Dock Leveller Working Range: Match Trailer Heights

A dock leveller can reach a trailer floor yet still leave an unsafe route for your forklift. The dock leveller working range must cover your vehicles’ changing bed heights while maintaining a suitable gradient and secure lip support.

If you’re choosing equipment or replacing an existing unit, vertical travel alone won’t confirm suitability. Start with the vehicles using the bay, then check the platform, lip and surrounding loading-bay equipment together.

Key takeaways for leveller selection

• Measure trailer bed heights when loaded and empty, including visiting hauliers, rigid vehicles and tail-lift trucks.
• Check the selected model’s separate above-dock and below-dock limits, rather than relying on a combined travel figure.
• Assess gradient, lip bearing, bumper projection and handling-equipment limits alongside vertical movement.

A suitable specification needs to cover normal loading conditions throughout the operation. Reaching an unusually high or low trailer once doesn’t prove that forklifts can cross safely or that the lip will remain supported as the vehicle moves.

What the dock leveller working range covers

Above-dock and below-dock travel

Working range describes the permitted vertical positions of the leveller relative to the warehouse dock floor. Manufacturers usually state an upper limit and a lower limit separately.

For example, a specification showing 410 mm above dock and 370 mm below dock describes two operating limits. It doesn’t mean either direction allows 780 mm of travel. Also distinguish usable working positions from the raised position needed to deploy the lip. The deployment height isn’t automatically a permitted loading position.

Movement throughout loading

Trailer height can change during the loading cycle. As freight leaves or enters the vehicle, suspension movement can alter the floor level and the leveller angle.

The HSE’s loading-area design guidance highlights differences between vehicle and bay heights, including changes between loaded and empty vehicles. Therefore, assess the full loading cycle rather than the trailer’s arrival height alone.

Check the model’s operating instructions for how its deck follows vehicle movement. The lip must retain the specified support, and the platform must remain within its permitted operating envelope throughout the task.

Measure trailer heights against the actual dock

Record the fleet and loading conditions

Build your assessment around every vehicle type that uses each bay. Include articulated trailers, smaller rigid trucks, tail-lift vehicles and third-party hauliers. Occasional deliveries can introduce the largest height differences.

Record vehicle floor heights at the loading interface under representative loaded and empty conditions. Also note air-suspension settings, yard slope and whether vehicles berth squarely against the bumpers.

Take measurements through a controlled site procedure without exposing anyone to reversing vehicles or an open dock edge. A competent surveyor can establish dimensions that operators can’t safely obtain.

Calculate the required rise and fall

Compare vehicle bed height with the finished dock level, using consistent measurements. For a 1,250 mm dock, a 950 mm vehicle deck requires 300 mm below-dock travel. A 1,550 mm deck requires 300 mm above-dock travel.

Those figures describe the height difference, not a guaranteed equipment specification. The selected leveller still needs acceptable gradient, capacity and lip support at both positions.

Allow for floor finishes and installation tolerances when measuring the dock. Resin or screed can change the relationship between the stored deck and warehouse floor. For an existing bay, check actual elevations rather than relying entirely on original construction drawings.

Compare published ranges model by model

There isn’t one universal dock leveller working range. Published specifications show substantial differences between products.

These examples illustrate why the exact model matters:

Model	Above-dock travel	Below-dock travel
ASSA ABLOY DL6210SA	0 to 410 mm	0 to 370 mm
ASSA ABLOY DL6130C	Up to 620 mm	Up to 700 mm
Dock Solutions DSHLPM	312 mm	300 mm

The larger figures aren’t automatically the better choice. Values stated as “up to” need checking against the selected size and configuration, rather than treating them as available on every version.

ASSA ABLOY’s DL6130C literature lists nominal lengths of 3,000, 3,500, 4,000 and 4,500 mm. However, that doesn’t establish that every listed length offers the same maximum rise and fall. Obtain written confirmation for the configuration proposed for your bay.

Similarly, the DSHLPM sheet lists a 2,000 mm width and 2,500 mm length. Those dimensions don’t establish suitability for your fleet without the remaining checks.

Keep operating mechanism separate from working range. Our guide to hydraulic and mechanical dock levellers covers the different controls and loading patterns. Powered operation doesn’t compensate for unsuitable geometry.

Ask the supplier to identify the exact technical sheet, installation arrangement and permitted loading conditions supporting its recommendation.

Check platform length against the permitted gradient

Longer decks reduce the slope

For the same height difference, a longer horizontal travel distance produces a gentler slope. This matters because a steep transition can affect forklift stability, load security and clearance beneath handling equipment.

