GB2341169A - A dosage control system - Google Patents

Abstract

A dosage control system comprises a first meter 12 which gives a electrical output indicative of the water flow rate, and a second meter 16 which gives an output indicative of the dosant 14 introduced into the water. From this the concentration of dosant 14 in the water is calculated by means such as a controller 11, and compared to a desired level of dosant 14 which has been programmed into the controller 11. The controller 11 then adjusts the flow of dosant 14 in order to reach the desired concentration level. The system may operate with different types of pump and flowmeter. Maximum target volumes of dosant which can be introduced into the water line 13 can be set, to avoid overdosing. The system can optionally have means to record the date and time of any changes to the parameters. It may be set up and governed via a control panel, and data may be transferred to the system via a smartcard 18. Input and output ports may also allow the transfer of data to and from a remote processor.

Description

234116.9 Improvements relatinq to Water Treatment This invention relates

to water treatment.

Water companies do not generally convey water directly from their sources, such as reservoirs, into the domestic supply. Additives, or dosants in this specification, are introduced to improve quality and safety.

obviously, it is desirable to vary the amount according to the flow and generally govern the dosing in a carefully controlled manner. Hitherto this dosing has usually been carried out by operators acting on imprecise information, relying to some extent on intuition and experience.

It is the aim of this invention to make the dosing of water supplies accurately controllable and easily adjusted.

According to the present invention there is provided a is dosage control system for a water supply equipped with a first meter capable of giving an electrical output indicative of water flow and a second meter capable of giving an electrical output indicative of dosant introduced into the supply, the system comprising means for determining from those outputs the concentration of dosant in the water, means for setting a desired concentration of dosant in the water, and means responsive to the determined and desired concentrations for modifying the introduction of dosant so that the determined concentration converges to the desired concentration.

There are various kinds of flow meter currently available, and the system will preferably be capable of working with any one of them by having means for setting it 2 up electronically according to which type of flow meter is in use.

Likewise there are various kinds of dosing pumps, and the system will preferably be capable of working with any one of them by having means for setting it up electronically according to which type of dosant pump is being used. The second meter will not generally measure the dosant delivered from the pump, but the electrical input to the pump which will be directly related to the amount delivered.

once this system has been set up according to which flow meter and dosant pump are in use, it can be arranged that those parameters are locked in and cannot be altered without special measures being taken.

It is not always appropriate to introduce dosant in its concentrated form and often it will be diluted in a solution in a selected concentration. The system will therefore conveniently have means for electronically setting up this concentration and to take that into account when the concentration of dosant in the water supply is being set.

It is important that there should be no over-dosing.

The system may therefore incorporate means for setting a maximum target volume for the dosant, means for setting a total water flow target beyond which dosing should not be carried out, and alarms that are activated when either of these targets are reached.

The system will also preferably have a date and time recording capability, so that all events that change the state of the system can be logged.

3 The operative will conveniently have a simple control panel by which the system can be set up and governed, consisting of an LCD display and a few keys. The display will show in plain language and figures information on the current set-up of the system, and by manipulating the keys the operator can alter values, change from one parameter to another on the display, and confirm or cancel selections, as described in more detail below.

many such dosing systems are at remote locations, overseen by one operative. To minimise the risk of mistakes, this system may be adapted to be used in conjunction with a smartcard. All or at least the most important settings can be stored on such a card, which may be coded so that it can only be used at a particular location at a particular time. This is sent to the operative in the field who, on entering the correct code, can load the settings from the card.

The system preferably includes means for setting a maximum adjustment value for limiting the modification of the introduction of dosant so that the amount of dosant after modification does not exceed the maximum adjustment value.

The dosage control system may include means for transferring data to and from a smart card, as well as input/output port capable of transferring data to and from a remote processor and data storage. The data transfer may occur via a wireless link.

