GB2315335A - Monitoring weight loss from articles - Google Patents

Abstract

The weight loss from an article, e.g. the loss of carbon dioxide from a fire extinguisher cylinder (12), is detected by a pneumatic or hydraulic weighing rig which comprises a support ring (10) which can be lowered down over the cylinder and has equispaced feet (14). Each foot (14) houses a piston (26) within a chamber connected through passages in the ring to a pressure sensor. The cylinder (12) is supported solely by the feet (14). If a loss of cylinder contents occurs, then the pressure drops and triggers an alarm. The apparatus can detect a weight loss of the order of 3 to 4%.

Description

METHODS OF AND APPARATUS FOR MONITORING WEIGHT LOSS This invention relates to methods of and apparatus for monitoring weight loss, especially of the contents of cylinders in fixed fire extinguishing systems. The invention is particularly concerned with monitoring the loss of gas contents, especially carbon dioxide.

Fixed carbon dioxide fire extinguishing systems are used in applications where one requires fire protection measures for the extinguishment of fire.

Fixed systems are installed in order totally to flood a protected area with carbon dioxide. The carbon dioxide extinguishes the fire by reducing the proportion of oxygen to a level below which combustion cannot take place.

Regulations and standards exist on the installation of carbon dioxide systems, in order to ensure that a design is appropriate for a given application, such that the fire can be extinguished and that necessary precautions are taken to avoid danger to human life. Additionally, there is now a requirement to monitor any loss of stored carbon dioxide, so that in the event of a discharge the amount of gas available is sufficient to extinguish the fire.

Carbon dioxide is stored as a liquefied gas under pressure in cylinders. In a typical cylinder, the weight of carbon dioxide is 45kg. The monitoring apparatus must detect a loss of 10%, i.e. 4.5kg in this case. The total weight of the cylinder is typically 120kg, so the percentage loss of the total weight which the apparatus must be able to detect is 3.75%.

Various methods have been used to detect such losses. One method utilises a balance which has to be placed under the cylinder. It is a disadvantage of this method that two people are required in order to install the device. Another method utilises a frame, which supports the cylinder, and a head attachment which consists of a counterweight. A weight loss in the cylinder upsets the balance of the counterweight, which falls and activates a trip switch. A disadvantage of this method is that a frame is required, in addition to the counterweight, thereby increasing the cost and complexity of the system.

It is an object of the present invention to provide methods of and apparatus for monitoring weight loss which overcome the disadvantages of these known methods.

It is a further object of the invention to provide a system which can be operated easily by one man and which minimises the number of system components, hence reducing the cost of the installed system.

In order that the invention may be more fully understood, one presently preferred embodiment of weight monitoring apparatus in accordance with the invention will now be described by way of example and with reference to the accompanying drawings. In the drawings: Fig. 1 is a view of a support ring which forms part of the apparatus in accordance with the invention; Fig. 2 is a sectional view through the support ring, positioned adjacent to a cylinder, and showing one of the supporting feet of the apparatus turned inwards towards the cylinder; Fig. 3 is a part-sectional view similar to Fig. 2, but showing additional detail; Fig. 4 is a partial view, showing the supporting foot turned outwards; Fig. 5 is a view similar to Fig. 2, showing the supporting foot in a lowered position; Fig. 6 is a partial view, on an enlarged scale, through one of the supporting feet and through the support ring; Fig. 7 shows the housing of one of the supporting feet, without the piston; Fig. 8 is a plan view of the housing shown in Fig.

7; and, Fig. 9 is a part-sectional view to illustrate the hydraulic connections between the supporting feet.

The weight monitoring apparatus is shown here as being based upon the use of a support ring 10 which is dimensioned and shaped to fit around a cylinder 12 which holds the fire extinguishant, for example carbon dioxide. The support ring 10 has an internal diameter which is substantially the same as the outside diameter of the cylinder 12 which is being monitored. It can therefore be slid up and down the cylinder, for installation or removal. At the base of the support ring 10 are a plurality of supporting feet 14, one of which is shown most clearly in Figs. 7 and 8. In the illustrated embodiment, three such supporting feet 14 are provided, spaced 1200 apart around the circumference of the ring 10. Each supporting foot 14 comprises a base portion 16 and an upstanding leg 18 which incorporates a circumferential groove 20 for an O-ring seal 22. The base portion 16 has a downwardly open recess 24 which houses a piston indicated generally at 26. The recess 24 comprises a cylindrical portion with, above it, a tapering portion which can communicate by way of a passage 28 with a port 30 in the top surface of the leg 18. The piston 26 comprises two components 31 and 32 secured together by a screw 34 and carrying a circumferential seal 36. The piston is arranged to be displaceable within the cylindrical portion of the recess 24, as can be seen from the drawings. The chamber 38 above the piston 26 is filled, in use, with hydraulic fluid which can enter the chamber via the passage 28.

