AU647983B2

AU647983B2 - Liquefied gas flow control

Info

Publication number: AU647983B2
Application number: AU31998/93A
Authority: AU
Inventors: John Keith Clark
Original assignee: LPG Engineering Pty Ltd
Current assignee: GAS CYLINDER SERVICES Pty Ltd
Priority date: 1989-12-22
Filing date: 1993-01-22
Publication date: 1994-03-31
Anticipated expiration: 2010-12-21
Also published as: AU3199893A

Description

647983

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

Applicant(s): LPG ENGINEERING PTY LTD A.C.N. 006 843 750 Actual Inventor(s): John Keith Clark r Address for Service: PATENT ATTORNEY SERVICES 26 Ellingworth Parade Box Hill Victoria 3128 Australia Title: LIQUEFIED GAS FLOW CONTROL Associated Provisional Applications: No(s).: The following statement is a full description of this invention, including the best method of performing it known to me/us:- LIQUEFIED GAS FLOW CONTROL This invention relates to liquefied gas flow control apparatus, particularly although not exclusively for dispensing LPG or other liquefied gas in the filling of vehicle fuel tanks.

In the filling of vehicle LPG fuel tanks, there are various ways or techniques in which vehicle owners can knowingly or inadvertently obtain more LPG than has been metered by the metering means. There techniques result in substantial losses to the owners and operators of fuel supply stations.

In all vehicle LPG tanks there is provided a limiting valve or "AFL" valve which is designed to limit the extent to eeoe• which the tank is filled, generally to 80% capacity. The limiting valve is intended to function in such a way as to reduce the rate of flow of LPG into the tank to a maximum of 30 litres per minute) and to close entirely when the vehicle tank is 80% full. However, it is believed that such valves fail Sto fully close when the tank has reached 80% capacity, and in o oe fact allow a flow rate of, for example, 5 litres per minute.

This flow rate is below the flow rate at which the metering Smeans associated with the tank filling system can operate or, at least can accurately meter the flow. Therefore, by leaving the dispensing hose connected to the vehicle fuel tank and the dispensing pump running for a long period, substantially more LPG than is measured by the metering means can be loaded into the tank.

A further technique for extracting more LPG from the dispensing apparatus without paying fully for the total amount of LPG loaded into the storage tank involves relatively rapidly opening and closing the flow control valve so that a pulsing 0 e V effect is created. The pulsed flow can lead to significant inaccuracies in the actual flow metered.

Another source of inaccurate flow measurement is the inherent limitation of currently used LPG flow metering apparatus. Particularly as the metering apparatus is used over a period of time and wear of components occurs, the meter effectively allows un-metered LPG to flow through to the vehicle tank. Also at relatively flow rates, the metering apparatus is generally inaccurate and understates the actual LPG that has been dispensed. Although there are official standards applied to metering apparatus, these standards must be complied with down to a flow rate of 15 litres per minute. There are no standards which currently apply below that flow rate and with which manufacturers must comply, whereas it is at flow rates approaching and below 15 litres per minute that significant un-metered gas flow through the metering apparatus can occur.

It is an object of the present invention to provide a oo liquefied gas flow control apparatus which can reduce the incidence of un-metered LPG or other liquefied gas being dispensed in a motor vehicle fuel tank filling operation or other liquefied gas dispersing and metering operation.

According to the present invention there is prov a liquefied gas flow control apparatus for use ,M-fcontrol of liquefied gas dispensed through a dispe ing line during a liquefied gas dispensing operati the apparatus being usable with an associated flow resonsive means which, in turn, is operatively associat ed with the liquefied gas dispensing line through *h-fch liquefied gas flows during the dispensing tion, the flow responsive means in use generating a flow According to the present invention there is provided a liquefied gas flow control apparatus for use in control of liquefied gas dispensed through a dispensing line during a liquefied gas dispensing operation, the dispensing line having a gas flow metering means associated therewith for metering the liquefied gas flowing through the dispensing line, the apparatus being usable with an associated flow responsive means which, in turn, is operatively associated with the liquefied gas dispensing line through which liquefied gas flows during the dispensing operation, the flow responsive means in use generating a flow 9 o 9 9 signal which is related to the rate of flow of liquefied gas through the dispensing line, the apparatus including a signal analysing means for receiving and analysing the flow signal from the flow responsive means so as to categorise the flow rate according to its magnitude, a terminating means which is operative in response to the signal analysing means to create a terminating signal for terminating the gas dispensing operation if the flow rate is less than a predetermined minimum flow rate threshold as determined by the signal analysing means, said minimum flow rate threshold being set at a flow rate below which \liquefied gas flow metering means can be inaccurate as a result of the metering means being incapable of accurately S metering flow at low rates.