For a better understanding of the invention, one 4 embodiment will now be described, by way of example, with reference to the accompanying drawing, in which Figure 1 is a schematic diagram of the dosage control system, including a dose control unit; 5 Figure 2 is a diagram of the dose control unit, and Figure 3 shows menus associated with the unit. In Figure 1, an overall diagram of a dosage control system according to the preferred embodiment is shown. A dose control unit 11 receives an input from a flow meter 12.

The flow meter 12 outputs an electrical signal corresponding to the flow of a water supply through a pipeline 13.

The flow computer 11 is capable of outputting a signal to a dose pump 14. The dose pump 14 is capable of injecting a specific dosage of a dose solution 15 into the pipe 13.

The dosing point is normally downstream of the f low meter 12.

The flow computer/ controller 11 can also receive an electrical signal from a device positioned at a sampling point 16. the sampling point 16 is downstream of the flow meter 12 and dosage point 13.

The flow computer 11 is also connected to alarms 17 and a smartcard read/write device 18, which will be described below.

Currently, there are four main types of dosing pump which can be categorised as:

Pulse Modulation (Pump switched on for longer or shorter times) Blipped, (Pump delivers a known volume each time it receives a signal) FlipFlopl (Pump delivers a known volume each on/off cycle) 14-20mAl (Pump rate is proportional to the 5 current) There are also four main types of flow meter, namely:

Pulsed flow meter (i.e. 1 pulse per 100 litres), Paddlewheel flow meter, 0-20 mA flow meter, 4-20 mA flow meter A dosing controller governs the dosant supplied in direct proportion to the flow in the main pipe. As the flow in the pipe increases or decreases the controller will alter the dose flow to compensate. The controller keeps a running total of both the dosant used from one of the dosing pumps identified above and the flow in the main pipe from one of the flow meters identified above, and can be set to stop dosing when one or both of these totals reach a particular target. It can also sound an alarm when the main flow reaches a set target.

Referring now to Figure 2, the controller 11 is microprocessor based and housed in a unit 201 with a display panel 202 and an input/output panel 203.

The display panel 202 has:

Two indicator LEDs 204 and 205 Six keys 206, each with a positive 'click, when pressed, and A two line alphanumeric backlit Liquid Crystal Display 6 207, each line capable of showing twenty-four characters.

The input/output panel 204 has:

A power input socket 208, Two 4-20 mA outputs 209 and 210, one echoing the input flow, and one representing the dose flow, Four relay outputs 211-214 whose functions are:

Failsafe: the relay 211 is activated while there is power to the controller Dose_R: the relay 212 controls the dose pump, shutoff 1: the relay 213 is activated when a main flow target (described below) is reached, Shutoff 2: the relay 214 is activated when a dose target (described below) is reached.

one universal input 215, that can accept various types of input from whichever flow meter is used, A sampling input 216 from a 4-2OmA sensor located at the sampling point 16.

A serial input/output 217, which is a socket that can be connected to a PC or a smartcard. The serial 1/0 port 217 may be replaced by or fitted with a wireless communications interface which can allow the flow computer to be set up and controlled remotely via a wireless link, e.g. telemetry, GSM modem or radio link. This provides the facility to set up the computer remotely by transferring signals via the port instead of pressing the keys on the flow controller as described below. This can be advantageous because a human operator does not need to go to the location where the controller is fitted, thereby 7 possibly decreasing maintenance costs and allowing the computer to be placed in a location which would otherwise be inaccessible. Real time data can also be transferred from the flow computer to another machine via the port.

Internally, apart from the microprocessor, there is:

2k of battery backed RAM to store the user settings when power is removed, and A beeper to confirm key presses and to sound on alarm conditions Information on the existing setup, flow/dose rates and alarms are displayed in plain English using the controller's LCD display 207, in conjunction with the two indicator LEDs 204 and 205 and the beeper. All the parameters can be set using this display and the controller's keys 206, which are 6a UP -Increase value 6b Down -Decrease value 6c Left -Previous digit or menu item 6d Right -Next digit or menu item 6e Enter (marked OK)-Select current value or move to the selected menu 6f Escape -Cancel current value or move to the previous menu When the unit 11 is switched on, an introduction message will scroll onto the LCD display 207. Pressing any one of the keys 206 will bring up the main menu, which is one of f our as shown in Figure 3. The main menu includes options to start and stop the system and to display current 8 settings. The set up menu includes options to set the dose rate, dose solution concentration and maximum target volumes. The sampling menu allows the user to set up parameters relating to the input received from the sampling point 16. The special menu includes option to conf igure the dose pump and flow meter.

