Water treatment plants dissolve a surprising variety of powders into a surprising variety of tanks, and every one of those tanks needs its contents kept in suspension long enough to be dosed at the right strength. The MC3PVST02 vertical solid shaft gearbox is the drive for that job: three helical stages in an upright case, a keyed solid output coupled to the agitator shaft, and a torque arm that takes the reaction instead of a baseplate.
These notes take the drive through a dosing house: the chemicals it meets, the way it is held down, the alignment it demands, and the figures a plant should send with an enquiry.
A Small Tank With a Strict Job
Dissolving tanks look unimportant next to the filters and the clarifiers, and they are the reason those units work. A polymer that has been sheared too hard does not flocculate; a coagulant dosed at the wrong strength either fails to settle the turbidity or carries it straight through.
The mixing duty is therefore gentle, steady and repeatable, and the drive is judged on whether it delivers the same slow turn every day rather than on how much power it can put through the shaft.
What the T Adds to the Code
The designation settles the mounting in six characters.
| MC | Industrial gear unit family built for continuous plant duty |
| 3 | Three helical reductions inside one upright case |
| P | Parallel-shaft layout, input and output on parallel axes |
| V | Vertical build, output axis pointing down into the tank |
| S | Solid output shaft, keyed and coupled to the agitator |
| T | Torque-arm reaction, no baseplate and no floor drilling |
Said in one line: three-stage industrial unit, parallel shafts, vertical, solid output, torque-arm reaction, second frame of the band.
A Torque Arm Instead of a Baseplate
On a small tank top, a baseplate is often the most expensive item in the drive package. It needs machining, it needs to be landed flat, and it needs bolt holes drilled through a cover plate that was never designed to be drilled.
A torque arm removes all of that. The case hangs from a bracket, the arm takes the reaction into a structural member, and the tank top is left as a cover rather than turned into a machine base. It also means the drive can be lifted off with the bracket still in place when the tank needs to come out of service.
Coupling a Solid Shaft to the Agitator
A solid output has to be joined to the agitator shaft, and on a vertical arrangement that joint sits inside the tank unless the drive is spaced off the cover. Spacer couplings, drop-out sections and a removable cover panel are the usual way to make the joint serviceable.
The joint also has to tolerate a small amount of misalignment without loading the gearbox bearings, which is what a flexible element in the coupling is for. A rigidly bolted flange on a fabricated tank top will bend the shaft every time the tank expands.
Chemicals That Fight Back
Ferric chloride is acidic and stains everything it touches. Lime slurry is alkaline and sets in any gap it can find. Polymer solutions grow a skin on every surface above the water line and turn that skin into a slippery film when the tank is washed out.
None of that reaches the gears, and all of it reaches the case, the fasteners and the seal area. A finish and a fastener grade chosen for the chemical actually in the tank cost almost nothing at order stage and save a repaint every second year.
Three Stages for a Propeller at Sixty
Dosing tank agitators turn at speeds from thirty to a hundred revolutions a minute, which is well below a four-pole motor and well above what a single helical mesh can reach in one step. Three stages land in that window with a compact case and no need for a belt drive.
Three stages also spread the load across three meshes, which keeps the gear teeth small and the noise low. In a dosing house beside an operator's desk, that last point is not a technicality.
Alignment Across a Coupled Shaft
A vertical drive with a solid output depends on alignment more than a hollow-bore unit does, because there is no bore to hold the shaft straight. The case must be set plumb, the coupling must be aligned in two planes, and the agitator shaft must run true in its own steady bearing.
Where the shaft is long enough to need a steady, the steady belongs to the tank and the alignment belongs to the fitter. A drive asked to hold a shaft that its own steady is fighting will fail a bearing and be blamed for it.
Oil Level in a Case Bolted to a Tank Top
The oil level in an upright case is read at the working attitude, and the working attitude on a tank top is rarely perfectly level. A cover plate that slopes two degrees for drainage is enough to move the level line at the sight glass.
The practical answer is to level the pad under the case, not the whole cover, and to check the level after the tank has been filled and the structure has taken its load. Checking on an empty tank gives a reading the plant will not see again.
Splash, Wash Water and the Seal
Dosing houses get hosed down, and the hose does not discriminate between the floor and the drive. An output seal that sits below the top of the tank wall will be asked to keep wash water out of a bearing housing several times a week.
A raised mounting, a slinger disc on the shaft and a lip seal protected by a labyrinth are the three cheap defences. The expensive defence is renewing a bearing that has been running in emulsified oil for a year.
Sizing on Viscosity, Not on Volume
A tank of water is easy to stir; a tank of five percent polymer solution is not, and the difference is not in the volume. The selection has to be made on the viscosity the agitator actually meets, at the concentration the plant actually doses.
