Chemical metering pump

#The present invention relates to the delivery of liquids and includes a liquid delivery means, a liquid delivery and calibration arrangement, a liquid delivery system and a cradle for supporting containers from which the liquid is to be delivered.

#In many regional country town water supplies the only economical way that hazardous chemicals can be delivered to water treatment plants is by portable chemical containers (20 to 40 liter capacity). More often than not, a chemical metering pump, which accurately meters the required amount of chemical into the water, needs many times the capacity of a single container and therefore a vat is used in which the chemical is stored. The main problems associated with manually handling the chemical from the portable containers to the vats is that it is a slow, laborious and hazardous task for treatment plant operators. Whilst a number of methods have been introduced to reduce the time and risks involved, the exercise of “double handling” of the liquid chemical still remains a significant problem.

#Other users of hazardous liquid chemicals, such as farmers, who also have a need to accurately meter a wide range of chemicals into water, also have major problems with this “double handling” process. Here again, a number of initiatives have been proposed to reduce the time and risks involved in transferring hazardous chemicals from portable containers into vats and tanks. These initiatives include battery-operated transfer pumps, purpose-built stands with special chemical syphons and innovative vortex systems, all of which improve the process, but do not remove the “double handling” problem.

#In order to facilitate a more comprehensive understanding of the nature of the invention several embodiments of the chemical metering pump in accordance with the present invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:

#FIG. 1 illustrates a prior art electronic chemical metering pump;

#FIG. 2 illustrates a first embodiment of a chemical metering pump according to the present invention in situ;

#A prior art electronic chemical metering pump 10 illustrated in FIG. 1 has an inlet 12 which draws liquid chemical from a vat 14 and a discharge valve 16 through which liquid lo chemical is metered to a flow stream 18. The pump 10 includes a built in electronic controller 20 for controlling the operation of the pump 10 so that it accurately meters the required volume of liquid chemical into the flow stream 18. The liquid chemical held in the vat 14 may be, for example, liquid chlorine (a concentrated solution of sodium hypochlorite) which is metered into the water supply flow stream 18 at the rate of between 0.05 to 10 liters/hour.

#As noted above, one of the problems with this type of prior art metering system, is that the vat 14 must be periodically refilled with liquid chemical. This task is done manually, and in addition to being laborious and time consuming, may also be dangerous, particularly when handling hazardous chemicals.

#FIG. 2 illustrates a first embodiment of a chemical metering pump 24 in accordance with the present invention. Instead of having an electronic controller built into the pump, a remote electronic controller 26 is provided (in this case shown as a wall-mounted unit), which is connected by cable to the chemical metering pump 24. The electronic controller 26 performs essentially the same function as the conventional electronic controller 20 of FIG. 1, however it differs from the prior art controller in that it is capable of safely transmitting a low voltage, variable, control signal to one or more chemical metering pumps via suitably screened cable(s). Furthermore, as it is preferably mounted in a separate, wall-mounted unit, it can be positioned in a more convenient environment, such as a plant control room, where it can be viewed (at eye level) and adjusted in total safety and isolation from the pumping installation.