The menus are displayed option by option on the top line of the display 207, with the existing option flashing in the centre of the screen.

The user can "navigate" through the menus using the keys 206 on the front panel. Thus by pressing key 206c the user moves to the previous option, and by pressing key 206d he moves to the next option. Once satisfied, the OK key 206e is pressed to select the currently flashing option and is to move to the next screen. The 'Escape, key is pressed to return to the previous screen/menu.

In general pressing the OK key 206e will move down, the menus (or accept the changes made), and pressing the Escape' key 206f will move 'up' the menus (or cancel the changes made.) Certain values will generally only need to be set once and these include:

The Flowmeter settings (eg paddlewheel type, flow at 50hz and maximum expected flow) The Dosepump settings (eg blip type pump, volume/blip and time/blip) The Logging interval (eg log flows every 5 minutes) The System Date and Time 9 The Calibration Details for mA inputs only These values are normally hidden, and not accessible unless a Supervisor, link has been placed on the PCB.

However, this will be the case at the outset, when a Supervisor will key to the Special Menu and set the controller up as follows:

First the type of flow meter is selected. Using the UP' and 'DOWN' keys 206a and 206b the various types listed above appear in order on the display 207. Pressing the OK key 206e selects the flow meter.

The Supervisor will then be asked to enter the volume per pulse, the flow rate at 50Hz or the flow at 20mA depending on the meter selected.

Then the supervisor sets the type of dose pump in a similar manner, again using the keys 206a and 206b to select and the key 206e to confirm.

The supervisor will then be asked to enter the maximum dose rate, the dose volume and time per blip,/Iflipflopl, or the dose rate at 20mA, depending on the meter selected.

Thirdly the supervisor sets the system date and time.

This clock continues running even when the controller is switched off. The clock does not have to be set for the controller to operate properly, and is used only when logging data to the smartcard, to be referred to below.

Next the input amplifier is calibrated, this only being necessary for the 0-20 mA and 4-20 mA flow meter types due to very slight errors during manufacturing causing each amplifier to have a small offset when it should read zero (around + or - 200 counts). To correct this the controller must be told when it is reading 0 mA and 20 mA. The supervisor connects the inputs together to ensure an input current of 0 mA, waits for the value to settle and presses the OK key 206e to set the zero offset. The value on screen should now be showing zero (+ or - a couple of counts).

Next the supervisor connects a 20 mA supply to the inputs, waits for the value to settle, and presses the OK Key 206e to set the amplifier range. The final calibrated value should now read one thousand times the input current. (eg 10 mA reads 10,000).

The 'Log Intl option in the Special menu lets the supervisor set the logging interval. At each logging interval the system will save the current flow and dose rate to memory. This is currently in 1/20ths of a second, so an interval of 18000 is 15 minutes.

The supervisor link is then removed.

Before operation there are other parameters that must be set and for this the user goes through the main menu to the setup menu where the various options are as follows:

The 'ResetTOTI option allows the user to reset the flow integrators back to zero. To confirm zeroing the totals, the user presses the left' key 6c to select 'YES', and then presses the OK key 206e.

The lAlmFlowl option sets the total volume through the flow meter required to trigger an audible alarm, e.g. alarms 17. When the flow totaliser reaches this volume, the controller will sound a long beep every 4 seconds until a key is pressed.

