Gear Reducer Maintenance: Oil, Mounting Position and Checks

Gear reducer maintenance on our units comes down to four things our catalogues actually specify: keeping the oil at the level the unit's mounting position was built for, using the breather, sight glass or dipstick the housing already gives you, keeping the unit inside the thermal capacity its cooling arrangement allows, and respecting a short list of per-series rules that are easy to break during installation. This guide covers each of those from the gear reducer catalogue data, and is explicit about the things our catalogues do not publish — oil grades, change intervals and fill volumes — so that nobody on a plant floor has to guess them. It is written for the engineer who already owns the unit; if you are still choosing one, start with the gear reducer selection guide.

Key definitions

• Mounting position: the orientation a unit is installed in. It is part of the order, not a site decision.
• Breather (breather cap or plug): the vent that lets the housing equalise pressure as the oil heats. Every series has one, and its position changes with the mounting position.
• Oil sight glass / oil dipstick: how you read the level without opening the unit. R, F, K and S units carry a sight glass; ZDY and DBY units carry a dipstick.
• Drain plug: the lowest point for the mounting position the unit was built in.
• Dip (oil-bath, splash) lubrication: the gears run through a bath and carry oil with them. Standard on P, horizontal H/B, and ZDY/DBY.
• Forced lubrication: oil is pumped to the mesh. Used on vertical H/B units and available on request for P.
• Thermal capacity (PG1, PG2): the power a unit can run at continuously without overheating, tabulated by size, cooling arrangement and surroundings.
• Oil supply factor f9: a factor in the H/B selection, 1.0 for horizontal units and 1.05 with forced lubrication.
• ED duty cycle: the proportion of a reference period a unit may run. On SWL jacks the limit is 20% over a 30-minute cycle.
• Service factors f1, f2, f3: the driven-machine, prime-mover and starting factors applied to required torque, because the catalogue ratings assume steady load, a stated daily running time and a limited number of starts.

The mounting position is a maintenance fact

Our catalogues treat the mounting position as part of the type designation, and the reason is maintenance rather than drawing convention. The position fixes the oil fill and the physical location of the vent, the level indicator and the drain, and those are set at the factory.

Series	Position system	What the position fixes
R, F, K, S	M1, M2, M3, M4, M5, M6	Oil quantity, and the positions of the breather plug, oil sight glass and drain plug; also output-shaft side A, B or A+B and terminal box at 0, 90, 180 or 270 degrees
P	B500–B556 horizontal; V100–V130 vertical, output downward; V300–V330 vertical, output upward	Dip or forced lubrication, and whether a motor-driven oil pump is required
H / B	H horizontal, M horizontal without feet, V vertical	Dip lubrication horizontally, forced lubrication vertically; the f9 oil-supply factor, 1.0 or 1.05
ZDY / DBY	Four mounting arrangements, assembly designs I–IV	The oil-bath level and the dipstick reading
T	B3, B6, B7, B8, V5, V6	Which face carries the breather plug, given the shaft arrangement ordered
SWL	Structural type 1 or 2, assembly form A or B	Which way the screw or nut travels, and where the protective tube and dust shield go

The practical consequence is one sentence: a unit remounted on site in a position other than the one it was ordered in is no longer lubricated the way it was built. If a drive has to be re-oriented — a conveyor rebuilt, a mixer moved, a unit taken from the spares shelf for a different machine — the type designation on the nameplate tells you which position it was set up for, and we can tell you what the new position requires.

Lubrication, cooling and checks, series by series

Series	Lubricated with	Read the level at	Cooling available	Limits our data states
R, F, K, S	Oil, filled for the ordered mounting position	Oil sight glass; drain plug at the low point	None listed; housing is cast with bolted cover and gasket	Rated for steady load, a stated daily running time and limited starts; apply f1, f2, f3
P	Dip lubrication standard; forced lubrication on request	Breather cap and oil plug	Motor-driven oil pump required on larger vertical mountings	Thermal capacity PG1 21–437 kW in small confined spaces, 29–619 kW in large halls, 39–838 kW in the open (two-stage, horizontal)
H / B	Dip when horizontal, forced when vertical	Breather cap; lip oil seals on the shafts	Fan, cooling coil, or fan plus coil — each with its own table	Separate thermal tables for no cooling, fan, coil and fan-plus-coil; f9 = 1.0 horizontal, 1.05 forced
ZDY / DBY	Oil-bath (splash) lubrication	Oil dipstick	Fan, cooling coil or oil-pump circulation	PG1 13–1,020 kW without auxiliary cooling, by size 80–560 and ambient air velocity ≥0.5, ≥1.4 or ≥3.7 m/s; PG2 43–1,780 kW with coil or circulation
T	Oil, with a breather plug on the housing	Breather plug and end covers	None listed	Service factor 1.00–2.00 by load type and daily hours (≤2, 2–10, 10–24); bracketed values apply above 10 starts and stops per hour
SWL	Calcium-based grease ZGN-1 or ZGN-2, through the grease nipple	Grease nipple; dust shield or protective bellows	Not applicable	Grease −20 to 100 °C; indoor, no rain, −15 to 40 °C, below 85% relative humidity; 20% ED over a 30-minute cycle; input speed max 1,500 r/min

One construction note applies to all nine series and is worth knowing before anyone reaches for a brush: the external finish is a three-layer high-density polymer paint that seals out dust and tolerates high temperature. It is part of how the unit keeps dirt out of the seals, so treat damage to it as something to repair rather than ignore. The gears inside are precision-ground alloy steel and the bearings high-grade ball bearings; on H/B and ZDY the teeth are carburised and quenched. The grinding, hobbing and inspection equipment behind that is on our production capacity page.