A useful preliminary calculation is:

Required horizontal run = height difference / permitted gradient

For a 175 mm height difference and a 7% gradient, divide 175 mm by 0.07. The result is 2,500 mm of horizontal run.

That calculation is a starting point. It doesn’t prove that a nominally 2,500 mm leveller suits the bay. Hinge geometry, lip position and transitions also affect the crossing.

Use the handling equipment’s limits

A 7% gradient is an example, not a universal safe limit. Check the forklift or pallet truck manufacturer’s requirements alongside the leveller’s permitted slope.

Low-clearance pallet trucks need particular attention where the warehouse floor meets the deck or the lip meets the trailer. Even an acceptable overall gradient can include an abrupt transition that catches equipment.

Also verify capacity under the actual duty. Include truck weight, battery where applicable, operator and maximum carried load. Wheel contact loads and moving forces need separate assessment. A high capacity rating doesn’t make an excessive gradient or poorly supported lip acceptable.

Confirm lip reach and loading-bay door clearance

Vertical travel and horizontal reach are different requirements. A platform may reach the correct height while its lip falls short of secure support on the trailer floor.

Dock bumpers hold the trailer away from the building. Their projection uses part of the available reach, so measure the actual stand-off distance with the vehicle correctly berthed. Include the lip hinge position, trailer rear structure and any tail-lift arrangement.

A longer or telescopic lip may help with varying vehicles. However, it still needs the manufacturer’s specified bearing on a supported section of trailer floor.

More vertical travel cannot correct insufficient lip support. Confirm the landing condition at the highest and lowest trailer positions.

The shutter or industrial door also needs sufficient clearance for the loading operation. Check its bottom rail, guides, controls and opening sequence alongside the leveller. Our loading bay shutter guide covers these related door considerations.

Finally, keep people clear of moving equipment and trapping points. HSE’s safe loading and unloading guidance addresses guarding around machinery such as dock levellers. Don’t remove side protection to gain extra apparent clearance.

Turn the survey into a written bay specification

Before ordering, give the supplier a bay-specific record rather than a single requested travel figure. Include the lowest and highest measured vehicle floors, dock elevation, bumper projection, handling equipment and expected loading frequency.

Ask for confirmation that the proposed leveller meets those conditions together. Its dock leveller working range should cover the required heights without exceeding permitted gradients or losing the specified lip bearing.

For replacement projects, verify the existing pit, frame supports and structural fixing positions. Matching overall pit dimensions doesn’t prove the new platform will sit at the correct elevation or transfer loads safely into the structure.

Document any vehicle restrictions too. If a bay cannot safely accommodate a particular rigid truck or tail-lift arrangement, transport planners need that information before it arrives. Assigning different vehicle groups to suitable bays can avoid forcing one installation to serve incompatible loading conditions.

Keep the operating range safe through inspection

Control vehicle movement before crossing

A correctly sized leveller still depends on a stable, stationary vehicle. HSE’s loading and unloading checklist advises keeping vehicles as level, stable and stationary as possible, with vehicle and trailer brakes applied.

Use the site’s restraint, communication and departure-control procedures before anyone crosses. The trailer must remain in its agreed position throughout loading.

From a designated safe position, inspect the deck, lip, visible hinges, side plates and bumpers before use. Report oil leaks, uneven movement, damaged steel or insecure lip seating. Don’t send a forklift across to test a suspected defect. Stop loading and follow the isolation procedure.

Set maintenance intervals for the installation

There isn’t one HSE-set inspection interval for every dock leveller. Follow the manufacturer’s instructions, site risk assessment, operating history and previous inspection findings. An annual examination is an industry benchmark, not a blanket legal rule for every unit.

High-use bays, repeated impacts and deteriorating equipment may need more frequent attention. BS EN 1398:2009 addresses dock leveller safety requirements, including installation, maintenance and testing. Assess LOLER applicability separately rather than assuming every ordinary leveller falls within lifting-equipment examination requirements.

Keep door maintenance clearly assigned too. After an impact, inspect shutter guides, the bottom rail and controls as well as the dock equipment. Coordinate commercial door and shutter servicing with your wider bay inspection plan. Work beneath a raised leveller belongs with competent personnel using approved supports and isolation procedures.

Match the range to your real loading conditions

The right working range covers your vehicles throughout loading while preserving safe gradient and secure lip support. Manufacturer travel figures only become useful when matched to measured dock geometry and handling-equipment limits.

Keep those measurements, restrictions and inspection findings in the bay’s operating record. If the surrounding loading-bay door or shutter needs assessment, Contact Us for support.

A platform that reaches the trailer is only suitable when the complete crossing remains safe.