Chain Bucket Conveyor: Structure, Installation, Commissioning and Maintenance

A chain bucket conveyor carries material in steel buckets that are bolted directly to two parallel strands of roller chain. The chain runs on tracks inside a structural frame, the drive at the head pulls the loaded buckets up an incline, and the buckets tip and discharge into a chute at the top. Because the buckets are rigid and the chain is the only traction element, this machine handles abrasive, hot, lumpy and wet material at angles where a belt conveyor would need a very wide belt, a steep cleat profile or simply cannot hold the load. This guide covers the DS chain bucket conveyor from the inside out: how it works, its five subassemblies, how it is erected and aligned, the tolerances that decide whether the chain runs for years or wears out in months, how the running part is installed and tensioned, the no-load and load trials, and the lubrication and wear-part regime after handover. It is based on the Tianyi chain bucket conveyor training manual used by our service engineers on site. For the equipment range itself, see our chain conveyor page.

1. What a Chain Bucket Conveyor Is and How It Works

A DS chain bucket conveyor is a continuous bulk-handling machine in which a series of steel buckets is fixed to two endless strands of roller chain. The chains run in upper and lower tracks supported by a steel frame; the buckets travel between the two strands, open side up on the carrying run. Material enters through an inlet at the loading point, falls into the passing buckets, and is carried along the track to the head, where the chain wraps around the head wheel and the buckets turn over, discharging the material into a chute.

The working principle is simple, and that is exactly why the installation matters so much:

• There is no belt to train. Tracking is controlled by the chain, the sprockets and the track gauge — not by idler angles.
• The buckets are the carrying surface. A bucket that fouls the frame, the track or a neighbouring bucket cannot be fixed by adjusting tension; the geometry has to be right.
• The chain does two jobs at once. It carries the tensile load and it positions every bucket. Any misalignment shows up first as uneven bucket clearance, then as wear on the chain, the rollers and the sprocket teeth.
• Discharge is by gravity. The head wheel diameter, the chain path over it and the chute position determine whether the bucket empties cleanly or carries material back around.

2. The Five Subassemblies

Every DS chain bucket conveyor is built from the same five groups. Knowing what each one does makes the installation sequence obvious, because each group is the reference for the next.

2.1 Drive unit

The drive consists of a YE4 series super-high-efficiency motor, a ZSY series parallel-shaft reducer, a large and a small sprocket, and the transmission chain between them. The reducer output drives the head shaft through the sprocket pair; the transmission chain is the part that needs guarding and periodic tension checks.

2.2 Running part

The running part is two rows of sleeve roller chain with integral rollers, plus the buckets. The rollers are part of the chain itself, not separate trolleys, and each bucket is bolted to the side plates of both chains. This is why bucket alignment and chain alignment are the same problem: if the two chains are not parallel and in phase, the buckets sit skew.

2.3 Head

The head group comprises the head casing, head shaft, head wheel, rolling bearings and bearing housings. The head wheel is a one-piece casting in ZG310-570. It carries the full chain tension and transmits the drive torque, so its shaft alignment relative to the frame is critical.

2.4 Tail

The tail group comprises the tail casing, tail shaft, tail wheel, rolling bearings, bearing housings, compression springs and tension screws. The tail wheel is also a one-piece ZG310-570 casting. The screw-and-spring take-up at the tail is the only adjustment for chain elongation, which is why the manual insists that at least half of its travel remains unused after installation.

2.5 Intermediate section and accessories

The intermediate section is the frame that carries everything between head and tail: standard and reinforced connecting supports, legs and brackets, the upper and lower tracks, the upper and lower hold-down rails that keep the chain in contact with the track on curves and inclines, the feed inlet, inspection covers, access doors, the main and secondary discharge chutes, and the local control box.

3. Where a Chain Bucket Conveyor Is the Right Choice

The chain bucket conveyor occupies a specific niche: it is a bucket machine, but unlike a bucket elevator it can run at any inclination, including horizontal sections followed by a steep lift, and it can be loaded at several points along its length. Compared with the other bulk-handling options:

Typical duties are furnace and boiler ash, slag and clinker, limestone and lime, coke, mineral ore, sand and gravel, and other abrasive or hot granular materials where the buckets protect the material from the frame and the frame protects the plant from the material.