Nine checks, in the order to do them

1. Match the nameplate to the installation. Read the type designation and confirm the mounting position code is the position the unit is actually bolted in. This is the check that catches the most expensive mistake and takes the least time.
2. Read the level with the unit stopped and cool. Use the sight glass on R, F, K and S units and the dipstick on ZDY and DBY units. A reading taken while the gears are turning is not the level.
3. Check the breather is clear. A blocked vent pressurises the housing as the oil warms and pushes oil past the lip seals, which then reads as a seal fault rather than a vent fault.
4. Look at the output-shaft seal and the drain plug. Flat and lip (skeleton) oil seals on the output side and the drain plug at the low point are where loss shows first.
5. Confirm the cooling aids are actually running. If the unit was selected with a fan, a cooling coil or an oil pump, it was selected against that table and not the bare one. A stopped fan or an isolated coil silently moves the unit onto a lower rating.
6. Re-run the thermal check against the room, not the drawing. See below.
7. On K series units, confirm the direction of rotation. The spiral-bevel sets bear load in one direction only and the rotation direction, viewed from the output shaft, is stated at order. Reversing a K series drive after installation is an engineering change, not a wiring change.
8. On SWL jacks, grease and check the duty. See below.
9. Record the full type designation in the maintenance file. It is what we need to supply a spare, and it is on the unit rather than in anyone's memory.

Thermal capacity: the room changes the rating

The thermal figures in our catalogues are not single numbers per frame size. They depend on the surroundings, and that makes thermal balance a commissioning and re-commissioning check rather than only a design one.

• P series, two-stage horizontal: PG1 is 21–437 kW in small confined spaces, 29–619 kW in large halls and 39–838 kW in the open. The same unit is rated roughly twice as high outdoors as in a tight room.
• ZDY series: PG1 without auxiliary cooling is 13–1,020 kW depending on frame size 80 to 560 and on the ambient air velocity, tabulated at ≥0.5, ≥1.4 and ≥3.7 m/s. With a cooling coil or oil circulation, PG2 reaches 43–1,780 kW.
• H/B series: there are four separate tables — no auxiliary cooling, fan, cooling coil, and fan plus coil — and the f9 oil-supply factor is 1.0 horizontally against 1.05 with forced lubrication.

So a unit that was correctly selected and then boxed into a cabinet, walled into a pit, or had its airflow blocked by later plant has been moved onto a different line of the same table. If a reducer runs hot without anything inside it having changed, this is the first thing to check, and it is usually cheaper to restore the airflow than to add cooling. A worked example of a thermal check inside a full selection sits in the conveyor gearbox selection guide.

SWL screw jacks: grease, duty and environment

The SWL worm-bolt lifter is maintained differently from every other series because it is greased, intermittent and often outdoors in practice when it should not be.

• Grease, not oil: calcium-based ZGN-1 or ZGN-2, rated −20 to 100 °C, through the grease nipple.
• Environment: indoors, free of rain, −15 to 40 °C, relative humidity below 85%, normal factory dust. In dusty or outdoor locations specify the dust shield or the protective bellows — the Z protective tube and F anti-rotation device are catalogue options, not site fabrications.
• Duty: maximum 20% ED calculated over a 30-minute cycle, input speed no more than 1,500 r/min, and starting torque up to 200% of running torque. A jack that is cycling more than its ED rating is being overworked even though nothing on it is overloaded.
• Several jacks on one drive: the linkage factor derates each one — 1.0 for a single jack, 0.95 for two, 0.9 for three, 0.85 for four and 0.8 for five to eight. If jacks have been added to an existing lifting table, the original selection no longer holds. The screw jack selection guide runs that calculation in full.
• Efficiency is low by design: 13–23% on the normal (P) worm ratio and 8–13% on the slow (M) ratio. A jack that feels inefficient is behaving as specified; most of the input is paying for the self-locking that holds the load when it stops.

A related point, because it is the single most common wrong assumption about worm gearing: self-locking is claimed for the SWL jack and not for the S series reducer. Any drive that has to hold a load when power is lost needs a brake motor or a mechanical holding device, as the worm gear reducer guide sets out.

What our catalogues do not specify

Being exact about this is part of the job. Our data gives mounting positions, lubrication methods, cooling options, thermal tables, duty limits, grease types, service factors and the location of every plug and sight glass. It does not give:

• oil grades or viscosities for any oil-lubricated series;
• oil-change intervals, first-fill or re-fill intervals;
• oil fill volumes in litres per frame size and position;
• tightening torques for housing, cover or foot fasteners;
• bearing replacement intervals or calculated bearing life.

None of those are printed in the series catalogues, so none of them appear above. Send us the type designation and the Reducer Sales and After-sales & Spare Parts departments will confirm them from the master tables for your frame size and mounting position. A supplier who answers an oil question without asking which frame and which position has not looked it up.

Our recommendation

Treat the nameplate as the maintenance document. The type designation records the mounting position the oil fill was set for, the frame size the thermal table applies to, the mounting structure the seals belong to and, on motorised units, the motor power and pole count — which is everything needed to check whether the unit is still installed the way it was selected. Do the four checks that cost nothing first: position against nameplate, level at the sight glass or dipstick, breather clear, and cooling aids actually running. Re-run the thermal check whenever the plant around the unit changes, not only when the unit does.

Then ask for the figures our catalogues leave out rather than assuming them. Send the type designation, the mounting position as installed, the daily running hours, the starts per hour and the ambient conditions through the enquiry form, and we will return the oil specification and quantity, the applicable thermal figure and the spare-parts list for that unit. Yanfeng Group Co., Ltd. has built reducers and plastic weaving machinery in Wuyang Industrial Zone, Pingyang, Wenzhou since 1987; office hours are Monday to Saturday 08:00-17:30 and Sunday 09:00-17:30, China Standard Time (UTC+8).