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A magnetic safety valve
A magnetic safety valve
G. Bon Mardion, J. Challier, R. Prost and L. Senet
Vessels or apparatus containing liquefied gases or compressed fluids have to be protected by nlpture discs. These discs present several disadvantages, particularly with low working pressures they have large diameters and their flanges are cumbersome, heavy and expensive; after rupture has occurred the disc has to be replaced, the corresponding operations of dismounting and remounting take quite a long time; and the mechanical strength of the discs does not always last a long time: local corrosions sometimes cause a premature rupture.
description: immediate and total opening. The experimental calibration of the release pressure (vs distance 'd', with 28 magnets in operation) is shown in Fig. 2. From the shape of the magnetic circuit there is no demagnetizing effect on the used magnets ('ventouse magn~tique'). 2 Consequently the release pressure of the valve does not show any variation with time. Magnet supporting ring 28 magnets at maximum
We have developed a magnetic safety valve in order to avoid these disadvantages. It may be used in place of rupture discs when the operation pressure is low. In fact this valve is less cumbersome, substantially lower in cost, adjustable in pressure, free of wear, reliable and it provides a complete (total) opening once the release pressure is attained.
-Vacuum seal (Oring)
Lid
I
~ Holding chain ,2
6
#cOY. . . . .
\
Working principles of the magnetic safety valve
'
A lid, made partly or entirely of ferromagnetic material, closes the safety duct pressing against the seal. The force which is necessary to maintain the compressed seal and the pressure inside the duct, is generated by magnetic attraction between the lid and a number of permenent magnets attached to a metallic ring fixed on the duct. If the operation pressure increases slightly just above the value where the magnetic force is balanced by the pressure, the lid is set free almost instantaneously. The magnetic attraction decreases very rapidly once the lid starts to move away. Thus the valve gives an immediate and total opening. Remounting is simply achieved by putting the lid back in its seat. Adjustment of the release pressure is achieved by altering the number of permanent magnets or varying the gap between the lid and .the magnetic system.
Example of construction
Fig. 1
The valve is vacuum tight (no leak detected with a helium spectrometer) and operates in accordance with the above GB, JC and LS are at D T C E / S B T Centre d'Etudes Nucle'aires, 85 X 38041 Grenoble Cedex, France. RP is at C E C - L ' A i r Liquide BP 15 3 8 3 6 0 Sassenage, France. Received 12 February 1979.
Diagram to show the magnetic safety valve
"t
B maqnets 2. ._=-----
~- 0.4 % v 6 -
We have built a magnetic safety valve for a tube diameter of 150 mm (Fig. 1) in order to make sate a cryostat for a superconducting coil cooled with supertluid helium at atmospheric pressure. The lid is made of chrome coated steel. Twenty eight magnets are attached to a ring made of stainless steel. The ring is fixed to the tube by three screws. These screws are used to adjust the gap between the lid and the magnetic system. The gap is simply controlled by a calliper sqnare measuring the distance 'd' (Fig. 1).
NO*
0.5 magnets
a. e 02
/
OI
31 O0
1
J
51.50
32.00
d, mm Fig. 2
Calibration of the release pressure
References 1 2
Bon Mardion, G., Prost, R. Brevet 78, 34205 (France) UGIMAG BP 3, 38830 St Pierre D'Allevard, France
0011-2275/79/070424-01 $02.00 © 1979 IPC Business Press CRYOGENICS.
J U L Y 1979
425
G. Bon Mardion, J. Challier, R. Prost and L. Senet
Vessels or apparatus containing liquefied gases or compressed fluids have to be protected by nlpture discs. These discs present several disadvantages, particularly with low working pressures they have large diameters and their flanges are cumbersome, heavy and expensive; after rupture has occurred the disc has to be replaced, the corresponding operations of dismounting and remounting take quite a long time; and the mechanical strength of the discs does not always last a long time: local corrosions sometimes cause a premature rupture.
description: immediate and total opening. The experimental calibration of the release pressure (vs distance 'd', with 28 magnets in operation) is shown in Fig. 2. From the shape of the magnetic circuit there is no demagnetizing effect on the used magnets ('ventouse magn~tique'). 2 Consequently the release pressure of the valve does not show any variation with time. Magnet supporting ring 28 magnets at maximum
We have developed a magnetic safety valve in order to avoid these disadvantages. It may be used in place of rupture discs when the operation pressure is low. In fact this valve is less cumbersome, substantially lower in cost, adjustable in pressure, free of wear, reliable and it provides a complete (total) opening once the release pressure is attained.
-Vacuum seal (Oring)
Lid
I
~ Holding chain ,2
6
#cOY. . . . .
\
Working principles of the magnetic safety valve
'
A lid, made partly or entirely of ferromagnetic material, closes the safety duct pressing against the seal. The force which is necessary to maintain the compressed seal and the pressure inside the duct, is generated by magnetic attraction between the lid and a number of permenent magnets attached to a metallic ring fixed on the duct. If the operation pressure increases slightly just above the value where the magnetic force is balanced by the pressure, the lid is set free almost instantaneously. The magnetic attraction decreases very rapidly once the lid starts to move away. Thus the valve gives an immediate and total opening. Remounting is simply achieved by putting the lid back in its seat. Adjustment of the release pressure is achieved by altering the number of permanent magnets or varying the gap between the lid and .the magnetic system.
Example of construction
Fig. 1
The valve is vacuum tight (no leak detected with a helium spectrometer) and operates in accordance with the above GB, JC and LS are at D T C E / S B T Centre d'Etudes Nucle'aires, 85 X 38041 Grenoble Cedex, France. RP is at C E C - L ' A i r Liquide BP 15 3 8 3 6 0 Sassenage, France. Received 12 February 1979.
Diagram to show the magnetic safety valve
"t
B maqnets 2. ._=-----
~- 0.4 % v 6 -
We have built a magnetic safety valve for a tube diameter of 150 mm (Fig. 1) in order to make sate a cryostat for a superconducting coil cooled with supertluid helium at atmospheric pressure. The lid is made of chrome coated steel. Twenty eight magnets are attached to a ring made of stainless steel. The ring is fixed to the tube by three screws. These screws are used to adjust the gap between the lid and the magnetic system. The gap is simply controlled by a calliper sqnare measuring the distance 'd' (Fig. 1).
NO*
0.5 magnets
a. e 02
/
OI
31 O0
1
J
51.50
32.00
d, mm Fig. 2
Calibration of the release pressure
References 1 2
Bon Mardion, G., Prost, R. Brevet 78, 34205 (France) UGIMAG BP 3, 38830 St Pierre D'Allevard, France
0011-2275/79/070424-01 $02.00 © 1979 IPC Business Press CRYOGENICS.
J U L Y 1979
425