The leg 18 of each supporting foot is rotatable within a generally cylindrical bore in the support ring 10, which means that the supporting foot 14 can be rotated between an inoperative position, as shown in Fig. 4, where the foot 14 is turned outwards, and an operative position in which the foot 14 is turned inwards so that a portion of the foot is located below the cylinder 12 to provide support for it. Each supporting foot 14 can be locked in place, in the inturned operative position, by a grub screw 40 which is set into the external surface of the support ring 10 and which locates in an indentation 42 provided in the leg 18. Fig. 1 shows the ring 10 with one foot 14 turned inwards and one foot 14 turned outwards.

The bores in the support ring 10 which carry the legs 18 of the supporting feet extend upwards to the top of the support ring, where a jacking screw 44 is fitted. Each jacking screw incorporates a central bleed screw. The bottom of the jacking screw 44 is grooved to hold a further O-ring seal 46. The chamber 48 which is formed between the bottom of the jacking screw 44 and the top of the leg 18 is filled with hydraulic fluid which is in communication via the passage 28 with the chamber 38 above the piston 26.

Fig. 9 shows how the hydraulic connection between the individual supporting feet 14 is made. Pipes 50 which are in communication with the bores within which the legs 18 are carried connect the bores one with another, so that hydraulic pressure applied to one of the supporting legs is transferred to the other legs as well. This means that the supporting force exerted on the cylinder 12 is uniform around the circumference.

Above one of the jacking screws 44 there is located a pressure switch or pressure transducer 52 which acts as a sensor which monitors changes in the hydraulic pressure which arise in the event that the cylinder 12 loses weight.

In use, the support ring 10 is passed down over the top of the cylinder 12 which is to be monitored.

During this procedure the supporting feet 14 are rotated into their outwardly directed positions. Once the feet touch the supporting surface, for example a level floor, they are rotated through 1800 to fit under the lip of the base of the cylinder 12 and are locked into position by the grub screws 40. A hydraulic jack or an equivalent is attached to a nipple on one of the three supports and pressure is applied until the cylinder 12 is totally supported by the three legs. In this position the pistons 26 protrude from the base of the supporting feet 14. For a cylinder 12 having a weight of 120kg and with a diameter for the piston 26 of 8mm, this support is achieved at a hydraulic fluid pressure of 8 bar. The hydraulic jack is then removed and the system is ready for use.

If the weight of the cylinder 12 should decrease, due to loss of contents, then this will be reflected as a change in the pressure of the hydraulic fluid. If the weight of the cylinder should decrease by 4.5kg, i.e. 3.75%, a pressure drop of 0.3 bar would be detected by the switch or transducer 52. If a pressure switch is used then this will respond when a predetermined pressure drop occurs. If a pressure transducer is used then this can continuously monitor changes in weight. The output of the pressure switch or transducer 52 is connected to a control panel (not shown) which indicates a fault condition if the weight loss reaches 4.5kg or more. The fault condition can be indicated by an audible and/or visible warning.

It is to be noted that the cylinder weight and piston leg diameter referred to above are given by way of example only and that the apparatus is equally appropriate for use with different types of cylinder of different weights to those given above.

Although in the embodiment described above the support ring 10 is a one-piece component which is arranged to be slid up and down the outside of the cylinder 12, one could alternatively use a multi-part ring where the individual pieces are arranged to be brought together into a locking relationship around the outside of the cylinder. For example, one could use three arcuate sections each subtending an angle of 1200 at the centre. Alternatively, one could have a hinged ring, made in two parts with a hinge at one side opposite a closing/locking mechanism at the other side.

Yet again, one could achieve the same result with a supporting structure made up from a plurality of linked, equispaced parts, linked together to circumscribe the cylinder. They need not actually form a "ring" although they would ring the cylinder. In each case the intention is to achieve uniformity of the supporting force around the whole periphery of the cylinder. The truly annular ring, such as is shown, with equispaced hydraulic supports is preferred, but is not essential. Additionally, although hydraulic pressure is preferably used for the supporting of the cylinder, one could alternatively use pneumatic pressure to accomplish the same purpose.