Where the tank is used at several strengths, the enquiry should give the highest viscosity and the impeller that runs in it. Sizing on the dilute case and hoping is how a drive ends up tripping on the one day the batch is made strong.
The Enquiry List for a Dosing Package
A complete enquiry carries the tank diameter and depth, the chemical and its concentration range, the viscosity at the strongest batch, the agitator type and diameter, the output speed wanted, the shaft length, and the structural member available for the torque arm.
It should also say how the drive will be reached for maintenance, because a unit bolted to a cover under a pipe run can be perfectly sized and completely unserviceable.
Frame Two in the Chemical House
The second frame of the vertical band covers small and mid-size dissolving tanks, the sort that stand in pairs beside a dosing skid and run whenever the plant is making treated water.
Fitted with a torque arm on a real member and a coupling that can be reached, it does its job without a baseplate, without floor drilling and without a place on the plant's list of recurring problems.
Powders dissolved into water at a strength that has to repeat every batch:
- Polymer make-up tank agitator at a water treatment works
- Coagulant dosing tank mixer at a surface water plant
- Lime slurry dissolving tank agitator at a waterworks
- Ferric chloride dosing tank mixer at a treatment plant
- Activated carbon slurry tank agitator at a potable plant
- Antiscalant make-up tank mixer at a desalination plant
Full Frame Range of the M3 Series
| Model | Centre distance | Output | Typical duty |
|---|
| M3PSF50 | size 50 | solid shaft, foot | conveyors, feeders |
| M3PSF60 | size 60 | solid shaft, foot | crushers, mixers |
| M3PSF70 | size 70 | solid shaft, foot | ball mills, shredders |
| M3PSF80 | size 80 | solid shaft, foot | kilns, heavy conveyors |
| M3PSF90 | size 90 | solid shaft, foot | mill and kiln drives |
| M3RSF50 | size 50 | solid shaft, foot, right-angle | inclined conveyors, elevators |
| M3RSF60 | size 60 | solid shaft, foot, right-angle | screw classifiers, feeders |
| M3RHF70 | size 70 | hollow shaft, foot, right-angle | agitators, drum drives |
| M3PHT80 | size 80 | hollow shaft, torque arm, parallel | shaft-mounted conveyors |
| M3RHT90 | size 90 | hollow shaft, torque arm, right-angle | heavy shaft-mounted drives |
Every frame in the table can be ordered with alternative shaft and mounting styles. If you are matching an existing installation, send the nameplate details and we confirm the equivalent frame in writing.
Installation Snapshots
Lime kiln auxiliary drive
A lime producer fits a smaller industrial gear unit as the auxiliary drive of its rotary kiln. Turning the kiln slowly during shutdowns and start-ups is exactly the low-speed, high-torque duty the frame was chosen for.
Tunnel boring backup drive
A tunnelling contractor uses industrial gear units on the backup gantry conveyors of its TBM. The units arrived dimensionally matched to the gantry interfaces, so installation took hours rather than days.
Selection Example: Polymer make-up tank agitator at a water treatment works
Take a 2.2 kW motor at 1440 rpm turning the propeller at 60 rpm. The ratio follows directly: 1440 / 60 = 24, so a ratio near i=24 comes from the three-stage vertical band, and the frame is sized on the viscosity of the strongest batch the plant makes rather than on the dilute mix it normally doses. In this case frame two hangs from a torque arm bolted to a structural member instead of a baseplate, drives the agitator through a keyed solid output and a spacer coupling that can be inspected under the cover, and keeps the tank top free of drilled holes. Use the same method for any frame in the series, then confirm the service factor with us - it is the one number buyers most often get wrong.
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The selection path we follow when checking your enquiry.
Technical Q&A
How is the unit protected against dust and water ingress?
Housings are sealed to IP55 as standard with NAK oil seals and gasketed covers. Heavy dust, washdown chemicals or steam cleaning call for the higher protection option, which we specify together with the correct lubricant.
Do you support commissioning and after-sales service?
Every shipment includes an installation manual and a test record. Our engineers answer commissioning questions by e-mail or video call, and spare seals, bearings and shafts remain traceable to your original order for years afterwards.
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Typical installation environments for this gearbox family.
OEM Framework Pricing and Reserved Capacity
Building machines in series? One screen in the WGT Motor & Gearbox Online Selection System is usually enough to pin down the frame size; we confirm the service factor afterwards.
For OEM programmes we hold framework prices and reserve production slots for scheduled call-offs, so your line never waits on a gearbox. Ask for the framework terms with your first enquiry. Looking for a reducer for woodworking machine? Tell us the duty point and we will confirm the model in writing.
