By ProMinentPrepared by Neville McKee Feb 09

Revised June 09

Fluoridation of drinking water remains the most significant dental health program in New South Wales and Australia.

The advantage of water fluoridation is that the entire community benefits from the preventative measure, regardless of age, socio- economic level, educational achievement, individual motivation, or the availability of dentists

Fluoridation

Fluoride packages and installations have to meet strict guide lines.

In New South Wales where ProMinent Australia have supplied more than 50 systems, there is a fluoride code, ‘Code of Practice for the fluoridation of Water Supplies Act 1957‘ This code was published by the Oral Health Branch of the Dept of Health and revised in August 2002.

This code has also been accepted by other Australian states as the bench mark for fluoride installations.

Typical fluoride building

TYPES of FLUORIDE

Fluoride is available commercially in 3 different ways, 2 are powders the other a liquid. Each display different concentrations of available fluoride ions & solubility

PowdersSodium fluoride (NaF) - most expensive 44% by weight available fluoride ion (solubility is 4.0%)

Sodium Silicofluoride (Na2SiF6) - 60% by weight available fluoride ion (solubility = 0.4%, nominal solution strength 0.2%)

LiquidHydrofluosilicic acid (H2SiF6) - liquid - 24% by weight available fluoride ion

Sodium SilicofluorideA typical sodium silicofluoride package could consist of:

Hopper for 36 hours capacity (we would suggest 72) in 304SS

Hopper support frame and base - HDGMS

Bulk Bag loader – painted MS

Vacuum loader – 304SS

Manual bag loader

Control Panel

Dust extractor with exhaust water trap tank

Powder feeder – 316 SS

Loss of weight recording system with chart recorder or digital display

Solution tank – 316 SS - 10 minutes retention

Stirrer – 316 SS shaft and prop

Transfer pump – Spectra PC or Peristaltic or Gravity feed with flow control

Accessories like water softener, compressor etc. – as required

Sodium Silicofluoride General description

ProMinent offer varying packages for sodium silicofluoride preparation and dosing. A number of different powder loading methods are available such as:

Bulk bag with conveyor transferBulk bag with vacuum transferBulk bag mounted directly over the day hopperVacuum loader 25 kg bags. Manual bag loader for 25 kg bags

With all of the above either an integral or attached dust extractor is required, with the exhaust piped outside the room to near ground level above a water ‘dust trap tank’.

The control panel is normally mounted on the hopper frame so that it can be pre- wired and tested before leaving our works. If it is required that the control panel is to be mounted on the building wall, the package still has to be wired for testing in our works, separated for despatch and reconnected at site incurring additional costs.

Sodium Silicofluoride with vacuum loader

Vacuum loader

Hopper with at least 36 hours capacity

Hopper support frame with load cells

Stirrer

Powder feeder

Solution tank

Transfer pump

Fluoride Bulk Bag Installations

This shows the dust extractor, intermediate hopper and 2 flexible conveyors going off to feed two separate hoppers

This shows a wetting cone eductor feed package where the solution is fed up into the solution tank. This package has one preparation tank with fixed rate solution transfer and varying solution strength.

Top of flexible conveyor and entry chute into hopper

Dust tight bulk bag attachment, intermediate hopper and flexible conveyors.

This application required a single bulk bag loader filling two 7 day hoppers for dosing 2 separate supply mains.

Two tanks were supplied, a preparation and a dosing tank with duty/standby pumps for each dosing line.Due to height restrictions the powder feeder did not feed directly into the preparation tank, but metered into an eductor/wetting cone (at floor level) and transferred up an into the preparation tank.

For this site the requirement was to locate the bulk bag loader in a separate room to the hopper and solution tanks

Process DescriptionFrom the storage hopper the powder is fed via a ProMinent dry chemical feeder into the mixing tank. The mixing tank is equipped with a high speed stirrer, overflow and drain pipework and has a retention time of 10 minutes. The solution is then delivered to the injection point by a ProMinent DulcoFLEX peristaltic pump or a Spectra progressive cavity pump all controlled by an Allen Bradley Micrologic PLC.

On all our volumetric feed packages, load cells record the loss of weight of the hopper powder for comparing the usage rate with the mains total water flow, to ensure correct dosing (and not over dosing) has occurred. Normally 3 load cells are used but on some of the larger hoppers we have supplied with 4. A low level alarm is fitted with feed back to the PLC. Indication of weight is provided on the panel and a 4-20 mA signal is available for retransmission to the main control room or to the 24 hour chart recorder.

Package variationsThe standard package we would normally supply would have the feeder sitting above and feeding directly into the solution tank. The feeder rate would vary in accordance with the 4-20 mA mains flow signal to vary the solution strength. The solution is then transferred to the injection point with a fixed capacity Spectra progressive cavity pump.