4. Before Erection: Site, Foundation and Component Check

The manual is blunt about preparation: the installation site must be cleaned before work starts, and every component must be checked for completeness, damage and deformation. Anything damaged or distorted must be repaired before it is installed — not after it is in the air.

• Check the chain first. The conveyor chain must come with a quality inspection report and must meet the design requirements. A chain of unknown origin or unspecified grade is not acceptable, because chain is the one component that cannot be corrected on site.
• Check the foundation. It must be a concrete or steel structure foundation, and its elevation, inclination and plan dimensions must match the general arrangement drawing.
• Check the head and tail assemblies. Both are normally supplied assembled. Confirm that the sprocket set screws are tight and that the two sprockets are in phase — their teeth must occupy the same angular position, or the two chain strands will fight each other.
• Check the supports for transport damage. Twisted or bent support sections must be straightened before assembly. A support that is forced into place puts a permanent bend into the track line.
• Prepare the setting-out equipment. A theodolite, a fine steel wire, plumb bobs, a spirit level, a straightedge of at least 2 m, feeler gauges, shims and a welding set.

5. Setting the Centreline

The longitudinal centreline is the single reference for the whole machine: head, tail, every support, both tracks and the running part. The manual requires a theodolite, not a chalk line, because the tolerances are in millimetres over tens of metres.

1. Mark the intersections. Establish where the conveyor longitudinal centreline crosses the head centreline and the tail centreline. These two points define the machine axis.
2. Mark along the axis. Set the theodolite on the axis and mark a point on the foundation every 10 m along the conveyor.
3. Stretch the wire. Above these marks, stretch a fine steel wire. The wire is tensioned between points about 3 m beyond the head shaft and 3 m beyond the tail shaft, with plumb bobs hung from it so the wire can be transferred down to the machine.
4. Verify and protect. Check the wire against the marks at several stations, then protect it — a knocked wire invalidates every alignment done against it.

Every alignment step that follows refers back to this wire. When the manual says "the longitudinal centreline (fine steel wire)", it means this one, and it must still be in place until the frame is fully welded and bolted.

6. Erection Sequence and Alignment Tolerances

Installation starts at the tail and works toward the head. The reason is practical: the tail is the tensioning end and the reference for the track line, and the head is heavy enough that it should be positioned against an already-established frame rather than the other way round.

6.1 Tail alignment

The tail is normally supplied as a complete assembly. Before setting it down, confirm that the sprocket set screws are tight and that the two sprockets are in phase. The tail is correctly aligned when three conditions are met simultaneously:

• the tail shaft is horizontal;
• the tail shaft is perpendicular to the conveyor longitudinal centreline;
• the longitudinal centreline passes through the midpoint between the two sprockets.

The method is a sequence of three measurements:

1. Level the shaft. Set the tail shaft level with a spirit level, adjusting with shims between the tail casing and the foundation. Shims are not supplied with the machine. Permissible level error: 0.3/1000 of the bearing span.
2. Square the shaft to the wire. Place a straightedge of at least 2 m against the machined side face of the sprocket and clamp it temporarily. Measure the distance from each end of the straightedge to the wire. Adjust the tail until the two distances are equal and each equals half of X, where X is the distance between the two sprocket side faces — at that point the wire passes through the centre between the sprockets. Permissible perpendicularity error: 1/1000 of the bearing span.
3. Fix the tail frame. Only when both conditions are met, anchor the tail frame.

6.2 Head alignment

The head is lifted into position as a complete assembly and aligned by exactly the same three criteria and with the same tolerances as the tail: level shaft, shaft perpendicular to the wire, wire through the midpoint between the sprockets. Check the sprocket set screws and the phase of the two sprockets before lifting. Once aligned, tighten the connecting bolts.

