GB2169730A - Structural movement alarms - Google Patents

Abstract

A displacement detecting system for use in the detection of component movement and/or component support failure comprises at least one signal conductor, e.g. a thermocouple lead, routed through a shearing device (20), the conductors being located and clamped in grooves (36-42) of the device body (22) and grooves (44-50) of a plunger (28) slidable in the body (22). Movement of a component, such as a boiler, is arranged to displace the plunger (28) and sever the conductors thereby signalling a fault condition. <IMAGE>

Description

SPECIFICATION Detection of component movement or failure This invention relates to the detection of component movement and/or component support failure and is particularly applicable to such detection in severe environments of temperature, pressure and working fluid, eg. a nuclear reactor and associated plant such as boiler plant.

Although a wide variety of detectors are available for sensing displacement, commercially-available detectors are either unsuitable for harsh environments, expensive or are unsuitable when a long operating life is required with little or no maintenance or repair.

The object of the present invention is to provide a displacement detecting system which is relatively inexpensive and will operate reliably and positively even in severe environments involving high temperatures.

According to the present invention a displacement detecting system comprises at least one signal conductor which is routed through a cutting device, the cutter of which is operatively associated with a component whose displacement is to be detected, the arrangement being such that the cutter operates to sever the signal conductor(s) in response to displacement of the component.

The system may include means for sensing the interruption of signal transmission via the conductor(s) and, in this event, a visual or audible warning signal may be generated.

The signal conductor(s) may be in the form of an electrical cable(s) for electrical signal transmission, optical fibre cable(s) for light signal transmission or other means of transmitting failure detection, eg pressurised tubes.

In one embodiment of the invention, the cutting device comprises a first part having, for the or each conductor, a passage along which the conductor is routed, and a second part, the first and second parts being relatively movable in a direction transverse to the passage(s) such that the relative movement is effected by displacement of the component and causes the second part to move across the passage(s) and sever the conductor(s).

Preferably the second part also has, for the or each conductor, a passage which is normally in registry with the respective passage in the first part but, in response to relative movement between the two parts, is displaced out of registry to such an extent that the conductor is completely severed.

The passages in both parts are preferably in the form of channels to facilitate location of the conductors therein and, conveniently, means are provided for locating and clamping the conductors in the fixed part of the cutting device.

In use, the cutting device may be mounted on a structure relative to which the component may be displaced and the movable part of the cutting device is either coupled to the component or is located in its path of movement in the event of displacement of the component.

One embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a front elevation illustrating part of a restraint system for limiting tilting of a boiler in the event of failure of a supporting beam for the boiler; Figure 2 is an enlarged fragmentary view showing the cutting device of the invention in greater detail; and Figure 3 is a diagrammatic view, in exploded perspective, of the cutting device.

Referring to Figs. 1 and 2, the restraint system is intended to limit tilting of for example a boiler in the event of failure of one of a pair of support beams on which the boiler is mounted. If such a failure occurs, the boiler will tend to tilt to one side or the other depending upon which support beam fails. The restraint system comprises a fixed body 10 extending into a gap between one wall of the boiler casing and an insulated liner wall, the body 10 being fixed to the liner wall. The boiler wall has secured thereto a framework including top and bottom frame members 12 and generally vertically extending bearing plates 14 which carry packing pieces 16. Only one half of the framework is shown in the drawings; it will be understood that a second bearing plate with packing piece is located on the opposite side of the body 10.

If one of the support beams for the boiler fails, the tilting motion of the boiler causes the framework to move either to the right or to the left as seen in Fig. 1. Such movement is limited however by contact of one of the packing pieces 16 with an abutment pad assembly 18 of which there are two, one on each side of the body 10, the left hand assembly 18 being only partly illustrated. Thus displacement of the boiler is limited to the distance A (see Figure) between each pad assembly 18 and the adjacent packing piece 16.

To alert the operator's attention to the occurence of such a failure, and hence tilting displacement of the boiler to one side, the device 20 is employed, there being such a device associated with each pad assembly 18.

As shown in Fig. 3, the device 20 comprises a body 22 which is welded to the respective pad assembly and inlcudes a clamping plate 24 which, when bolted to the body, defines together with the body a bore 26 in which a generaliy cylindrical plunger 28 is slidable.

Normally however the plunger 28 is restrained against sliding and vibration movement by a shear pin (not shown) insertable into aligned holes 30, 32 in the body 22 and the plunger 28. The arrangement is such that the shear pin fixes the plunger 28 in a position at which it projects slightly beyond the outer face 34 of the pad assembly 18. Consequently, if the packing piece 16 moves towards the restraint body 10, it will initially contact the projecting end of the plunger 28. The loading involved in the event of tilting of the boiler will, of course, be considerable and the shear pin will simply break thus allowing the plunger 28 to be displaced relative to the body 22 as the packing piece continues to move into abutment with the pad assembly 18.

Such sliding movement of the plunger 28 relative to the body 22 is arranged to sever one or more signal conductors (not shown) which are routed through the device. In the illustrated embodiment, four such conductors are intended to be routed through the device via four pairs of channels 36, 38, 40 and 42.

Each conductor is clamped in position in the respective pair of channels by the clamping plate 24. In addition, the plunger 28 is formed with a number of channels 44, 46, 48 and 50 which, when the shear pin is in place, register with respective pairs of the channels 36, 38, 40 and 42 and receive respective conductors When the plunger 28 is displaced by movement of the boiler, the channels therein are moved out of registry with those in the body 22 and a shearing action is obtained which, by appropriate selection of the degree of projection of the plunger beyond the outer face 34, ensures that the conductors are completely severed.

The cables may be, for example, thermocouple cables for routing signal from the thermocouples associated with the boiler to monitoring instrumentation. If these cables are severed, the loss of signal will provide a clear indication that boiler movement has occured as a result of support beam failure. However, other types of signal conductors can be employed, optical as well as electrical.

Claims (8)

1. A displacement detecting system comprises at least one signal conductor which is routed through a cutting device, the cutter of which is operatively associated with a component whose displacement is to be detected, the arrangement being such that the cutter operates to sever the signal conductor(s) in response to displacement of the component.

2. A system as claimed in Claim 1 including means for sensing the interruption of signal transmission via the conductor(s).

3. A system as claimed in Claim 1 or 2 in which the cutting device comprises a first part having, for the or each conductor, a passage along which the conductor is routed, and a second part, the first and second parts being relatively movable in a direction transverse to the passage(s) such that the relative movement is effected by displacement of the component and causes the second part to move across the passage(s) and sever the conductor(s).

4. A system as claimed in Claim 3 in which the second part also has, for the or each conductor, a passage which is normally in registry with the respective passage in the first part but, in response to relative movement between the two parts, is displaced out of registry to such an extent that the conductor is completely severed.

5. A system as claimed in Claim 3 or 4 in which the passages in both parts are in the form of channels to facilitate location of the conductors therein.

6. A system as claimed in Claim 3, 4 or 5 in which means are provided for locating and clamping the conductors in the fixed part of the cutting device.

7. A system as claimed in any one of Claims 1-6 in which the cutting device is mounted on a structure relative to which the component may be displaced and the movable part of the cutting device is either coupled to the component or is located in its path of movement in the event of displacement of the component

8. A displacement detecting system substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.