the heating coil 9, the temperature of the siphon 8 is practically independent of the temperature of the liquid sodium inside valve housing 5 and, on the other hand, the point of the lowest temperature in the liquid sodium is not in the area of the siphon chamber 8' but in the coolable gap 1. Elimination and concentration of impurities therefore takes place practically only in this gap 1, where the impurities are relatively harmless. The liquid sodium operating medium remains in its liquid state between the siphon 8 and interior 5 of the valve housing 5, even at operating temperatures which are close to the solidification point of liquid sodium, so that the discharge capac ity of the siphon chamber 8 is ensured.
In a liquid metal system of high temperatures, for example, in circuits of nuclear reactors with sodium cooling, high temperature-variation velocities are to be expected. These particularly impair the behavior of the fittings. Due to the unsymmetry of the currents around the control body of the valves, particularly in corner valves, valve spindles assume greatly varying temperatures under non-stationary temperature conditions because of the high heat transfer coefiicients of liquid metals, so that the valve spindles are bent and a proper operation of the valve is no longer certain. Another advantage of the above-described embodiment of the apparatus according to the invention consists in that thi disadvantage is positively avoided, since, on the one hand, a hollow space 3', preferably filled with protective gas, is provided between the tube 2 and the valve spindle 3, and on the other hand, the tube 2 is only clamped on one end. It can therefore be freely deformed by the above-mentioned temperature shock, with only negligible siphon forces acting as restoring forces. The valve spindle itself remains unaffected by the temperature shock due to the insulating effect of the gas space, and therefore retains its shape. The tubular part can be so dimensioned that it has a practically unlimited life both in view of the corrosion stress at the high temperatures and of the internal stresses due to the temperature shock.
What I claim is:
1. In a spindle valve which includes a housing, an axially movable spindle having closure means formed on movable spindle, said siphon comprising a tube at said one end of said spindle spaced from the housing to form a narrow gap as compared to the length of the gap, and a bellows at said other end of said spindle spaced from the housing to form a siphon chamber; cooling means arranged on the housing adjacent said narrow gap; and heating means arranged on the housing adjacent said bellows, wherein the medium present in said narrow gap is cooled and that portion of the medium present in said siphon chamber is heated.
2. A spindle valve as claimed in claim 1 wherein said heating means is a resistance heating coil wrapped around a portion of said housing and heat insulating means surrounds said coil to direct the heat inwardly toward said siphon chamber.
3. A spindle valve as claimed in claim 1 wherein said liquid operating medium is sodium; said bellows is made of stainless steel and said heating means keeps the sodium in said siphon chamber at a substantially constant temperature of 300 C.
4. A spindle valve as claimed in claim 1 wherein said cooling means are cooling ribs attached to that portion of the housing surrounding said narrow gap.
5. A spindle valve as claimed in claim 1 wherein said narrow gap is an annulus and the inlet and outlet passages are at approximately right angles to each other.
References Cited UNITED STATES PATENTS 3,028,874 4/1962 Burkett 137340 3,075,542 1/1963 Diesing 137338 3,101,094 8/1963 McKenzie 137--34O 3,110,319 11/1963 Arata et al. 137-840 3,131,713 5/1964 Kelley 137-340 3,211,169 10/1965 Webb 137-340 3,228,414 1/1966 Zerigian l37340 SAMUEL SCOTT, Primary Examiner US. Cl. X.R. l37341