6.3 Drive installation

1. Weld the drive frame to the supporting structure (in ash-handling installations, typically the top of the slag silo) and make sure the top face of the drive frame is level.
2. Mount the motor-reducer on the drive frame.
3. Fit the transmission chain over the two sprockets.
4. Position the chain tensioner so that the roller face is parallel to the axis of the chain links, then weld the tensioner to the frame.
5. Adjust the tensioner, fit the chain guard and fix it.

The reducer output shaft and the head shaft must be parallel, and the centres of the large and small sprockets must lie on one straight line. A transmission chain that runs at an angle wears the sprocket teeth on one side and will fail long before the conveyor chain does.

7. Support, Track and Rail Installation

The supports carry the tracks, and the tracks carry the chain. Errors at support level are multiplied along the machine, so the manual sets tolerances here that are tighter than anything on a belt conveyor frame.

7.1 Connecting supports

Inspect every support for transport damage before installation; any twist must be corrected. Then install to these limits:

7.2 Tracks

Tracks are installed from the tail toward the head, following the track drawing, after the supports are in place. Before installation, every track section must be straightened; it is not acceptable to pull a bowed section into line with the bolts.

• Join track sections with fishplates and bolts, with the nuts on the outside so they can be checked and tightened from the walkway.
• After the tracks are aligned to the wire, weld the track to the track pads. Welding locks the gauge; do it only after the alignment has been checked and recorded.
• Fit the upper and lower hold-down rails. On inclines and curves these are what stop the chain lifting off the track under its own weight and the bucket load.

8. Running Part: Assembly, Installation and Chain Tension

The running part ships as loose components: chain links, buckets and the bolt sets that join them. Assembly is straightforward, but two details decide whether the machine runs true.

8.1 Assembling the running part

• Assemble the chain links and buckets using the bolt sets supplied with the machine, following the running-part drawing.
• Check that every bucket-to-chain bolt is tight before the chain goes into the frame. A loose bucket bolt cannot be reached once the chain is installed.
• Orientation matters. The bucket shape must match the running direction: the curved part of the bucket, on the upper track, faces the tail. A bucket fitted the wrong way round will not discharge cleanly and will foul the chute.

8.2 Two installation methods

The manual gives two methods; which one applies depends on whether there is space behind the tail.

Method A — pull the assembled run in from the tail. If there is enough room at the tail, extend the lower track to the foundation, assemble the running part outside the machine and pull it in with a rope. On an inclined conveyor, the run must be restrained at all times so that it cannot slide or run back.

Method B — feed the run in through an upper-track opening. Remove, or leave out during erection, a section of upper track at a convenient position. Feed the assembled running part through the gap and pull it along with rope, hooks or a hoist. On an incline, once the run has passed the sprocket, the two sides are no longer balanced and the chain can run back — restrain it before releasing the pull.

8.3 Tensioning the chain

When the running part is fully installed, both chains must be tensioned — equally and by the same amount. Tensioning one strand harder than the other skews every bucket and overloads one chain.

• On an inclined conveyor, the carrying rollers must not leave the track in the curved section. If a roller lifts, the tension is too low or the curve geometry is wrong.
• The correct tension is judged at the point of lowest tension — the horizontal section near the tail. A slight sag of the chain there is the sign of correct tension. A taut, singing chain is over-tensioned; a chain that hangs in a deep loop is under-tensioned.
• After tensioning, check that the take-up still has at least half of its travel available for future elongation.

8.4 Safety and auxiliary devices

Before the trial run, every safety and auxiliary device that does not interfere with inspection must be fitted — chain guards over the transmission, covers over the running part, and the guards at the head and tail. A machine is not ready to jog because the chain turns; it is ready when nothing exposed can be reached.

9. The No-Load Trial Run

The no-load run proves the geometry. It is not a formality: most installation errors — a reversed motor, a chain running to one side, a bucket fouling a cover — appear in the first few revolutions.

