Conveyor Bearing

A conveyor bearing supports a pulley or roller shaft so the belt runs straight and the drive power reaches the belt without losses. A belt conveyor uses three kinds: pillow block units on the head and drive pulleys, take-up units on the tail pulley, and small sealed deep groove ball bearings inside every idler roller. On light and medium conveyors the pulley bearings are almost always UCP pillow blocks and UCT take-up units with UC inserts. This page shows where each bearing sits, the pillow block sizes by shaft diameter, how take-ups work, why units fail, and what we check before a mounted unit leaves the factory.

Where the bearings sit on a belt conveyor

Position	What it does	Usual bearing
Head / drive pulley	Drives the belt; carries belt pull from both sides plus drive torque	UCP pillow block units, or spherical roller bearings in plummer blocks on heavy conveyors
Tail pulley	Returns the belt; sets belt tension	UCT take-up units in a screw frame
Snub and bend pulleys	Increase wrap on the drive pulley or change belt direction	UCP or UCF units
Carrying idlers	Support the loaded belt, usually in troughed sets of three	6204, 6205, 6305, 6306 2RS inside each roller
Return idlers	Support the empty belt underneath	Same sizes as the carrying idlers

The drive pulley carries the highest load: the tight-side and slack-side belt tension both pull on its shaft, and the gearbox or chain drive adds its own load. It usually gets bigger units than the other pulleys. Belt-driven fans use the same UCP units on their shafts; see the fan and blower bearing page.

Pillow block units for conveyor head and drive pulleys

A UCP unit is a UC insert bearing in a cast iron pillow block housing. The insert has a spherical outside diameter that sits in a matching spherical bore in the housing, so it lines up with the shaft even when the frame is slightly out of true. The insert is locked to the shaft with two set screws on an extended inner ring. A grease nipple in the housing lets you re-grease the insert.

The table lists the pillow block bearing sizes used on most light and medium conveyors. H is the shaft centre height from the base and J is the bolt spacing centre to centre.

Shaft d (mm)	Unit	H (mm)	J (mm)	Bolt
20	UCP204	33.3	95	M10
25	UCP205	36.5	105	M10
30	UCP206	42.9	121	M14
35	UCP207	47.6	127	M14
40	UCP208	49.2	137	M14
45	UCP209	54	146	M14
50	UCP210	57.2	159	M16
55	UCP211	63.5	171	M16
60	UCP212	69.8	184	M16

UCP204 bolt spacing follows JIS; ISO 3228 housings of this size use 96 mm. Housing dimensions such as bolt spacing can differ between the JIS and ISO versions of the same designation, so compare J against your frame before ordering. The UCP 200 series size chart adds base length and other dimensions.

Shafts in inch sizes take inch-bore inserts with the same housings; the bore is given in sixteenths after the dash, so UCP208-24 is a 1-1/2 in shaft. The inch bore pillow block page lists them. Where the pulley shaft passes through a vertical frame plate, flange bearing units such as UCF and UCFL do the same job as a pillow block.

A complete unit or the insert on its own can be quoted. If you need the housing on its own, ask us and we will confirm whether we can supply it. If only the insert is worn and the housing seat is undamaged, the UC208 insert bearing and its neighbours can be replaced without unbolting the housing from the frame.

Take-up units on the tail pulley

The tail pulley usually runs in two UCT take-up bearing units, one each side. Each housing has slots that run on a frame, and an adjusting screw pushes the housing back to tighten the belt. As the belt stretches in service, the take-up is set again at regular checks. A belt that runs slack slips on the drive pulley and wears faster.

The travel available is the length of the frame slot minus the length of the housing. Check that the frame leaves room for the belt stretch you expect over the life of the belt. Adjust both sides by the same amount. If one side moves more than the other, the pulley sits at an angle and the belt tracks to one side.

Sizes such as the UCT206 (30 mm shaft) and UCT210 (50 mm shaft) use the same UC insert as the pillow block of the same number, so one spare insert can cover both ends of a conveyor with the same shaft size.

Idler roller bearings

Every idler roller has a deep groove ball bearing pressed into each end cap. The common sizes are the 6204 bearing, 6205 bearing, 6305 bearing and 6306 bearing, chosen by roller diameter and belt load. They are 2RS sealed and leave the factory greased. The roller end cap adds a labyrinth seal in front of the bearing to keep out dust and water.

A conveyor has hundreds of idler bearings, and roller makers buy them in large numbers to the same specification. Their clearance class matters: some roller designs need a specific clearance to suit the shaft and end cap fit. State it in the order, and check the clearance marked on the bearings you are replacing.

Heavy conveyors: spherical roller bearings

On mining, quarry and port conveyors the pulley loads are too high for UC inserts. These pulleys usually run on spherical roller bearings, often 22200 or 22300 series on adapter sleeves, in split plummer block housings. The bearing tolerates shaft deflection and some misalignment, and the split housing allows it to be changed without pulling the pulley. FULI supplies the bearings. We also supply split plummer block housings (SN / SNL style); send the designation and we will confirm the details with the quote.

Why conveyor bearings fail

With set-screw units, the failure usually starts at the set screws. If they are not tightened to the correct torque, or they loosen under vibration, the inner ring is no longer held on the shaft. It creeps, wears the shaft and its own bore, heats up and finally the bearing seizes or the shaft is scored. Tighten both screws to the torque the manufacturer gives, and check them again after the first days of running.

Other common causes:

1. Misalignment between the two units on a pulley. The spherical seat absorbs small errors, but a frame that is twisted or a unit bolted on an uneven surface loads the insert from the side.
2. Over-tensioned belt. Too much take-up tension loads every pulley bearing. Set tension to what the belt needs to drive without slipping, and no higher.
3. Grease. Too little and the insert runs dry. Pumping too much into a sealed insert can push the seal out. Grease little and often. The bearing grease fill calculator helps estimate quantities.
4. Material build-up. Spilled material packed around the housing traps heat and grinds at the seals.

What we check on mounted units before shipment

Because set screws and housing fit decide how a mounted unit performs in service, our factory checks four things on mounted units before they ship:

1. The tightening torque needed when the housing is installed.
2. The fit between the insert bearing and the housing.
3. The consistency of the base-to-centre height, so units installed in a batch sit at the same height.
4. The internal clearance of the insert bearing.

If the pulley runs hot, for example near a dryer or kiln, state the clearance you need in the order, for example C3.

How to order conveyor bearings

1. The full unit designation, for example UCP208 or UCT210, or the insert and housing numbers separately.
2. The shaft diameter, metric or inch.
3. Bolt spacing J and centre height H if you are replacing existing units.
4. Complete units or inserts only. If you need housings on their own, say so and we will confirm whether we can supply them.
5. For idler bearings, the size, seal and clearance.
6. Quantities per item, and any marking or box requirement: your authorized brand, the factory brand or neutral.

Send the list to sales@fuli-bearings.com or through the contact page; the quotation request template shows the format. An inspection report can cover dimensions, radial clearance, rotation noise, vibration, appearance, material certificate and batch traceability. Export documents are the commercial invoice, packing list and CCPIT certificate of origin, plus an FTA Form COO where the destination country qualifies.

Backed by 20+ years of bearing export experience in Linqing, Shandong. FULI ships to 50+ countries & regions.