The 'Max Flow' option sets the total volume through the flow meter that should be allowed before the dosing system is shut down. When this limit is reached, the controller will light the input LED 4, activate the first shut off relay 13 to stop the system closing, and sound a long beep every four seconds until a key 206 is pressed.

The 'MaxDosel option sets the total dosant that should be allowed through the dose pump before the system should be shut down. When the dose totaliser reaches this volume, the controller will light the output LED 205, activate the second shutoff relay 214, stop the system dosing, and sound a long beep every four seconds until a key 206 is pressed.

The 'DoseCon' option lets the user specify the concen tration of the dose solution.

The IPPM/Ratl option enables the user to select the dosing rate in Parts Per Million (PPM) or some other agreed ratio. To select PPM the user presses the left' key 206c and then the OK key 206e, while to select Ratio he presses the 'right' key 206d followed by the OK key 206e. In carrying out this key operation, the user does not have to think about the concentration of the dose solution, which has already been entered and will be taken account of by the controller in setting the dosing rate.

The sampling option takes the user to a menu which sets up options relating to how feedback from the sampling input 216 is used by the flow controller. The options in the menu are as follows:

12 The "Calibrln" option is used to calibrate an amplifier of the sampling input 216, i.e. the controller is told when 4mA and 20mA is being received through the input 216. An input current of 4mA is fed into the sampling input and the current value in mA is shown on the screen. After the value has settled to around 4mA, the user presses the OK Enter key 206a to set the zero offset and the value on the screen is shown as zero. Similarly, a 20mA current is then supplied to the sampling input 216 and after the value on screen has settled to around 20mA the Enter key 206e is pressed to set the amplifier range. The final calibrated value normally reads 100 times the input current (e.g. 1OmA would show as 100). The OK Enter key is pressed again to conf irm the calibration.

The I'MaxPPM11 option sets the PPM that the sensor detects to give 20mA, i.e. 0 PPM gives the sensor an output of 4mA and the value set as MaxPPM gives 20mA.

The "Off/On" starts and stops the compensation, i.e.

determines whether the flow controller uses the signal received at the sampling input 216 for adjusting the PPM.

The "Pipe-Voll' option is used to enter the total volume of f luid in the pipe between the dosing point and the sampling point where the sensor for the sampling input is positioned. This volume value is required so that the controller knows when the "slug" of dose entered into the fluid at the dose point reaches the sample point. The Pipe 2.1000 Vol value is calculated as wR. x length, so the user enters the dimensions of the radius (R) and length of the 13 pipe between the two points.

The I'Max.Adj 11 option sets the maximum acceptable PPM increase (upward adjust) that can be made by the flow controller. For example, if the sampling sensor reads 1.8 ppm and the controller is configured to deliver 2.5 ppm then the controller adjusts the dosing up by 0.7 ppm to compensate (1.8+0.7 = 2.5). However, if the Max.Adj value is set to 0.5 then the controller would only be able to increase the dose by 0.5 ppm, giving an overall dose rate of 1.8 + 0.5 = 2.2 ppm. This maximum acceptable PPM value is intended to be a safeguard against a failure in the sensor which sends a signal to the sampling input 217. If in the example above the sensor continually outputs a value representing 1.8 ppm then the controller would increase the is dosing continually. Even after the required dosage is fed into the pipe, the sensor would still output a value representing 1.8 ppm and so the controller would deliver another 0.7 ppm which would result in an overdosing (i.e. the controller would deliver 2.5 ppm + 0.7 ppm + 0.7 ppm ±--).

The controller can also decrease the dosing rate if necessary. For example, if the desired dose is 2.5 ppm and the signal from the sampling point indicates that there is already 2.4 ppm of dosant in the water then the controller would reduce the dosing rate down to 0.1 ppm to achieve the intended target.

All these user settings may be stored on a smartcard, e.g. using read/write device 18, and the values stamped with 14 a unique code (e.g. the date and time the settings are to be used). This card can then be sent to the operative in the field who, on entering the correct code, can load the settings from the card. Indeed the set up menu may not be available f or the user to set the various parameters: it can be arranged that setting up can only be done by a smartcard.