9.1 Before the first start

Clean all debris out of the conveyor, provide lighting along the line, and assign the crew. Then check, item by item:

• Lubrication. Every bearing and the reducer are filled to the specified level with the specified lubricant.
• Backstop direction. The backstop must be installed to prevent run-back in the correct direction, not the opposite one.
• Bolts. All connecting bolts, including anchor bolts, are tight.
• Chain. Both strands are tensioned as described above.
• Electrical. All wiring matches the schematic and the motor rotation has been checked.
• Guards. All safety and auxiliary devices, including the chain guard, are fitted and working.

9.2 Running the test

Run continuously for about 8 hours. Start with jogging: press and release, watch, and deal with any problem immediately. Only when the jog starts are clean should the machine be run continuously.

During the run, check and record:

• Chain tension. If it is correct, all carrying rollers are on the track. Any roller hanging in the air means the chain is too slack or a track is out of line.
• Meshing. The chain must engage the sprocket smoothly. The sprocket teeth must not touch the inner link plates — contact there means the chain is running off-centre or the sprocket is misaligned, and it will wear through the plates.
• Tracking. The chain must not run skewed or to one side, and every carrying roller must rotate freely.
• Buckets. No bucket may catch or foul. The clearance between buckets and the frame, covers and chute must be even on both sides.
• Reducer. No abnormal vibration or impact noise, and no oil leakage.

After the no-load run, re-tighten every connecting bolt, and spot-weld the nuts on the bucket-to-chain bolts. Vibration will loosen a bolted bucket joint over time; the spot weld is what keeps the bucket on the chain.

10. The Load Trial Run and Handover

The load test starts only after the no-load run has passed. It lasts about 8 hours at design feed rate.

10.1 Starting procedure

1. Start the chain bucket conveyor.
2. Feed material into the buckets gradually. Never drop a full load onto the running part at once, and never start a loaded machine.

10.2 Normal stopping procedure

1. Stop the feed.
2. Let the conveyor run until the buckets are completely empty.
3. Stop the conveyor.

A machine stopped with full buckets restarts against the full weight of the material, and on an incline it may run back before the drive takes up. Emptying before stopping is not a convenience; it is part of the operating procedure.

10.3 What to check under load

• Backstop. Carry out 2 to 3 abnormal stops and confirm that the backstop holds the loaded machine reliably, without run-back.
• Loading pattern. Material must be evenly distributed across the bucket width, the feed must land in the centre of the bucket, and no material may spill over the sides.
• Chain tension. Re-check it under load; the chain will settle and may need a small amount of take-up.
• Temperature. Bearing temperature rise ≤ 40 °C under load.
• Capacity. Throughput must meet the design requirement.
• Controls. Every electrical control device must operate correctly and reliably.
• Record current, voltage and power, and compare them with the no-load baseline and the design figures.

After the load run, re-check the chain tension. Only when everything is normal is the conveyor handed over for operation.

11. Lubrication, Maintenance and Wear Parts

11.1 Lubrication schedule

11.2 Reducer oil

For a typical ZSY180-63-BSP reducer the oil charge is 14 litres, with the grade chosen by ambient temperature: L-CKD220 for 0–35 °C and L-CKD320 for 35–50 °C. The reducer is not filled at the factory.

• Fill until the oil level is between the upper and lower marks on the sight glass.
• Change the first oil charge after 300–600 hours, draining the old oil completely.
• After that: every 3 months if the machine runs more than 10 hours a day, every 6 months if less.
• If the oil temperature rise exceeds 70 °C, the oil temperature exceeds 100 °C, the oil quality drops or the reducer becomes abnormally noisy, stop the machine and investigate. If the cause is tooth-surface scuffing, the reducer must be repaired before it runs again.

11.3 Routine maintenance

Keep the machine and the area around it clean, and clear spillage at the tail promptly. Spillage at the tail is both a housekeeping problem and an early warning: it usually means the chain is slack, the loading point is off-centre, or a bucket is deformed.

11.4 Electrical protection

The thermal overload relay is set so that the machine trips before a jam damages the chain:

11.5 Wear parts to keep in store

Sprocket tooth blocks must be replaced when the tooth wear exceeds 6 mm, or when the chain no longer leaves the sprocket cleanly. A worn tooth profile makes the chain climb, which loads the next tooth in line and accelerates wear across the whole wheel.