There is a point on every vertical line where the tank stops being a vessel and becomes a civil structure with a roof. For this family it arrives around the sixth frame. The MC2PVSF06 vertical parallel shaft gearbox carries the two helical stages in one plane, the footed case standing on the rim, and the solid output shaft aimed downward - all of it familiar from the smaller frames - but sized for tanks where the drive specification arrives with a structural drawing attached.
What changes at this frame is not the principle but the paperwork. A plant buying frame two sends a torque figure; a plant buying frame six sends a plate thickness, a nozzle layout and a maintenance access plan. That difference is a good sign, because a drive this size fails for structural reasons far more often than for gear reasons.
Where the Sixth Frame Sits in the Vertical Band
The family's vertical line runs in single-number steps, each frame adding capacity without changing the footprint logic. The sixth is the point where the increase stops being a convenience and starts being a commitment: the case is wide enough that the plate under it needs its own load path to the bridge beams, and the shaft is long enough that its critical speed becomes a line in the specification rather than a footnote.
Plants arrive here from two directions. Some are exchanging a smaller vertical drive that has run out of margin after a process change; others are building a bigger vessel and skipping the intermediate sizes because the project only gets one shutdown window. Both groups want the same thing from the enquiry - a number they can give the fabricator on the same day.
Reading the Sixth-Frame Designation
The type string is a sentence once you know the words. Nothing about the construction hides in it; the only variable is the two-character frame field.
| MC | Industrial multi-stage gear unit family |
| C2 | Compact two-stage parallel-shaft series |
| P | Parallel stages - both shafts in one horizontal plane |
| V | Vertical build, output flanged facing down |
| S | Solid output shaft for a coupled connection |
| F | Foot mounting on a bridge, top plate or nozzle flange |
| 06 | Sixth frame of the vertical line |
Reading it backwards is how commissioning engineers check a delivery: the frame number sets the mounting drawing, the S tells them to expect a coupling register rather than a bore, the V tells them which way up the case goes and the P tells them what is inside. A unit that arrives with the wrong last character is a unit that has to go back, and the error usually traces to a quote written from a telephone call.
The Shaft Length Is a Transmission Line
At this frame the output shaft behaves less like a component and more like a transmission line. The driven element hangs at the end of it, the liquid pushes back at every pass, and both travel upward as bending and as vibration. Two numbers in the enquiry control the outcome: the unsupported length between the gearbox bearing and the driven element, and the mass and diameter of that element. Change either and a frame that ran quietly at another site will not run quietly here.
Suppliers who ask for the shaft drawing are not being awkward. They are checking the whirling speed of the assembly, the bending stress at the first bearing, and whether the coupling at mid-height should be spacer type so the seal can be reached without unbolting the unit. A twenty-minute upload at the enquiry stage buys a machine that does not need a vibration study later.
Bridge Structures and the Sixth-Frame Load Case
On a tank this size the bridge is not a platform that happens to carry a gearbox; it is the gearbox's foundation, and it deserves to be analysed as one. Three load cases matter: the running torque reaction, the bending moment delivered through the shaft, and the accidental case where a solid object stops the driven element before the drive electronics notice.
The practical consequence for the project file is a single page handed from the gearbox supplier to the fabricator at quotation time: reaction torque at the feet, unit mass, bolt pattern and the shaft's bending load. Fabricators who build from that page produce bridges that do not hum. Fabricators who build from an outline drawing scaled off a photograph produce bridges that become the subject of a meeting six months after start-up.
Duties Where Frame Six Is the Natural Choice
Frame six is specified where the vessel becomes a structure:
- Lime slurry agitator drives at a water treatment works
- Thickener feed well mixers at an iron ore beneficiation plant
- Digester agitators at a paper mill's pulping line
- Starch jet cooker vessel drives at a glucose plant
- Reagent mixing tank agitators at a base metals concentrator
- Brine saturator agitators at a chlor-alkali facility
Each of these shares one property: the process cannot pause for the drive to be inspected, because the tank contents would set, settle or degrade. That is the real argument for the vertical habit at this size - not that it is stronger than a horizontal arrangement, but that every check and every service happens above the liquid line while the vessel stays full.
Starting a Large Vertical Train Without Drama
A big paddle starting in a settled vessel draws far more torque than the nameplate suggests, and the whole installation feels it: motor current, coupling, shaft, plate, bridge. The way to keep the start quiet is to describe it honestly. Soft starter, variable frequency drive, part-wound motor, or a process interlock that guarantees the vessel is stirred before it is filled - each produces a different torque trace, and the selection engineer needs to know which one applies.
Where the answer is variable speed, frame six earns a second benefit: the drive can be run slow during settled starts and returned to duty speed once the liquid is moving, which turns a shock load into a ramp. Where the answer is a direct-on-line start, the service factor needs to carry the whole shock, and the honest way to say so is to put the worst observed start torque into the enquiry in words as well as numbers.
Oil Management on a Wide, Upright Case
Wide cases standing on end need deliberate oil routing. The factory fits galleries and dams to carry lubricant to the upper bearings that gravity would otherwise starve, and the level glass is calibrated for an upright case on a level plate. Two degrees of tilt at the plate is enough to move oil where the design did not intend it to go.