Thus the risk of incorrect settings is minimised, or at least the responsibility for them is carried by the authority issuing the card and not the operative in the field.

With everything set up, the user reverts to the main menu whose options are as follows:

The 'Status' option displays the current setup on the top line, and the current flows and totals on the bottom line. The user presses the left, and 'right' keys 206c and 206d to alter the top line, and the up, and down, keys 206a and 206b to alter the bottom line.

The 'Start/Stop' option starts and stops the system dosing. To stop the system dosing the user presses the left' key 206c and then the OK key 206e.

The 'Timer, option displays the dosing times, which runs while dosing is in operation. It can be temporarily frozen on the display 207 by use of the OK key 206e.

The 'Setup' option moves to the Setup Menu (which as mentioned above may not always be available if it has been locked via the smartcard).

The 'Logging' option starts or stops the system logging to the smartcard. The user presses the left, key 206c and then the OK key 206e.

The 'Special' option moves to the Special Menu (which as described above will generally only be available to a Supervisor).

The 'Info' option displays who designed and produced the Dose Controller, and this may only be available when specially activated.

When the dosing is started, the controller starts the timer, which stops when the dosing stops. This can be viewed on the display 207, as mentioned above.

The indicator LEDs 204 and 205 show the current status of the input and output. when the system is running, the input LED 204 flashes in proportion to the main water flow and the output LED 205 flashes when the dose pump is activated. with a current type dose pump it f lashes in proportion to the dose flow.

If the main target is reached, the input LED 204 comes on continuously, the alarm sounds and the f irst shut off relay 213 is activated. Similarly, if the dose target is reached, the output LED comes on continuously, the alarm sounds and the second shut off relay 14 is activated. Also if the desired dosing rate exceeds the maximum dosing rate, the controller will dose at the maximum rate and sound an alarm.

But, generally, the controller will ensure that the dosing tracks variations in water flow so that the concentration of dosant in the water remains substantially steady at the set value.

16

Claims (11)

Claims

1 A dosage control system for a water supply equipped with a first meter capable of giving an electrical output indicative of water flow and a second meter capable of giving an electrical output indicative of dosant introduced into the water, the system comprising means for determining from those outputs the concentration of dosant in the water; means for setting a desired concentration of dosant in the water, and means responsive to the determined and desired concentrations for modifying the introduction of dosant so that the determined concentration converges to the desired concentration.

2. A dosage control system according to Claim 1, adaptable to operate with different types of flow meter and further including means for setting up electronically which type of flow meter is used.

3. A dosage control system according to Claim 1 or 2, adaptable to operate with different types of dosant pumps and further including means for setting up electronically which type of dosant pump is used.

4. A dosage control system according to any one of the preceding claims, adaptable to operate with dosant in solution or diluted, and further including means for setting up electronically the concentration of the dosant in the solution or diluent.

5. A dosage control system according to any one of the preceding claims, and further including means for setting a 17 maximum target volume for a dosant, means for setting a total water flow target beyond which dosing should not be carried out, and alarms that are activated when either of these targets 5 are reached.

6. A dosage control system according to any one of the preceding claims, and further including means for recording date and time of events that change the state of the system.

7. A dosage control system according to any one of the preceding claims, and further including a control panel by which the system can be set up and governed, the panel having an alphanumeric display and a plurality of keys.

S. A dosage control system according to any one of the preceding claims, and further including means for setting a maximum adjustment value for limiting the modification of the introduction of dosant so that the amount of dosant after modification does not exceed the maximum adjustment value.

9. A dosage control system according to any one of the preceding claims, and further including means for transferring data describing the state of the system to and from a smartcard.

10. A dosage control system according to any one of the preceding claims, and further including an input/output port capable of transferring data to and from a remote processor and data storage.

11. A dosage control system according to Claim 9 or 10, wherein the data is transferred via a wireless link.