GB2102351A - Pressure indicating device - Google Patents

Abstract

A pressure indicating device (10) for a fluid transporting vehicle, e.g. a slurry tanker, comprises a cylinder (11) in which piston (14) is slidable in response to the pressure in a pressure vessel (13) of the vehicle. An indicator rod (19), having markings (24) thereon, is attached to the piston (14) and extends out of an end wall (20) of the cylinder (11). A spring (21) biasses the piston (14) towards the pressure vessel (13) throughout all or the vessel remote half of the piston's travel; in the latter case a second spring (21) biasses the piston (14) away from the vessel (13) throughout the other half of the piston's travel. In alternative arrangements one of the springs may be replaced by a body of gas trapped in the cylinder (11), and the cylinder may be transparent so that the position of the piston (14) can be seen directly. <IMAGE>

Description

SPECIFICATION Pressure indicating device This invention relates to pressure indicating devices and has particular application to such devices as applied to bul fluid transporting vehicles such as slurry tankers or the like.

Vehicles of the aforementioned type are subjected to underpressure of vacuum in order to draw into the tank the fluid to be transported, and are subjected to overpressure, simply referred to as pressure, in order to deliver such fluid from the tank. It is known to provide a tanker vehicle with pressure gauges of conventional form for the purpose of indicating the vacuum or the pressure within the tank during the take-up or delivery operations respectively. However such pressure gauges are expensive and add considerably to the cost of the vehicle. Furthermore such gauges are delicate instruments which in this particular context are extremely prone to breakage and/or being clogged with the fluid transported in the tanker vehicle. As a consequence frequent replacement or maintenance is required which adds to the operational costs of the vehicle.

It is an object of the present invention to provide a pressure indicating device which is simple in operation, robust, inexpensive to produce and requires little maintenance, and therefore more suited to use in the context of fluid transporting tankers such as slurry tankers and the like.

The invention provides a pressure indicating device comprising a cylinder adapted to be connected to a fluid transporting vehicle and when so connected having one end thereof in fluid flow connection with a pressure vessel of said vehicle, a piston slidably disposed in said cylinder and movable in response to changes in the pressure within said one end, and means indicating said pressure by reference to the position of said piston in said cylinder. Said indicating means may comprise an indicator rod secured to said piston and extending through a wall of said cylinder, and preferably through an end wall remote from said one end.

A seal may be provided in said end wall to sealably engage said indicator rod passing therethrough. Alternatively or additionally said piston may be resiliently biassed in a direction towards said one end at least when said piston is disposed between a mid position and a position further removed from said one end. In the latter case the piston may be resiliently biassed away from said one end when disposed between said one end and said mid position.

The indicator rod may have markings thereon whereby an indication of the pressure within said pressure vessel may be given. A fixed indicating means may be provided on said cylinder adjacent which said indicator rod moves. Alternatively the cylinder may comprise a transparent wall having markings thereon.

The invention also provides a tanker vehicle for the transportation of fluids comprising a pressure vessel, compressor means adapted to apply an overpressure or an underpressure to said pressure vessel and a pressure indicating device comprising a cylinder having one end thereof in fluid flow connection with said pressure vessel, a piston slidably disposed in said cylinder and movable in response to changes in the pressure within said pressure vessel, and means indicating said pressure by reference to the position of said piston in said cylinder.

Embodiments of the invention will now be described with reference to the accompanying drawing in which: Fig. 1 is a sectional elevation of a first embodiment, Fig. 2 is a sectional elevation of a second embodiment and Fig. 3 is a sectional elevation of a third embodiment.

Referring now to Fig. 1 there is shown a pressure indicating device 10 comprising a cylinder 11 having one end 12 screwed into a pressure vessel 13, for example the tank of a slurry tanker or the like. A piston 14 is disposed within cylinder 11 and seals 1 5 on the piston provide that passage of fluid between upper and lower compartments 16,17 respectively cannot occur. Lower compartment 1 7 is in fluid flow connection with the interior of pressure vessel 13 by virtue of passageway 1 8 in the cylinder end 12.

An indicator rod 1 9 is secured to piston 14 and extends through upper compartment 16 and end wall 20 of cylinder 11. In each compartment is a spring 21 which extends between the piston 14 and the respective end 1 2, 20 of cylinder 11, the two springs 21 being in equilibrium with the piston 14 in a mid position in the cylinder 11 when the pressure in pressure vessel 13 and upper and lower compartments 16,17 is atmospheric. An indicator 22 is mounted on cylinder 11 so as to be adjacent the indicator rod 1 9 and is positionally adjustable on mounting post 23 by means of screws 25 for the purpose of initial setting.

In order to take in or discharge a charge of slurry or other fluid into pressure vessel 1 3 the vehicle of which vessel 1 3 forms part is provided with a compressor of pumping device (not shown).