We have supplied variations to the above continuous flow packages by supplying batching systems and eductor transfer systems. Batching packages would be supplied for the following reasons.

Firstly for small water supplies where the solution tank size and powder feed rates are below easy to manage capacities, we offer a package that continually (automatically) makes up a fixed known percentage solution. This is then dosed into the water supply with a metering pump suitable for the pressure and capacity in proportion to a 4-20 mA flow signal.

The metering pump can be locked to a maximum capacity to meet the safety requirements of the Act and can be set to give a readout of total litres dosed.

The walls of the fluoride room have to be smooth and have no horizontal grooves to catch fluoride dust. Windows are to be flush on the inside.

Provision has to be made for storing 90 days supply of fluoride powder inside the fluoride room.

Fluoride packages can be gravity fed or transferred to the injection point via a ProMinent Spectra progressive cavity or peristaltic pump.

With gravity feed packages, to ensure a 10 minute retention time in the solution tank, we include flow regulators on the incoming water.

This shows a manual bag loader with dust extractor attached. Product caught in the dust extractor falls back into the hopper.

Cheaper grades of fluoride are available from different countries. A ProMinent crumbler is located between the bag loader and the hopper for removing lumps from poorer quality sodium silicofluoride.

On water supplies with rapid flow rate changes, a 2 tank batch make up system can be supplied. Tank 1 makes up a constant known solution strength and is sized to retain the solution for at least 10 minutes. Solution then gravity feeds to tank 2 when lower level in tank 2 is reached.

Make-up rate into tank 1 would be approximately 15% above maximum usage rate.

The two tank system is also suitable for when there are two dosing points and you wish to handle them with one makeup package.

Height restrictionsWhen height poses a problem, we offer a specially designed eductor and wetting cone arrangement for mixing the fluoride and transferring it up and into the solution tank. This lowers the hopper considerably and reduces the building height requirement.

Package sizesThe powder usage rate will influence the type of package required for your water supply. For a flow of 50 Ml/d or above we would recommend a bulk bag loader. From 6 to 50 Ml/d we would offer a vacuum loader dry feed system and for flows below this we would more than likely offer a sodium fluoride saturator package..

Powder loading

Bulk bagThe bulk bag loader we offer would normally come with an electronically operated hoist for lifting the bags and placing them in position. It has a lifting capacity of 1250 kgs and operation is controlled via a hand held push button pendant on a drop cord.

The double wall design bulk bag interface provides a dust tight sealed connection to the bulk bag outlet spout via a spout lock clamp ring. A bulk bag flow control valve is always supplied, designed to control material flow from the bulk bag and allow outlet spout reclosure during the emptying process.

A dust collection system is manifolded between the bulk bag unloader and the day hopper with the exhaust piped outside to above a water trap tank.

At the base of the loader is an intermediate hopper from where the powder is conveyed to the day hopper, via a motor driven spiral conveyor of capacity up to 5,000 l/h.

As an alternate to the electric hoist we can supply a unit where the bags are lifted into position using a fork lift.

Typical Fluoride Room

Inside a typical sodium silicofluoride room, this plant suitable for 20 Ml/day water supply.

ProMinent use 3 load cells on smaller packages and 4 on larger, for the loss of weight recording. The 24 hour recorder chart would normally be replaced only when hopper is refilled.

Control panel showing the mimic and a circular (24 hr) chart recorder to record loss of weight.

A digital indicator may be accepted as an alternative.

If the water hardness exceeds 75 mg/l as calcium carbonate a water softener may be required.

Stainless circular solution tank with floor mounted stirrer. ProMinent PE tanks with tank mounted stirrer are an alternative.

Tank has a baffle to prevent the direct passage of powder that has not dissolved short circuiting to the outlet. The outlet from the tank is about 100 mm from the bottom.

Low level switch is required to protect the equipment.

High level is set to alarm on overflow and can be set to close a solenoid valve on the inlet water.

ProMinent Fluid Controls have a sodium fluoride saturation system suitable for adding fluoride into water supplies up to about 6 Ml/day

ProMinent’s standard saturator is a down flow type with a vacuum loader for handling the powder and we recommend the use of sodium fluoride granules.

.

Fluoride Saturator - Sodium fluoride

General description

Sodium fluoride powder is more expensive than sodium silicofluoride but the capital equipment cost is less for smaller water supplies.

Sodium fluoride is almost always used in a saturator.

Different methods of loading the powder include dissolvable 5 kg bags, manual bag loader for 25 kg bags and manual bag loader for 10 kg bags.

Process DescriptionProMinent’s sodium fluoride down flow saturator is suitable for water supplies up 6 Ml/d. The equipment is mounted on skids for ease of installation at site and operates as follows:

Sodium fluoride has a reliable saturation solubility of 4%. By keeping excess sodium fluoride powder in a dissolving tank, a constant 4% sodium fluoride saturated solution is maintained. This is then dosed into the water supply, via a ProMinent metering pump, in proportion to the mains 4-20 milliamp flow signal.

