Most gearbox failures in the first year are not gear failures - they are installation failures that a proper commissioning routine would have caught in an afternoon. A drive filled to the wrong plug, a guard fouling a torque arm, a coupling aligned by eye: each runs quietly for weeks and then presents its bill at a time nobody chose. The gearbox commissioning checklist below exists to move those discoveries from month eight to hour one.

It is written for the person standing in front of the drive, not the designer. Every line is checkable with hand tools, a thermometer and a notebook, and the whole routine costs less than one unplanned stop.

Before First Fill: Checks at the Bench and on the Job

Commissioning starts before the unit is even put to work. Open the crate and compare the nameplate against the order: frame size, ratio, mounting arrangement and shaft diameters. A ratio mismatch discovered here is a phone call; discovered after the coupling is fitted, it is a shutdown. Check the case for transit damage, turn the input shaft by hand where the design allows, and confirm the breather, plugs and any accessories ordered with the unit are actually fitted.

On the machine, verify the mounting interface before the case goes on. For a footed unit that means the bedplate is level, grouted and free of soft foot; for a flanged unit, that the machine face is clean, undamaged and flat; for a shaft-mounted drive, that the driven shaft measures to drawing, the keyway is burr-free and there is enough plain shaft beyond the bore for retention and, ideally, for withdrawal later. Every one of these is far cheaper to correct before the gearbox is hung than after.

The Gearbox Commissioning Checklist at a Glance

Print it, laminate it, and let the fitters tick it. The checklist is deliberately short: each line is either a ten-second look or a ten-minute job, and every line has a failure story behind it somewhere.

Filling Oil to the Right Plug, Not the Nearest One

The single most common commissioning error on industrial gear units is filling against the wrong level plug. A hung case - shaft-mounted builds, vertical or angled installations - may sit at an attitude the workshop never saw, and the plug that read correct on the bench reads wrong in the air. Fill to the plug that corresponds to the installed attitude, with the breather at the high point, and write both facts on the commissioning sheet.

Use the grade specified on the drawing, from sealed containers, and resist the shelf of part-drums: incompatible oils mixed in a sump is a slow problem that appears as premature bearing wear long after anyone connects the two. Check the level again after the first loaded hours - oil finds its way into every gallery, and a level that was correct at standstill can read low once the mesh has taken its share.

Rotation, First Starts and the No-Load Run

Confirm rotation direction before the coupling goes on or the case goes over the shaft. A reversed rotation on a machine with a holdback or a pump of any kind is not a small mistake; it is a destroyed backstop and a flooded inlet, in the worst case within seconds of the start. Motor phasing is a two-minute check that protects hardware worth weeks of lead time.

With rotation proven and guards fitted, give the drive its no-load run: start, watch, listen, and stop. You are feeling for rubs at the guard, knocks that follow a rhythm rather than the load, and leaks that only show when the case is pressurised by its own running. Then apply load gradually if the process allows. A drive that has run free for a few minutes and taken load in steps enters its working life with its worst installation surprises already behind it.

Shaft-Mounted Drives: the Extra Commissioning Lines

Shaft-mounted builds compress the checklist rather than shortening it. There is no coupling to align and no bedplate to grout, but the bore, the key and the torque arm now do all of the work a foundation used to do, and each deserves its own tick. The bore should seat fully along the shaft, the key should fill its keyway without rock, and the retaining hardware should be torqued to figure rather than to feel.

The torque arm is the item most often left half-done. Its bushings belong at mid-travel with the machine at rest, so the shaft's small movement under load has room in both directions; its bracket bolts belong torqued and re-checked after the first loaded weeks; and its guard must clear the arm through its whole sweep. Our MC2PLHT07 torque arm gearbox page shows the arrangement and the installation sequence in full - worth ten minutes before the first hang if the crew is new to the build.

One line more: after the first loaded hours, look at the bore mouth. A fine rust-coloured dust there is fretting, and at commissioning time it almost always means a fit or a bolt that is not as tight as the sheet claims. Caught in week one it is an afternoon; caught in year two it is a shaft repair.

The Records That Turn a Start Into a Baseline

Commissioning is not finished when the drive runs - it is finished when the drive has a written baseline. Three numbers, taken on a schedule, do most of the work: case temperature at a fixed point after the first shift, again at a day and at a week; oil level with every top-up noted; and noise described in words at the usual load, because words date better than memory.

Those pages become the reference for everything that follows. A rising temperature trend against a flat baseline is a breather, an oil grade or an airflow problem - all cheap. The same trend without a baseline is an argument. And when the drive is eventually stripped years from now, the commissioning record is what tells the workshop whether it ran its whole life well or carried a hidden fault from day one.

Frequently Asked Questions

How long should a new gearbox run before full load?
There is no break-in ritual demanded by modern industrial gear units - the oil film protects the mesh from the first turn. What matters is stepping the load up where the process allows, and using those first loaded hours to watch temperature, level and noise rather than to impose a fixed number of free-running hours.

What oil level should I expect to hold in the first weeks?
A small drop after the first loaded running is normal as the mesh and galleries take their share; a repeated need for top-up is not, and points at a leak or a level plug mistake. Record every top-up on the commissioning sheet - the record is what distinguishes a settling level from a sealing problem.

Do I need to re-torque anything after the first run?
Yes - anything that clamps. Foot bolts and bracket bolts settle, flange bolts relax a little as faces bed in, and on shaft-mounted drives the torque-arm bracket in particular deserves a re-torque to figure after the first loaded weeks. It is ten minutes with a wrench against a loosened joint running a machine.

When should the first oil change be done?
Follow the maker's interval, which for new units usually calls for an early first change to remove the running-in debris the mesh sheds in its first weeks. Take a sample at that change and keep it: the first sample is the baseline every later oil analysis will be read against.

The Bottom Line

A gearbox commissioning checklist is not paperwork - it is the cheapest inspection the drive will ever receive, performed at the moment when every fault it finds is still an adjustment instead of a failure. Run the ten lines, write the three baseline numbers down, and the installation has done its part.

Before the order that starts all this, run the duty through the numbers: our online selection tool cross-checks ratio, torque and service factor against your machine, and our engineers confirm fill quantities, attitude and fittings in writing with every unit we supply.