GB2223312A - Pressure and temperature measurement in tanks - Google Patents

Abstract

Tank contents are monitored using a bubble tube (13) which extends into the tank and the temperature and/or the presence of water are sensed using connections through the same hole in the tank. The apparatus comprises an electrical junction box (21) having a chamber (22) in a conduit between the pressure connections (15) and the tube (13). The apparatus includes a sealed electrical socket (28) mounted to the junction box with one set of terminals (29) in the chamber, to which the temperature monitoring wires can be connected; the other set, outside the casing may be optionally connected to a transmitter. A sealable opening (31) to the chamber gives access to the terminals (29) and a closure member (34) is provided for making a sealed closure to the chamber. <IMAGE>

Description

TANK CONTENTS MONITORING APPARATUS The present invention relates to a tank contents monitoring apparatus incorporating means for sensing pressure and temperature of the contents using a single hole in the tank.

In the monitoring of data in a tank, electrical wiring is used in the detection of water in the tank contents and for the monitoring of temperature. Pressure is monitored using a unit comprising one or more bubble tubes connected to respective probe heads as described for example in our patent specification No E48589. The monitoring of temperature then takes place through a different hole in the tank.

The object of the present invention is to provide a unit which will enable the electrical wiring to pass through the same hole in the tank as the pressure monitoring unit. Outside the tank the wiring has to be connected up to monitoring equipment and the wiring must leave the unit without allowing pressurised gas to escape from the unit.

According to the present invention there is provided tank contents monitoring apparatus comprising a bubble tube for passing into the tank, a probe head comprising a port for connecting to a supply of gas under pressure and a port for connecting to pressure monitoring apparatus, and a conduit connecting the probe head to the bubble tube sealed against an leak of pressurised gas, wherein the conduit passes through an electrical junction box which is disposed between the probe head and the bubble tube and includes a casing defining therein a chamber having an sealable opening, the apparatus further including a sealed electrical socket mounted to the casing with one set of terminals in the chamber and the other set outside the casing, the opening to the chamber giving access to the said one set of terminals and a closure member being provided for making a sealed closure to the casing.

Advantageously the apparatus carries a transmitter which can be electrically incorporated into the circuitry to amplify and transmit a signal if required.

The transmitter can be attached either to the electrical connector or to the closure member.

Where the transmitter is used a covering cap is preferably provided to protect the transmitter.

The invention will now be described, by wa of example, with reference to the accompanying drawings in which: Figure 1 is a side view of a tank monitoring apparatus in accordance with the present invention, Figure 2 is a side view of the apparatus of Figure 1 in the direction A- > Figure 3 is a view of the junction box casing of the apparatus of Figure 1, Figure 4 is a cross section of the casing of Figure 3, and Figure 5 shows the electrical connections to and from the transmitter of the apparatus of Figure 1.

The tank monitoring unit 11 illustrated in the drawings is designed to be fitted outside a tank to the top of a bubble tube 24 which extends into the tank (not shown) and via which pressure measurement is taken in the normal way, for example in accordance with details in patent specification No EPO No 48589 . In this embodiment two concentric tubes 24 and 13 are used for pressure measurement. A first probe head 14 has a pressurised gas inlet 15 and a pressure reading sensor port 16 for the inner tube 24 and a this is duplicated in a second probe head 17 for the outer tube 13.The first probe head 14 and the tube 24 are connected by a sealed conduit.To enable temperature readings or the presence of water also to be monitored electrical wires (not shown) are run down the inside of the tube 2t, two for the monitoring of water presence and three for temperature sensing. The present invention is concerned with getting the signals to the outside of the unit without allowing the escape of pressurised gas.

To this end an electrical junction box 21 comprising a casing containing a chamber 22 is fitted between the probe head 14 and the inner tube 24 with the chamber in the path of the gas flow therebetween. There are two conduits to the chamber 22, a first 27 passes upwardly and is coupled and sealed to the probe head li allowing pressurised gas to enter the chamber and the second conduit 25 leaves the chamber downward through a second coupling 26 to the inner tube 24 (or alternativelv a tube extension ). The second coupling is a screw threaded and sealed connection and allows gas to pass between the tube 24 and the chamber 22. At this same position the extension arm 23 for the second probe head 17 is also coupled with a welded joint to the outer tube 13.The coupling 26 is made within the extension arm and the gas in the tube 24 and conduit 25 are sealed from the gas between the tubes 24 and 13 which reaches the probe head 17 via the extension arm 23.