Claims (12)

CLAIMS:

1. A method of monitoring an article for weight loss, which comprises peripherally supporting the article hydraulically or pneumatically with a uniform supporting force around its whole periphery, monitoring the pressure which generates said supporting force, arranging for a loss of weight of the article to cause a decrease in said pressure, and arranging for a decrease in the pressure to a predetermined value to cause a fault indication to be triggered.

2. A method as claimed in claim 1, which includes hydraulically or pneumatically raising the article until it is supported entirely by peripheral support means.

3. A method as claimed in claim 1 or 2, which includes lowering a ring-shaped circumferential support over the article, moving the support into an article-engaging position, and raising the article via the support.

4. Apparatus for monitoring an article for weight loss, which comprises hydraulically or pneumatically actuated support means arranged to provide a uniform supporting force around the whole periphery of the article, and sensing means to monitor the hydraulic or pneumatic pressure which generates said supporting force and to trigger a fault indication in response to a decrease in said pressure to a predetermined value.

5. Apparatus as claimed in claim 4, in which the support means comprises a plurality of telescopically acting struts arranged to be equispaced around the article.

6. Apparatus as claimed in claim 4 or 5, in which the support means is arranged to be lowered over the article and includes feet which are displaceable between an out-turned position for the fitting of the support means and an inturned position in engagement with the article for the lifting thereof via said feet.

7. Apparatus as claimed in claim 4, 5 or 6, in which the support means comprises an annular ring with equispaced feet.

8. Apparatus as claimed in claim 6 or 7, in which each foot includes a chamber housing a piston, the chambers being connected for joint pressurisation.

9. Apparatus as claimed in claim 4 or 5, in which the support means comprises a multi-part ring arranged to be closed around the article.

10. Apparatus as claimed in any of claims 4 to 9, adapted for monitoring the weight of a fire extinguisher cylinder.

11. Apparatus as claimed in any of claims 4 to 10, in which the sensing means comprises a pressure switch or pressure transducer.

12. Apparatus for monitoring an article for weight loss substantially as hereinbefore described with reference to the accompanying drawings.

12. A method for monitoring an article for weight loss substantially as hereinbefore described with reference to the accompanying drawings.

13. Apparatus for monitoring an article for weight loss substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows

1. A method of monitoring an article for weight loss, which comprises arranging a support comprising a plurality of telescopically acting struts around the periphery of an article, moving the support into an article-engaging position, hydraulically or pneumatically raising the article via the support until the article is supported around its whole periphery, monitoring the pressure which generates said supporting force, arranging for a loss of weight of the article to cause a decrease in said pressure, and arranging for a decrease in the pressure to a predetermined value to cause a fault indication to be triggered.

2. A method as claimed in claim 1 wherein the support is ring-shaped.

3. A method as claimed in claim 1 or claim 2 wherein the support is lowered over the article.

4. Apparatus for monitoring an article for weight loss, which comprises hydraulically or pneumatically actuated support means arranged to provide a uniform supporting force around the whole periphery of the article, and sensing means to monitor the hydraulic or pneumatic pressure which generates said supporting force and to trigger a fault indication in response to a decrease in said pressure to a predetermined value; wherein the support means comprises a plurality of telescopically acting struts arranged to be equispaced around the article.

5. Apparatus as claimed in claim 4, in which the support means is arranged to be lowered over the article and includes feet which are displaceable between an out-turned position for the fitting of the support means and an inturned position in engagement with the article for the lifting thereof via said feet.

6. Apparatus as claimed in claim 4 or 5, in which the support means comprises an annular ring with equispaced feet.

7. Apparatus as claimed in claim 5 or 6, in which each foot includes a chamber housing a piston, the chambers being connected for joint pressurisation.

8. Apparatus as claimed in claim 4, in which the support means comprises a multi-part ring arranged to be closed around the article.

9. Apparatus as claimed in any of claims 4 to 8, adapted for monitoring the weight of a fire extinguisher cylinder.

10. Apparatus as claimed in any of claims 4 to 9, in which the sensing means comprises a pressure switch or pressure transducer.

11. A method for monitoring an article for weight loss substantially as hereinbefore described with reference to the accompanying drawings.