The maintenance routine for a case this wide is short but must be exact: check level at the glass with the unit stopped and settled, read temperature at the marked patch, confirm the breather is clear, and look at the seal area dry before and after the shift. Oil volume at this frame is large enough that a slow leak takes weeks to show as a level drop - so log the glass reading instead of remembering it.
Cooling the Case in an Enclosed Hall
Vessels this large usually live indoors or under a roof, and roofs trap heat. The drive sits in the warm layer above the tank, and a summer afternoon pushes that layer several degrees above whatever the weather station reported. The rating conversation therefore belongs in degrees measured at the drive's own elevation, over a working week, in the season the plant will actually run hardest.
A thermometer hung on the bridge for a week in July costs almost nothing and settles arguments that otherwise surface during the first heatwave. Where the trace comes back close to the limit, the answers are ordinary - a fan guard cleared of lint, a louvre opened, a cooling coil fitted at order time rather than retrofitted later. What is not ordinary is learning the ceiling from a product that has started drifting off specification.
What the Oil Sample Says Before the Noise Does
A gearbox of this size holds enough oil to tell a story months before a bearing does. Samples drawn on a fixed interval - quarterly, always from the same point, always hot after running - build a trend, and the trend is what carries meaning: iron rising steadily, silicon appearing after a breather fault, water climbing after a steam hose was left too close.
Single samples judged in isolation mislead everyone. A number with no history is a conversation, not a diagnosis. Plants that keep four consecutive reports know exactly when to schedule a bearing inspection; plants that sample once a decade discover wear through the noise, and by then the repair belongs to a shutdown they did not plan.
Commissioning Checks That Prevent Future Meetings
Commissioning a sixth-frame vertical drive is a two-hour job done properly and a two-year problem done quickly. The sequence that works: verify the plate is level and clean, set the unit down and torque the feet in a star pattern, take coupling alignment in two planes, bump the motor to watch shaft runout at the driven element, then run up slowly with one person at the bridge and one at the vessel.
Record everything taken that day - alignment figures, running current, temperature after two hours, vibration velocity in three directions. Those readings are the baseline every later trend is compared against, and on a machine that will outlive its installation crew they are the only reliable witness to what changed.
What to Send With the Enquiry
An enquiry that closes without a second round contains: vessel diameter and depth; driven element type, diameter and mass; shaft length from plate to element; thrust arrangement; motor power, speed and starting method; required output speed and its tolerance; duty hours and batch pattern; atmosphere above the liquid; and the plate drawing with bolt pattern and thickness.
Send those and the response is a firm quotation with an outline drawing, a drilling template and a date the shutdown can be planned around. Frame six is not a difficult machine to buy - it is a machine that punishes an incomplete brief, because at this size nothing in the installation is small enough to be improvised.
Selection Example: Digester agitator drive at a paper mill pulping line
Take a 37 kW motor at 1470 rpm turning the digester agitator at 32 rpm. The ratio follows directly: 1470 / 32 = 45.9, so a ratio near i=46 is drawn from the two-stage band, and the frame is checked against the bending a long impeller shaft delivers to the top bearing rather than against torque alone. In this case the vertical build stands on the digester roof plate, and the solid output shaft is coupled below a spacer coupling so the shaft seal can be opened while the vessel stays full and hot. That is the whole calculation. If your duty involves heavy starting, frequent reversing or many stops per hour, tell us and we raise the service factor.
Which Frame Size Do You Need?
| 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 |
Foot-mounted frames are listed below; torque-arm (T), hollow-shaft (H) and vertical (V) variants are available across the size range. Ask for the outline drawing to check the interface before ordering.
Answers to Common Questions
Can this unit mount on my existing installation without redesign?
Yes - the series is manufactured to the same centre distances, shafts and flange dimensions of the common industry frames, so couplings, guards and foundations stay untouched.
Which lubricating oil should be used?
GB L-CKC220~460 or Shell Omala 220~460 as supplied. Under normal duty the housing is lubricated for life; in hot or continuous-duty environments an oil change after the first 400 hours and then every 4000 hours is recommended.
What warranty and documentation come with the gearbox?
A one-year warranty covers material and workmanship. Each unit ships with a test record (noise, temperature rise, backlash), a dimension drawing and an installation manual.
![gearbox sizing steps for engineers]()
Four steps from your application data to a firm model number.
Case Notes from the Field
Dust-extraction fan bank
An environmental-equipment plant uses reducers on the rotary valve feeders of its dust-extraction systems. Compact size, quiet running and food-grade oil options made the approval easy.
Steel mill run-out table
On the run-out table of a small steel mill, units handle the repeated starts and stops of hot billet handling. The 42CrMo output shafts tolerate the thermal cycling, and torque-arm mounting keeps the drive clear of the roller frames.
![industrial gear unit application overview]()
A cross-section of the installations we supply every month.
Framework Stock for Critical Spares
Can your plant afford downtime? Try the WGT Motor & Gearbox Online Selection System, then send the result sheet - we return a complete datasheet, drawing and price the same day.
For critical drives we can hold finished units or long-lead internals against a framework agreement, ready to dispatch when your shutdown starts. Ask for the spares-coverage proposal. Looking for a gearbox for belt conveyor? Tell us the duty point and we will confirm the model in writing.
