GB2078955A

GB2078955A - Improvements in detecting an interface between two media

Info

Publication number: GB2078955A
Application number: GB8021040A
Authority: GB
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1980-06-26
Filing date: 1980-06-26
Publication date: 1982-01-13

Abstract

A tuning fork is disposed with one prong 3 arranged horizontally within a vessel containing a medium, such as a foam, and the other prong 4 outside the vessel. Excitement of the prong outside the vessel causes sympathetic excitement of the prong within the vessel. If the vibration of the outer prong is stopped suddenly the vibration of the inner prong dies away with a decrement which depends on whether the inner prong is immersed in the medium or is above the surface of the medium. It is therefore possible to determine when the level of the medium within the vessel rises or falls above or below the inner prong. By utilising two tuning forks it is possible to determined upper and lower level limits for the medium within the vessel. <IMAGE>

Description

SPECIFICATION Improvements in detecting an interface between two media The present invention concerns a detector for detect ing an interface between two media. In particular, the invention concerns a detector for detecting the level of a medium in a vessel.

According to the present invention a detector for determining the level of a medium in a vessel comprises a tuning fork having a first prong within the vessel and disposed in a substantially horizontal plane and a second prong outside the vessel, means for exciting the second prong to effect sympathetic excitment of the first prong and means for detecting a decrement in the oscillations of the first prong upon a sudden stop of the oscillations of the second prong, the rate of decrement being dependent upon whether the first prong is immersed in the medium or above the surface of the medium and hence dependent on the level of the medium in the vessel.

The medium in the vessel can be a foam as used in a mixed oxide fuel plant. A foam is a two phase system composed of a gas or vapour phase dis persed in a continuous liquid phase. However, the invention is not confined to use with foam media and can be used to detect the leveis of liquids.

The invention will be described further, by way of example, with reference to the accompanying di agrammatic drawing which is a view, from above, of a foam level detector.

In the illustrated example, the detector is utilised to detect the level of a foam used in a mixed oxide fuel plant. The foam, which can be an ammonia foam, serves as a cushion for substantially spherical fuel pellets.

In the drawing, which is a diagrammatic plan view, the foam 1 is contained in a vessel, a wall of the vessel being denoted by reference numeral 2. An elongated tuning fork passes through the wall 2 such that one prong 3 of the fork is within the vessel and the other prong 4 is outside the vessel. The distance between the prongs can be considerable, for exam ple, two feet or more, hence the use of the express ion "elongated". The fork is arranged such that the prongs are substantially horizontal.

The outer prong 4which is in the normal plant environment outside the vessel containing the foam is excited electro-magnetically. An electro-magnet is denoted by reference numeral 5. Excitation of the "prong 4 results in a sympathetic excitment of the prong 3. If the prong 4 is stopped suddenly, the oscillation of the prong 3 decays with a decrement which is determined by the medium about the prong 3. In other words, the decrement will be different when the prong 3 is immersed in foam to when the prong 3 is above and out of the foam. There is a clear and distinct difference which can be measured by a transducer 6 which can, for example, be an accelero meter. The block 7 denotes a means for actuating the electro-magnet and electronic means for processing the signal from the transducer.Such electronic means can determine the time or the number of fork oscillations between two fixed amplitudes.

A singie tuning fork arranged as described can be used to determine when the foam rises or falls above or below the level of the prong 3. Conveniently, it is desirable to employ two tuning forks, one fork to determine an upper level for the foam and the second fork to determine a lower level. The foam level will normally be between the prongs of the two forks. If the foam rises to immerse the prong of the upper fork then an appropriate difference signal is noted at the transducer. Likewise, an appropriate difference signal is obtained if the foam falls below the level of the prong of the lower fork.

Although described with reference to a foam it is envisaged that the invention can also be used to detect changes in level of liquids.

CLAIMS (Filed on 10/6/81) 1. A detector for determining the level of a medium in a vessel comprising a tuning fork having a first prong within the vessel and disposed in a substantially horizontal plane and a second prong outside the vessel, means for exciting the second prong to effect sympathetic excitment of the first prong and means for detecting a decrement in the oscillations of the first prong upon a sudden stop of the oscillations of the second prong, the rate of decrement being dependent upon whether the first prong is immersed in the medium or above the surface of the medium and hence dependent on the level of the medium in the vessel.