The terminating means preferably includes a timing means, the terminating means being operative to generate the terminating signal if the flow rate as determined by the signal analysing means is below the minimum flow rate threshold for a predetermined time as determined by the timing means. In this embodiment, the timing means is preferably only operative to commence measuring of the predetermined time when there has been within a particular dispensing operation a liquefied gas flow in excess of the minimum flow rate threshold and subsequently the flow rate falls below the minimum flow rate threshold, whereby the terminating signal will not be generated until a valid dispensing operation has commenced and liquefied gas has actually being flowing.

The terminating means is preferably further operative in response to the timing means and to the signal analysing means to generate the terminating signal if there has been no flow for a predetermined time. Preferably, the timing means is operative to commence measurement of the predetermined time only after there has been a metered flow occurring in the dispensing line so that the terminating signal is not generated if a liquefied gas dispensing operation is not commenced for a period exceeding the predetermined time period.

In a further preferred aspect, the terminating means is preferably operative in response to the signal analysing means to generate the terminating signal if there is a pulsed flow of L liquefied gas detected by the signal analysing means. In this embodiment, the terminating means may include a pulsing sensor for sensing a pulsing of the flow signal and which indicates user manipulation of the flow control apparatus, whereby deliberate pulsing in order to achieve unmetered or inaccurately metered liquefied gas flow can be detected and the dispensing operation terminated. The pulsing sensor may be operative to Sinitiate the terminating signal if there are a predetermined number of pulses of the flow rate within the predetermined time S: period.

0 In the preferred embodiment the flow responsive means constitutes a part of a metering means for measuring and displaying or recording the amount of liquefied gas flowing through the dispensing line.

The present invention also provides a liquefied gas dispensing system including a dispensing line having an associated metering means, the system including a liquefied gas flow control apparatus according to the first aspect of the present invention.

Possible and preferred features of the present invention will now be described with particular reference to the accompanying drawing. However it is to be understood that the features illustrated in and described with reference to the drawing are not to be construed as limiting on the scope of the invention. In the drawing: Fig. 1 is a block diagram of a liquefied gas metering apparatus embodying the presint invention.

The liquefied gas metering apparatus illustrahed includes a metering means 10 which includes a flow responsive means and .0 which is mounted to an LPG or other liquefied gas dispensing line 11 through which LPG or liquefied gas flows during a coco.: S dispensing operation. The metering means 10 generates a flow signal on line 12 which is related to the flow rate. The metering means 10 can be generally conventional in construction o. o .0t, and operation. For example, the flow signal may comprise a pulse train having a frequency proportional to the rate of flow Sof LPG or liquefied gas through the line 11.

A signal analysing means 15 receives and analyses the flow S. signal from the metering means 10 so as to generally categorise 2b' the flow rate according to its magnitude. Compensating means is connected to the signal analysing means 15 and applies a compensating factor so as to produce a compensated flow signal on line 21 dependant upon the categorisation of the flow rate by the signal analysing means 15. If the flow rate is less than a first or "low" flow rate threshold as determined by the signal analysing means 15, the compensating means 20 is operative to create a compensated flow signal indicative of a higher flow rate than the actual metered flow rate. A terminating means is operative in response to the signal analysing means 15 if the 1 flow rate is less than a predetermined minimum flow rate threshold as determined by the signal analysing means 15 to create a terminating signal on line 26 for terminating an LPG or liquefied gas dispensing operation.

The signal analysing means 15 may be operative to analyse the flow signal on line 12 so as to categorise the flow rate into a number of mutually exclusive but contiguous flow rate ranges. For example, the signal analysing means 15 may be operative to firstly determine if the flow rate is less than the :2:O low flow rate threshold. If the flow rate is above the low flow rate threshold, the compensated flow signal on line 21 may oo S correspond substantially to the flow signal on line 12 generated by the metering means 10. That is, if the flow rate is above the low flow rate threshold, the metering means 10 is considered C C o to be substantially accurate and no compensation of the flow *e C signal is produced by the compensating means On the other hand, if the flow rate is determined by the

CCCC

signal analysing means 15 to be less than the low flow rate S. threshold, the compensating means 20 is operative to produce a compensated flow signal on line 21 which is different from the flow signal generated by the metering means 10 by a factor determined to more accurately indicate the actual flow rate.