The casing, the front of which is open, has on its back wall an aperture into which is fitted the socket 28 of a sealed electrical connector. One set of socket terminals 22a on the ends of wires 22b is located inside the chamber and is connected to wiring entering the chamber through the second coupling. The wiring entering the chamber is crimped to the terminals 22a. The output terminals (not shown) of the socket are outside the casing and a plug 30 pushed into the socket from the outside makes contact with these terminals.

For detection of water in the contents of the tank two wires will pass through the tube 24 to a conductive element in the tank. Conduction will only take place when water is present, the element otherwise being nonconductive. The upper ends of the wires pass into the chamber through the conduit 25 and are connected to the terminals using the opening in the front of the casing.

The casing is then sealed by fixing a cover plate 34 across the opening by bolting it to threaded holes 35 in each of two peninsular pieces 36 on the casing. Sealant foam is applied to the surfaces of the casing before the cover plate 34 is fixed to ensure a fully sealed closure. Alternatively a rubber sealing gasket 31 and adhesive such as "locktite" RTnI can be used. For water detection electrical signals are fed directly from the plug 30 to the monitors (not shown) in the pneumatic cabinet.

For temperature detection a three wire platinum resistance element (not shown) is used. The wires from the resistance element are connected to the terminals 29 and the closure sealed as described above. The signal from the resistance element is weak and so it is preferable to use a transmitter 37 to amplify and forward the signal to the monitor (not shown). In Figure 1 the transmitter 37, which converts the signal to a 420 m/amp current loop, is connected to the back of the plug 30 of the sealed connector 28 via a housing adaptor 32. The transmitter is contained in a housing 38 in the form of a plastics material moulded bod having a screw on cap 39 . The transmitter input terminals 41 comprise three separate terminals connected by respective wires 42 to respective terminal pins 43 of the plug 30 by soldering. The other two terminals on the transmitter comprise a power input terminal 44 for receiving a 24V power supply from the pneumatic cabinet and a single output terminal 45 for delivering the 4-20mA signal to the monitor in the pneumatic cabinet.

It is envisaged that it might be possible to situate the transmitter in the junction box with both sets of transmitter terminals connected in the casing.

Under these circumstances the wiring from the resistance element would be connected to the transmitter terminals and further wiring would connect the transmitter output terminals to the terminals of the socket 28 inside the chamber. This arrangement would reduce the visible wiring outside the box.

In either case it will be noted that the apparatus is constructed in one hand held piece as a unit so that when it is to be fitted only the connection to the tank, the connections to the probe heads of the gas supply and monitoring leads need to be made. The electrical connections between the wiring in the tube 24 and the terminals in the casing and to the transistor terminals 44 and 45 will also hae to be made. The fact that it is in one piece considerabl eases the setting up of the tank monitoring system.

Claims (6)

1. Tank contents monitoring apparatus comprising a bubble tube for passing into the tank, a probe head comprising a port for connecting to a supply of gas under pressure and a port for connecting to pressure monitoring apparatus, and a conduit connecting the probe head to the bubble tube sealed against any leak of pressurised gas, wherein the conduit passes through an electrical junction box which is disposed between the probe head and the bubble tube and includes a casing defining therein a chamber having an sealable opening, the apparatus further including a sealed electrical socket mounted to the casing with one set of terminals in the chamber and the other set outside the casing, the opening to the chamber giving access to the said one set of terminals and a closure member being provided for making a sealed closure to the chamber.

2. Apparatus according to claim 1 wherein a transmitter is electrically connected to the socket terminals and is physically connected to the junction box.

3. Apparatus according to claim 2 wherein the transmitter is fitted to the closure member.

4. Apparatus according to claim 2 wherein the transmitter is disposed in a housing fitted to a plug which engages the electrical socket.

5. Apparatus according to any of the preceding claims wherein the component parts are formed as a single hand-held unit.

6. A tank monitoring apparatus substantially as herein described with reference to the accompanying drawings.