2. A detector as claimed in claim 1 including upper and lower tuning forks each having a first prong within the vessel to determine respectively upper and lower levels of the medium within the vessel.

3. A detector for determining the level of a medium in a vessel substantially as herein described with reference to and as illustrated in the accom panyingdrawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

SPECIFICATION Improvements in detecting an interface between two media The present invention concerns a detector for detect ing an interface between two media. In particular, the invention concerns a detector for detecting the level of a medium in a vessel.

According to the present invention a detector for determining the level of a medium in a vessel comprises a tuning fork having a first prong within the vessel and disposed in a substantially horizontal plane and a second prong outside the vessel, means for exciting the second prong to effect sympathetic excitment of the first prong and means for detecting a decrement in the oscillations of the first prong upon a sudden stop of the oscillations of the second prong, the rate of decrement being dependent upon whether the first prong is immersed in the medium or above the surface of the medium and hence dependent on the level of the medium in the vessel.

The medium in the vessel can be a foam as used in a mixed oxide fuel plant. A foam is a two phase system composed of a gas or vapour phase dis persed in a continuous liquid phase. However, the invention is not confined to use with foam media and can be used to detect the leveis of liquids.

The invention will be described further, by way of example, with reference to the accompanying di agrammatic drawing which is a view, from above, of a foam level detector.

In the illustrated example, the detector is utilised to detect the level of a foam used in a mixed oxide fuel plant. The foam, which can be an ammonia foam, serves as a cushion for substantially spherical fuel pellets.

In the drawing, which is a diagrammatic plan view, the foam 1 is contained in a vessel, a wall of the vessel being denoted by reference numeral
2. An elongated tuning fork passes through the wall 2 such that one prong 3 of the fork is within the vessel and the other prong 4 is outside the vessel. The distance between the prongs can be considerable, for exam ple, two feet or more, hence the use of the express ion "elongated". The fork is arranged such that the prongs are substantially horizontal.

The outer prong 4which is in the normal plant environment outside the vessel containing the foam is excited electro-magnetically. An electro-magnet is denoted by reference numeral 5. Excitation of the "prong 4 results in a sympathetic excitment of the prong 3. If the prong 4 is stopped suddenly, the oscillation of the prong 3 decays with a decrement which is determined by the medium about the prong
3. A detector for determining the level of a medium in a vessel substantially as herein described with reference to and as illustrated in the accom panyingdrawing.

3. In other words, the decrement will be different when the prong 3 is immersed in foam to when the prong 3 is above and out of the foam. There is a clear and distinct difference which can be measured by a transducer 6 which can, for example, be an accelero meter. The block 7 denotes a means for actuating the electro-magnet and electronic means for processing the signal from the transducer.Such electronic means can determine the time or the number of fork oscillations between two fixed amplitudes.

A singie tuning fork arranged as described can be used to determine when the foam rises or falls above or below the level of the prong 3. Conveniently, it is desirable to employ two tuning forks, one fork to determine an upper level for the foam and the second fork to determine a lower level. The foam level will normally be between the prongs of the two forks. If the foam rises to immerse the prong of the upper fork then an appropriate difference signal is noted at the transducer. Likewise, an appropriate difference signal is obtained if the foam falls below the level of the prong of the lower fork.

Although described with reference to a foam it is envisaged that the invention can also be used to detect changes in level of liquids.

CLAIMS (Filed on 10/6/81)

1. A detector for determining the level of a medium in a vessel comprising a tuning fork having a first prong within the vessel and disposed in a substantially horizontal plane and a second prong outside the vessel, means for exciting the second prong to effect sympathetic excitment of the first prong and means for detecting a decrement in the oscillations of the first prong upon a sudden stop of the oscillations of the second prong, the rate of decrement being dependent upon whether the first prong is immersed in the medium or above the surface of the medium and hence dependent on the level of the medium in the vessel.

2. A detector as claimed in claim 1 including upper and lower tuning forks each having a first prong within the vessel to determine respectively upper and lower levels of the medium within the vessel.