Preferably the signal analysing means 15 is operative to categorise the flow rate if it falls below the predetermined low flow rate threshold into more than one flow rate category, e.g.

into any one of a number of mutually exclusive but contiguous ranges of flow rates, and the compensating means 20 is preferably operative in response to the signal analysing means for applying differing respective compensating factors so as to produce compensated flow signals dependant on the particular category into which the flow rate is categorised by the signal analysing means For example, in one possible embodiment which is not to be understood as limiting in any way upon the invention but is merely exemplary of a possible signal analysing means 15 and responsive compensating means 20, the signal analysing means may be operative to categorise the flow rate firstly according to whether it is above or below a low flow rate threshold of, 4* ":X0 say, 25 litres per minute. If the flow rate is above that value of 25 litres per minute, the compensating means 20 does not S" apply a compensating factor. However, if the flow rate is below litres per minute, a compensating factor of 0.5% may be applied so as to produce a compensated flow signal on line 21 15 representative of a flow rate of 0.5% above the flow rate indicated by the metering means 10, the addition of 0.5% to the measured flow rate compensating for inaccurate metering of the actual flow at flow rates below 25 litres per minute.

Compensating factors as follows may be applied for the following *2 ranges of flow rates indicated by the metering means Measured Flow Rate Compensation 22.5 25 1/m 20.0 22.5 i/m 1.8% 17.5 20.0 i/m 2.4% 12.5 17.5 1/m 4% 12.5 I/m 6% I- A compensation applied by the compensating means 20 to the flow signal on line 12 from the metering means 10 can vary depending on the particular metering means employed. For example, metering devices for LPG and other liquefied gas dispensing operations are manufactured and supplied by several manufacturers. The different commercially available metering means can vary in their performance, particularly at low flow rates, so that differing metering apparatus can require differen, compensating factors to be applied to the flow %X0 signal. Therefore, to enable the apparatus according to the preferred embodiment of the present invention to be usable with *seio ••metering means manufactured by different manufacturers and having different performance characteristics, the compensating means 20 may be operable to apply compensating factors selected SO OS for the particular metering means. The compensating means may, for example, be operative to apply compensation factors Sfrom at least two predetermined sets of such compensating eoso factors, the particular set of compensating factors being S. selected by the installer or user of the apparatus depending on the type of metering means with which the present invention is to be used. As shown in the drawing, the apparatus may include a selector 22 which can be operated at the time of installation and commissioning and calibration of the apparatus so that the particular set of compensating factors applied by the compensating means to the flow signals are selected and set for the particular installation.

According to the present invention, the terminating means is operative in response to the signal analysing means 15 to create a terminate signal on line 26 if the flow rate falls below a predetermined minimum flow rate. In the example given above, if the flow rate falls below 7.5 l/m, the terminate sign,} may be generated. Preferably, the terminating means includes a timing means 27, the terminating means 25 being operative to generate the terminate signal if the flow rate as determined by the signal analysing means 15 is below the minimum flow rate for a predetermined time as determined by the timing means 27. For example, if the flow rate is less than the minimum flow rate for, say, 15 seconds, the terminate signal on line 26 may be generated. Preferably the timing means 27 is r: only operative to commence measuring of the predetermined time •e g.

S when there has been in a particular dispensing operation a flow in excess of the minimum flow rate and subsequently the flow rate falls below the minimum flow rate. With this arrangement, *0 the terminate signal on line 26 will not be generated until a valid dispensing operation has commenced and LPG has actually been flowing.

oe Preferably the terminating means 25 is further operative in response to the timing means 27 and to the signal analysing 0* 0 means 15 to generate the terminating signal if there has lj n no flow for a predetermined time, e.g. for 30 seconds. Preterably the timing means 27 is operative to commence measurement of the predetermined time only after there has been a metered flow occurring so that the terminate signal on line 26 is not generated if an LPG dispensing operation is not commenced for a period exceeding the predetermined time period.

Furthermore, the terminating means 25 is preferably operative in response to the signal analysing means 15 and to the timing means 27 to generate the terminate signal if there is a pulsed flow detected. The terminating means 25 may include a sensor for sensing a pulsing of the flow signal on line 12 which indicates user manipulation of the flow itrol apparatus. With this arrangement, deliberate pulsing in order to achieve un-metered or inaccurately metered LPG flow can be detected and the dispensing operation terminated. The pulsing sensor may be operative to initiate the terminate signal on line 26 if there are, say, six pulses of the flow rate within a time period of, say, 15 seconds.