Such compressor applies an underpressure or vacuum to pressure vessel 1 3 whereby the fluid charge is taken in, and the vacuum thus created is transmitted to lower compartment 17. Since the pressure in upper compartment 1 6 is maintained at atmospheric the pressure differential across piston 14 causes the piston 14 to move towards end 12 against the compressive spring force generated in the spring 21 in lower compartment 1 7. In consequence the indicator rod 19 moves adjacent indicator 22 by an amount proportional to the vacuum in compartment 17, whereby the value of that underpressure or vacuum is readily determined from the scale 24 marked on indicator rod 19.When the charge of slurry of other fluid is to be discharged from the pressure vessel 1 3 the compressor applies an overpressure thereto and that pressure is transmitted to lower compartment 17. The piston 14 is thereby raised against a compressive force in spring 21 in upper compartment 16. Again the value of the pressure created in pressure vessel 13 can be determined by the position of indicator 22 relative to the scale 24 on indicator rod 19.

In the embodiment shown in Fig. 2 many of the parts are identical with those of the embodiment of Fig. 1, and are designated by the same numerals. In this embodiment however upper compartment 1 6 is sealed from the atmosphere by seal 26 around indicator rod 1 9. The pressure in upper compartment 1 6 is atmospheric when the piston 14 is in a mid position in cylinder 11. If the pressure in pressure vessel 13, and hence in lower compartment 1 7, rises or falls during discharge or charging of pressure vessel 13 as described above, the piston 14 will move upwardly or downwardly respectively to a new position of equilibrium under the influence of the pressures in compartments 16 and 17.The value of the pressure or vacuum in vessel 13 may be determined with reference to scale 24 on indicator rod 19 as indicated by the marking of the scale 24 visible adjacent the seal 26.

In the embodiment of Fig. 3 upper compartment 1 6 is again subject to atmospheric pressure as in the embodiment of Fig. 1. However in this embodiment a single spring 21 is provided in compartment 1 6 of a length such as to force piston 1 4 to the bottom of its travel when the lowest pressure to be created in vessel 13 in use in applied thereto. Any pressure in vessel 13 above this lowest value, or highest vacuum, will cause piston 14 to rise. The spring rate of spring 21 is chosen so that when the pressure in vessel 13 is atmospheric the piston 14 is in mid position in cylinder 11.

By means of the invention a simple, inexpensive, reliable and robust pressure indidating device for use with a fluid transport vehicle such as a slurry tanker is provided. The scale 24 may be accurately graduated or may simply show operating pressure, operating vacuum and neutral, i.e. atmospheric pressure. Aiternative embodiments of the invention will be readily apparent to persons skilled in the art. For example the cylinder 11 may be secured to a feed line to the vessel 13 instead of to the vessel 13 directly, whilst maintaining the fluid flow connection therebetween, or may be mounted at some other location on the vehicle.

As a further alternative in each of the embodiments described herein and shown in the accompanying drawings, the cylinder 11 may be formed of a transparent material, in order that the position of the piston 14 within the cylinder 11 may be determined directly. In such a case the rod 19 may be dispensed with, unless required for stability purposes, and a scale 24 be marked on the outside of cylinder 11.

Claims (12)

1. A pressure indicating device comprising a cylinder adapted to be connected to a fluid transporting vehicle, and when so connected having one end thereof in fluid flow connection with a pressure vessel of said vehicle, a piston slidably disposed in said cylinder and movable therein in response to changes of the pressure within said one end, and means indicating said pressure by reference to the position of said piston in said cylinder.

2. A device according to claim 1 wherein said indicating means comprises an indicator rod secured to said piston and extending through a wall of said cylinder.

3. A device according to claim 2 wherein said wall is an end wall of said cylinder remote from said end.

4. A device according to claim 3 comprising sealing means disposed in said end wall and adapted to sealingly engage said indicator rod passing therethrough.

5. A device according to any one of claims 2 to 4 wherein said piston is resiliently biassed towards said one end at least through a portion of its path of travel remote from said one end.

6. A device according to claim 5 wherein said piston is resiliently biassed away from said one end through a portion of its path of travel adjacent said one end.

7. A device according to any one of claims 2 to 6 wherein said indicator rod has markings thereon whereby an indication of said pressure may be given.

8. A device according to any one of claims 2 to 6 comprising a fixed indicating means having markings thereon and adjacent which said indicator rod is caused to move.

9. A device according to claim 1 wherein said cylinder comprises a transparent wall having markings thereon adjacent which said piston is caused to move.

10. A tanker vehicle for the transportation of fluids under pressure comprising a pressure vessel, compressor means adapted to apply an overpressure or an underpressure to said pressure vessel and a pressure indicating device according to any of claims 1 to 9.

11. A tanker vehicle according to claim 10 wherein said cylinder is screwed into said pressure vessel.

12. A tanker vehicle according to claim 10 or claim 11 when dependent on any one of claims 4 to 6 wherein when said pressure is atmospheric said piston is in equilibrium under the forces thereon when in a mid-position in said cylinder.

1 3. A pressure indicating device substantially as hereinbefore described with reference to and as illustrated in any figure of the accompanying drawing.