Bucket Elevator and Belt Conveyor Safety Points Buyers Must Plan

Guarding, access and stop logic are not items to sort out once the line is running. They are decided at ordering, because guards, platforms, the position of each emergency stop and the interlock logic are all part of the equipment layout. Adding them afterwards is expensive. Not having them is more expensive.

Guarding: settle what is covered while the drawings are open

The dangerous places on vertical and horizontal conveying equipment are known in advance, so they can be planned for:

• Elevator head and boot: the chain and bucket run, the drive, and the return side.
• Chain and sprocket drives, couplings and belt drives: guarding on every rotating part.
• Belt conveyor drive drum, tail drum, snub pulleys and return idlers, which is where hands and clothing get drawn in.
• Every point where a person on a platform, a ladder or at an inspection opening can reach a moving part.

Guards should be fixed rather than resting in place, and removable with a tool, so that taking one off is a decision instead of a habit. Where a guard has to come off in normal operation, for sampling for example, design the opening to expose as little as possible. Guards removed for convenience are the start of many conveyor injuries.

On site, make a missing guard an equipment defect in the daily checklist rather than a housekeeping remark. That one change is what keeps guards on.

Access: platforms, ladders and inspection points

• Head and boot have to be reachable safely for inspection, lubrication and clearing. A ladder propped against the casing is not access.
• Handrails and toe boards on platforms, and openings that are not trip hazards.
• Boot clean-out doors and inspection hatches are part of the design, not an option. The boot is where material collects and somebody will have to clear it.
• No reaching into an inspection opening while a machine runs, and no clearing material by hand around the head or the boot. Clearing a jammed boot is a lockout job.
• Headroom at the elevator head must allow lifting gear and a person, not just the casing.

Start, stop and emergency stop logic

Conveying equipment should be interlocked, not started by shouting along the line.

• Start against the material flow: dust collection and the furthest downstream machine come on, then each stage back towards the feeder. Stop with the material flow: feeder off, then each stage as it empties.
• On a fault, the upstream feeder stops at once while downstream equipment runs on for a set delay to clear material. The delay is set against the length of the line and what the chutes hold, and it belongs in the contract technical agreement.
• An emergency stop has to be within reach of the person in trouble, not a walk away: at the control panel, on both sides of a screen, at the elevator boot and head, at intervals along a long conveyor, at discharge points and beside inspection doors.
• After an emergency stop is reset, the machine must not restart by itself. Restarting has to be a deliberate act, after confirming that nobody is inside the machine. Resetting and having it run again is how second injuries happen.
• Protection should trip, not merely alarm. A jam sensor that sounds a buzzer in a noisy building is not protection.
• Overload settings that have been raised, or bypassed, to stop nuisance trips leave the motor and the drive unprotected. Every such change has to be recorded and justified.

All electrical work involved here, emergency stops, interlocks, sensors and their wiring, is for a licensed electrician, with the supply isolated, locked out and voltage verified, and installed to the local electrical code.

Belt tracking, and the maintenance that prevents it failing

Tracking problems are usually created by the layout rather than by the belt:

• Loading off centre pushes the belt sideways. Line the chute up with the centre of the belt and in the direction of travel.
• Pulleys not parallel to the frame, idler sets not square to the belt, and unequal take-up on the two sides all produce a steady drift in one direction.
• Spillage from a worn or short skirt, or from a failed belt cleaner, looks like a belt fault and becomes a tracking fault, because material carried back on the return side builds up on the tail drum.

Training idlers correct a belt, they do not cure it. Forcing a belt back with training idlers while the cause remains wears the belt edges until the belt has to be replaced. In addition, do not clear material from drums, pulleys or idlers with the belt running, and do not adjust tension or change a belt without locking out and confirming that neither the belt nor the material can move under its own weight.

Housekeeping and dust accumulation

Dust lying on casings, beams, duct tops and floors is a fire and explosion risk in a grain plant, and it is an early sign that the dust collection is not doing its job.

• Collect dust where it is made: elevator head discharge, chute transfers, belt loading points and screen bodies.
• Clean on a schedule by area, not just when dust becomes visible.
• Do not blow settled dust around with compressed air. That puts it back into the air and onto hot surfaces. Vacuum it or sweep it up.
• Keep the area around drives and motors clear, and keep cabinet filters and cooling intakes clean.
• Clean spillage at transfer points and at the boot before it is walked through the rest of the plant.

Actions to take before ordering

• Ask for a guard schedule with the offer, stating which parts are guarded, whether fixed or interlocked.
• Mark on the layout where each emergency stop will be, and check that each operating position can reach one.
• Write the interlock logic, the start and stop order, fault behaviour and delays into the technical agreement.
• List the access points that need platforms, ladders or inspection doors, and confirm the heights against the drawing.
• Include guards, interlocks, sensors and emergency stops in the commissioning checks and test each one. Protection that has not been tested is not protection.
• Put a periodic test of emergency stops and interlocks into the maintenance schedule, with the results recorded.