.Co The compensating means 20 as shown applies the compensated *5 flow signal on line 21 to the meter display/recording means The terminating means 25, when operative, applies the terminate 55 So signal to appropriate components of the metering system including for example the meter display and recording means to the pump of the dispensing system (not shown), and to the metering means The signal analysing means 15, compensating means 20 and terminating means 25 may be comprised by, for example, a suitably programmed microprocessor having appropriate input and output interface circuits. However, it will be appreciated that discrete circuits, or electro-mechanical components may be utilised to achieve the same functions.

It will be seen that the liquefied gas flow control and metering apparatus according to the preferred embodiment of the present invention as herein described and illustrated enables accurate metering of LPG or other liquefied gas during filling of a vehicle fuel tank, or in other situations where inaccurate metering is believed to occur. The present invention is based on the hitherto unrecognised sources of un-metered LPG dispensing flow, particularly the low flow rate inaccuracies of the metering means, and the inadequate operation of the limitiaig valves used in vehicle fuel tanks which to allow low rates of flow even after the respective tanks have exceeded their predetermined "capacity" of It is to be understood that various alterations, modifications and/or additions may be made to the features of the possible and preferred embodiment(s) of the invention as herein described without departing from the scope of the :.0O invention as defined in the appended claims.

S

Claims

2. Apparatus as claimed in Claim 1 wherein the terminating 25 means includes a timing means, the terminating means being operative to generate the terminating signal if the flow rate as SC.. determined by the signal analysing means is below the minimum flow rate threshold for a predetermined time as determined by Z AAthe timing means.
3. Apparatus as claimed in Claim 2 wherein the timing means is only operative to commence measuring of the predetermined 2 0. 255 1 3a time when there has been within a particular dispensing operation a liquefied gas flow in excess of the minimum flow rate threshold and subsequently the flow rate falls below the minimum flow rate threshold, whereby the terminating signal will not be generated until a valid dispensing operation has commenced and liquefied gas has actually being flowing.
4. Apparatus as claimed in Claim 2 or 3 wherein the terminating means is further operative in response to the timing means and to the signal analysing means to generate the o terminating signal if there has been no flow for a predetermined S time.
5. Apparatus as claimed in Claim 4 wherein the timing means is operative to commence measurement of the predetermined time only after there has been a metered flow occurring in the 15 dispensing line so that the terminating signal is not generated CS.. if a liquefied gas dispensing operation is not commenced for a period exceeding the predetermined time period. CS S6. Apparatus as claimed in any one of the preceding claims wherein the terminating means is operative in response to the S* 26 signal analysing means to generate the terminating signal if there is a pulsed flow of liquefied gas detected by the signal analysing means.
7. Apparatus as claimed in Claim 6 wherein the terminating means includes a pulsing sensor for sensing a pulsing of the flow signal and which indicates user manipulation of the flow control apparatus, whereby deliberate pulsing in order to achieve unmetered or inaccurately metered liquefied gcs flow can be detected and the dispensing operation terminated.
8. Apparatus as claimed in Claim 6 or 7 wherein the pulsing sensor is operative to initiate the terminate signal if there are a predetermined number of pulses of the flow rate within the predetermined time period.
9. Apparatus as claimed in any one of the preceding claims wherein the flow responsive means constitutes a part of a metering means for measuring and displaying or recording the amount of liquefied gas flowing through the dispensing line. A liquefied gas dispensing system including a dispensing line having an associated metering means, the system including a :.X0 liquefied gas flow control apparatus as claimed in any one of the preceding claims. Dated this 22nd day of January, 1993 15 9 PATENT ATTORNEY SERVICES Attorneys for 9 LPG ENGINEERING PTY LTD o 2* ABSTRACT A liquefied gas flow control apparatus for use in control of liquefied gas dispensed through a dispensing line (11) during a liquefied gas dispensing operation. An associated flow responsive means, normally part of a metering means generates a flow signal related to the rate of flow of liquefied gas through the dispensing line. A signal analysing means receives and analyses the flow signal and categorises the flow rate according to its magnitude. A terminating means responsive to the signal analysing means creates a terminating signal for terminating the gas dispensing operation if the flow S rate is less than a predetermined minimum flow rate below which S. a liquefied gas flow metering means can be inaccurate as a result of the metering means being incapable of accurately metering flow at low rates. A timing means (27) enables the terminating signal to be generated if the flow rate is below the minimum threshold or if there is no flow for a predetermined time. The timing means commences measurement of the predetermined time only after there has been a metered flow "N'2 occurring. The terminating means can be also operative to generate the terminating signal if there is a pulsed flow of liquefied gas detected by the signal analysing means.