A UV stabilised translucent PE tank is first filled with a small layer of filtration sand and make up water. Sodium fluoride powder is then added to the tank to create the fluoride solution. By having more powder that can readily dissolve, a saturated solution is formed and ready to be dosed. Prior to the dosing pump, the fluoride solution will pass through a sand filter bed, a suction lance and an 80 micron filter to remove any solids prior to reaching the metering pump and being dosed into the mains water.

The saturator comes as a package all mounted suitable for ease of installation complete with overflow, drain, calibration cylinder, isolation valves, metering pump and a current sensing relay (CSR).

The CSR is used as one of the two mandatory flow indicators. A flow switch is to be fitted by others as the second.

A calibration cylinder is provided to accurately calibrate the metering pump against the dosing conditions.

The vacuum loader especially designed for fluoride, is mounted on the saturator and comes complete with dust extractor, suction wand and a flexible hose. The ProMinent vacuum transfer system is designed to transfer powder from the 25kg bags to the solution tank.

The metering pump is set to display the total amount dosed. This is compared daily against the total water flow to ensure correct dosing has occurred.Metering pumps are supplied with a flow failure monitor and alarm relay to alarm if dosing stops.

System components –standard package

500 litre PE Saturator Tank c/wSuction lanceCalibration cylinderIsolation valvesBowl filterFloat valveMounting for Vacuum loader

Fluoride Dosing Pump c/wMultifunction valveInjection valveFlow failure monitorTubing x 10 metresReadout to give total litres dosed

Vacuum Loader for 25kg bags c/wSuction wandSuction wand holderBuilt in dust extractorVacuum pumpExhaust piped outside to a water trap

Control PanelVacuum loader controlsCurrent sensing relayAlarms

Vacuum Loader Exhaust TrapWater tank with float valve

CompressorSmall compressor to supply air for the vacuum loader

ProMinent

PromVac

Vacuum Transfer System

Vacuum Loader

The ProMinent vacuum transfer system is designed to transfer powder from a shipping bag, or container to a hopper or direct to a process.

The ProMinent vacuum loader is suitable for both the sodium silicofluoride packages and the sodium fluoride saturators.

As the powder enters the collection unit, the large volume inside the unit causes the air velocity to drop, allowing the powder to fall to the bottom of the unit.

The air is then drawn upwards, through a filter to remove any powder particles that are still airborne, before leaving the unit via the vacuum motor.

A pneumatically actuated valve at the bottom of the collection unit is used to dump the collected powder into the hopper, or to isolate the hopper from the vacuum system.

There is a second valve on the suction side of the filtration to prevent powder from blowing out of the wand during the cleaning cycle.

Description

The ProMinent Vacuum Transfer System is available in 2 models and includes:

collection unit

compressed air handling system

hand held vacuum wand

vacuum motor

air supply (either a compressor or plant air)

Item Part Number Description

1RB50-510 Vacuum Motor, 1.5kW 240VAC, suit

Model ‘A’ Vacuum Transfer System

RB60-720 Vacuum Motor, 4kW 415VAC, suit Model ‘B’ Vacuum Transfer System

2 Vacuum Relief Valve

Vacuum Pump

Vacuum relief valve

Model A is 240 Volt and would empty a 25 litre bag in 5.0 to 6.0 minutes (250 to 300 litres per hour)

Model B is 415 Volt and would empty a 25 litre bag in 3.0 to 3.5 minutes (400 to 500 litres per hour)

Chamber

Collection chamber

Inlet valve assembly

Vacuum hose

Dump valve actuator

Dump valve

Cleaning Cycle air purge solenoid

Electrical connection junction box

Open/Close solenoid valve for dump valve and Inlet Valve

Air Accumulator

Pressure Switch

Compressed Air Inlet Tee

Air Equipment

Operation

With the vacuum loader switched on, the wand is inserted into the container or open bag. The vacuum motor will operate for 40 seconds before stopping.

At this point, the inlet valve will close, and the dump valve will open, allowing the collected powder to drop into the hopper.

A cleaning cycle will also begin. Once the cleaning cycle has completed, the dump valve will close, the inlet valve will open and the vacuum motor will start.

The vacuum wand is constructed from two different diameter stainless steel tubes.

The larger is used to transfer the powder from the bag to the filtration unit via the vacuum hose. The smaller allows air to be mixed with the product for efficient transfer.

For the continuous monitoring of fluoride levels in water supplies, a ProMinent fluoride analyser is available with milliamp retransmit and alarms.

The analyser is normally supplied as backboard mounted with temperature, fluoride and reference electrodes.

A magnetic stirrer is also provided to assist with the single or two point calibration.

Standard unit measures free fluoride with an optional unit available for total.

Fluoride Monitor